Aquastat diagnostic questions - heating boiler aquastat control troubleshooting set #3.

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.

Aquastat Diagnostic & Settings Q&A #3

Recent questions and answers about aquastats posted orignally at AQUASTAT TROUBLESHOOTING. Be sure to see the aquastat diagnosis and repair advice given there.

On 2021-04-22 by (mod) - tapping on a control as a diagnostic step

@Neil,

When tapping on an electrical control causes it to operate I suspect burned contacts or a failed relay or a loose electrical wire connection.

On 2021-04-22 by Neil

Boiler will call for heat and boiler turns on but the burners do not ignite. After a couple of taps on the aquastat the burners will fire and heat as it should. Honeywell L8148E

On 2021-04-20 - by (mod) -

Dave:

About that humming aquastat,

Please find your recently-posted question(s) or comments along with our reply now at the Reader Q&A section near the bottom of the article above on this page. You may need to clear or refresh your browser cache to see the updated page. We welcome your further photos, comments, questions.

On 2021-04-20 - by (mod) -

@Dave,

I suspect that there is a failed relay in the actress that if the humming is actually coming from that device. If the humming is coming from my oil burner motor then it's probably a seized motor

On 2021-03-29 - by (mod) -

@Annoymous, sorry but I still don't know what you're pressing. "the dial" - and "on top" vary all over the place depending on how the aquastat was mounted.

The common controls are HI limit, LO limit, and DIFF or Differential.

In any case if you're pressing one of those and your heat runs the control is not working normally.

On 2021-03-29 by Annoymous

I am pressing on the center of the dial on the top of the Aquastat. As soon as I press it in the systems turns on and runs. When I remove pressure the system turns off. It’s a L6006A and I’m applying pressure at dial that goes from 100-240 degrees in the center at the screw.

On 2021-03-29 - by (mod) -

@Annoymous, if I understand that you are actually pressing on one of the controls or dials on your aquastat and not on a relay, and if only in that case does the heat run, then yes it sounds as if the control has failed. Please keep in mind that nobody can make a fully accurate guess at a "no-heat" diagnosis from a single 1-line text note.

On 2021-03-23 - by (mod) -

@Dave,

I'm unclear about using a Peerless tankless boiler for heating your room, but in any event, if your heat is by hot water radiators or baseboards there can be a bit of "over-shoot" - when the thermostat is satisfied and the boiler is turned off, remaining hot water in the baseboards or rads continues to heat the room a bit over the set temperature.

If your thermostat is one that includes a heat anticipator you can change the anticipator setting to reduce that problem.

See HEAT ANTICIPATOR ADJUSTMENT https://inspectapedia.com/heat/Heat_Anticipator_Adustment.php

On 2021-04-20 by (mod) - boiler just quit, aquastat hums

@Dave,

I suspect that there is a failed relay in the actress that if the humming is actually coming from that device. If the humming is coming from my oil burner motor then it's probably a seized motor

Turn off power to the system.

Let it cool down.

See if there is a reset button on the oil burner motor (if it's an oil system)

See if there's a reset button on the aquastat.

Push those - if they click and stay in you've reset the system.

Turn power back on.

Watch out: If the system does NOT start and run normally leave it off - for safety and call for repair.

Use the InspectApedia.com on-page search box for HVAC NOISE DIAGNOSIS: HUMMING SOUNDS to find HUMMING SOUNDS from A/C or Heat Pump system where you'll find more diagnostic suggestions.

On 2021-04-20 by Dave

Its an old one honey well l8124a

My furnace just quit ..the aquastat makes contact and hums till it trips please help

On 2021-03-29 - by (mod) -

@Annoymous, sorry but I still don't know what you're pressing. "the dial" - and "on top" vary all over the place depending on how the aquastat was mounted.

The common controls are HI limit, LO limit, and DIFF or Differential.

In any case if you're pressing one of those and your heat runs the control is not working normally.

On 2021-03-29 by Annoymous

I am pressing on the center of the dial on the top of the Aquastat. As soon as I press it in the systems turns on and runs. When I remove pressure the system turns off. It’s a L6006A and I’m applying pressure at dial that goes from 100-240 degrees in the center at the screw.

On 2021-03-29 - by (mod) -

@Annoymous, if I understand that you are actually pressing on one of the controls or dials on your aquastat and not on a relay, and if only in that case does the heat run, then yes it sounds as if the control has failed. Please keep in mind that nobody can make a fully accurate guess at a "no-heat" diagnosis from a single 1-line text note.

