Heating aquastat repair:

Guide to diagnostic troubleshooting for heating boiler aquastat controls: this article describes common operating problems with heating system aquastat controls and how these troubles are diagnosed and fixed.

We discuss aquastat problems such as improper adjustment, improper wiring, and relay buzzing or failures.

Aquastat Boiler Control Diagnostic Troubleshooting Guide

Shown above, a hydronic heating system circulator pump relay control with its cover removed. The basic components and connections in the circulator relay include:

• Green arrow: Line voltage in - 120VAC power to operate the circulator pump (white and black wires) usually labeled L1 and L2
• Blue arrow: thermostat wires - low voltage circuit from thermostat that operates the circulator relay usually labelled T and T1
• Yellow arrow: 24VAC transformer that operates switches and controls within the relay control assembly
• Red arrow: the circulator relay switch
• Circulator control terminals C1 and C2 are at the lower right side of the circuit board in our photo
• Burner control terminals B1 and B2 are at the upper right on the circuit board in our photo

[Click to enlarge any image]

How to Diagnose & Fix an Aquastat Control on a Heating Boiler

If you have not already done so, we suggest reviewing the basic operation of a heating boiler aquastat described

at AQUASTAT CONTROLS

Then see AQUASTAT HI LO DIFF SETTINGS to be sure your control has been set properly.

[Click to enlarge any image]

Question: what basic tests can I do to diagnose a clicking aquastat relay or other issues?

Just install a new aquastat to my gas boiler it continues to click. so turn it off. - Wayne, 2017/11/29

This Q&A were posted originally

at AQUASTAT CONTROLS - home

Reply: try these basic Aquastat troubleshooting steps to check for power

Wayne,

Check first for a loose wire or bad electrical connection.

If clicking continues let's look more closely at what is clicking - probably a relay switch in the aquastat.

If so, check the connections to the circulator or burner that the aquastat is trying to operate. If those were working before, and apologizing that I am shooting from the hip, let's do these basic aquastat tests. If none of those sort this out I'm left suspecting a bad relay and thus a bad control.

Tell me the control brand and model and I'll check further.

How to Conduct Basic Boiler Aquastat Controller Tests:

1. Turn thermostat down -

Turn the wall thermostat all the way down so it is not calling for heat.

2. Check incoming voltage -

Using a DMM or VOM check for line voltage (120VAC) at the power terminals to the aquastat (i.e. power is on) by finding 120VAc at the two Line-IN terminals, L1 and L3 are typical markings.

Watch out: opening the cover and / or touching electrical connections while power is on to any electrical device risks shock or death by electrocution. If you know do not know how to do this safely STOP and ask for help from a trained service technician or licensed electrician.

3. Check the low voltage transformer output:

Check for 24VAC at the T and TV terminals - you will find 24VAC at one of these and 0 VAC at the other.

If both terminals show 0 volts then the transformer is bad.

4. Check thermostat switch terminals:

Now turn the Thermostat all the way UP so that it is calling for heat (remember to set it back down later). You should see 24VAC on BOTH of the thermostat or TT terminals inside the aquastat. If you don't then the thermostat is not calling for heat and most-likely you've got an open thermostat wire or a bad thermostat itself.

5. Check burner power terminals:

Now while still calling for heat, check that the aquastat is sending 120VAC voltage to the burner (the two B terminals B1 and B2) confirming that the aquastat is trying to turn on the burner (oil burner) or trying to open the gas valve if it's a gas boiler. This should be turning on the burner.

6. Check circulator terminals:

Now while still calling for heat, check that the aquastat is also sending voltage to the circulator pump - look for 120VAC at the C1 and C2 terminals. This should be turning on the circulator.

If voltage is everywhere it should be and a relay is clicking constantly OR a transformer is buzzing, those component(s) are probably bad.

Separately at RELAY CONTROL SWITCHES using a water pump pressure control switch as an example we discuss clicking and chattering relay switches.

While it is possible to replace a bad relay switch on an aquastat few technicians do so. More often the tech replaces the entire control.

Also see CIRCULATOR PUMP RELAYS & OTHER CONTROLS.

Question: are there re-built primary controls for boilers?

i had an issue with my boiler , i figured it out it was my aquastats l8124,any I called my local place and was told a used one was 190.00 rebuilt?? i was told by another place there are no rebuilt aquastats.help!
ptsd1969@hotmail.com - Anon 10/3/12

Reply:

Some heating equipment suppliers can provide re-built as well as new primary controls. The folks who told you there are no rebuilt aquastats - well I'm not sure if that's because they didn't know or they didn't sell.

Question: Buzzing sounds from heating controls

When my oil burner is starting up I hear a loud buzzing from the boiler room.

Reply: check for a bad relay or a relay that is being impeded by the control cover

Buzzing noisy aquastats, also any other heating controls that use relays, such as some cad cells, stack relays, and circulator relays: if you hear a buzzing sound coming from your aquastat check to see if the control cover is pressing down on one of its relays. Details, photographs, and an explanation are

at HEATING SYSTEM NOISE DIAGNOSIS.

Also check for a bad relay in the control. Often a failing relay unit will buzz in a heating system control.

Question: Boiler won't run: when one of my three thermostats calls for heat the circulator runs but the boiler does not

I have a three zone hot water baseboard heating system. I have three zone valves and only one circulator pump.

My zone valves are made by honeywell and I believe they are the newer version. When I raise the thermostat (upstairs zone) I can hear the circulator pump kick on, the switch on top of the zone valve is in open position and I can hear a click come from the boiler.

The problem is that the boiler never comes on to heat the water to a sufficient temperature. When I put my hand on the pipe directly coming out of this zone valve the it is warm at best. My baseboards upstairs never really get that hot and are unable to raise the temperature in the upstairs of the house.

When I operate the other thermostats in the other zones of the house, the furnace kicks on and heats the the water to temperature. What could be causing the furnace to not kick on in the in the one zone? - Joe.

Reply: from reader Joe P.

If it is only in the one zone you describe: it may be that the boiler is up to temperature and does not need to "kick on".

Observe the temperature on the gauge. Small loops/zones do not take the heat away as fast. Also, there could be blockage. I have also seen in homes that set the thermostats to low, that freezing occurs in the loop, and thus, poor heat output.

You also may have air in the lines which will have to be purged. Turn down t-stat to lower temperature so that all heating goes to the troubled loop and see what happens.

Clarification: Turn down the t-stats to the two other loops (that are working) so that all heat goes to the troubled loop that you have activated (via t-stat for troubled loop).

