Boiler Aquastat Relay Troubleshooting and Control Wiring!

In this HVACR Video, I go over the Boiler Aquastat, How it Works, Troubleshooting, and Control Wiring. I power the relay and follow the voltage through to show how it works and what should happen! Supervision is needed by a licensed HVACR Tech while doing this as Experience and Apprenticeship garners Wisdom and Safety.
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⚠️ Disclaimer:
Information in this video is intended for educational purposes only. Any work related to the topics in this video should be performed by licensed technicians or by apprentices under the supervision of licensed technicians. AC Service Tech LLC is not responsible for any possible damages or injuries caused by the use or misuse of any information provided. ▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬
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[@acservicetechchannel]

Tool List- www.amazon.com/shop/acservicetech Support- www.patreon.com/acservicetech For those that are looking for the tools used in the videos: (Links in the Description Section)

[@mqira00]

Great video. Very much appreciate your time and effort. Just wanted to point out the reason you dont read 24v from B2 to TV is they are both on the common,....the same leg/potential.

[@mackenziegray2090]

Thanks to this video I have outsmarted my trainer. The call I was on with him had voltage and calling for heat. The relay was pulled in but was not passing power to the limit. He believed the vent damper was bad. It was horizontal and wasn't open. He ordered the new damper and installed it. Unit still never came on. I got a pair of jumpers and hooked them to Z and top of the limit, the boiler fired up.... he was pissed.

[@rthinds]

Holy smokes! This is a great video! My boiler took longer and longer to fire up until one day it just didn't. Not wanting to spend $1000 or more on a service call, I found this video and followed the path of the voltage to the Z terminal, which was not conducting any to the W terminal (despite calling for heat) and, by extension, none to the T. Shutting off all electricity, I unscrewed the Z terminal and out-popped a small piece of paper in the perfect shape of the screw head. Obviously whoever installed mine decades ago just ripped a paper tab off instead of removing it. It was probably "barely working" for decades! No wonder it took an hour or more to "fire up" in the fall. Once I tightened the Z terminal (and all the other terminals) down - everything is working perfectly! Thank-you so much for such a detailed video!!

[@samjg1]

Best video I've seen explaining the workings of the aquastat. Thank you.

[@Melvinschroeder]

Your knowledge and communication skills make you videos the best at helping us to understand what we are looking for!

[@acservicetechchannel]

Thank you Melvin!

[@uslandmanagement1]

Best video I have seen in a long time. Great explanation, very knowledgeable !

[@acservicetechchannel]

Thanks USlandmanagement1!

[@andreagate542]

Great Vid!!!! Came across one of these well in the field today and had a few questions that I did not get an answer..... you nailed it for me🙏🏾🙏🏾🙏🏾

[@WaltonStinson]

Thanks for the verbal diagram of the operation. I couldn't find a schematic of this unit and now can draw one myself based on your excellent explanation of this circuit.

[@acservicetechchannel]

Awesome Walton, thanks!

[@beemerkon]

How can anyone put a thumbs down this video

[@geoffreyahmann320]

Fricken life saver man!!!! Just trying to upgrade the thermostat from an old turn dial to a programmable digital. Thermostat manual made it seem so easy, followed it to a T and got nothing! Read both boiler and thermostat manual, scoured Honeywell's site, scoured Google, but had no clue what to look for. Stumbled on your videos and now I understand exactly what is going on! Great simple teaching and explanation! Thank you so much!!!!

[@davidallen4804]

Great explanation of how the high and low voltage work under what we se o the surface of the control.👍

[@Pretzel114]

thanks for the reply Acservicetech. You always help me out.

[@acservicetechchannel]

Glad to help Nick!

[@androidresults]

Fantastic video! My niece just bought a new house and her thermostat was wired incorrectly. This video was exactly what I needed to fix her problems! Thank you!!

[@acservicetechchannel]

Great to hear!

[@deependz3231]

@@acservicetechchannel "AC Service Tech LLC AC Service Tech LLC 1 year ago "Great to hear!".................That's you responding only to self praise, and anyone who had required a technical question be damned, pretty pathetic on your part. Next time you post anything, do everyone a favor who might waste their time asking a question, turn the comment section OFF.

[@christopherlarson3136]

Terrific, well explained, thorough, and most of all helpful video. Thank you for taking the time to create and share this! I was able to diagnose a High Limit cutoff failure on my L8148e.

[@gyver471]

Great instructions and explanations.