On 2021-03-29 by Annoymous

My aquastat for my buderus lt200/2 with only make make the call for heating water if I hold the dial in. Is that just a sign it needs to be replaced or a relay somewhere else?

On 2021-03-23 - by (mod) -

@Dave,

I'm unclear about using a Peerless tankless boiler for heating your room, but in any event, if your heat is by hot water radiators or baseboards there can be a bit of "over-shoot" - when the thermostat is satisfied and the boiler is turned off, remaining hot water in the baseboards or rads continues to heat the room a bit over the set temperature.

If your thermostat is one that includes a heat anticipator you can change the anticipator setting to reduce that problem.

See HEAT ANTICIPATOR ADJUSTMENT https://inspectapedia.com/heat/Heat_Anticipator_Adustment.php

On 2021-03-23 by Dave

Why is my room temp higher than the thermostat is set for. Hydronic system with Honeywell digital aquastat on peerless tankless boiler?

On 2021-02-17 - by (mod) -

Jon

I recommend stepping through the diagnostic suggestions found (via the ARTICLE INDEX) in the article HEAT WON'T TURN OFF

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

On 2021-02-17 by Jon

I just replaced my Aquastat L8148 E 1257 because the Damper controls was not working. Now, randomly, I we will come home to the house too Hot. What makes the heat stick on?

On 2021-02-12 by (mod): check for bad aquastat relay or control board vs. thermostat wiring

Jack

If you jump or connect together the two thermostat terminals on the Honeywell L8148 you're eliminating a bad thermostat wire or bad thermostat from the problem.

With that connection if the relay pulls in and stays in, then the problem is not the aquastat nor its relay but is the TT OR TT Wiring.

With that connection if the relay keeps buzzing or chattering and there are no loose wires then I suspect a ba relay or bad aquastat control board.

On 2021-02-12 by JACK

I newly installed a L8148e Aquastat. When it called for heat the relay keeps engaging and disengaging. I am wondering why.

On 2021-02-03 - by (mod) -

William:

Check your aquastat settings; if the LO is set too close to the HI then you're locking out the circulator.

On 2021-02-02 - by (mod) -

Let's step through the diagnostics at

OIL BURNER WONT RUN

and if that fails, see

HEAT WON'T TURN ON

On 2021-02-02 by Mary

Bought a new oil burner and aquastat hooked it up and bleed it, it fired up no problem then cut off and now won’t kick back on we have been trying to get it running for 3 days.

On 2021-02-01 by william woods helen woods

My circulator pump is not starting when the boiler starts. Checked the electrical terminals that go to the circulator pump and there is no electrical current going to the pump. I connected the circulator pump to an outside source and it run s fine The only problem with that is the pump run continuously.

On 2020-12-09 by (mod) - heating service tech was in a rush: air bound heating system trouble

Timothy

Intermittent mechanical problems are often a devil to locate. I usually look first for a loose or corroded electrical connection or a failing relay or control board, but when you're confident those are not the issue we start meandering among fields of possibilities.

In the land of the blind, the one-eyed heating service technician is king. Let's don't buy a beer until we find out what actually fixed the trouble. From a remote spot with limited information I'm offering mere guesses. Do let me know what you ultimately find as that'll help other readers too.

Then it'll be a Dos Equis if I'm in Mexico or a Castle Danger Ale if I'm still covid-sequestered in Minnesota.

I know what you mean about the plumber or heating service technician being in a hurry to leave - the photo below is one I snapped as a, frankly in my opinion terrible and therefore unusual heating service was rushing to leave the job, spinning his tires on the pavement and smoking up the driveway. Fortunately the heating company is a good one and their service manager sent a better man to finish the job right.

Maintaining pressure isn't the solution to an air-bound heating system; you should never need to add water to a hydronic (hot water) heating system - except when water was drained for service or repair; else there's a leak to be found and fixed.

See AIR-BOUND HEATING SYSTEMS

not that I can promise this is the problem with Mrs. Ex. heating system. But sometimes an air bound system can be subtle - such as just partial blockage or even intermittent blockage of the heating delivery or return piping. The diagnosis can be as simple as feeling for temperature changes along the pipes when the circulator is (supposedly) running.