Reply-DF:

Joe, from your description we can exclude the case that the boiler does not run because it's already up to temperature - since you say that you feel no heat in the problem circulator piping and baseboards.

We like Joe P's advice to see what happens when you turn down or up thermostats to the other zones. Here are more diagnostics:

Heating zone air bound or stuck zone valve: Joe P. refers to a possible blockage in the problem heating zone. Indeed if the zone is air-bound.

See AIRBOUND HEAT SYSTEM REPAIR by WATER FEED VALVE

Or if the zone valve motor is itself stuck then even though the system circulator runs, it never pushes hot boiler water out into the problem heating zone and therefore it never pushes cold water back from the problem heating zone into the boiler where that cooler water would cause the boiler to turn on.

See ZONE VALVES, HEATING

Question: Boiler sometimes won't run": some of my zone thermostats call for heat, the circulator runs, but the boiler won't come

When one or sometimes two of my three heating zone thermostats call for heat, the circulator runs, but for two of the zones, the boiler won't come on until the third zone thermostat is also calling for heat. - DF

Reply: check for a bad control, switch, or relay

This problem could be due to a wiring error or a control problem, as we detail below.

Burn-up on Honeywell Type L8182A, C L8151A Aquastat control board leaves one or two heating zones inoperative

[Click to enlarge any image]

We recently observed the symptoms, debugging, and solution to a similar no-heat in one zone problem. The zone was not air bound. Three thermostats control three individual zone circulators (Taco brand).

The thermostat for zone 3 in a house would call for heat, trip on the circulator, but the boiler would not turn on unless one of the other zones was calling for heat.

The second service tech (from Bottini Fuel, Poughkeepsie, the first fellow said he couldn't see anything wrong), traced the problem to a burned-out circuit on the aquastat control board. We replaced the aquastat and indeed now any thermostat that calls for heat can both turn on the circulator and if appropriate (based on temperatures at the boiler) turn on the boiler's oil or gas burner when it should.

Our photo of this very Honeywell L8124A aquastat control circuit board, with the wires removed, shows brown burn marks around the ZC terminal on the device.

(Photo above). Aside from more sophisticated circuit testing, you might spot this kind of trouble by simple visual inspection of electrical controls and components. Nothing should look "burned-up".

Watch out: a miswired multiple zone or multiple circulator pump system can also prevent one or more of the zones from operating correctly. So can a mix of different brands of zone valves that require different wiring.

Question: temperature difference between on and off too great

I have a 17 year old Rheem boiler which works just fine. However the temperature differential between on and off has become too great despite my setting the thermostat to 5 degrees. It is time for a new thermostat, but I don't know what to buy.

The cover on my thermostat says honeywell aquastat type l8100. eco thermostat. The body says L4005A2080. another part of the body says C0704. I have a blue and white wire to connect to the gas control. There is one bare copper wire going from the center of the thermostat screw on to the left side. That's all the description I have. - Alan 8/21/12

Reply:

Take a look at our room thermostat troubleshooting information

at THERMOSTATS, HEATING / COOLING

- it would be a shame to replace equipment when all that was needed was to blow or vacuum dust off of the existing unit.

Question: Boiler will run but the circulator pump(s) do not ever start.

When any of my three heating zone thermostats call for heat, the boiler will run, but it seems to take forever for the baseboards to get warm, especially on the longer runs.

I finally figured that none of the circulators is running. Because there are three circulator pumps and circulator relays, each controlled by an individual wall thermostat, it seems unlikely that all of them are bad. What should I check? - Charlie G., Calais, Maine.

Reply: check the aquastat control settings for crossed or reversed HI LO controls, then check primary control relays

The photo (above left) illustrates Charlie's aquastat with improper settings for the HI and LO. The HI is set to 180 and the LO is set to just under 200!. Sorry Charlie G. but that's not going to work right.

We have found this problem lots of times when a homeowner or someone else messed around with the HI, LO, and DIFF settings on the aquastat without having a good idea of what those dials do. Aquastat manufacturers such as Honeywell make clear that

The HI should always be set at least 20 °F. above the LO.

If you "cross the controls" - that is, if you set the LO to a temperature that is less than 20 degrees lower than the HI setting, you have basically locked out the circulators.

The oil burner runs, but the LO control is preventing the circulator from coming on. Take a look at the definitions of HI and LO above and this will be more obvious.

Our photo immediately above shows settings that OK - the HI is set to a little over 180 and the LO is set to 160.

Question: my heating boiler won't start

this morning the boiler was not heating. It worked very well during the night. No light in the furnace. I turn off and turn on the gas ignition and nothing happened. What can be the problem? has the damper related to this issue?

I change the button from one side to another side and nothing.

Also, how can I switch on the spill gas? I think that the problem is the sensor, because it was smoke near the boiler area and maybe the sensor shut off the gas but I do not know where is it. My boiler is UTICA model. - Anon 11/7/12

Reply:

Anon, with just the information you state, I'd start at the beginning of our no-heat for boilers,

see DIAGNOSE & FIX HEATING PROBLEMS-BOILER - troubleshooting. Indeed there could be a bad flue gas spill sensor, but I wouldn't start there.

Question: Indirect fired water heater operation when a tankless coil is also available

I have a strange configuraton.

My DHW tank is a zone (tank was added after the fact), but only triggers the LO setting, so it doesn't get the the hotter water that my heating zones get. To complicate things, the water still passes through the tankless and the "Temp-A-Rator" mixing valve.

So, in effect, I pre-heat my hot water. Bypassing the tankless would be expensive and I guess I'd need to then have the tank wired so that it triggers a higher water temp (additional aquastat?). I also don't understand this [apparently obsolete] mixing valve. Is it manual? Should I replace it?

Ok, I'm rambling. Would appreciate any and all thoughts. - Chris - Chris 5/10/12

Reply:

Chris,

When domestic hot water is made by a separate tank heated by a zone on the heating boiler, we call that an indirect-fired water heater system. The LO and DIFF settings have nothing to do with that water heating method - the LO and DIFF make sense and are used when there is a tankless coil in use.

The heating zone, control, and circulator pump (or zone valve) that heats your separate hot water tank just looks like another heating zone as far as the heating boiler and its controls are concerned. Hot water from inside the boiler itself circulates through a heating coil in the bottom of the hot water tank in response to a thermostat on the hot water tank.

