Recent aquastat diagnostic questions - heating boiler aquastat control troubleshooting.

These questions & answers help you to troubleshoot & repair the aquastat control on heating boilers.

This article series explains how aquastats work and what the different aquastat controls are, what they do, and how they are set.

Page top photo: a Honeywell L8148 Aquastat in use on a gas fired Crown heating boiler, discussed on this page.

Aquastat Diagnostic & Setting Questions & Answers set #3

Recent questions and answers about aquastats posted here or at AQUASTAT CONTROLS or at AQUASTAT TROUBLESHOOTING.

Be sure to see the aquastat diagnosis and repair advice in either of those two articles.

On 2018-11-12 by (mod) - Buderus Hydronic Boiler GC144 overheating problem solved!

John

Nice going. Let me know what the installer says when they show up. Your comments and troubleshooting will surely help other readers so I'll be sure to keep this information around. Thanks again for the follow-up.

On 2018-11-12 by John M The installer reversed the supply and return lines to the boiler.

Thanks for your quick reply. I also believe that I found the problem. The installer has reversed the supply and return lines to the boiler.

As installed right now the temperature sensor on the Aquasmart is reading the cold return flow from the baseboards, not the hot water exiting to heat the house.

This is causing the sensor to confuse the Aquasmart. I have already placed a call to the installer to contact me. Thanks Again John

On 2018-11-11 by (mod) - Buderus Hydronic Boiler GC144 overheating problem

John

For normal hydronic heating boiler,
Something certainly sounds wrong with the aquastat or boiler controls. It would be quite unusual for a boiler to reach temperatures over boiling. That would mean that the system is under pressure and that the control high limit is abnormally High.

In fact I wonder why the temperature and pressure relief valve isn't opening.

It's possible that this is an unsafe condition. Have you tried giving a call to the manufacturer's technical support line?

On 2018-11-11 by John M

My new Buderus Hydronic Boiler GC144 seems to be overheating water in the Economizer Mode. I hear popping noises from boiler and see water temperature going to 248F after the burner stops.

The circulator is not running in Economizer Mode, and I can not set Economizer to OFF.

Technicians that have come out say that it must be air in the system, but I think water is boiling in bottom of boiler. I have purged air from system and see no difference.

I have no problem with the heat circulating thru the system with a normal call for heat when the circulator runs. Suggestions on what to do next?

On 2018-10-26 by (mod) -

Anthony

Of course I could be mistaken but I can't think of any direct way in which the failure of a circulator pump would cause an aquastat to fail. The aquastat is basically a sensor of the boiler water temperature.

It has to be able to do that job including controlling the temperature or shutting the burner off at high temperature regardless of whether or not water is circulating through the boiler.

On 2018-10-26 by Anthony

If the recirculating pump is not working properly would that cause the aquastat to fail

On 2018-08-14 by Anonymous Liberty II Aquastat Honeywell L7224/L7248 error code

The furnace is a liberty II, the aquasta is a Honeywell L7224/L7248 (electronic aquastat). The error code comes up 1.

Is there a way to reset the aquastat? Or is it common for them to go? Furnace is about 5 years old.

On 2018-08-14 by (mod) -

Let's start with the brand and model of the control. Then we can look at the manual and the error code instructions.

On 2018-08-13 by Clarence

Is there anyway to reset the unit with an error code that says the assistant is bad or do I need to buy the whole new unit

On 2018-07-26 by Paul D. - using the jumper position on a Honeywell Aquastat on a Crown boiler

Thank you so very much for all of the information. Again, thank you for your service!

On 2018-07-25 by (mod) -

Your aquastat is discussed HONEYWELL L8148 AQUASTAT INSTRUCTIONS & MANUAL

Sorry for the delay in accepting the images - sometimes the reader comment/posting volume gets us a bit behind.

I suspect a bad solder joint or board just as do you.

Though it's worth noting that for an electronic ignition gas pilot/flame we could have a bad sensor/thermocouple or for electronic ignition, a bad wire, connection, or igniter.

At our page giving access to Crown boiler manuals

CROWN BOILER AGE PARTS MANUALS

you can find the manual for your AWI boiler

inspectapedia.com/heat/Crown-AW-BW-CW-16-34-Gas-Boiler-User-Manual-Standing-Pilot.pdf

In your boiler model number AWI is the series, 061 is the MBH (input BTUs), and the S suffix tells us it's meant to have a standing polot.

You'd want to check the thermocouple before replacing the Honeywell Aquastat Controller L8148E used on your boiler.

