I have a Weil McLain
CGM-4-P1
Series 9
105000 BTU per hour
The unit will not shut off when then thermostat has reached temp. It continues to go until I kill the power. It did this once last winter but not again till this winter. I have elimated the thermostat because while it was calling for heat I undid the thermostat wires at the unit itself and it contined to function. The unit does buzz a little when calling for heat. I think it has to be the combination transformer-relay control center but before dropping money and time on that I wanted to get a second opinion. Anyone had these go bad and is there a way to test it?
Much appreciated for any insight. Thanks!

 

Hi Benn,

The relays on those combo controls do have a tendency to stick from time to time. I believe it's only about a $20 part and it plugs into a socket on the control.

Let me see if I can find the part number for ya... standby.

 

Here ya go.................................

510-350-223 - Weil Mclain 510-350-223 - Plug In Relay w/ 24V Holding Coil

 

Thanks NJ! Really appreciate the quick help and for even providing the actual part needed. Have a great night!

 

You're welcome, I just hope it's the problem!

What happens when the boiler continues to run and you give the relay a 'love tap' with the handle of a screwdriver? Does it shut off then?

One other question: when the burner continues to fire, can you tell if the circulator stops?

 

If I tap it it does shut off. The pump is going the whole time while its calling for heat even though the desired temp had been achieved. I got the part today so hopefully it works out. Will let you know!

 

Well... yes, that's what should happen... the pump should run during a heat call whether the burner is firing or not...

You said:

When the thermostat reaches temp, the burner AND the circ should shut down.

I was interested in knowing if the burner kept going AFTER the pump shut down at the end of heat call, or if they BOTH kept running after thermostat was satisfied.

Yes, change out that relay and let us know what happens.

 

We are on the same page. When the thermostat reaches temp the circulator pump continues to pump and the boiler will fire when water temp drops to 160ish up to 190. When I tap the relay everyhing shuts down when it realizes it's at temp. I got the part today as I said put looks rather different than what is current in place.

 

Hopefully nobody has changed out the control over the years and it has a different relay!

Takes about ten seconds to flip that wire 'bail' over and pull the relay.

 

bennhamm1's Library | Photobucket

 

Looks ok to me.......................

Turn off the boiler power, flip the wire bail over, pull out the relay and look at them side by side.

 

Ok problem solved! I had it my head that the "part" I was replacing was the thing next to it with all of the terminals on it. Thanks again for your help NJ. Your the man!

 

Just signed up to say THANK YOU to NJ Trooper. You saved my ass. Fixed my CGx-5 with that relay.

 

You're welcome Dave! Glad I could help!

 

NJ Trooper, I am having the exact same issue with my Weil McClain CG gas boiler and after reading a couple similar forums including this one I ordered the new replacement relay, installed it and the boiler still won't stop on desired thermostat temp. What would be the next item that I should check to diagnose this problem? Any help would be greatly appreciated. Also, when I first started having problems I replaced the thermostat with an exact replacement and that does appear to be functioning properly.

 

Do you only have one thermostat on this system, rather than several individual 'zones'?

I'm trying to define the problem in my mind...

If the relay had been the trouble, what would have been happening is that the boiler water itself would be getting too hot.

What you are describing sounds more to me as if the problem is that the ROOMS are getting too hot even when the thermostat is not calling for heat...

Is that correct?

Can you tell me what the boiler pressure / temperature gauge is reading?

Have you observed the boiler during a call for heat from the thermostat? When the thermostat setting is reached and the room is warm, do you know if the main burner stops firing? Does the circulator pump stop running?

 

I have my home in separated into two zones. One controls the majority of my home while the second controls about 1/4 of my home in which my mother in law lives. THe second zone(MIL) thermostat is set at off and I have the water valves set to "open" at the boiler so basically the main thermostat should be curently running the total home system.

"What you are describing sounds more to me as if the problem is that the ROOMS are getting too hot even when the thermostat is not calling for heat...

Is that correct?" Yes that is correct.