But if a heating boiler uses a tankless coil as a pre-heater or post-heater for the water entering the hot water tank, then indeed you've got two water heating methods in parallel - which can be confusing. In fact, you can think of them separately, and controlled separately.

Take a look at the water piping that brings cold water from the building water supply into your hot water heating tank. If the cold water runs first through the tankless coil, then yes you are pre-heating water entering the hot water heater tank.

Some plumbers pipe in the opposite direction, that is, allowing hot water leaving the hot water tank to pass through the tankless coil for a boost that takes effect when the hot water in the separate tank is nearly used up or is cool.

See INDIRECT FIRED WATER HEATERS for details of how these systems work.

Question: L4081B aquastat doesn't seem to be behaving like it should

Great information here. I had to read a few times to put it all together, but I think I finally got it. I have an L4081B aquastat and it doesn't seem to be behaving like it should.

From a cold start with no call for heat (I turned down the thermostats) the burner stayed on all the way to the HI setting (in my case 180°). Shouldn't it cut off at the upper limit of the LO setting?

My Hi is set to 180° and LO at 130 with a 20° DIFF. I have a tankless coil. - Steve 11/7/2012

Reply:

If there is no call for heat but the boiler cycles on, I'd expect that ON cycle to be driven by the LO and DIFF controls just as you describe.

Question: my heater won't turn off; replacing the thermostat did no good, what do I try next?

my heater just don't stop heating my house i tried a new thermostat what should i try next please - Frank Carr 11/12/2012

Reply: things to check when the heat won't turn off, & some Safety Warnings

Buddy said: Frank, You may have a problem with your boiler controls or a check valve in the hot water piping system.

Take a look at "Guide to Heating System Boiler Check Valves & Flow Control Valves" [to see if this information helps you determine if a check valve is sticking open.

In any case, you will probably need the services of a service technician to check out the controls or a plumber to replace a check valve if it is sticking open. - Buddy 11/12/2012

See CHECK VALVES, HEATING SYSTEM

Daniel (Moderator) said:

Frank: in addition to Buddy's suggestion just above, some other reasons that heat may not turn off in a building include:

• The thermostat is continuing to call for heat because
  
  it is in a draft, is damaged, or stuck
• The thermostat wires are shorted together
  
  anywhere in their run - this is the same as leaving the thermostat set to its highest setting.
• The aquastat or high limit temperature sensors
  
  are not properly sensing boiler water temperature because of a bad sensor or because the sensor was not properly mounted in its well on the boiler.
  
  The manufacturers recommend using a temperature-conducting grease, aka thermal grease, properly also called
  
  AQUASTAT SENSDOR PROBE HEAT CONDUCTING COMPOUND though some techs I know like to leave the grease off in hope of avoiding
  
  an AQUASTAT SENSOR PROBE STUCK in the AQUASTAT WELL
• The heating system is unable to adequately warm
  
  the room where the thermostat is located
• If the heating boiler keeps running but is unable to satisfy the thermostat, 
  
  that is it can't get the room temperature up to the thermostat SET temperature there could be other problems such as
  • An air-bound heating pipe, baseboard or radiator that is just not delivering heat to the room where the thermostat is located.
    
    See AIRBOUND HEAT SYSTEM REPAIR by WATER FEED VALVE
  • The thermostat is on a cold exterior wall or is in a cold draft and is not properly sensing room temperature.
    
    See THERMOSTATS, HEATING / COOLING for details on thermostat installation, wiring, and setting.
• Watch out: some safety things to check when your heat won't turn off include
  • Check the heating boiler temperature gauge 
    
    If the boiler temperature is at or above the HI limit set on your boiler aquastat or upper limit control switch then something is abnormal and unsafe and you should turn the system OFF immediately and call for heating system service and repair.
    
    See GAUGES ON HEATING EQUIPMENT
  • Check for discharge, drips, leaks, or spillage at the boiler's temperature/pressure relief valve.
    
    If if the boiler temperature is at or above the HI limit set on your boiler aquastat or upper limit control switch and the relief valve is not dumping hot water and pressure then something is abnormal and unsafe and you should turn the system OFF immediately and call for heating system service and repair.
    
    See RELIEF VALVES, BOILERS
    
    or for steam boilers see RELIEF VALVES, STEAM BOILERS
  In any case you should call a heating service technician to inspect and repair the system promptly.

Question: how do I find a replacement Aquastat for a Honeywell L8024B1048 (triple aquastat) ?

I have a Gas Hydrotherm 86000 Model R108 furnace. I cannot find a replacement Aquastat. I have called Hydrotherm they say call Honeywell. Honeywell say its discontinued they have no information for a universal replacement.

The hot water tankless is disconnected as I have a gas hot water tank.

I heat most of the time with a coal stove so the only time the furnace runs is if I go away for a few days. I'm 73 retired firefighter (36 yrs) .

The furnace is in good shape hate to replace just because cant find aquastat. Do you have any Ideas for a replacement universal aquastat relay. attached is all I have on unit.

Any suggestion is welcome. I usually have to clean contacts to get it running when I use it. - J.M. 12/28/2012

Photo (left) of a Honeywell L8024B & the wiring diagram below were provided by reader J.M.

Reply: parts substitution & replacements for the Honeywell L80241048B,D triple aquastat, Wiring Diagram for Hydrotherm Duo-Service

J.M.

Contact your local heating supplier with the part number (inside the cover check that you correctly identified your Honeywell Aquastat as the Honeywell L8024B1048 (triple aquastat, also the L8024D) - that's probably all they need) from the original aquastat; there are tables of substitution and changeout part numbers and names for just about every control ever made.

I'm sure they'll be glad to help you select the correct one. In fact I'm confused that you report not obtaining help from Honeywell themselves; we have usually found that the company's technical support personnel to be informed and helpful.

[Click to enlarge any image]

I'm not sure about the L8024B series information you've received, and I understand that there is not necessarily "universal" replacement for all applications, but in fact the Honeywell L8124 series (AQS8124B1039 or the Honeywell Multi Function Aquastat L8124B1039) can substitute for many of the controllers in the L8124 and L8024 aquastat line.

We regularly see that controller advertised as replacing the Aquastat models with part numbers L8124B1039, L8124B1021, L8024B, and L8024D.

Indeed it might work for you as well. Also check out the Honeywell, the L7224U Universal Aquastat controller.

Be sure to review your control and how it was used with your heating service supplier;

I would be quite surprised if they couldn't immediately give you the part you need, but if you don't have success let us know and we will research further.