On 2020-12-08 by Timothy

Dan, thanks for the reply with good suggestions. The plumber ran new thermostat wire on zone in question (not sure why that was needed) so it is not likely to be a wiring problem, but I will check. As for air-bound suggestion - that seems reasonable (likely even?). Ex-wife said plumber was grumpy and eager to get out of there so might not have properly bled system. Not dissing the plumber, she makes me grumpy, too :-) I will talk her through using "skate key" to bleed air from (circa 1945) radiators. Will be mindful to add water to cool boiler line to maintain proper pressure (12 - 15 psi?). If it happens again after that, may replace aquastat but prefer cheaper, easier solutions so thanks for providing two of those to try first!

On 2020-12-08 by (mod) - intermittent heat failure - bad zone circulator: hot motor, cold zone, not pumping!

That does sound like it could be loose or damaged thermostat wiring.

Turn up the thermostat. Does the circulator relay pull-in?

If the circulator pulls-in, does the circulator motor run?

If the circulator runs, do the pipes on the output side (or input side if the circ is on the return side of the loop) get hot?

Is it possible that the system is sometimes air-bound? When work was done on the piping it's possible that the plumber didn't get all the air out, and that your air bleeders are not handling the problem reliably.

Intermittent heat loss traced to bad circulator pump

Of course there can be a more subtle failure: recently in a Minnesota home we found that the cast iron baseboards in one of the heating zones would not warm up even though the thermostat was calling for heat and the circulator appeared to be running;

Bleeding air didn't do a thing: there was no sign that the system was air-bound.

Next we thought that the zone could have frozen, as the homeowner was leaving the basement heat set very low (50°F) during -22°F outdoor temperatures.

But, we noted, this home was built in the 1960s and had not suffered a known frozen baseboard line over its life.

A better heating diagnostician than I (Kevin from Cavallin Heating, Two Harbors MN) checked out the circulator and seemed to get it running again.

A few hours later we found the basement zone freezing cold again and yet the circulator "seemed" to be running.

When I felt the circulator motor itself, it was very hot. This circulator is installed on the return side of the heating zone loop. So we felt the zone piping close to the circulator: it was stone cold. That told us that the circulator motor may have been hot but the circulator pump wasn't pumping.

Mr. Cavallin replaced the circulator pump: problem solved.

Lesson: look around and feel the pipes and get help from someone with heating system troubleshooting experience.

• Thank-you to
  
  Cavallin Plumbing and Heating, 112 7th St., Two Harbors MN 55616, Tel: 218-834-4542
  

On 2020-12-08 by Timothy

Help, please! I am trying to diagnose a hydronic system heat problem in my ex-wife's house 1000 miles from me (we are still friendly). House has 4 zones, three are on Taco zone valves and run through ZVC403 board. They heat fine when calling for heat, running a common circulator pump.

The problem is in the "main" zone, heating two floors of the main part of house. There is an INTERMITTENT failure on the call for heat, works fine most of the time, but sometimes it just never gets heat to radiators. That Tstat is wired to the two TT terminals in the aquastat, and that drives burner and different circulator pump for that zone.

She calls in panic that house is cold, turning on and off at Tstat and/or main power switch on furnace does not fix problem. I walk her through those steps and taking off Tstat, connecting red and white wires.

Shes not comfortable with electrical stuff so did not ask her to jumper the T-T screws to see if burner/circulator gets going. As I said, its intermittent - happened twice last winter, twice since Thanksgiving this year.

I suspect the aquastat may have a bad relay, but I am not there to check by manually switching it. Any idea what is going on here? Aquastat is L8124C1102. Taco zone valves and ZVC unit were installed by plumber a few weeks before this issue started late last year.

On 2020-12-08 by (mod) - Which aquastat is a replacement for Honeywell L4006A 1058?

Duane

The Honeywell L4007A series aquastats are still sold by plumbing and heating suppliers,

Specifically to replace your Honeywell L4006A1058 you would

use the Honeywell L4006A1017

Other Readers: for help choosing the exactly-correct replacement aquastat see

AQUASTAT SELECTION GUIDE

where we include both instructions and also heating and cooling system parts cross-reference guides and charts.

On 2020-12-08 by Duane

Which aquastat is a replacement for Honeywell L4006A 1058

On 2020-09-24 by Anonymous - start at the thermostat to be sure that it's really calling for heat

I'd start at the thermostat to be sure that it's really calling for heat - or jump the TT wires at the zone valve. If that opens the valve then we know the problem is in the TT or its wires.