The water pressure gauge reads 20 PSI and the temp gauge reaches 180F and then the bolier shuts off and continues to circulate. After a while the boiler restarts and continues to heat my home past desired set temp. It does not appear as though the water gets too hot and the limiter seems to be doing it's job I believe.

I had completely disconneted the wires to the main thermostat with the second themostat(MIL) in the off position and the boiler continues to run. The only way I can control the boiler is to turn it on/off using the main power emergency switch.

This sounded so much like the prior persons problem I just went out a purchased the relay thinking that was probably the problem but after installing the new one the system continues to heat beyond thermostat setting.

Thank you for your help!

 

It sure does!

What is the full model of your boiler? CG(what?) ... look on the 'data plate' attached to the boiler.

 

By 'water valves', you must mean electric zone valves?

What make / model are they?

Set that valve back to "AUTO" and see if boiler stops heating.

 

Model is Weil McClain CG-4 PIDN Series #11.

"By 'water valves', you must mean electric zone valves?"

Yes the electric zone valves. I set them back to auto and the problem persists.

I will post the zone valve manufacturer and model number when I stop home for lunch.

I am mechanically inclined although I admittedly have limited experience with gas boilers, but this issue has me baffled.

Thank you again NJtrooper and will follow up with further info around lunch time.

 

I won't be able to view the manual until later this evening anyway...

Do you own and know how to use a multimeter?

 

The zone valves are manufactured by Taco and on one side the model number is 571 and on the other 573.

I do own and can use a multimeter.

Yes and thank you for viewing the manual and any additional help. No worries, I'll check back later this evening.

 

The first thing to do would be a couple easy checks at the zone valves themselves.

Measuring between terminals 1 & 2 , you should see 24VAC when the thermostat IS calling for heat and zero when it is not.

When BOTH of the valves are CLOSED, you should read 24 VAC between 2 & 3

When EITHER ONE of the valves are OPEN, you should read ZERO volts between 2 & 3

 

Not able to locate the series 11 control supplement, but I suspect that it is no different than the series 12 which I do have.

So...

There aren't really too many things that can cause your issue.

You've already replaced the relay, so that isn't it.

The other main thing would be the zone valves or the wiring to them, so the tests in the previous post need done and reported... and then we'll go from there.

 

Here are my meter readings



"Measuring between terminals 1 & 2 , you should see 24VAC when the thermostat IS calling for heat and zero when it is not."

571 valve reads 24 VAC but 573 valve reads 0 VAC



"When BOTH of the valves are CLOSED, you should read 24 VAC between 2 & 3 --- All of these meter readings are good."



"When EITHER ONE of the valves are OPEN, you should read ZERO volts between 2 & 3" --- All of these meter readings are good.


So the only anomaly appears on the 573 Taco valve reading 0 VAC.

Thank you again for all of your kind help!

 

Maybe... but that would mean that valve would never open. This is a different problem than the boiler continuing to run with no call for heat.

Let's clarify the test though.

Each valve is controlled by it's own thermostat. I'm not sure this was clear.

Maybe it should read as follows?

"Measuring between terminals 1 & 2 , you should see 24VAC when IT's OWN thermostat IS calling for heat and zero when it is not."

Is that how you tested? Measured 1 & 2 while manipulating the thermostat that controls that particular zone?

 

If this is true, and PRESUMING that they gave you the correct relay and that it was a good part, it means that there's a wiring problem inside the boiler.

 

Is there a wiring diagram for your boiler pasted on the inside of front cover?

If so, can you take and post a photo of it so I can be certain that it's the same wiring as the series 12 ?

 

"Measuring between terminals 1 & 2 , you should see 24VAC when the thermostat IS calling for heat and zero when it is not."

I took the readings after turning up mother-in-law zone thermostat to call for heat for that particular zone. The other "main" thermostat was in the "not calling for heat" position. After taking readings with both main and MIL thermostats calling for heat both zone valves read 24 VAC on terminals 1 & 2....my mistake sorry.

All other readings checked out also after second testing. I will send wiring diagram.

 

OK, so far so good.

Take some pics if you can of the inside of the front of the boiler where all the wiring is too.