The wiring schematic for the Honeywell L8024B triple aquastat (thanks to your photos) is reproduced at left.

Your aquastat, the L8024B controller, also sold in the L8024D model, is being used in your case to control a Hydro-Therm natural gas-fired heater and possibly a circulator pump; often a review of exactly how a controller is being used in a given application can make more clear just what replacement aquastat will work best.

If you cannot find a suitable replacement control such as the 8124B 1039, we may find a "new old stock" (NOS) L8024B,D, etc. series control available from a reseller.

Reader question: Honeywell R8182D replaced three times

My Honeywell R8182d 1111 keeps tripping the red safe button. This is the 3rd unit installed, they seem to last about 5 years and quit. I installed a new aquastat control about two weeks ago. It worked fine for 2 days, then went away for 4 days and when we returned the Beckett oil burner afg was off.

[...]

If i knew what to replace I would. I'm concerned about the heating season. We use the furnace for heating our hot water ,Utica external 40 gal tank, (not tankless). can you help with your expert advice? thank you, J.& J. 8/24/2013

Follow-up:

The reader ultimately let us know that the new control had been defective. Details about this case are now

at HEATING SERVICE SNAGS

Reader Question: my bad heating system aquastat only runs after we give it a good smack

Thank you for a wonderful and informative website! We have an boiler for our radiator system in our home but it's not starting up unless we smack the cover of the aquastat repeatedly ... and then it clicks a few times the burner flames eventually starts up - after a few smacks. If you can provide any insight to our problem, we'd greatly appreciate it. Thank you, J.D. 11/27/2013

Reply: smacking the aquastat - things to check: loose wires, buzzing, overheating, burning, damaged aquastat control

Nice question. Where is the aquastat mounted? On the boiler itself or remotely say, on or next to the oil burner?

I ask because part of diagnosing why smacking or tapping on an electrical control does something involves figuring out what you may be jiggling in the control when you rap, tap, or smack it.

I suspect a loose wire, loose connection, failing aquastat relay, or possibly a bad connection between the aquastat's temperature sensor and the sides of the well into which the sensor is inserted.

Of course there may be some other issue we haven't thought-of - something that would be immediately apparent to an astute heating service technician.

Start by turning power off (watch out for fatal electrocution hazards) and checking that all of the connections are tight.

Don't forget to check the thermostat wires too. Also listen for buzzing relays in the aquastat.

In the aquastat photo above left I'm pointing to a relay that may be buzzing if it's failing.

While the cover is off of the control, look with care for evidence of overheating or burning around any of the wire connectors or contacts At below left are burn marks around the lower-left power-connection screw.

In my photo at above right I'm pointing to burn marks on the printed circuit board of a Honeywell L8124A aquastat on the reverse side of the overheated wire connection terminal shown above.

This aquastat was behaving erratically for a year or more before a sharp heating service tech from Bottini Oil (Poughkeepsie) spotted the damage.

We replaced the control.

Some contemporary aquastat wells are smaller in internal diameter (often 3/8" ID) than those found on some older boilers (sometimes 1/2" or 3/4" ID) and are typically 1/2" or 3/4" in nominal spud thread or tapping diameter and in varying lengths, comprised of brass, copper or stainless steel, also referred to as insertion wells or shells.

Oil Burner Short Cycling Traced to Poor Aquastat Temperature Sensor Contact: use the heat conductive grease

We have observed occasional short or sporadic oil burner (and some gas burner) "on" cycles that were hard to track down. Technicians even replaced aquastats on a test system we've been monitoring, only to have the problem continue.

Way back we traced the burner on cycle problem to poor contact of the aquastat's temperature sensor in the sensor well.

After assuring that the problem was not in the room thermostat, that there were no loose wires, that the aquastat relay was working normally and in fact that the whole aquastat was new, it was following the manufacturer's installation instructions to use a heat-conductive grease in the aquastat sensor well that fixed the problem.

See these additional details that could explain why your aquastat is not sensing boiler temperature properly, now found in the article listed just below - on using heat conductive compound.

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Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

On 2023-03-28 by InspectApedia Editor - Universal Replacement Aquastat, the L7224U

@Dave Y,

Take a look at the aquastat described by Honeywell as a Universal Replacement Aquastat, the L7224U

AQUASTAT L7224U UNIVERSAL OPERATION & ERROR CODES

On 2023-03-28 by Dave Y

I am replacing my Honeywell L8124A-1114 aquastat on my oil fire ,coil less , 20 year old EFM . it is discontinued what is the best replacement to use?

On 2023-03-02 by InspectApedia Editor

@Michael Twomey,

Our article on this

AQUASTAT L8148 DIAGNOSIS & REPAIR

includes links to installation and repair guides for this control. Looking through those we don't see an option to replace just the sensor bulb.

The sticking point would be the need to disconnect the cap tube from the aquastat control board - a feature not provided.

On 2023-03-01 by Michael Twomey

Can you replace the thermostat for the boiler temperature in a L8148J or do you need to replace the whole unit!

On 2023-02-07 by InspectApedia Publisher

@Garry,
And I appreciate that you understand that while we want to help come we're pretty blind when we have so little information to go on and can't see the installation. Have you tried the very basic tests like jumping thermostat terminals T T at the aquastat (with the actual thermostat wires disconnected) - that simulates turning up the thermostat and calling for heat?

On 2023-02-06 by Garry

@InspectApedia Publisher, I appreciate your patience with me. It's a brand new module (2nd one) and the 3 service providers around here are booked weeks out. I can't even get assistance from Honeywell. Discouraging. It's cold.

The wires are connected properly according to the schematic as well as the picture taken before removing the old unit. I can't wrap my head around it. Proper voltages to the inputs and nothing to the output.i could take it apart and measure the voltages on the back of the board, I'm thinking it ends at the input of the coil and the relay. My 15 pound sledge probably won't help things either.

On 2023-02-05 by InspectApedia Publisher

@Garry,

I'm sorry and certainly understand the frustration.

We've reached a point where, flying blind from our end, other than recommending the standard test sequence, we can't see or test more of your aquastat wiring than you've described.

It's time to call a heating service technician, ask them to help you diagnose and fix the trouble, and then please tell us what you found, as that will certainly help other readers facing the same difficulty.

On 2023-02-05 by Garry

@InspectApedia Publisher, I have, thank you. It's very infuriating. It is all wired correctly according to the schematic as well a picture I took before removing the failed unit. I could take the PC board out and find where the voltage is ending, but that promises to be quite the headache.