On 2018-07-24 by Paul D. - Crown boiler aquastat jumper wire wiggling

This pic is where I took the old jump wire off and added another minus the the female adapter plug seen in the first pic I sent with the green wire

. If I wiggle this, it goes on! Bad solder joint? Again, sorry about the pic problem. To keep you from having to blow up the pic of the series, model, and serial numbers, here they are respectively:
3/1/2005 (aka: date?)
AWI061SNST1PSU
CROWNB000369658

...

I’m sorry...I posted more than 1 pic, but it appears I have to do so in/with separate comments, so am doing so here:

On 2018-07-24 by (mod) - where to get CROWN BOILER MANUALS - Crown

Paul you don't give the model of your Crown gas boiler but we list some manuals and contact information to obtain other old Crown boiler manuals at

CROWN BOILER MANUALS - Crown -> Velocity Boiler Works https://inspectapedia.com/heat/HVAC-Manuals-Air-Conditioners-Boiler-Furnaces-A-E.php#Crown

Post a sharp photo of your boiler and another of a closeup of its data tag and we can assist further.

On 2018-07-24 by Paul D. Gas fired Crown boiler Aquastat jumper wire problem

I have a gas fired Crown boiler that I decided to test prior to the upcoming Michigan Upper Peninsula winters...lol.

Had to relight pilot. When I turned up the thermostat, it wouldn’t light.

Checked everything I could, and found that the b1 & b2 were reading zero.

I decided to check the jump connection just above that which was giving me problems last year. After wiggling it a bit, it fired. Now then, I’m including a few pics to help with my descriptions...hope they help.

The jump wire that I tested last year for a good connection looks like the 2nd pic (1st is the Aquastat).

If you notice where the green jump wire used to be, I replaced it with a more solid jump wire minus the female part of the connector.

It is this new jumper that I wiggled again this year and it fired, thus giving b1&b2 a 24v reading.

Furnace is again functioning as should (temp gauge at circa 180, pressure at circa 15lbs, very minimal spits of yellow flame above burners), but I want to get to the bottom of this bad jumper connection.

For the record, I did use dialectric silicone compound on connection.

Anyway, the transformer does have a constant humming noise, not real loud, but nonetheless there.

And, probably not important to the matter at hand, but the circulator runs constantly...a very low hum can be heard by it as well as the Safegard Low Water Cut-off.

Also, as should be noted, this system bypasses the damper (it's there, but not wired)...I’m assuming because it vents into the existing chimney just below the hot water heater vent.

Suffice it to say that this is an older system, 1994, but I cannot be sure if the Aquastat is that old, though it appears to be. Any advice and/or instructions will be most welcomed! Thanks in advance!

On 2018-07-19 by Margie

Im trying to turn on the boiler and get a ted flashing light. Starts nlue. But then turns red. Its a honeywell

On 2018-01-31 by (mod) - boiler not at set temperature - why?

Ed

That could be perfectly normal.

With the room thermostat set all the way up so that the call for heat will be continuous, check the boiler temperature on the boiler gauge when the boiler's burner has just turned off. The temperature gauge should read close to 180F.

(These are not precise lab-grade instruments). If the gauge is way off then I suspect the gauge is defective.

On 2018-01-31 by Ed

My aquastat is set to turn off at 180. According to my new temp/pressure gauge the water temp is only 150. Any advise

On 2018-01-06 by (mod) - circulator won't run

If the circulator pump runs on a coal for heat in the problem is not the Aquos. It's more likely that your heating system pipes are Airbound

Search inspectapedia for that phrase to read details

On 2018-01-06 by Victor

My furnace comes on, I have hot water. I put in a new circulation pump but it isn’t circulating the water through my house. Could it be my Aquastat.

On 2018-01-01 by (mod) -

If the tech wants to and can try replacing just the relay, I'd give that a shot.

On 2018-01-01 by Brian

Tech said assistant relay needs replacing and I also think control switch also needs replacing

On 2017-12-02 by (mod) - acuastat buzzes for a few mins then it is fine

Often a failing relay or transformer.

On 2017-12-01 by Tina Barbour

My my furnace turns on, the acuastat buzzes for a few mins then it is fine. What could be causing this? It has been doing this ever since we lost power a month ago.

On 2017-06-15 by Chris

I have no clue what it is I'm looking at on this boiler. Is there a way to shut the water off to the baseboards without shutting off the bath hot water.

At least until my landlord get here to look at this? 90 degrees in the house in June at 9 o'clock at night is simply not acceptable.

