Weil McLain CG Boiler wont start after relay replacement

tlmaurer63 · February 13

I had an issue where my boiler wouldn't shut off after we reached the desired temperature. If I shut off the tstat, it would continue to run until I turned off the power to the boiler. I found out that if I tapped the relay, the boiler would shut off. I replaced the relay but now the boiler will not ignite. The flue/damper will cycle past the open position back to the closed position. It will keep doing this periodically and never stop at the open position and no heat. If I put my old relay back in, immediately, the flue will cycle to the open position (and stay there) and the boiler will start. Again, it will not stop when we reach the set temperature. Any ideas out there?

Jamie Hall · February 14

IU assume that the new relay is an exact replacement for the old one? Operating contacts? pin configuration? The lot?

109A_5 · February 14

Hello @tlmaurer63,
The troubleshooting chart in this manual may help.

https://www.weil-mclain.com/sites/default/files/field-file/cg-series-12-gas-control-supplement_1.pdf

tlmaurer63 · February 14

The current relay is a 90340 so I ordered 2 from Amazon and both behave the same. I then ordered the official part (510-350-223) from supplyhouse.com and received another 90340 and it acts the same. It is really baffling.

EdTheHeaterMan · February 14

The relay you call a 90340 was copied from a Honeywell R8222D1014 many many years ago.

That relay can come in several configurations. The R8222D1014 for example is the one that has the greatest amount of capabilities. It has a 24 VAC coil that the thermostat can operate, then there are 6 other terminals setup as a DPDT relay.

the R8222U1006 is a SPDT relay with only 3 additional terminals
The R8222U1079 is a DPST relay that has only 4 additional terminals that work as two switches, each with one set of NO contacts. And no NC contacts. That relay also comes in the R4222 variety. It looks the same but the coil is line voltage 120 VAC or 230 VAC. So I would look closely at the plug-in terminals of each relay you received and compare it to the original relay

Notice the green arrows are pointing to terminal pins that are missing

I have a feeling that you have a relay that has a different set of contacts than the original one you removed from the boiler. Look at the pins that are on the old relay and the new relay. I also feel that there may be a holding circuit that was inadvertently made with some type of additional wiring by a previous technician. At some point something changed that initiated the holding circuit.

Is it possible that the problem started soon after you upgraded to a new thermostat or some other event?

OR

You may have had an overheating issue that melted some insulation off of a thermostat wire inside the boiler jacket that is completing a holding circuit that is not supposed to be there. A close inspection of all the low voltage wires inside the boiler front door may reveal the problem.

tlmaurer63 · February 15

Ed, both the old and new relay are of the DPDT as shown in your pictures. Oddly enough, the wiring diagram on the inside of my boiler panel says it should be a DPST. The issue with the relay sticking has been happening on and off for a couple weeks now so I finally decided to replace it. We also happened to have a new Amazon smart thermostat sent to us by ComEd so I thought I'd put that in too. Of course nothing is ever easy and I only had 2 wires to the tstat. The new tstat required a separate 24v wire to power it so I ran new 5 wire for it. I did find a "spare" 24v wire that was disconnected from some odd little contraption sitting unused inside the boiler cover, so I used that to power the new tstat. I powered up the new tstat with the old relay and everything worked as before...the only issue being the boiler would not shut off when it reached the tstat temp. I just tapped the relay and it would shut off. After replacing the relay (with what I think is an exact replacement), the damper rotates through the open position and closes without any gas flow or ignition. The old relay still works but just wont shut off with out me rapping on it. Can you make any sense of that?

tlmaurer63 · February 15

Ed, I'm trying to upload some pictures but it is failing...not sure why

tlmaurer63 · February 15

Here is a link to the pix

https://photos.app.goo.gl/vMVsujc89qHXe6kL8

EdTheHeaterMan · February 15

So I can be clear with what you have done so far.
1. Some time ago (weeks months or more) the boiler was working fine with a two wire thermostat.
2. Since that time you have run a 5 conductor thermostat wire.
3. You installed a smart thermostat from ConEd
4. You did find a "spare" 24v wire that was disconnected from some odd little contraption sitting unused inside the boiler cover
5. And now you have a problem with the boiler that will not shut off with one relay or will not start with another relay.

Does that about sum it up?

If I got the information correct, then I will need a picture of how the boiler is actually wired. A photo of the wires inside the front door. A picture of the wiring diagram that is on the boiler (or the inside of the door), and a picture of the disconnected contraption.

Nevermind, I saw the photo you posted.

I can work with that.

