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Phil, Mechanical Engineer
Category: HVAC
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Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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Weil McLain gas boiler model cga4spdn won't stop running

Customer Question

Weil McLain gas boiler model cga4spdn won't stop running unless I turn off the system at the boiler. If I turn down or switch off my Honeywell ct3200 thermostat the system will still run. I replaced the 24v relay and now have the opposite problem....the heat will not come on unless I tap the replaced relay....so I put the old relay back in for now and just manually turn off the heat at the boiler. What else can I try to fix my issue?
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Submitted: 11 months ago.
Category: HVAC
Expert:  Rick replied 11 months ago.

I have to leave for about an hour but in the mean time try putting the new relay back then jump the R & G terminals (should be where thermostat leads are connected) on the transformer and tell me if the burner fires up. I'm assuming your unit has a standing pilot (lit all the time). I'll respond when I get back.

Customer: replied 11 months ago.
How do I jump wires?
Customer: replied 11 months ago.
I have a standing pilot
Expert:  Rick replied 11 months ago.

Just connect the R & G terminals with a small piece of wire. Best to turn the power off first then make your connection then turn the power back on. I'll get back to in in about an hour

Customer: replied 11 months ago.
Not sure which red and green wires. See attached pics and advise. I don't want to jump the wrong ones.
Expert:  Rick replied 11 months ago.

That's not what I said. I said to connect the R & G TERMINALS on the transformer next to the relay. I didn't say anything about connecting wires (at least not yet). Give that a try and let me know what happens

Expert:  Rick replied 11 months ago.

It looks like it may be difficult to jump the terminals since your transformer has all spade connections.

Customer: replied 11 months ago.
Did you mean the wires coming into the thermostat? Wires are yellow and white. See attached pic
Customer: replied 11 months ago.
OK sorry. Now I understand. Yeah that will be tough to do
Expert:  Rick replied 11 months ago.

So the alternative would be to connect the 2 wires the thermostat leads connect to. Looks like you have thermostat wire with a white outer cover and they used the typical red & white wires to the thermostat. So remove the blue wire nuts then twist those wires together. Looks like red & white connect to 2 black wires (which is typical). The tag identifying the thermostat connection looks like it may still be attached to the black wires. The point here is to twist the 2 blacks together

Expert:  Rick replied 11 months ago.

Power off first then back on once you make the connection

Customer: replied 11 months ago.
Twist the 2 black on their own or together with the attached red and white?
Expert:  Rick replied 11 months ago.

Doesn't matter

Customer: replied 11 months ago.
Ok. And you want me to turn off the power, not the breaker for the boiler, right?
Expert:  Rick replied 11 months ago.

You can turn of the power to the boiler either at the breaker or the service switch near,on the side of the boiler

Customer: replied 11 months ago.
Need to continue later today.I'll update you when I'm back at the boiler. Thanks, Adam
Expert:  Rick replied 11 months ago.

ok

Customer: replied 11 months ago.
I put the wires together and turned the power back on and nothing happened. My thermostat shows that heat should be calling, but the boiler isn't responding. Now what?
Expert:  Rick replied 11 months ago.

Is the vent damper open?

Customer: replied 11 months ago.
Closed
Expert:  Rick replied 11 months ago.

Ok, put the old relay back and tell me if the burner fires up

Customer: replied 11 months ago.
Posted by JustAnswer at customer's request) Hello. I would like to request the following Expert Service(s) from you: Live Phone Call. Let me know if you need more information, or send me the service offer(s) so we can proceed.
Expert:  Rick replied 11 months ago.

There is a additional charge for a call. Let me know if you still want a call. Or we can continue here if your like.

Customer: replied 11 months ago.
No change with the old relay
Customer: replied 11 months ago.
We can communicate like this for now
Customer: replied 11 months ago.
Vent damper is still closed.
Customer: replied 11 months ago.
Now what?
Expert:  Rick replied 11 months ago.

Ok, so I just wanted to be sure you had the right relay. If it fired up with the old relay then the new one would have suspect. So I assume the thermostat wires are still connected together. Next check the blocked vent switch. Turn the power off and put the new relay back. Then press the button between the 2 wires on the blocked vent switch. It's attached to the draft diveter (see attached pic). If you push the button and it clicks you have reset t and the unit will fire up with any luck when you turn the power back on

Customer: replied 11 months ago.
The button doesn't push in?
Expert:  Rick replied 11 months ago.

Then it wasn't tripped. There are 2 more devices in that circuit hat you need to jump out/bypass by connecting the wires together. One is the limit. The device with the dial where you set the boiler temp. The other is the rollout sensor (see attached) which is just outside of the where the burners are. If you jump both of these and nothing happens then you need a multi-meter for the next step. jump these devices 1 at a time. I'm assuming the black thermostat wires are still connected together.

Customer: replied 11 months ago.
How do I jump these out?
Expert:  Rick replied 11 months ago.

Ok, you got the 2 devices. The limit you can connect the 2 terminals with a piece of wire and leave the leads attached. The rollout sensor you'll have to take the leads off and use a paper clip or piece of wire in the connectors. They should have an open round section on each side of the connector that you can jamb a wire into. It needs to be a pretty tight fit