On 2023-02-05 by InspectApedia Publisher

@Garry,

Did you try the diagnostic steps above on this page - a pretty good basic place to start.

On 2023-02-05 by Garry

@InspectApedia Publisher, thank you for replying. I gave the voltage readings just to assure is voltage making it to the module.

It's the 2nd brand new unit doing the same thing. I'm just clueless. Honeywell is a good brand. The input is good, it's just not going anywhere.

On 2023-02-04 by InspectApedia Publisher

@Garry,

119VAC is common on a 120VAC circuit;

27VAC is also common, on the lower-voltage circuit that supplies power to wall thermostats and to heater controls.

But if you are testing the proper points in a control where there should be voltage, and find none, then there may be a wiring error.

Watch out: if you're not familiar with safe, proper electrical wiring you could be shocked or killed. Which would be terrible.

On 2023-02-04 by Garry

Installed a new unit. I'm reading 119 Volts at power and 27Volts at the thermostat in put. There is no voltage going beyond the inputs. Any ideas would be appreciated. High level is set at 200.

On 2022-12-08 by InspectApedia (Editor) - boiler will only fire if associated thermostat is calling for heat

@Jay,

If your aquastat is for heat only, no domestic hot water coil, that may be by design.

What are the aquastat settings?

On 2022-12-08 by Jay

Installed new aquastat, boiler will only fire if associated thermostat is calling, circulator runs with it.

On 2022-10-16 by InspectApedia (mod)

@Andy G,

As you replace the aquastat and therefore you're pretty confident that you don't have a bad relay we left suspecting a thermostat or wiring error.

On 2022-10-09 by Andy G

I have a lenox xeb-4 boiler, the rely in the aquastat continues to click and not suck down. I replaced the aquastat, same results. I test voltage from b2 to TV I get 23.8v, I tested
B2 to t and only get 17.4v. What is the issue and how to fix

Thanks

On 2022-08-18 by InspectApedia-911 (mod) - 120v electric to kickspace heater is dead

@mike,

If that voltage is there simply to run a fan, the fan on-off control would indeed be through the thermostat and aquastat.

Actually whether or not you find live voltage at the heater depends on how the wiring was run. If power runs first to the control and from there to the heater then the heater won't see voltage until there's a call for heat.

On 2022-08-18 by mike

the 120v electric to kickspace heater is dead i checked all breakers etc does this stay dead until the aquastat closes and completes the circuit? I would have expected the 120v to always be alive to the heater

On 2022-05-26 by InspectApedia-911 (mod) - use thermal grease when installing the sensor for an aquastat control

@Anonymous,

Thank you for a helpful question about using the thermal grease when installing the sensor for an aquastat control.

The answer is yes, the thermal or heat-conducting compound is necessary.

See details

at AQUASTAT SENSOR PROBE HEAT CONDUCTING COMPOUND

But we don't think there is an L8123A aquastat - I think you meant to ask about the

Honeywell L8124 Aquastat Relay described in

AQUASTAT L8124 A-M INSTALLATION & OPERATION MANUAL [PDF]

These immersion type controllers provide high limit, low limit, and circulator control in forced hydronic heating systems that include domestic hot water.

On 2022-05-26 by Anonymous - Is heat conducting compound needed when installing an L8123a aquastat [L8124 Aquastat - Ed.]

Is heat conducting compound needed when installing l8123a aquastat

On 2022-03-26 by Inspectapedia Com Moderator - aquastat is shutting off the boiler because of a safety concern

@Vlad,

Thank you for the helpful diagnostic question.

My best guess is that the ERROR code on your indirect water heater is because it's not getting re-heated when its thermostat calls for that service from the boiler.

An indirect water heater is heated by an internal coil through which hot water from the boiler circulates.

When the indirect water heater temperature drops its thermostat calls for a circulator to run to circulate boiler water through that coil.

Sure, at night you'd expect the water heater to not need much hot water but it might still call for heat as it cools.

Key in your question is that you have to press the oil burner (boiler's aquastat) RESET button.

That tells me that the aquastat is shutting off the boiler because of a safety concern such as a smoky or defective flame.

In turn that might indeed happen at night when a boiler is called-on to run less often. In that condition it's starting from a colder condition, perhaps contributing to poor ignition or a poor flame.

So I suggest asking a heating service technician to inspect, clean, and adjust your boiler for proper performance. If the problem continues she may need to replace the flame sensor or another control part.

On 2022-03-26 by Vlad

My oil burning Weil-McLain WTGO-3 boiler stops every night between 4AM and 6AM with ERROR sign on indirect-fired water heater display. During the day it works normally.

After resetting power on water heater Error signs turns to normal 120F, but boiler does not start unless I push the red button on oil primary control. After that it works normally (stops and starts) the rest of the day till early morning then stops again with ERROR on the heater display.

I think it most likely connected with hot water consumption during the day and not using it at night, but not sure what need to be fixed. Any suggestions? Thanks.

On 2022-02-13 by Inspectapedia Com Moderator

@Dan,

Usually the electric heating elements in an electric boiler or furnace are cascaded and additional units turn on as needed, under control of a circuit board and temperature sensors.

Assuming we're discussing an electric heating boiler with multiple heating elements, all four heating elements might turn on at about the same time if the building temperature is very low or if other conditions such as extremely-cold fresh air intake from outdoors, into a furnace (forced warm air heat) are present.

On 2022-02-13 by Dan

Hello , is it normal that when aquastat clic back on all 4 of my boilers element power on at same time? Thank you

On 2022-01-25 by Inspectapedia Com Moderator - strap on aquastats may be less safe

@Bill Conlan,

There are replacement aquastats and possibly strap-on type but frankly it's not one that I recommend as I think they're considerably less safe.

For the time being it sounds as if your heating system will work if you leave it set to the lower temperature you cite.

It's also possible that the only problem is poor thermal contact between the back of the aquastat and the pipe to which it is strapped. So it could be worth trying to clean that surface up as a temporary measure.

On 2022-01-25 by Bill Conlan

The aquastats in my systems (2) may be as old as 70 years. They are strap-on and have no external power source other than, possibly, the pilot thermocouple. One of them seems to have a runaway condition if I leave it set to 160°.

If I turn the setting down to 150¯ or so it will shut down the burner when the water reaches that temperature or the thermostat tells it to shut off.

It's going down to well below zero tonight so I don't dare remove the aquastat. As near as I can read the numbers on the back, they appear to be LA109A1X0A1. Is there a replacement that I can use without adding an external power supply?