[@hermansummers487]

Love the detail in your video

[@dougjones4987]

Great explanation, thanks a bunch this really helped me out.

[@acservicetechchannel]

Glad to help Doug!

[@kennyw7453]

Great demo and explanation, as usual.

[@acservicetechchannel]

Thanks Kenny!

[@michaeldower4335]

Great video. Very informative, thank you.

[@acservicetechchannel]

Thanks Michael!

[@jimmyung3212]

Thank You for the detail. You are a very teacher.

[@acservicetechchannel]

Thanks Jimmy!

[@jimmyung3212]

Hi could you make a video on economizer.

[@rcytb]

Very helpful. Thank you!

[@fern284]

Great video, very thorough

[@PBS-nm1uu]

love your videos, still do not understand how you understand the sequence so well, keep them coming.

[@Sfey3386]

Extremely helpful. Thank you

[@acservicetechchannel]

Glad it helped Steve!

[@ingridhen619]

You are a LifeSaver! Thank you so much!

[@acservicetechchannel]

You're welcome!

[@wildgoose6596]

Without this video, I would have had to call for what I am sure would have been a very expensive repair as there are unfortunately so many "parts changers" out there. Thanks! We have heat again! I just needed to know these basics, and I was able to diagnose my newer and slightly different L8148E. Way better that other videos out there!

[@PBS-nm1uu]

this is a great explanation, thanks

[@MikeJamieGavin]

Fantastic video. It's pretty much the same troubleshooting the L8148A, except it doesn't have the 24V transformer. All the voltages are 120V on the L8148A. You'll need a separate 24V transformer for your thermostats. Adding this info so that others can find if if they are trying to troubleshoot at l8148a since it's pretty much the same thing.

[@dritanshabani6396]

What a awesome video very informational

[@acservicetechchannel]

Thank you very much Dritan!

[@bigthey1827]

Great video 👍

[@billwatson3713]

Excellent video

[@acservicetechchannel]

Thanks for the visit

[@marvincarranza096]

God bless you brother !! 🦾

[@patohara8430]

Very good video. Thanks.

[@acservicetechchannel]

Thanks Pat!

[@rickychavez1473]

Nice!!! good explanation 👍👍 👍

[@acservicetechchannel]

Glad you liked it!

[@amirmf1814]

man you are really the best for training . appreciate if you put up some video about taco and tekmar control for boiler. again thanks . merci

[@jashua2089]

Thank you 🙏

[@uslandmanagement1]

Thank you very muck

[@acservicetechchannel]

Thanks USlandmanagement1!

[@devinmccloud]

Thank you so much for sharing this info. My Becket AFG burner would not start the blower and fuel pump. I thought maybe the blower motor was shot. I could feel the relay box vibrating.The Honeywell Aquastat Relay was humming but the motor and Becket burner would not start when turned on. The light indicated that it was locked out. The relay was stuck so I pushed it a few times. I then turned on the burner and for the first time it started the motor, burner and circulating pump. Hope this info helps someone else.

[@acservicetechchannel]

It may have been out of alignment or the contacts were pitted and not making goo contact, thanks Devin!

[@mp-mh3wf]

Thanks any way for your help on the question I had on my boiler it was the aqua stat

[@acservicetechchannel]

Thanks m p!

[@gyver471]

Great information can you do one of these for the new hydrostat controls.

[@hvac01453]

At 3:40 it appears you in fact DO have voltage on the contact on the right , like 26 or 27... or maybe you didn’t let the meter Seattle down. That’s the one hing I do prefer about analog meters, the needle would swing... good explanation on its workings.

[@andreaalcalde7458]

Hi, thanks for the video. Our transformer started smoking. Is it possible to replace the transformer only? Or do we need to replace the whole system for the aquastat

[@smidi0924]

Great video! Does both jumper are connected from your voltage tester or separately? Thank you

[@FigGolf]

My thermostat intermittently loses power usually in the middle of the night or when I'm not at home (both are not very good times). My Google Nest Thermostat will show a no power condition making me believe that the transformer on my L8148E is going bad. I will have to check for loose connections, but when I pulled on the wires they seemed to be tight. The unit is over 17 years old, so I had a new one ready to go. Thanks for the video!

[@pubchat2913]

Awesome vid thank you. Where would the inducer motor be connected? P.s I got your AC book, amazing. Do you have one for the heating season too?