On 2020-09-24 by Stephen

I have a R8182H controller and I have one of two zones that doesn't come on when the thermostat is raised beyond ambient temperature. I have confirmed that the zone solenoid valve and the thermostat are in working order. Before I spend a lot of money on a new controller is there a way to diagnose it for being defective for only one zone?

On 2020-08-28 by Anonymous

when asking for heat, and there is power to the aquastat but the boiler wont fire up and the thermostats are calling for heat but the relay is making clicking sound

On 2020-08-28 - by (mod) - main cause when you have to Jump L1 to C1 to get the boiler to fire up?

Nelson that sounds as if a circulator relay in the aquastat is shot, the circulator is not running, so the boiler water stays hot, doesn't get cooled down by being pumped through the radiators or baseboards.

On 2020-08-28 by Nelson

What is the main cause when you have to Jump L1 to C1 to get the boiler to fire up?

On 2020-05-31 - by (mod) -

George

If you have power to the aquastat but no power to the burner then the aquastat relay is not closing to power the burner.

That could happen because the aquastat that is off on safety and needs to be reset or there could be a defective relay in the control.

On 2020-05-31 by george

oil boiler ....have power to aquastat and circulating pump....but no power to the oil burner....?

On 2020-05-14 - by (mod) - need heat conducting paste to get aquastat sensor working

Nice work. I'm impressed.

OK sure, don't over-bend and ruin the probe.

Do let me know what Honeywell says. You can pretty much figure that none of us is likely to encounter a problem that no one has met before, and we can further bet that somebody already has a solution.

On 2020-05-14 by Clay

Thanks for the quick reply! I actually did remove the well and I cleaned the exterior (inside boiler) side

. It was coated with black deposits, but cleaned easily with a 3m finishing pad. I will try to clean out the well and probe once more and reinsert.

I do have some heat conductive past left from the packet included with the new Astat. I even used a syringe to place some paste into the well prior to inserting the probe.

The probe fits quite snug with the heat conductive paste. Without it the probe slides in and out, but still appears to have contact with the side of the well. I'm afraid if I try to bend the probe I may not be able to reinsert it into the well. It just baffles me why it's not making good contact. I think I'll call Honeywell also. Thanks for the advice!

On 2020-05-14 by (mod) - the boiler overheating and the pressure relief valve leaking or totally dumping

Clay

Thank you for a thoughtful question.

My first suspicion is the same as yours.

I would remove the probe, clean out the well, maybe scrubbing it with a stainless steel scrubby sponge,
then
to re-insert the probe, instructions remind us to bend its leader slightly down so that when coated with the conductive grease it makes good contact with the sensor well.

There is a more-subtle possibility that's a bear to fix: the sensor well itself may be coated on its exterior - the boiler water side - with scale or rust, interfering with temperature transfer.

These wells are replaceable but I'd be rather nervous about pulling the well on an old boiler - worried that the threads and mount will disintegrate, leaving me with a dead boiler.

Let me know your assessment of the boiler's age, scale level, and condition of the sensor well and it mount.

And of course honeywell Tech support may have other advice.

General Support, except home products
US: 1 (877) 841-2840
INT: 001 (480) 353-3020

On 2020-05-14 by Clay - Honeywell L4080D 1036 error

I'm new to boiler maintenance, but I have a good grasp of how the system works and how to properly maintain it. Recently, my circ pump failed, and while I was diagnosing this I noticed the boiler overheating and the pressure relief valve leaking or totally dumping (old pump was a near silent Grundfos - I never heard it run in 25 years).

After some investigation I also discovered the aquastat (Honeywell L4080D 1036) appeared off by anywhere between 20-50 degrees from the boiler temp gauge causing a runaway condition. Temp / pressure gauge seems fine - PRV was dumping as expected when temp reached ~230 and pressure climbed ~30 d/t steam formation.

I purchased a compatible replacement recommended by Honeywell, but new Astat (Honeywell L6006A 1145) is behaving the same. Switches work, verified by manually lowering Astat temp to ~130-140F once the boiler temp exceeds high limit (180F), and burner shuts off as expected and allows circulator to continue. Pipes are hot, distribution system heat feels normal, but high limit does not function as it should to stop the burner. On re-heat after reducing Astat temp to ~130-140F, system heats to ~180 and shuts off burner (Astat set to 135F).