 

When you pull the relay, does the boiler shut down?

 

Have been trying to upload photo of wiring diagram and keep getting rejected with error code. Will attempt again in the morning.

Will also try pulling the relay when the boiler is running to see what happens and report.

Thank you again for your patience and help.

 

Maybe too large size...

Try a free account at Photo and image hosting, free photo galleries, photo editing and post a link to the album here.

 

Good morning. Here is the link to boiler photos and wiring diagram. Please let me know if you need any other photos or details.

Also pulled relay while boiler was running and the boiler did shut off.

karen_hoffman1's Library | Photobucket

Thanks again for your patience and all of your help!

 

This is strange... it definitely points to the relay being 'stuck' because:

Measuring between terminals 2 & 3 on the zone valves with both zone valves CLOSED and not calling for heat has yielded 24VAC, which means that the zone valves are NOT telling the boiler to fire.

This means that the relay is NOT being 'told' to pull in and fire the boiler. Both of the zone valve endswitches are OPEN.

This rules out a wiring issue, such as a burnt and shorted wire...

Now, let's go to the wiring diagram:

I've traced the 24VAC line in RED. This is the line that tells the boiler to fire. CR1 is the relay contact responsible for energizing the line to the right of the "Y" terminal and sends the 24VAC ultimately to the "TH" terminal on the ignition control.

Circled in BLUE, the RELAY COIL that gets energized by the THERMOSTAT or ZONE VALVES (also circled in BLUE)

What is supposed to happen is that when the thermostat or zone valves CLOSE, they provide power to the RELAY COIL, which pulls the relay in and CLOSES the CR1 relay contacts. This sends 24 VAC through the safety switches and ends up at the "TH" terminal which tells the boiler to fire.



Click here for full size image

 

If pulling the relay caused the boiler to stop firing, it means that the relay contacts are CLOSED.

With the relay re-installed and the boiler running:

Take your multimeter and put one lead on the "C" terminal (which is grounded to the chassis, so any clean unpainted chassis connection will do) and put the other lead on the " Y " terminal.

When there is NO CALL for heat, there should be ZERO volts at that point.

Leave the one lead on C or GROUND, and measure the " G " terminal. When there is no call for heat, there should also be ZERO volts at that point.

 

What the above will tell us is whether the relay is being 'told' to close, or if the new relay is bad.

If you have ZERO on the " G " terminal, and 24VAC on the " Y " terminal, there is nothing but a bad (or WRONG) relay that can cause this problem!

 

If on the other hand, you DO HAVE 24VAC on the " G " terminal, it means that the relay is being TOLD to pull in.

BUT, this seems very unlikely due to the fact that you reported:

Which is why I'm leaning toward a bad or wrong part.

What is the part number of the OLD relay, and the part number of the NEW relay?

 

First I want to make sure I'm taking the readings from the right terminals. I have enclosed a link to a drawing I sketched of the terminal board with which I am taking the readings from to make sure I'm doing this in the right location. It's a little tight when trying to read the terminals designations even with a droplight/flashlight so please bare with me.

karen_hoffman1's Library | Photobucket


If I am taking the readings in the right spot when taking the reading from terminal Y to chassis(ground) with the boiler running but thermostats not calling for heat I'm getting 24 VAC. Also taking the reading from terminal G to chassis(ground) I am also getting 24 VAC.

I hope that I was doing this properly and if not let me know and I will go back for more readings.

The original relay(which I did replace) had a part number of 91-11206-11000 and the new one that I ordered and now have installed was cross referenced to 510-350-223. The (new) part they shipped me shows being cross referenced on the invoice to 570-350-223 and described as "RLY DSPT 24V". The new part has a sticker on it and the part number reads Honeywell R8222U-1006.

Hope this helps and thank you again for your help.

 

The fact that you have 24V at the G terminal is saying that the boiler is being 'told' by some external source to run.

This is contrary to what you are reading on terminals 2 and 3 of the zone valves.

Those two blue wire nuts... undo and disconnect one of them.

Does the boiler stop?