[@samuelferrer805]

thanks for the video, I have the L8148E, and I want to change my thermostat for the RTH6580WF. I only use the heat and my old thermostat works with two wires. where you should connect the wires for the other thermostat. Thanks

[@jcstevegigs]

Great video. My boiler at my rental has a summer/winter hookup. The tenant says heat works fine but that the hot water is hot, but not like it used to be. She says it’ll get cold for a little and then warms up after a few minutes. I guess if the heat works then the problem would be the mixing valve? I’m assuming the boiler is kicking on to supply heat but NOT kicking on when running the hot water? Any ideas? Thanks.

[@Pretzel114]

Hi Acservicetech! Thanks for the video. I been waiting for this one. One question. The temp dial on this single aquastat, is that the same as the red dials on the triple aquastat? Do they serve the same purpose? Thanks again.

[@acservicetechchannel]

Yes it is like the red dial except this is always just the high limit. You can add a low limit to this externally. Also if you see the two red dials then that is a high and low limit so your burner can heat up the water before circulating, thanks

[@elijahgoodman3140]

Great video! Question, due to the high limit cutting off the burner @ 180 degrees or so, the thermostat can still be calling for heat correct? If this is the case, then the burner will cycle on and off on high limit until thermostat is satisfied, or am I missing something?

[@12jason223]

Awesome video, helped my identify the issue with my aquastat. Is it possible to replace just the circulator relay or does the entire aquastat need replaced?

[@acservicetechchannel]

Usually you need to replace the whole aquastat, thanks!

[@firstjohn26]

Jason, I run my circulators on a hot circuit all winter to get around the relay and it works fine. I retain the relay only for the 24V to the gas valve.

[@arielhernandez2911]

How come at 3:56 time frame when you tested voltage from b2 to w you had 22volts if that jumper isn’t hooked up wouldn’t it be zero volts thanks video are so helpful

[@olderrol1968]

How do you check the relay. What wire connections do you check. Can you illustrate like how you showed how to check the Transformer?

[@viper22304]

Thanks for the video.. question: a loud humming sound is going out from the transformer? This mean I need to replace whole relay? Is it bad if i leave it running until replacing it?

[@acservicetechchannel]

They may get a little louder as they get older and if the resin wears down. It just depends on how loud really but at some point it would need to be replaced, thanks!

[@jackpast]

Nice one, Craig. I’m guessing on the wires going to the thermostat that the 24 v. common is not run to the thermostat? If not, makes trouble-shooting harder when checking for 24v at the thermostat.

[@acservicetechchannel]

Yeah typically you have a battery operated stat or mechanical due to the VA size of the transformer in the aquastat, thanks Jack!

[@adzar4148]

Great video.I have the bad relay that when i call for heat does not get sucked in when i push it down with a wood stick the system start working.it’s any way that relay can be fixed Thanks

[@Kevin-to9gq]

Thanks man, I like the way you teach. You have a gift... I need help with my L8124A regular for C1 C2 . I am checking the voltage on C1 and neutral C2 and it reports back 13.42 volts when I jumper the thermostat connection. Is that the correct amount of voltage that it is reporting? Issue: circulator pump not activating when furnace is fired up and on. when I jumper L1 and C1 as a test, it works fine with no issues. I am focusing my troubleshooting on the honeywell relay that you are displaying next to the multimeter (not sure what that relay is called) Im so close to fixing this thing man and its getting cold.......any suggestions? I will look over your vid again, maybe I missed something in regurads to cleaning contacts etc...

[@Katana_00]

Grade A content

[@smidi0924]

Goog morning I have relay switch honeywell R845A( which is # 1,2,3,4, 5&6 and T-T). Do i need to follow the same test you did to check if my relay works before i wire it. Thank you.

[@EnjoyCalculus]

Craig, can you please do a boiler sequence of operation video? I have yet to find one

[@markbrassette3406]

Awesome video, thanks! Quick question ... so I need 24VAC for Ecobee smart thermostat. Looks like I can get that from B and Z terminal for continuous power. Ecobee support said I I need a separate transformer to power the stat, and not to use the one on the boiler. This is running 3 zone valves then signal back through end switches to fire burner etc? Any reason for that you know of we'd need an extra transformer?