Can I add an external power supply (required to operate a relay in a newer aquastate) without affecting the thermocouple's control of the gas valve? The old aquastats use a mercury switch on a bimetal coil to control the burner. The boilers are 98-years-old and otherwise operating without any problems.

On 2022-01-15 by Inspectapedia Com Moderator

@Jerry,

I guess if the burner is shutting down on safety, something is not running perfectly despite appearances: a flame, temperature, exhaust or similar defect or hazard is being detected, OR there is a defective safety device.

Having no information about your system, any further guessing would be so speculative as not to be useful.

On 2022-01-15 by Jerry

I have a packet burner with a separate high limit control the burner runs perfect for about a minute then shuts down in safety has to be reset but runs perfectly

On 2022-01-04 by Inspectapedia Com Moderator

@Harold,

It could be a bad sensor, but possibly simply a bad sensor placement in the well, lacking good thermal contact and no thermal grease.

On 2022-01-04 by Harold

I have a Honeywell aquastat controller on gas boiler I know the correct settings on hi 180 degrees and lo 20 degrees less however if I set mine to this the boiler will run and over heat I had to adjust my hi to 140 and lo to 120 still runs boiler to 200 degrees before shutting off do I need a new controller or is there temp sensor some where for the controller.

On 2021-12-03 by Inspectapedia Com Moderator

@Tony,

That's great but help me out in helping others: did you in fact find the exact board for the Honeywell L7224C or did you sub the different model?

If the latter, I guess that could work perfectly well but you've in essence changed the model of your control from L7224C to the new board like the L8148A1017

On 2021-12-02 by Tony

@Inspectapedia Com Moderator, I ended up replacing the board and everything worked as it should! Thank you for responding

On 2021-12-02 by Inspectapedia Com Moderator

@Tony,

I would not assume that you can exchange control boards between two different model aquastats. It's likely that the circuits are different.

If the aquastat was killed by the power loss, maybe by a power surge, you'd replace it in kind or with a universal replacement model.

But first check that power is being delivered to the existing aquastat from its supply circuit.

On 2021-12-01 by Tony

I lost power today and when it came back on i noticed that there was no heat.

I have a smart thermostat and it is sending a call for heat but the aquastat has no lights on.

I checked for 120v at L1 and L2, it is getting power but no other lights on it or the low water shut off which normally has a green light.

Would i need to remove it to test it? Or do I need to reset it somehow?

I have an L7224C, i saw that home Depot has a Honeywell aquastat and the board looks identical. Would this work? Model is L8148A1017

On 2021-11-28 by Inspectapedia Com Moderator

@Tim,

That sounds like a wiring error, or somebody has not found and replaced the defective part; for example on a gas boiler, a bad gas valve, bad thermocouple, bad igniter.

On 2021-11-28 by Tim

Two new Honeywell aquastats with the same problem. They both make the pump relay, but won't power up the 24 volt burner circuit. Any ideas?

On 2021-10-02 by (mod)

@Mac,

Look at the AQUASTAT L7224U UNIVERSAL OPERATION & ERROR CODES

https://inspectapedia.com/heat/Aquastat_Honeywell_L7224U.php

On 2021-10-02 by Mac

Does anyone know what aquastat replaces the Honeywell L8151A?

On 2021-08-07 by (mod)

@Vincent Antonuccio,

A tech will check for power at the relay terminals; if it's getting power but doesn't close the relay has probably failed.

Take a look at the wiring diagrams we include in the PDFs above. In general, the thermostat acts as a low voltage switch powered by the transformer to operate the relay that switches the 120V circulator relay on a call for heat.

Details are on the page above.

If your aquastat is the R8182D, be sure to find details we give at AQUASTAT R8182-SERIES CONTROL https://inspectapedia.com/heat/Aquastats.php

That page includes the PDF download for that aquastat and from that PDF you'll see the Aquastat internal wiring schematic wiring diagram I include below.

On 2021-08-06 by Vincent

On the honeywell r8182d 1038 aquastat. Why would the left side relay (burner motor and ignition relay) not work?

I can manually make it engage, but it will not automatically work.

Do you know what supplies power to this relay? Basically, what items make it turn on?

Thank you.

On 2021-07-19 by (mod)

@Albert Pogash,

Check to see if your system uses a tankless coil to make domestic hot water; if so, the boiler runs to keep hot for making hot water;

If not then the aquastat can adjusted or its wiring changed to stop heating the boiler unnecessarily;

See AQUASTAT LO & DIFF DISABLED https://inspectapedia.com/heat/Aquastat_LO_DIFF_Disable.php

On 2021-07-19 by Albert Pogash

Buy New York or oil burner kicks on a lot and it’s summertime what’s the problem

On 2021-05-24 by (mod) - Denys repairs burned components on printed circuit board in Aquastat Controller

@Denys Picard,

Thank you for the update.

I'm not sure what you mean by "The gravitational switch ..."

I am guessing your reference to pump's "propeller" refers to the impeller inside the fuel unit- nobody replaces those, though it's technically possible; typically they'd replace the whole fuel unit;

When you push the relay closed and nothing happens I figure the problem is current supply;

It's possible to replace the transformer - I'm guessing you mean the on-board transformer not the wall -mounted 24VAC supply to the thermostat controls.

Is it possible that your oil pump (fuel unit) is itself simply failing, perhaps with a bad bearing, causing excessive current draw?

On 2021-05-24 by Denys Picard - my Aquastat circuit board repair worked fine, the oil primary started to work again...but guess what..it's the pump again

Dear Dan, my repair worked fine, the oil primary started to work again...but guess what..it's the pump again. It start and stops after a few seconds...The gravitational switch I guess...(so the overload probably occurred after many attempts at restarting.

You know this, it starts, stops after about 10 to 15 sec. And tries again after a minute or so as long as a heat call is coming. Knowing that the starting brings the load over its average limit...the Aquastat's board did not have time to cool down between each new try so it might get it to flash burn...)

I will do the pump in a few weeks (it's warm now here), other spring chores for the moment. I think it might be the propeller, I think it is not perfectly aligned but the shaft looks OK. It's funny, if I had not ask you for advice, I think I would not have ventured so far with my repairs.
Thank you, Have a nice summer.

On 2021-05-14 by (mod) - simple visual inspection finds location of damage on printed circuit board

@Denys Picard,

sorry Denys, my workload has made me slower than your ability to poke into the circuit board;

I'm fine with experimenting as long as you don't get zapped or start a fire.

