HVAC help. Gas water boiler furnace failing to heat occasionally until reset.

[Vovchandr]

Question for anybody who's familiar with HVAC systems.

Trying to figure out what's going on with my gas water boiler furnace.

I've noticed on my nest reports that a month ago there was an occasional day where it "heated" for like 18 hours for no reason.

Every other day has been normal about 4 to 5 hours.

Happened about 3 times since in a similar manner.

When I went down there during the last event yesterday there was no light on but it was making some sort of noise (water circulating?)

Triggered temperature up and down a few times to get it to cycle back on it I heard an electrical box switching on the unit but no fire.

Turned heat entirely off through thermostat and turned it back on triggered it to resume and light as normal.



Obviously something minor is going off and some sensor is disagreeing with conditions. Turning everything on and off bypasses the fault?

I know there is a flame sensor somewhere on the unit, but if that was faulting, my understanding is that everything would light as normal and then it would kill itself because it doesn't see the flame. Wouldn't it keep cycling on and off in that case? Or would it just do it a few times and stay in a fault condition? That could explain it being dead hours later and not continue to try to light.

Any help appreciated before I call somebody for something likely relatively simple.

Unit isn't crazy old. 10 to 15 years?

Other data: Water pressure is at about 20psi. No leaks. No low water fault light on.

[Vovchandr]

pics

[PurplePackage]

nothing is maintenance-free (maybe solar, if you're lucky with it).
post the model number. I can find the service manual for it and lookup the maintenance schedule. you'll very likely find a problem going thru that checklist.

[Vovchandr]

nothing is maintenance-free (maybe solar, if you're lucky with it).
post the model number. I can find the service manual for it and lookup the maintenance schedule. you'll very likely find a problem going thru that checklist.

I'll get the actual number later when I get home.

Quick internet sleuthing finds this that looks identical but can't confirm it's the same until I get home

GWB84-E Boiler

https://www.lennox.com/products/heat...oilers/gwb84-e



This might be the manuals

https://tech.lennoxintl.com/C03e7o14...b84-e_2101.pdf

https://www.manualslib.com/manual/19...page=30#manual

[boosten lebaron]

Sounds a little like air trapped in the system.

[burnham]

Weird. I could see a relay hanging up and that in turn having a zone of heat constantly run. The boiler would burn as much as it needed to, holding temperature in the bandwidth.

What I'm curious about is how the nest thermostat would know about it? I assume they track run time just by when they're calling for heat.
Makes me wonder if the thermostat is just wrong, broken, or being back fed somehow when the boiler is running on it's own.

[Vovchandr]

Weird. I could see a relay hanging up and that in turn having a zone of heat constantly run. The boiler would burn as much as it needed to, holding temperature in the bandwidth.

What I'm curious about is how the nest thermostat would know about it? I assume they track run time just by when they're calling for heat.
Makes me wonder if the thermostat is just wrong, broken, or being back fed somehow when the boiler is running on it's own.

Nest knows its calling and sending signal and then sees how temp changes.

Kind of neat, but Nest has a safety algorithm in place too for these situations.

We've noticed due to looking at our use charts and one morning being cold, but it's still nice to have extra safety.

"Your heating system failed to heat your home

Based on your local weather and recent heating system performance, your home should’ve become warmer while the heat was on between 4:31 PM and 8:50 PM on January 2, 2022. Instead, the temperature decreased by 4°F"

Going to get a natrual gas alarm/sensor today just in case as well. I'm fairly certain the systems fault to "off" condition, but I'd rather be safe than sorry and make sure it's calling for gas and just not lighting it.

[Kurlon]

The Nest is recording the amount of time it's calling for heat. I'm a bit surprised that it didn't throw a warning that it didn't think the system was providing heat (it seeing a temp increase in a reasonable amount of time) if the furnace wasn't cooperating. On the furnace front, when the Nest calls for heat, the circulator pump will run, independent of what the furnace is doing. The furnace will also get the call to run, and should fire up if the water temp is below the min, and will stop once it hits the max set point, and will cycle like that as long as there is a call for heat. My setup doesn't use an outdoor temp reset, so my set points are fixed at 160F min, 180F max for example. Newer controls will adjust those temps based on perceived load and / or outdoor temps to improve efficiency. I've had my furnace fault out, which resulted in the system calling for heat for an extended period, running the circulator but no actual heat, I don't recall how long it was like that but the Nest was showing the 'Is your system working?' message when it happened.

[Vovchandr]

On the furnace front, when the Nest calls for heat, the circulator pump will run, independent of what the furnace is doing.

Thank you! That explains the noise that was being made when I would turn the temp up to have Nest call for heat. It would make a noise by the boiler and the baseboards would make a noise upstairs but no light was turning on. Couldn't quite figure out what was happening.