[@acservicetechchannel]

It is so that you don't go over the VA of the transformer on the board. You can just run a transformer from the main 120v and come off that to power the stat to be safe. Make sure the transformer is inside of an electrical housing and that no 120v wires are exposed, thanks

[@stifflers69mom1]

Yes I just went through this myself the problem is the the transformer in the honey well is not meant to run the burner,rely AND your new thermostat it over loads it and could possibly shorten the life ...just listen to this guys advice and buy a separate transformer to power the thermostat

[@jameseiden2340]

I don’t get it it’s only a thermostat how many VA is going to be

[@lolsimon]

Hi I replaced an old one with a new model today and when I switched on the boiler I had 24 volts at b1 and b2 while the thermostat was calling for heat. After a minute or so, b1 and b2 was reading less than 10 volts. Circulator was still running fine and the transformer was still outputting 24 volts. Do you think there is a short somewhere that caused the relay to go bad? Thank you

[@KeepItReal1973]

Hey there. I came across this video and found it very informative but I have a question that I hope you can help me with. First off my aquastat works fine, it turns on when needed and fires up the boiler but I don't seem to have any 24v reading from the B2 to any connection from the Z W or T. My volt meter is working fine too because it reads a car battery no problem. Any ideas as to what is going on? My aquastat looks exactly like the one you have in the video.

[@jeffhopkins979]

Great video, I have the L8148E aquastat relay. My boiler previously heated up to 180 and shut off, now it is heating up to 200 before it shuts off. There is a stationary arrow on the side of the temperature sensor that I assume indicates where the temperature dial should be set and mine is pointing to 180. The circulating pump is circulating and does stop when the burner kicks off at 200. I can only think that the temperature sensor or the Thermopile that sets in the well has gone bad. Is another option that might be causing this issue? I assume that I need to replace the entire aquastat relay as I had not found any information of people only replacing parts of the aquastat relay. Thank you for your help.

[@jls1337]

Can you recommend how to test the high limit dial? I get continuity between the tow leads (B-R) but when I check voltage between that B screw where the blue wire attaches and B2 I only get 12V. The burner doesn't turn on. I get 0 volt between B1 and B2. And if it went bad, can it be replaced or does one have to get a whole new aquastat?

[@kennethdavis5077]

Is it possible to wire a Nest thermostat to this aquastat . Where would I connect the common ?

[@integrity5264]

Hi Craig, love your subjects, your a great teacher. I know this is an old post but I was just wondering what the differential is on this high limit control? Is it 10 degrees ? Thanks for sharing your knowledge . I have your book, great information their.

[@smitty03281964]

I have Aquastat L8148G, which I don't see anywhere but it's almost identical to this L8148E except that it doesn't have the Z to W connection. It's actually set up TV--T--Z. My question is from the thermostat does it matter whether the common go on TV or T. Also I don't have any power on the temp controller, but my gas valve open and closes. I also notice that it heats the water up to 230 degrees, maybe even 240. My first issue with that is why it doesn't have power. Everything else works as it should. It's been that way since the early 90's. Recently I had a problem with no heat and took the Aquastat apart and found a frayed wire that was touching the outside of my transformer. I was actually getting 20 volts on the outside of the transformer. The relay was sticking. Taped up the wire and now I don't have the relay sticking, or the 20 volts on the outside of the transformer. After watching your very great video. I'm going to go look the entire system over.

[@shelby50411]

Great video.....is the relay within the aquastat replaceable?

[@acservicetechchannel]

No not unless it was unsoldered off the board, thanks

[@uncle_mike]

I have the Honeywell L8148A attached to my boiler. The high limit works fine but the boiler will not fire when the water temp is low. Is there an existing low limit or "limit range" on the relay that I missed or should test? Thanks in advance...

[@danieldummett3731]

Hey quick question regarding gas valves. On old furnaces with the combination gas valves if it says mv on it that means that the main gas valve only opens when 24v dc from the pilot flame is powered to it through the t-stat? Or would it still work on a 24v transformer system?

[@acservicetechchannel]

Hey Daniel, the pilot valve must be opened first before the gas even gets to the main valve. Have you checked this video out yet?- kzbin.info/www/bejne/bZ6Yi3eshNSJrbc -- also I have written 32 articles and have videos over on patreon.com/acservicetech if you are interested. The access is the community level at $3 per creation but you can set a monthly max at $3 per month. It is also something that can be canceled easily. Anyway just letting you know and it also includes email q/a as well thanks

[@jimbobigdude]

Thank you for taking the time to show how this is supposed to work. In my case, the circulator sometimes runs intermittently, so I know it's not frozen. How can you troubleshoot the aquastat when the circulator IS operating correctly? Or do I have to troubleshoot it when the circulator doesn't turn on? I'm thinking that either the relay is bad in the aquastat or the temp control. But if the relay operates sometimes and does turn on the circulator, could it still be bad? Maybe just changing the aquastat completely would take care of both possible issues within the aquastat? It's a l6006a Honeywell. Thanks again.