Heck, I've been experimenting and trying to figure out how stuff works ever since I was four and took the wheels off of my new red wagon - much to the irritation of my Dad. "It's mine," I'm reported to have answered, "you gave it to me. "

Don't worry about trying to assuage threats of complaints here.

My cautionary remarks are standard to anyone thinking of fooling around with electrical, heating, or other safety-related systems.

Nice going Denys. I can't tell you how many times I too have found an electrical problem (or the effects of one) in a control by simple visual inspection.

My friend Ed Nisley, another IBM engineer (back in the ancient days), would sometimes de-solder and replace components on a blown control board. But no HVAC service tech could nor would try that. Labor cost alone usually makes it equal cost or cheaper (and more-reliable) to toss the old control and put on a new one.

I will be sure to add "take a close look by eye" to the diagnostics above.

Now before installing the new control do we have a guess at why that burn-up appeared on the control printed circuit board? Power surge, accidental short, overloaded, not used as intended?

On 2021-05-09 by Denys Picard

As a final addendum, All of the devices out of the Burner and Pump work on 24V, so wattage is quite low: 61 Watts total (take account that I did a typo on the Zone valves, they are 0.27 Amp each, not 0.57).

I further installed a Heat Shrink tubing insulator as a measure of safety on the new soldering...

I never expect you to say go ahead. Never expect you to say Stop, but you may say Stop and I will listen.
Thank you.
Denys

On 2021-05-09 by Denys Picard

Dan, while I was waiting for any suggestions or extra observations, I tabulated the energy load, which I thought was fine but...I observed within the inner box label of the Honeywell L8148A Aquastat that Max load is 7 Amps @ 120V.

Yet, my original installation (in 2000 with the Weil-McLain Oil Boiler and circulating Pump (B&G) done by a professional draw a bit more than this.

(The Burner with valve, heating coil and fan draw up to 5.5 Amp @120 V and the Pump is rated at 1.75 Amp@ 120V). This puts us at 7.25 Amp. But this is a conventional setup, does it mean that most installations start from a potential overload structure?

My other components are modest in contribution, and some are mutually exclusive in terms of when they use load, but you know this better than I do:

Zone Valve 1 : 0.57 Amp; Zone Valve 2: 0.57 Amp; Transformer for zone valves: Max 1.5 Amp; Actuator Valve VC-8711-11: 0.2 Amp; Dual Control Energy Switch: 0.17. No one who worked on the system ever indicated or inferred that there could be an overload.

System has been working on Dual Zone Dual Energy for 4 years fine...Anyway, tell me what you think. Could the Aquastat been over taxed for so long...?

I am putting a picture of my soldering "repair"...if you want to comment (I checked along the middle line, it tested perfect "ZERO" Ohms wherever I put the meter nods, between the yellow arrows. And tested perfect "1" when testing the line against any soldering purple arrows pods.). I haven't re-installed it yet. Waiting to hear from you.

PS: In describing the system in the original post I used the expression "Primary Control Switch" when saying I verified all the connections; what I meant was the connections in the "Primary Service Switch Box" (which is also Honeywell).
Thank you again.

Even if I do stuff which may lead you to believe I am not listening to you, I do read with attention you posts.

Just communicating to you gives me the confidence to do some actions, and hope that if I am about to make a mistake, you will say: "STOP". And again, without engaging you in any responsible manner if you don't say anything (my choices, my actions, my risks, my responsibility).

On 2021-05-08 by Denys Picard - what created the short circuit on this Aquastat board?

Thank you Dan. I finally took the circuit out, wanted to investigate. Your questions come at the right time. Damage is clear on the printed side. I was wondering if one of the sitting foot (#2 in the pictures) could have created the short. It is slightly misaligned and appears damage, loose and slightly goes down in the opening at proximity of opposite poles. That is where the burn is, as you can clearly see.

The unit had always made sound, sometimes more, sometimes less. One of the service person told "...me it was because the plates stick, just give a tap and it should stop...", which I did a few times over the years.

Could humidity have built on the loose foot #2 enough to create a short, or do you believe the short was provoked by the defective relay. As I told you, it is 21 years old, was installed new with the Oil Boiler.

I added the electric boiler dual energy system in 2006, that is when the system became a bit more complicated, and the splitting of a single zone into 2 in 2016.

Do you believe I could or not a good idea to re-solder the damaged half inch segment on the circuit with normal electronic solder wire, or this would be a mistake.

The use of the Aquastat is regular except the environment is a bit more structured than a single boiler installation. The Amp limit is not met. But the environment was humid from 2000 to 2003, before I started addressing the problem.

Now its fine (between 40 to 50% year round, sometimes dryer in the winter when the oil boiler work a lot in cold spells. But the board looks like quite new from my insight, but as I told you, I am not a Pro, have not seen much of these, it is my only one.
Thank you.

On 2021-05-08 - by (mod) -

@Denys Picard,

Nice going Denys. I can't tell you how many times I too have found an electrical problem (or the effects of one) in a control by simple visual inspection.

My friend Ed Nisley, another IBM engineer (back in the ancient days), would sometimes de-solder and replace components on a blown control board. But no HVAC service tech could nor would try that. Labor cost alone usually makes it equal cost or cheaper (and more-reliable) to toss the old control and put on a new one.

I will be sure to add "take a close look by eye" to the diagnostics above.

Now before installing the new control do we have a guess at why that burn-up appeared on the control printed circuit board? Power surge, accidental short, overloaded, not used as intended?

On 2021-05-08 by Denys Picard - burned aquastat board component found

@Denys Picard Here Dan, two other pictures with the model number and the dark spot.,

On 2021-05-08 by Denys Picard

Dan, I took a bit more time this morning and checked the high limit terminals, they too did not get any Voltage. Since the terminals for the transformer are on the other side of the circuit board...I took my courage with both hands and proceeded to remove it partially, and there POW!.

Dark black spot on the paper insulator, I turned my eyes towards the back of the circuit and saw the melting flash-point (putting pictures), which in just under the relay switch. The funny thin is that when putting the current this morning, the relay was clicking and pushing outwards

. If I have to remove the relay alone from the board, I don't have the equipment...do Honeywell usually do these repair, or is the whole thing be thrown out the window?

The have a office here in montreal (QC). I live in Mtl, but am a dual citizen (USA and Cad), so don't be scarred about canadian authorities putting their nose here, I am contacting you as an American citizen.

