Boiler fires but no call for heat

Rob_12

There was a problem with one of the thermostats at the church my wife attends. I have become the one they call when there is an issue, I have fixed the themostat problem but I noticed something when I was diagnosing the issues. First of all I am just a somewhat advanced DYI and I have experience with hot water heat in my own home and picked up a few things here and there, but this one has me stumped.

It is a hot water system with two zones, the relays from the thermostats are all working okay but for some reason the furnace/boiler comes one despite the fact that there is no call for heat. In addition to the thermostat wiring there is a control attached directly to the boiler and I am pretty sure that is a stop gap to prevent the boiler from overheating, different place then mine at home but pretty sure that is what it is. There is a second control just like the one on the boiler but it is attached to the wall with two leads coming out of it. One is inserted to a cavity on one of the return pipes and one goes to the outside wall. If I lower the temp setting on this control the boiler will shut off, but it also won't come on if the thermostat is activated. If I raise the temp setting on that control the boiler will fire and eventually shut off at what I am guessing is the setting on that control.

Does this control keeps the water hot for a more rapid heat up of the system? If it is it would seem to me to be a waste. I am also unsure if this is 100% safe situation if my assumptions are wrong so I have the heat shut off for right now.

I am looking for someone to have a look but I figured if I can find a quick suggestion or answer here I could save some money for a church that can really use it. If not I will try to locate a pro to come in and have a look.

Thanks in advance for any suggestions.

Ron Schroeder_2

It sounds like it has a low temperature control that keeps the boiler from going below a set point. It's common. What are the model numbers of the controls? Is one of them something like a Honeywell L8124A or something similar?

Rob_12

I don't have the part number here, I will have to go over there to get them. One thing though, if I do set it to a low temperature then the boiler won't fire even if the thermostat calls for heat.

Ron Schroeder_2

It might be wired wrong. If the boiler is above the low temp cutoff and a zone calls for heat, the burner should fire to bring the boiler up to the high temp cutoff.

joel_19

hmm

The boiler doesn't have to fire on a call from the thermostat. almost NONE of my boilers fire on a call. Why? we almost always install out door reset. that controll on the wall your adjusting does one of the probes go outside??? You said it went to the wall. If so your tstats probably just turn the pump on or open a zone valve but do not fire the boiler.That controll your adjusting may be the only thing firing your boiler which is A OK if that's what it is.

joel_19

legal disclaimer

Of course it could be wrong, which is why you should get a pro. Don't attempt to remove covers, switchers lines or hardware on your own. It wasn't my idea, you figured it out YADAYADA YADA etc blah, blah, to infinity and beyond!

Rob_12

Thanks, that makes sense, The thermostats do turn the pumps on. I think I see how it works. My home thermost turns the pump on and fires the boiler. This system seems to be wired differently where the water is kept hot and then the pumps turn on when heat is needed.

however this seems a pretty inefficient for this situation. Most of the time the church thermostat is set at 55. The thermostats are programable for the few times the higher temperatures are needed. Wouldn't it be more efficent to just have the boiler fire when one of the pump turns on?

Also, what temperature should that control on the wall be set to. I am guessing it is however hot you want the water to remain when the pumps are off.

Looks like the system is safe unless I am missing something. Thanks to both of you for the input.

From your other email, Looks like you want a release of liability, here it is. This is the internet and only I am responible for any of my actions. I hold all harmless for any information I receive. Any actions I take will be of my own determination no one else is responsible.

That said, Looks like the system is operating as intended. If someone here thinks it is a good idea to remove that control and use the thermostats to fire the boiler and run the pump the I will have a pro come in to do the conversion as I am not that comforable doing that conversion myself.

Rob_12

Everything is working great now. Thanks again for the help, looks like all I needed was an understanding of how the system works to dispell any lingering fears that something was not working right. After a little more thought and viewing how it actually works I now see the reason for this type of control. Spent about an hour and a half there making sure things were turning on and off as intended and it is good to go. Thanks again for the help, I now know a wee little bit more about one more thing.