[@acservicetechchannel]

Unfortunately, we usually need to have the system problem occurring while checking readings in order to determine what the problem is. If you don't have another circ or zone controller and the wires are providing a good 24-29v under load then it may be the aquastat, thanks

[@jimbobigdude]

Thank you for the quick reply. I'll give that a shot...single zone, one circ. Thanks again!

[@lalaniathielen8917]

Good question

[@MikeJamieGavin]

For anyone else reading this years later, I had that exact problem. My issue was the solder joint under the relay had cracked. So I wasn't getting 120v at the circ pump terminal, but the relay was closing. The contacts checked out good so I checked for continuity (with power off) from the relay to the C1 and had no continuity no mater what position the relay was in. Pulled the board and saw the crack. Resoldered it, checked again, and was back in business.

[@jasonschroeder8671]

​@MikeJamieGavin so what happens when you manually close the relay and it fires up? My relay won't close at all. It's humming to get going, but no closure of the relay.

[@jamesdago13]

I have a L8124A, C using a nest and trying to do an add a wire kit, is there no constant on these boards for my smart thermostat?

[@gyver471]

Does it matter if different probes touch different screws? Like at one point the red touched l1 but then you switches and it touched b2. I ask because I don’t want to short anything out.

[@zeeshawn15]

Do I put T Stat's red(r) to TV or T? Where does the white(heat) from T Stat go? TV or T? Some Aquastat says TH instead of TV right? Tv and T both are powered I believe but which one is for T stats power and which one is for T Stats (heat)?

[@erikengquist2216]

My thermostat's white (heat) wire is connected to TV, and red (power) is connected to T.

[@Xbreaselx]

Same concept for millivolt aquastat and B2 still common or would b3 be common?

[@zekeilleyva1735]

Do you have a part number for the thermostat switch(you refered to it as a "relay")? Is it a universal part as long as it has the 120 v / 24 voltage capability?

[@gjones5153]

I have this controller on a castiron powervent boiler also using a taco SR503 switching relay. my problem is that when the thermistat is calling for heat the taco sends power to c1,c2 which also send power to the blower vent motor. When the high limit shuts off the boiler and the thermistat still calling for heat the blower motor continues to run sucking warm room temp out of building. this continues to short cycle until the thermistat is satisfied. Is there any way to use the high limit to shut off the blower motor

[@jetmike747]

Awesome video. So if I understood correctly, if you were to get a thermostat that required a C wire, could the C wire be hooked up to terminal B2?

[@acservicetechchannel]

I wouldn't add an extra load onto this setup. The transformer may not be upsized to handle the extra thermostat load, thanks

[@TheSchwartz36]

@@acservicetechchannel im new to this! how would i add an extra load ?

[@dannyolivares6757]

Have the same concern right now, were you able to run the common on B2 without any issues??

[@powerram92]

my relay just melted n was wondering if any other testing should be done once i replace the relay so i know it wont melt again.

[@AkA-me-Kenny2]

What might be causing the oil hydronic burner, to once it reaches the high limit temp. and shuts down, it immediatily fires up again before you could blink an eye or take a breath? Three Facts, 1- boiler high temperature has been reached, and 2- there is no call for circulator to run, 3- no domestic water is being used at the time! What should I be looking for? Thank you for your help!!!

[@ricoz8649]

Is it common for failure of the temperature sensor to expand the bladder under the temperature dial and not close the switch? If so is this a part that can just be replaced?

[@johnnylightning1967]

With a T-stat connected you have a cold start boiler.

[@forevertwowheels717]

I have a honeywell hydronic zone valve control panel. In the panel it has 2 wire connection for boiler. Do i connect that to the T & TV on aquastat.

[@Batalia122]

Hello, hopefully you can answer this question. My boiler has been turning on without the thermostats connected and I think it's the Aquastat. When I remove the Thermostat wires from the Aquastat both or the white the boiler doesn't turn on but when they are connected it turns on. I've cut the wires to the Thermostats so I know they aren't connected. Do you think the Aquastat is bad and bridging the wires without the thermostat? Thanks

[@KamberBCT]

Don't know if you'll even see this since the video was posted a while ago but I have an Aquastat Relay Type L8148J and unfortunately only have a R and W wire going to the thermostats on the Upper and Lower Floors. I am trying to add a wifi thermostat to make scheduling easier but don't have a C connection. What would I connect to make this work or am I out of luck? Having a hard time getting an electrician to come out since it is such a small job.