Water temp was dead cold but it wouldn't relight until turn off and turned on (through the app. Temperature increase/decrease wouldn't trigger it. Going on/off condition triggered it)

I got the message from Nest for first time yesterday. This would be about the 4th time the issue has happened.

[jimmycapp]

Any diagnostics available on the furnace controller?

[SRTie4k]

What Kurlon said.

Not sure how your system works, but mine has a triple aquastat that will fire the burner once it sees water temp has fallen below a certain threshold (and which is usually adjustable). This happens independently of the thermostat calling for heat (which, as Kurlon said, just triggers the circulator).

You need to figure out what calls for the burner to fire in your system, and investigate why it isn't firing when water temp drops. Does your unit also do DHW?

[burnham]

I get you now, the thermostat is calling for a long time, but the boiler isn't necessarily running the whole time.

[PurplePackage]

https://tech.lennoxintl.com/C03e7o14.../240012889.pdf

pgs.29-31

[PurplePackage]

also money

[MattR302]

Had an issue with my gas boiler a couple weeks ago. Thermostats and indirect water heater were calling for heat, the zone controller was working, but the boiler wasn’t kicking on.

Turned out the automatic damper valve on the flue vent. The steel vent piping above the valve was rusting, and rust dust was causing the valve to stick closed. If the valve is closed the boiler won’t ignite. Vacuumed it out real good, but it was still intermittent after that. Switched it into the manual open mode and ordered a new valve and going to replace the piping.

[burnham]

^ A lot of power vented boilers will have a proving switch that closes when the fan has created a draft. Some use a sail switch, which as the name implies looks like a little motherfuckin sail that swings in the breeze. The other style I've seen is a vacuum hose that goes to a switch.

The vacuum style is easy enough to check, when the t-stat is calling for heat you can pull that hose and see what the boiler does. Also, if the t-stat is calling and the boiler won't fire, you can pull the hose and suck on it. Sometimes you can hear the switch close, sometimes the switch was working fine, sometimes the boiler lights and you've found your problem. I'm pretty sure you can move the sail style switch manually, but it depends on the brand of switch.

Either type is pretty easy to jump out, or ring out with a continuity tester. I would start there.

[virtualbong]

Here is a thread when I noticed that my heater was not actually doing anything. I had to manually add pressure to fire up the system and then I just watched to make sure the pressure doesn't go over the max limit. When it got close, I discharged some of the water to relieve some pressure.

https://www.justanswer.com/hvac/9e4u...sage-says.html

[Stoneman]

My situation was a bit different, so it may not apply to you. For reference, our furnace is propane FHA.

A year or two ago, it would behave as you describe. The control board referred to a faulty pressure switch. Changed it, worked for a couple days, then started the same shit. But it was throwing another code for a part that I can't remember. That particular one required someone who knows more than me to replace. Again, it worked for a couple days, then shit out again. But now the control board was asking to be replaced. Swapped that out and it worked for a couple more days, then back to fucking up. On a whim I decided what the fuck, may as well get a new thermostat while we're fucking around. Bam! All that bullshit and it was a faulty thermostat.

[scubasteveRR]

The Nest is recording the amount of time it's calling for heat. I'm a bit surprised that it didn't throw a warning that it didn't think the system was providing heat (it seeing a temp increase in a reasonable amount of time) if the furnace wasn't cooperating. On the furnace front, when the Nest calls for heat, the circulator pump will run, independent of what the furnace is doing. The furnace will also get the call to run, and should fire up if the water temp is below the min, and will stop once it hits the max set point, and will cycle like that as long as there is a call for heat. My setup doesn't use an outdoor temp reset, so my set points are fixed at 160F min, 180F max for example. Newer controls will adjust those temps based on perceived load and / or outdoor temps to improve efficiency. I've had my furnace fault out, which resulted in the system calling for heat for an extended period, running the circulator but no actual heat, I don't recall how long it was like that but the Nest was showing the 'Is your system working?' message when it happened.

what this guy said. the furnace is just there to heat the water to a certain temp then shut off. the circulators will run as long as the systems calling for heat. once it sheds enough heat ( i.e the water cooling of from shedding it's BTU load) through what ever means you're heating your house then the boiler will re-fire till it hits that max temp again or the thermostat is satisfied.

there is also an order of operation when the boilers fires... for simpler models like the one you have (i.e. not a tankless) the order of operation for start up most likely goes like this...
1.) confirm pilot is lit
2.) does the vent hood damper open to let exhaust escape
3.) have either roll out switches been tripped or failed (2 of them - one near the burners and one on the draft hood
4.) does the gas valve open.

if one of these fails then it wont light. you can jump any one of the sensors by first unplugging both leads and using a jumper wire to jump out the sensor