Weil-McClain boiler wont kick on

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Old 11-21-13, 05:00 PM
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Weil-McClain boiler wont kick on

My Weil-McClain CG-5-SPDN hot water baseboard system suddenly stopped working today. I need help testing it. Im pretty handy with a multi-meter so I hope to test a few components and find something that is bad.

1. There is 24V at the thermostat
2. The thermostats in both zones engage (relay clicks)
3. A few moments later I can hear the relay click in the zone valve (seen in the bottom picture below) and get 24V across terminals 1 &2 or 1 & 3 (R & W or R & G)
4. Usually when this happens, the pump kicks on, stack valve opens, and the burner kicks on. However I get none of this extra activity.
5. The pilot light is lit.

I am wondering if it my might be the coil / relay. The system is fairly old. 1991 is the date of manufacture. Thank you very much!
 
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Old 11-21-13, 05:13 PM
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There should be an electrical schematic pasted inside the cabinet. With your multimeter, find out where the 24V is being lost when there is a heat call. I prefer to start at one of the devices this isn't working, and work backwards toward the voltage source.
 
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Old 11-21-13, 05:58 PM
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get 24V across terminals 1 &2 or 1 & 3 (R & W or R & G)
Voltage between 1 & 3 is irrelevant, doesn't tell us anything.

If the zone valves are working properly,

when there is NO call for heat, you should see:

ZERO volts between 1 & 2

24VAC between 2 & 3

when there IS a call for heat, you should see (after a short time for the valve to open):

24VAC between 1 & 2

ZERO volts between 2 & 3

If this happens consistently then the problem is probably with the relay on the control inside the boiler.

We'll troubleshoot further after you let us know about the valves.
 
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Old 11-21-13, 06:09 PM
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Hicks, is the model number correct? is there any further information on the data plate? Seems that W-M doesn't have wiring diagrams on the website.

If there's a diagram inside the cover, please take a high res photo that we can read, and post it to a free account on photobucket.com so that it doesn't get squashed down by the forum. Then post a link to the photo so we can view.
 
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Old 11-21-13, 06:21 PM
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Thanks NJ Trooper.

Here are my results. I tried multiple times across both of my two zones. Results are consistent across both zones:

No call for heat:

1&2: 0V
2&3: 0V

call for heat (valve clicked):

1&2: 24V
2&3: 0V


Out of curiosity I removed the 6 pin relay and tried the same tests. Here are those results:

No Call for heat:
1&2: 0V
2&3: 5V


Call for heat and the valve opened (clicked):

1&2:24V
2&3: 0V
 
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Old 11-21-13, 06:32 PM
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Yes, model is correct. Here is the schematic from inside the unit:

http://www.weil-mclain.com/en/multim...ams/cg-117.pdf
 
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Old 11-21-13, 08:38 PM
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No call for heat:

1&2: 0V
2&3: 0V

This was no call for heat on EITHER ZONE?

call for heat (valve clicked):

1&2: 24V
2&3: 0V


Out of curiosity I removed the 6 pin relay and tried the same tests. Here are those results:

No Call for heat:
1&2: 0V
2&3: 5V


Call for heat and the valve opened (clicked):

1&2:24V
2&3: 0V
What voltage do you read from the R and C terminals on the boiler control?

You should read 24VAC there at all times.

If NOT, suspect a bad transformer on that control... but check also to make sure that 120VAC is present at the primary.
 
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Old 11-21-13, 09:10 PM
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Curiosity, did you try jumping across 2&3 on zone valves. Those are the terminals that operate the boiler. What is your voltage coming from the transformer that runs the zone valves.

Something else you can try is jumping TT on the boiler and see if it works. That will eliminate your boiler if it comes on.
 
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Old 11-22-13, 05:45 AM
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This was no call for heat on EITHER ZONE?
CORRECT!

What voltage do you read from the R and C terminals on the boiler control?
I read 0V from R&C in this picture:
If NOT, suspect a bad transformer on that control... but check also to make sure that 120VAC is present at the primary.
There is 120V going into "Plug-in DPST Relay" if thats what you are asking.

Do you suggest it is the "inside" transformer? I have two transformers. The one on the outside gives 24V at the thermostats and I think is what powers the zone valves.
 
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Old 11-22-13, 06:45 AM
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Curiosity, did you try jumping across 2&3 on zone valves. Those are the terminals that operate the boiler. What is your voltage coming from the transformer that runs the zone valves.
Yeah, no change.

Something else you can try is jumping TT on the boiler and see if it works. That will eliminate your boiler if it comes on.
Im not sure what you mean. Are you suggesting jumping the R wire from the working transformer and touch it to the R on the "inside" transformer? (see pics)
 
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Old 11-22-13, 07:20 AM
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Are you suggesting jumping the R wire from the working transformer and touch it to the R on the "inside" transformer? (see pics)
No, I don't think that's what he means.

The T T on your boiler is analagous to the R and G terminals that the thermostat is shown connected to in your boiler schematic.

If you have voltage going to the primary side of the 'inside' transformer, and 0 Volts on the secondary, that transformer is bad.

Look for a Honeywell AT72 (or equivalent) transformer to replace that with. You can also get the whole control for under like $25 or so... go to pexsupply.com and search for " R8285 " and you should find the equivalent control. Make sure the relay is DPST if that's what you have in your system now.
 
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Old 11-22-13, 11:38 AM
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That did it. I had to buy the fan center at a local supply so it was double the price. But the wife was getting cold so it had to be done. Ironically one of my zone valve heads also stopped working. It got real hot but would not engage. Even though they are on separate transformers, I wonder if one fried the other??

Lastly for what its worth, I recently replaced the thermostat in this zone with one of those fancy wifi thermostats that requires a C wire. I dont think that put extra strain on the transformer; especially since that power comes from the transformer that DIDNT die.
 
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Old 11-22-13, 01:58 PM
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Even though they are on separate transformers, I wonder if one fried the other??
I can't see how that's possible, but stranger things have happened! I suspect coincidence, or perhaps the other zone valve has been 'out' for some time and you've just not noticed it until poking around to fix the no-fire ?

Possibly, when the inside transformer dookied, the zone valve was open and calling for heat for hours and hours and the heat from the heat motor took out the valve. They are rated for only INTERMITTENT duty and they can self-destruct if open for long periods of time.

I recently replaced the thermostat in this zone with one of those fancy wifi thermostats that requires a C wire. I dont think that put extra strain on the transformer; especially since that power comes from the transformer that DIDNT die.
You pulled the "C" wire from the outside transformer, yes? No, doubtful it's a factor.
 
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