I believe this is a well contact or probe issue. Probe fits in Iwell fine, and in fact was too loose prior to adding heat conduct paste - now I have problems getting it in and out of the well (which, obviously I'm not trying to do often as I want best contact). I've done everything I can think of to ensure good contact with the immersion well (pulled the well and cleaned it, put it back, used thermo conductive paste, even HELD IT IN AGAINST THE WELL WHILE IT HEATED).

The high limit does not function at all, and boiler is in runaway condition until I shut it down. I'm about lost as to why this is happening. I know HW Astats are not scientific accurate, but I definitely don't think this is correct operation.

Any insight or advice on what might be the problem here? I really don't want to drop another $150 for another new Astat. The Iwell seems fine, but it's cheap to replace so I could try getting a new one before calling in reinforcements. Good news is the weather in NW Ohio looks like it's good behave like summer from now on, but I'd like to get this all figured out before putting the boiler to bed for the season.

While system was drained to replace circ pump / pull Iwell (just to clean - did not replace), I went ahead and replaced / repaired several other components. I added several isolation valves so (hopefully) I won't have to drain the entire system again. Work completed while down:

1. Replaced Grundfos pump w/Taco pump & added iso flanges

2. Added iso valves at air scoop for vent and ET

3. Repaired solders on air scoop loop (left side)

4. Replaced backflow preventer due to slow leak / age

5. replaced copper w/PEX for cold water feed from pressure inlet to halfway down to system tap (didn't want PEX to get too hot)

SYSTEM:

Boiler: Burnham Series 2 Model B (204) - installed 1995 / no major issues until now
Astat: Honeywell L6006A 1145 (replaced old L4080D 1036 2)

On 2020-04-18 - by (mod) -

Leon

When the reset button (presumably on the primary control or aquastat or cad cell relay) pops or trips then the system safety control thinks that the burner has had power and has been trying to start for more than 20 seconds without producing a flame.

So it sounds as if there's power to the control but not power to the burner itself. Could be a bad connection, wire, or burner or even a bad relay in the primary control.

I'd call for help from a service technician.

On 2020-04-18 by Leon

Boiler reset button is tripped, but when pushing it back (with switches all on, and thermostat cranked up), no sounds of boiler spinning, just silence. After about 30 seconds the reset trips again. Physical motor reset is not tripped. Beckett ASF boiler, Honeywell reset and thermostats.

On 2020-03-19 - by (mod) -

Linda

Your settings on an aquastat can "lock out" the circulator pump if the LO setting is not set to 20 degrees or more below the HI setting.

For example if HI is set to 180F then the LO must be 160F or lower.

On 2020-03-19 by Linda

The auquastat isn’t sending the message to the circulator pump unless I keep turning the low setting down. We have radiant heat and an outside boiler.

On 2020-01-30 by (mod) - A circulator that stops when it should keep running

A circulator that stops when it should keep running suggest to me a loose electrical connection, a bad circulator relay, or possibly even a feeling circulator pump that's overheating.

On 2020-01-30 by DJ

I have a L8148a Aquastat relay running on a Rheem Oil fired boiler. I use a conventional thermostat to ensure simplicity.

I set the temperature to 70 degreesThe boiler will fire up from time to time, but after it goes out the circulator pump stop pumping even though the requested temperature is not reached. The circulator pump is new and functioning properly, could this be a malfunction of the relay.

On 2020-01-28 by (mod) - boiler does not shut down until it reaches 220 deg

Marc

Watch out: This condition is dangerous. Right now the TPR valve is doing what it's supposed-to: relieving the pressure; however ultimately scale formation by that dripping water at the relief valve could cause it to clog, risking a serious BLEVE - an explosion.

The most common cause of temperature overshoot when an aquastat isn't working properly is improper setting of the aquastat's sensor probe into the sensor well: it may not be contacting the sides of the immersion well or it may lack the temperature-conducting-grease recommended by Honeywell.

Other causes of an aquastat whose high-limit is allowing temperatures to exceed that setting include a failed sensor probe itself or possibly a defective relay or circuit board in the aquastat.

If re-setting the probe properly with conductive grease doesn't fix the problem it'd be proper to replace the aquastat.

Do let us know how you proceed and what happens as that will help others.

On 2020-01-28 by MarcL

My Honeywell aquastat is set to a Hi limit of 180* however the boiler does not shut down until it reaches 220*. This raises the boiler pressure to 25 psi. I first noticed the issue due to dripping from the 30 psi PRV. How do I troubleshoot?