On 2017-06-14 by (mod) -

Chris

SOunds like a zone valve stuck open or a check valve at the boiler stuck open. Use the on-page search box at the top or bottom of this page to find our article on HEAT WON'T TURN OFF to read details, please take a look at that article, then ask more questions as you need.

On 2017-06-14 by Chris

Thermostats turned all the way down, 89 degrees outside, baseboard heaters are hot... why is that? Is there a way to prevent those from heating making the house hotter than it needs to be? Not to mention burning gas and running up that bill?

On 2017-06-11 by (mod) -

Anon

Is this a new problem with an existing control or is it a problem that has been present since the control was installed?

On 2017-06-11 by Anonymous

I have a dual switch Honeywell aquastat with high limit manual push reset button on my ACE BEUHLER BOILER.The high limit reset button keeps tripping after the water reaches 140 degrees the boiler will not come back on unless the red button on high limit is reset manually several times a day.

The aquastat has two thermocoupler copper tube running to boiler ,one on the reserve tank line coming to the boiler and another tube to the boilers outward line.Any one knows why the boiler is not turning on on its own.thanks

On 2017-04-22 by (mod) -

Hylton

We'd need to know more.
With a new control board and voltage to it, does the gas valve open or not? Does the igniter spark or not?

There could be a bad gas valve or a bad connection to it.

On 2017-04-20 by Hylton - Our aquastat sends 24v to the electrical ignition but the boiler doesn't fire up.

Strange gas boiler problem. Our aquastat sends 24v to the electrical ignition but the boiler doesn't fire up.

Tried replacing the electrical ignition board (thought the board was bad) but it still doesn't start up. Thoughts?

Strange gas boiler problem. Our aquastat sends 24v to the electrical ignition but the boiler doesn't fire up. Tried replacing the electrical ignition board (thought the board was bad) but it still doesn't start up. Thoughts?

On 2017-04-22 by (mod)

Hylton

We'd need to know more.
With a new control board and voltage to it, does the gas valve open or not? Does the igniter spark or not?
There could be a bad gas valve or a bad connection to it.

On 2017-02-02 by AEG - splitting one radiator into two, piping alternatives

I had a contractor divide one room into two. We removed one large and long radiator and replaced with two smaller radiators on each side of the divide. Can you split a hot water supply line to supply two radiators? Or should you go into one radiator, then supply the second one out of the return from the first radiator? They did the first.

Reply:

AEG:

You can, with proper plumbing run the existing long radiator with two separated ones - you just need access to run the pipe to the second rad and then its return back to the original point of return or to another one that works. That is a "daisy chain" or sequential piping arrangement.

But working from the floor or ceiling below, if the plumber found it more convenient - that is it depends on heating pipe routing - she might feed radiator 1 and 2 separately off of an existing hot water heat supply line (and of course returns) - either is possible, it's a matter of which gives easiest plumbing.

On 2017-01-29 by Steve S - Honeywell L4006E aquastat troubleshooting

Hi. Your site is fantastic.

I believe I looked everywhere on your site and have not been able to find an answer.

I have a gas hydronic heating boiler that is used for baseboard heating, as well as for our hot water. The hearing is for one zone only, and there is a circulator as necessary.

There is a combination aquastat that controls the high and low limits. In addition, there's a manual reset high limit aquastat (Honeywell L4006e) set for 200 degrees).

Recently, when there was no heating going to the baseboard, we noticed that the manual reset button was tripped.

We reset it and it worked ok for a few hours. Each time we reset it, it seems to work ok, but only for a short period. I believe the boiler shuts off on high limit as set in the combination aquastat, BUT the temperature still rises substantially and therefore power gets tripped by the high limit manual reset aquastat (set for around 205 degrees).

I figured I can adjust the combination aquastat settings so that it would not trip.

I set the low limit at 155, the high at about 185, the differential at 15, and the manual reset at 205. This should have helped (in my opinion) but it still tripped.

One final point, there are three other identical boilers in the room next to ours, and the high, low, differential, and manual reset settings are all just about the same. Their low is about 165, the high about 190, the differential at 15, and the manual reset at 200. The other three are working fine.

What can be causing this? What can I test or look out for? I appreciate your response.

Reply:

Steve:

When the aquastat reset button is tripped off then the control found an unsafe condition (or the control is defective which is less likely).

The instructions for the Honeywell L4006E (the "E" means it has a high limit reset switch), include this advice for testing the aquastat limit switch:

In checking out the system, adjust the limit setting low enough so that the temperature of the controlled medium (water) reaches the high limit setting. When the limit setting is reached the Aquastat controller locks out and the burner shuts down.