[@Arieldny]

hi can you make a video how would you wire this to a 2 or 3 Honeywell system (4 wires, thanks)

[@mark.r8900]

hi, do you have to drain the boiler first before replacing this aquastat? due to the fact that the probe is touching the boiler water. thank you.

[@acservicetechchannel]

Hey Mark, the sensor is in a well. The well is what keeps the water in the boiler and that doesn't get changed out, thanks!

[@jasonschroeder8671]

So what's the issue if the relay isn't getting sucked in? Checked everything I could without tearing apart the switch, even replacing batteries in the thermostat control in the living room, and everything seems good. I can manually push it and it works fine so I assume contacts are functional. Just replace it or somewhere else to look?

[@BelleRiverHeating]

Does the temperature sensor actually sit in hot water or just into a hole on the side of the boiler?

[@geojor]

could you explain how a L8124A triple aquastat works in a combination wood/oil hot water boiler, it also has an isolation relay ...

[@acservicetechchannel]

Are you talking an outdoor wood boiler connected to the return side of an existing oil burner with a plate heat exchanger?

[@geojor]

no, a combination wood/oil New Yorker boiler in the basement of a house ...

[@markgattinger3958]

I have a L8148E and need the relay on that board. I'm only finding the entire board and box complete. Is that relay available anywhere?

[@michaelmace924]

Question: I have a customer that's been using me for a long time, 20-22 yrs. He has an older Columbia boiler that needs an AquaStat but other than that it's in perfect shape. The transformer blew out, replace the AquaStat & be done. Normally this is the case, but this boiler is old and the damper is old and AquaStat is old. The damper doesn't have the molex plug on the end of the wires, and the new aqua stat has the molex plug in it. I'm trying to save the old man money, he's on a fixed income. Is it gonna be a mission to replace the transformer in the AquaStat or is it pretty much just unsolder then resolder?

[@wownycrrcom]

I have a Honeywell L8148E relay and I have 3 zone valves going to 3 different floors, My Question is if the relay was bad would all 3 zones not be able to call to the Boiler or can separate zone still be able to call to the boiler with a bad relay.

[@acservicetechchannel]

The zones may still call if they are on a zone controller powering a circ pump instead of the l8148e

[@christinestrahan8727]

I have a Honeywell Aquastat relay #L8148B for my gas furnace. I had a electrician hook up a plug to my power switch so I could use my furnace with a generator if I lose power. We had power to the relay but when we tried it with the generator the furnace would not work. We removed the generator and had to wait about a half hour to the furnace would run. Is there any safety delays in the relay or any idea what’s going on.

[@acservicetechchannel]

That doesn't sound right. Is it possible, the power is feeding into this backwards with the hot being common and common the hot accidentally?

[@firstjohn26]

Great video! Would you be comfortable spraying some kind of lubricant on that relay to keep it moving properly later in life? Mine has been acting up a bit.

[@stifflers69mom1]

firstjohn26 do you hear it clicking? It s a common failure point .....my advice to you if you plan on keeping the boiler for sometime ...order a new one and have it on hand

[@gerardtom]

Can a aquastat lock out the burner and put the light on the burner button?

[@deependz3231]

What causes a oil boiler to continuously run, even with the relay in the open position (non energized)? In other words, you can switch the power on/off but relay doesn't move either way, stays in open position, power on, boiler starts.

[@dvonpache]

Correction @ 05:30: the 24V line is in the RED wire and that's why @ 06:30 you've clearly tested ~(21 - 24)V (while you were saying "we have nothing") in the BLUE and B1 wires because the aquastat was closed. So annoying to have expert tell you something when I see it with my own eyes it isn't so and no errata was issued...WTF?

[@SeongJinShim]

Can I use Honeywell L8148E instead of L8124E?

[@learndaanswers3066]

7th boiler mechanic who can't solve the issue of why my boiler aquastat will not shut off my steam boiler from running constantly. They disconnected the house thermostat but soon as the water got cool the boiler started up and ran which heated the whole house until the tenants turn off the emergency switch. Is this something that can be fixed or is the company just not knowing. They changed the aquastat three time already....can you suggest maybe a new type of aquastat?

[@zoglchaim5634]

what connects W to T? is that a resistor? by me, its open... does it mean that resistor burned out?