I have a Weil-McLain Boiler. When the house thermostat is set at say 68 the boiler keeps heating past this temperature and keeps going. The model is CG-6-PIDN with serial No. 12. Since the wires from the thermostat go into the Transformer Relay do I need to replace it? I have appliance protection and have had several gas people look at it and they have tried a few things with no success.

 

I think we need a bit clearer idea of what the exact problem is here...

When you said:

You mean that the temperature in the house climbs above the 68 degree setpoint, correct?

When you say it "keeps going" ... what exactly does that mean? 80? 90? 100? ...

Replace what? the thermostat? the relay?

I'm not at all surprised.

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OK, let's get on with this.

Can you actually hear and see the burner still firing? Can you tell if the circulator pump continues to run?

The reason I'm asking so many questions is because what you are describing could be a few different things...

You may in fact have a problem with the controls that are keeping the boiler running after the heat call is satisfied.

You may have the 'anticipator' in the thermostat improperly set.

You may have what is called 'gravity flow' where heated water from the boiler continues to flow AFTER the boiler is shut off due to 'thermo-siphon' action. This happens because hot water is lighter than cold water and will 'float' upward into the home, and the cool water will flow back to the boiler... all by itself.

This is usually caused by improper installation, or a faulty flow-check valve.

So, let's all understand what is happening before we go off down the wrong path.

 

Yes the furnace keeps going 80 90 100. Untill we shut it off. We have to turn off the power to the unit to shut it off. Sometimes it will stop at the set temperature but more than half of the time it will not. I have replaced the wall thermostat with no results. It is as though the signal to stop is not getting to the furnace. The furnace worked fine for the first 5 years we have had it just two winters ago the furnace started to not respond to temperature setting. It starts fine. It seems to run fine. It just wont stop at the temperature.

 

This is a gas-fired boiler? URGENT:

This could be a stuck or sticking gas valve, which is dangerous. Do you have a voltmeter and know how to use it? Set it to AC volts.

When the burner is running, with no call for heat, see if there is 24V across the fuel valve's electrical terminals. If not, then the valve is stuck open. (In which case, shut the manual gas shut-of valve to the boiler until the fuel valve is replaced.) If there is 24V, then there is a problem with the controls - also possibly hazardous - manually shut off the gas.

If this doesn't make sense to you, best to call another service person ASAP.

 

Mike, if it stops firing when the main power is turned of it can't be the gas valve sticking open.

I can think of a few other things that might be causing the problem. How capable are you (Michael) working with/around electricity? Do you have a digital camera? If yes, please take several pictures of the controls on the boiler and post them on a photo hosting site and the public URLs here.

 

Do you want the gas controls settings that seems like the only place where there are controls. On the side where the thermostat hooks in is just the Transformer Relay it think it is called. Anyway, which controls do you want pictures of?

 

The more the merrier. The "transformer relay" is likely an aquastat and relay assembly. Take the cover off when you take the pictures. Also post the manufacturer and model numbers of anything that remotely looks like some kind of control.

 

OK, I agree. Cancel my alarm.

 

I believe that Michael's boiler uses the Honeywell R8285 control center, and a high limit control. If that is the case, if it is the relay sticking, it should be a 'plug in' Honeywell R8222 model.

This may not be the exact model, they come in several 'flavors' (different relays, smaller/larger transformers), but it will look like this.

R8285 control center

Here's the part numbers W-M has listed for the relay:

Honeywell R8222U1006
Products Unlimited 9001-241Q223
White-Rodgers 91-322000-11000

And here's a source for the relay that replaces the discontinued 1006 from Honeywell:

Patriot Supply - R8222U1079