On 2020-01-18 by (mod) - My boiler won’t shut off.

Mike

CHeck the "heat wont' turn off" diagnostic suggestions at HEAT WON'T TURN OFF

and let me know what happens.

On 2020-01-18 by Mike

My boiler won’t shut off. The relay magnet switch on the aqua stay will not shut off. At the thermostat the temp controls do not turn on or off the boiler. Only way to control it is by turning the thermostat on or off.

On 2019-11-05 by (mod) - circulation pump runs constantly.

Randall

The ARTICLE INDEX above provides a article that's going to outline the diagnostic steps in

CIRCULATOR PUMP WON'T STOP RUNNING

On 2019-11-04 by Randall

My furnace cycling properly but my circulation pump runs constantly.

On 2019-11-04 by Patrick C

I have a Honeywell L4081B 1120 aquastat and need to replace it.
What is the replacement or upgraded replacement aquastat I need?

On 2019-08-14 by (mod) - Tapping on the aquastat to get it to work

Tapping on the aquastat to get it to run suggests to me a failed or failing relay or a loose electrical connection.

$2,200 to replace an aquastat sounds crazy. Prices are in the $80 to $225. range for the control, + labor to install.

Find a different heating company.

On 2019-08-14 by Joe

My brother has to tap the aquastat on his boiler to turn on the burner to get hot water. His boiler is 45 years old and we got a quote today of $8,000 to replace it.

He is 67 and on Medicaid doesn’t qualify for Social Security. He lives in a small ranch house. $2,200 to repair and not replace.

One time I took the cover off the aquastat and blew in it and it started. Please comment as we are of limited resources.

On 2019-03-24 by (mod) -

Thanks for the followup- yes go ahead and disable the low limit as we describe. "not a tankless coil" needs to be edited to clarify that that includes the presence of a tankless coil that is not in use.

On 2019-03-23 by Bob

I appreciate your help. That kink says to disable the low/dif control if not using a tankless coil to heat domestic hot water. This boiler does heat hot water, but I would actually like to disable it because an electric hot water heater was installed in series with it because it didn't heat water fast enough for my sister's beauty shop.

I wanted to clarify this because of the notice in the link about disconnecting the blue wire if thete us not a tankless coil. Thank you for your help. Five servicemen have been called but nobody has fixed it, which is why I'm now the designated repair guy!

On 2019-03-23 by (mod) - Honeywell L8124a c aquastat, zone controls bypassed, wires run direct to the aquastat.

Bob

take a look at AQUASTAT LO & DIFF DISABLED https://inspectapedia.com/heat/Aquastat_LO_DIFF_Disable.php

and let me know if that does what you need.

On 2019-03-22 Bob

I have a Honeywell L8124a c aquastat with zone controls bypassed so that the thermostat wires run directly to the aquastat. The when the thermostat is turned down, the burner runs for a while, then shuts down, sometimes for a minute, sometimes for 5-10 minutes, then fires back up. The circulating pump is running whether or not the burner is firing.

When the burner is during, it shuts down when I turn down the upper limit switch, and acts just like when it shuts down as above. It keeps running like this until it gets so warm I have to shut off the power. I realized while working on this, that when the burner shuts down and I turn up the thermostat, the burner doesn't start running, I gather, until it calls for hot water again.

When the burner is off, but the thermostat is turned up, there is no voltage at the burner terminals, but the circulator is still running. Does this make any sense?

I did replace the old thermostat.

On 2019-02-19 by (mod) -

I would start by checking all of the electrical connections

On 2019-02-18 by Mike

I have an l8148j Honeywell aquastat that I have replaced the well the pop off the entire aquastat and controller my boiler turned on reached a hundred eighty degrees and turn the gas off worked fine for about five and a half hours and now will not turn on even though there is a call for heat from the thermostats it has two zones any help would be appreciated

On 2019-02-08 by (mod) -

Ron

Assuming we already know the thermostat is calling for heat (boiler fires up) but the circulator never runs,

I would check for

Power in to the aquastat

A bad aquastat relay

Then see the diagnostics at CIRCULATOR PUMP WON'T START https://inspectapedia.com/heat/Circulator_Pump_No_Start_Repair.php

On 2019-02-08 by ron

aquastat l8148a boiler fires up but circulator pump never turns on pump will run on 115V on its own. do not have 115 across c1 c2.