On 2021-05-07 - by (mod) -

@Denys Picard,

Thank you for the aquastat diagnosis and troubleshooting question. Please read the article above on this page where I have outlined exactly the steps that you can take. Let me know if any of those are unclear and I'll be glad to elaborate or correct or update the material.

On 2021-05-08 by Denys Picard - can an aquastat printed circuit board be repaired?

Dan, I am not sure, but I think someone just erased my last messages. I will repeat.

I understand pictures are moderated, but I could see them, and then the pictures and messages all disappeared at once. So I will try again, in the hope it is not redundant. This morning I had a second look. I tested the terminals on top of the high limit, which I had not done before contacting you.

Same as for C1 and C2, not current. But when putting the switching on the primary control, I did notice the relay was pushing outwards when it emits its clicking sound (but all the buzz sounds were gone).

And then took a bit of courage and decided to pull the circuit out of the box to identifiy the terminals of the transformer and test them. But then as I pulled, I notice a black spot on the paper insulator. Looking towards the back of the panel I noticed the dark flash-point damage on the circuit just under the relay.

I don't have the equipment to change the relay (especially pulling it out without damaging the circuit board.

Do you know if Honeywell repairs this, they have an office here in Montreal (QC). I live in Mtl but have dual citizenship (USA and CAD)

I am contacting you as a US citizen, so don't worry about canadian authorities bugging you. I read comments on your website that sometimes you get a bit too much attention. from canadian authorities because laws are different here concerning DIY. I don't and won't hold any of your advice for any mishap which could ensue from my actions.

Now, is this repairable or should the whole unit be thrown out the window and replaced. I am putting pictures so you can see for yourself. Thank you.

On 2021-05-07 by Denys Picard

I thought I had already followed most of them, but was wondering if the presence the regulator on a dual-energy system may hide a different problem? Further, if I press on the relay, and nothing gets out of C1 or C2, does this effectively mean the relay is out or could it be the transformer of the aquastat which I don't believe you explain who to test by itself.

Can I replace the transformer alone if it is the problem and is it possible the regulator is creating a loop because neither of the regulator nor the aquastat describe the setup for a dual energy system.

One would believe my heating systems are being sabotaged. Got pink insulation stuff in my cheminey, got 2 bolts on the circulator pump unscrewed all in the pas 2 weeks, and last saturday morning, my oil secondaryb (primary) regulator screen went blank. It is driven by an Aquastat L8148A.

I have a dual-energy system (Electric Boiler as primary and Oil boiler as secondary) on a hydronic system driven by a G&C circulator.

I have determined that while 120V is getting to the Aquastat, (and the zone transformer and dual energy swticher a transformer are functioning properly) the C1 and C2 terminals are not sending any voltage to the pump.

The C2 goes directly to the pump, while the C1 bifurcates through the OIl burner regulator R7284 Honeywell also. I did not try to determine whether it was the relay switch which is defective or the transformer within the aquastat.

The oil boiler is a WeIl McLain (WGO series 3) and the electric boiler is a local manufacturer (Thermo2000).
What test can I do? No terminals appear burnt nor any funny odor emanating from the aquastat.

And what components can be easily replaced.

The Aquastat L8148A is 21 years old, it had made funny vibrating noises in past (which a professional told me it was the switch sticking, nothing to worry about).

The Regulator R7284 is 2 years old, it replaced an old one which went kaput

They are 2 zones valves (their main transformer works fine and the valves do to. When the current is set, nothing, blank, on the regulator screen, which I believe it simply means it is not getting any electricity from the Aquastat....I did check all the connection in the primary control switch, everything fine.
Thank you.

On 2019-05-14 by (mod) - How do you get a aquastat out of the thermal grease

Skip,

Thank you for a great question and one that has plagued lots of service technicians.

To have room for a detailed answer I repeat your question and reply at

https://inspectapedia.com/heat/Aquastat-Immersion-Well-Thermal-Grease.php#ProbeStuck

Please take a look, let me know if that helps you out, post photos (one per comment) of your aquastat and probe, and we can take it from there.

On 2019-05-13 by Skip

How do you get a aquastat out of the thermal grease that is acting like glue??

Do we need that heat-conductive grease in the aquastat sensor probe well?

This topic has moved to AQUASTAT SENSOR PROBE HEAT CONDUCTING COMPOUND

Free Up Aquastat Temperature Sensor Probe Stuck in Old Thermal Grease

This discussion has moved to AQUASTAT SENSOR PROBE STUCK in the AQUASTAT WELL

...

Continue reading at AQUASTAT RESET BUTTON or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see AQUASTAT DIAGNOSTIC FAQs questions and answers about diagnosing an repairing heating boiler aquastat problems

Or see these

Recommended Articles

• AQUASTAT CONTROLS - home
  • AQUASTAT HI LO DIFF SETTINGS
  • AQUASTAT LO & DIFF DISABLED
  • AQUASTAT L4006, L4006E, L4007 HONEYWELL GUIDE [PDF]
  • AQUASTAT L4080B,D & L8080A HONEYWELL MANUAL [PDF]
  • AQUASTAT L4080B,D,F,G & L8080A HONEYWELL MANUAL [PDF]
  • AQUASTAT L6006A HONEYWELL GUIDE
  • AQUASTAT L7224U UNIVERSAL OPERATION & ERROR CODES
  • AQUASTAT L7224U UNIVERSAL DIAGNOSIS
  • AQUASTAT L8124 AQUASTAT INSTALL / REPAIR
  • AQUASTAT L8148 AQUASTAT INSTALLATION
  • AQUASTAT L8148 HONEYWELL DIAGNOSIS & REPAIR
  • AQUASTAT R8182-SERIES CONTROL
  • AQUASTAT RESET BUTTON
  • AQUASTAT SENSOR PROBE HEAT CONDUCTING COMPOUND
  • AQUASTAT SENSOR PROBE STUCK in the AQUASTAT WELL
  • AQUASTAT SETTINGS vs HEATING COST
  • AQUASTAT SELECTION GUIDE
  • OUTDOOR RESET MODULE AQUASTAT ADJUSTER
  • REMOTE THERMOSTAT CONTROLS for HVAC
  • TANKLESS COIL HOT WATER HEATER TEMPERATURE CONTROL
• MANUALS for HEATING & A/C SYSTEM CONTROLS

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AQUASTAT TROUBLESHOOTING at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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INDEX to RELATED ARTICLES: ARTICLE INDEX to HEATING BOILERS

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