When temperature of the controlled medium drops to the high limit setting, minus [the] differential [setting], push the manual reset button and the system should again be operative. Reset control to proper high limit setting.

To me this points out that if the control is not damaged, your system is either set to too-high a temperature or its temperature control is not working properly.

There might be a small temperature rise after a boiler reaches its limit due to residual heat in the steel or cast iron of the boiler but that ought not be enough to be causing trouble.

Your High (185) minus Diff (15) = 160. Reset the aquastat when the temp is below 160. Then if the problem recurs I suspect a defective temperature sensor or a defective control.

In the article above I'll be sure we include a link to the instructions for the AQUASTAT L4006, L4006E, L4007 HONEYWELL GUIDE [PDF]

On 2017-01-15 by (mod) Before replacing a control I'd want to run some diagnostics

Before replacing a control I'd want to run some diagnostics (such as are given in the control's installation and repair manual) and maybe change the flame rod.

On 2017-01-15 by Louis hood

lhood@mwmech.com Honeywell C99-100 with flame sensor boiler control having to reset boiler gits to 160 and trips out this control cost a lot what is my problem is their another control that I can use?????

On 2017-01-15 by (mod) Honeywell C99 controller

Louis

I can't say from just your brief e-text if the problem is with the Honeywell C99 controller, a flame sensor, or another control or burner operating safety problem.

I think by "flame rod" you refer to an igniter system for gas fired heating equipment. IF that's the problem, for example if the igniter is sparking but not igniting the flame, I would replace it using a compatible replacement, perhaps the Honeywell Q3400A1024 30-Inch Igniter Flame Rod Assembly. (About $40. U.S.D.)

On 2017-01-15 by Louis hood

I have a Honeywell c99-100 with flame rod keep shutting down boiler gets to about 160 have to reset

On 2017-01-15 by Joiry

Hi, I have a wiring/installation question regarding triple aquastats. I am interested in converting my Honeywell dual aquastat to a triple aquastat heat manger, perhaps the Hydrolevel Hydrostat or the like. I have a separate domestic hot water source.

The dual aquastat presently operates a two zone hydronic oil fired boiler running at 82% eff. Unfortunately both zones are controlled by simple line voltage thermostats. After reading the schematics on triple aquastats, it seems apparent that low voltage wiring is necessary, especially for the heat manager to work properly. Is this true?

Is there no way to operate a triple aquastat with two zone line voltage thermostat wiring?

It is possible for me to convert the thermostat wiring to low voltage fairly easily in the house as well as wire in a switching relay to allow the second zone to communicate with the triple aquastat. I'd appreciate any advice on whatever options will prevent the boiler from running to high limit 24hrs a day during the heating season. I know that was a lot of questions. Thank you for your time!

On 2017-01-05 by Anonymous

The thermostats were off, so with them being off, is it still possible for them to trigger the interval firing of the boiler?

I have a gas water heater that is not heated by the boiler. I was thinking about disabling the LO limit but the regular interval firing is the confusing issue. Thanks.

On 2017-01-05 by (mod) heater is firing at a very regular interval

John,

When a heater is firing at a very regular interval I suspect that some other timed component or feature is causing it.

Look for a thermostat with a clock timer or schedule that is improperly-set or is malfunctioning (Nest heat schedule?) or even something indirect such as a leak in a hot water pipe spilling hot water from a plumbing system whose hot water is heated by the heating boiler either via tankless coil or an indirect fired water heater.

On 2017-01-05 by John

Why is my hot water baseboard boiler firing every 24 minutes for about 2 minutes and 40 seconds each time even though the thermostats are off? The boilers seems to be on a timer but the thermostats are off. I have a honeywell triple relay aquatstat on the boiler. Thanks.

...

Continue reading at AQUASTAT TROUBLESHOOTING that explains the best settings to use & how & when to disable the LOW & DIFF controls or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see AQUASTAT DIAGNOSTIC FAQs-3 - more recent questions and answers about troubleshooting a heating boiler aquastat controller.

Or see these

Recommended Articles

• AQUASTAT CONTROLS - home
  • AQUASTAT HI LO DIFF SETTINGS
  • AQUASTAT RESET BUTTON
  • AQUASTAT SENSOR PROBE STUCK in the AQUASTAT WELL
  • AQUASTAT SETTINGS vs HEATING COST
  • AQUASTAT SELECTION GUIDE
• MANUALS for HEATING & A/C SYSTEM CONTROLS

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AQUASTAT DIAGNOSTIC FAQs-2 at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

Or see this

INDEX to RELATED ARTICLES: ARTICLE INDEX to HEATING BOILERS

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