On 2019-02-08 by (mod) - circulator pump never turns on

Ron

Assuming we already know the thermostat is calling for heat (boiler fires up) but the circulator never runs,

I would check for

Power in to the aquastat

A bad aquastat relay

Then see the diagnostics at CIRCULATOR PUMP WON'T START https://inspectapedia.com/heat/Circulator_Pump_No_Start_Repair.php

On 2019-02-08 by ron

aquastat l8148a boiler fires up but circulator pump never turns on pump will run on 115V on its own. do not have 115 across c1 c2.

On 2019-01-28 by (mod) - set my aquastat to run the lowest number of hours? Economy Switch on the Aquastat?

Steve, what are the Aquastat brand and model? The ID and thus manual are needed.

Some heating boiler aquastats have an Economy Mode switch or control that basically tells the aquastat to run at a lower temperature setting.

The claim is that the lower temperature setting gives a longer on-cycle and thus lets the boiler get up to full operating temperature and thus run more efficiently.

However the thermal conductivity of water in heating baseboards is exponentially greater at hotter water temperatures, so I'm still looking for a credible engineering study that proves that the "economy switch" on the aquastat really produces a net savings in heating cost.

On 2019-01-27 by steve

i am trying to find out out how to set my aquastat to run the lowest number of hours. the one i have has a knob that says economy. Is the another setting to make the unitrun run less? there are more numbers that run up 10. the economy setting is not right.

On 2018-11-27 by Kyle K

I have an outdoor wood boiler connected to an indoor oil furnace. My circulator pump will not turn on. However when I jump the T and TV terminals the relay trips and the circulation pump starts. Why is the relay not working with the thermostat?

On 2018-11-25 by (mod) -

The difference between the high and the lawn needs to be 20 degrees or more. So you're probably okay on that score.

I'm not quite clear on the question when you say the temperature goes past do you mean the temperatures falling below the low or going above the low

I'm confused

On 2018-11-22 by Mack - 1991 Utica gas boiler with Honeywell aquastat model L8148E

1991 Utica gas boiler with Honeywell aquastat model L8148E, cycles through high and low temperatures Roughly 180 on the high side and 158F the low side. At 180°F burner shuts off Damper close. At 158°F damper opens boiler fires up. Eventually goes past low setting of 160F without restarting Circulator pump runs fine. L1L2 show 118 V C1C2 show 118 V. Thinking I may need to increase my offset

On 2018-11-16 by John M

The boiler pressure never rose about 15 psi as far as I observed, and relief valve never opened.
In fact the technician replaced the relief valve on one of his visits, but knocking sound still occurred.

What I did observe was Temperature climbing to 248F on Aquasmart after burner shut down, but the temperature on the Pressure/Temperature gauge never climbed above 170F.
With the system piped properly now all seems well, so I will call technician if any further problem occurs.

Thanks for your help. It is beneficial to have an independent view and input on the problem..

On 2018-11-15 by (mod) -

Extended warranty sounds reasonable but of course I can't assess your boiler by text.

What does concern me, and that you have not addressed is a question that I posed to you earlier.

If your boiler was at abnormally high temperatures, what was the boiler pressure? If the pressure was over 30 PSI and the relief valve was not spilling, something is seriously wrong, and dangerous.

On 2018-11-15 by John M

@John,
The installer visit finally wound up with him reinstalling the supply and return lines in their correct locations. But it started with an unpleasant heated conversation of Installer was correct and Customer must be wrong.

Once I showed him that Aquasmart was measuring the return temperature from the baseboards everything changed.
We just had the first quite night of boiler operation.

On leaving, he offered to extend the warranty on the unit because of all the aggravation this has caused me.

Do you think that the past two months of overheat operation has damaged the boiler? I could insist that they replace the unit with a completely new boiler.

On 2018-11-15 by John

Im using a triple aquastat. My boiler will work but only after I shut off power and turn back on. Once boiler cools down it will not restart unless I repeat shutting it off and on. This also happens when I need hot water. I am using a Honeywell L8124A, C. I see this Aquastat has terminals for zone control but I do not have separate zones.

On 2018-11-12 by (mod) - Aquasmart is reading the cold return flow from the baseboards, not the hot water exiting to heat the house.

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

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) -

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?

...

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.

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AQUASTAT DIAGNOSTIC FAQs-3 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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