The black contraption is a sparker that will relight the pilot of it blows out, That was an aftermarket add-on that would relight the pilot if it was blown out for some reason. That problem has since been fixed since your pilot is staying lit.

You can remove it from the boiler and cap off that remaining wire that is connected to it.

Let me do some homework on your problem with this new info. All of a sudden I'm having problems uploading pictures also. Maybe @Erin Holohan Haskell can look into this

tlmaurer63 · February 15

Close...we were having the trouble with the relay before the new tstat.

tlmaurer63 · February 15

wiring diagram

https://photos.app.goo.gl/4EuwFgqWu6XtvSVG7

EdTheHeaterMan · February 15

I can see where you may have a problem. The Smart Thermostat must be wired as I show on the diagram. R from the thermostat MUST be wired to the black wire that is connected to R on the transformer.
W on the thermostat MUST be wired to the black wire that is connected to G on the transformer
C on the thermostat MUST be wired to the C terminal on the transformer

Sometimes R and W from the thermostat can ger connected backwards, this is not a problem on 2 wire thermostats, but it is a real problem if you connect a third wire from C on the thermostat somewhere in the transformer. IT MAKES A DIFFERENCE. R to R. W to G. C to C. If you get that wrong then you can have real problems.

You must remove the RobertShaw black box and disconnect the blue wire from its source. or cap it off.

Where does the red and white wire go on the Limit? (letter B on the picture). Those wires must be removed. the only wires on the screw terminals MUST BE the Yellow and the Black. Not jumper or other control may override the High Limit. That is a safety feature and must not be jumped or bypassed. the red and white wire may be a jumper or bypass that may cause a dangerous condition.

Will post photo as soon as I can. EDIT. The file has the diagram ...but for now the unedited diagram is on page 4 of this I/O manual

109A_5 · February 15

Hello @tlmaurer63,
Looks like the Blue (the actual C wire) of the five conductor should have gone to the Blue of the abandoned ignition box (not Blue to Red), which actually goes back to the Green and the Blue wire on transformer.

The Red and White of the five conductor needs to be verified at the transformer (through the black wires) and at thermostat end too. Looks like they may be swapped.
Red wire to the R terminal on the transformer.
White wire to the G terminal on the transformer.

Back when it was a two wire thermostat it did not matter as much if R and W was swapped.

EdTheHeaterMan · February 15

Able to post pictures again. looks like @109A_5 has the correct info for you

A in the photo is going to the Spill switch on the draft hood
B is the photo is the limit that MUST have the red and white wire removed
C in the photo is the roll out TFE
D in the photo is the 6 pin plug to the vent damper

File below for zooming in

Mustangman · February 15

I have had a few run ins with Field vent dampers. I do know they are polarity sensitive. The directions even mention what the unit will and will not do if polarity is an issue. Another issue we have been running into a lot is the homeowner installs a smart thermostats which draws its power from the appliance transformer, All the sudden nothing works. The VA is used up operating the thermostats. We just ran into this last week. The system is a monster. He has 11 heat ones on 2 Taco Sr506s. We ended up adding a third Taco swithing relay to take the stress off of the transformers. Just something to keep in mind.
Steve

tlmaurer63 · February 15

Ed, R and W from the tstat were reversed. The R and W from the limit go to the device in the picture below. Should I still detach them? The W lug on the transformer has no power so is it ok to leave it attached to the blue wire from the sparker? That wire leads back to the C lug in the transformer?

C

tlmaurer63 · February 15

Actually, I see that since reversing the R and W from the tstat, the B wire has 24v. Should B still go to the W lug?

tlmaurer63 · February 16

OK, so after switching the tstat R and W and attaching the tstat B to the W lug, I'm up and running with the new relay. Thanks to all that helped me out!!

tlmaurer63 · February 16

Ed...one other thing. What is that device hanging off my limit? Should it stay or go?

EdTheHeaterMan · February 16

The R and W from the limit go to the device in the picture below. Should I still detach them?

Yes. That device is another limit control and is in the wrong location. The one in the boiler is all you need.

The W lug on the transformer has no power so is it ok to leave it attached to the blue wire from the sparker?

Remove it from the W lug on the transformer and remove the sparker from inside the boiler. It is just another thing that will confuse the issue in the future. If you don't need it, get rid if it.

That wire leads back to the C lug in the transformer?

What wire? if it is the blue wire then get rid if it. if that is the wire you are using to feed the thermostat C then just connect it directly to the C. You don't need more connections that can fail in the future. and it is a sign of poor workmanship. "I better not take it off because I don't understand it". You want it to be easy to follow the circuit, and have as few connectors as possible.

Weil McLain CG Boiler wont start after relay replacement

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