Weil-Mclain CG gas boiler: no ignition

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Old 04-10-20, 09:50 AM
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Weil-Mclain CG gas boiler: no ignition

I have a WM CG gas water boiler with an Argo ARM842 4-zone relay. Yesterday, we noticed that the heating is off despite water was circulating. So, I spent most of the afternoon and night debugging this issue. This is what I have found:

1. when a thermostat calls for heat, relay turns on green LED and turns on the circulation pump, but the boiler won't start - damper won't open, and no ignition. I measured the voltage: between X-X terminals, it is always 10~11VAC no matter it is calling for heat or not. I unplugged the Camron LY2 20VAC relay and measured the pings, it looks fine. I swapped the relay to another circ pump relay, did not change anything. is this normal?

2. according to the the service manual (see below URL), page 51, I measured C&Y terminal voltage is 4VAC when not calling heat, and 26V when any thermostat is calling for heat. is this normal?
https://www.weil-mclain.com/sites/de...1-manual_1.pdf

3. the Effikal damper has power, using the button on the back, if I switch to keep open mode, I can see it turns to open position; if I switch back to automatic, it closes. However, it won't open automatically when calling for heat.

4. in the manual, page 51 above, it asks for terminal C and yellow wire of the vent damper connection - I had to unplug the molex cable to measure, but the voltage is 0, even when calling for heat.

5. from the diagnosis diagram on page 51 above, it says "Check for open thermostat, LWCO, high limit, spill switch or rollout thermal fuse element contacts or check for loose wire connections".

5.1. I checked the thermal fuse, it is continuous (0 resistance), so I suppose it is ok.

5.2. I don't know if my system has low water level or high pressure - my gauge is damaged and I could't tell. I added water to the system using the manual Watt regular valve until it won't flow in. But the pressure relief valve starts leaking water, indicating that the water is likely too much in the system.

From the above description, would you see anything I can do/try to fix the problem?

All pictures of the relay, piping and boiler circuitry can be found in this shared folder

ttps://photos.google.com/share/AF1QipOrGp_uAkwkCG86_GpF6ftWf78vIf8nmR1UsF89Dcq9ByAMkF92z1NY6FaiE1OlBQ?key=elVqMjBLelZMUXQtSjBFeDZyVE9iZzFBNFFtdWZ3

My model is CG-7-PIDN made in 1991. The circuit looks almost the same as in the CGa Gold manual on Page 34 (Fig. 23).

Your help is much appreciated!
 
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Old 04-10-20, 10:12 AM
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I want to mention two things that might be related - perhaps give some hints on what I might did wrong in the past

1. I have two Emerson Sensi wifi thermostats (the other two are Nest). I noticed for several times that Emerson thermostat does something wield when it loses connection to the wifi (either due to low battery, or router offline). When this happens, it repeatedly calling and un-calling heat- making the relay keeps clicking. I noticed this happened yesterday noon, right before the heating went off.

2. my water circulation pipes often has water flowing sound, and I thought it was trapped air but did not know to purge them, so in the past, I simply manually push up the feed-in water regulator to add a little bit water. Because my boiler's pressure/temperature gauge is broken, so I am not sure what is the water level. I know this may not be be best thing to do, but was not motivated to fix the broken gauge because the air sound went away, making me think that adding water was the right solution.

I am not sure if the failure to ignite is related, just leave these here in case it is helpful for diagnosis.
 
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Old 04-10-20, 10:14 AM
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Hi, will it fire when you manually open the damper?
Are there any flashing LED’s?
Do you have 24 VAC on terminals C,R on the transformer?
Are the terminals X X on the bottom left of the ARGO control closed? use you volt meter to test.
Geo
 
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Old 04-10-20, 10:32 AM
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Welcome to the forums.

One problem I can see from the get go is that controller will not run 4 wifi stats properly.
It only has a 24va transformer which is not sized to handle much external load.

That schematic in that manual shows a control module.
You don't have that..... or at least not shown in your picture.
The module in your picture is for ignition only.
 
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Old 04-10-20, 11:15 AM
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@Geochurchi and @PJmax , thank you so much for your prompt replies.

>Are there any flashing LED’s?

no, I don't see any flashing LEDs in the relay or the boiler

> Do you have 24 VAC on terminals C,R on the transformer?

yes, C&R has 24 VAC present, regardless if the thermostat is calling or not

> Are the terminals X X on the bottom left of the ARGO control closed? use you volt meter to test.

I measured it, it always shows 11-12VAC no matter the XX LED is on or off (XX LED turns amber/on when any thermostat is calling for heat). I swapped the relay with another one, same readings.

> One problem I can see from the get go is that controller will not run 4 wifi stats properly.
> It only has a 24va transformer which is not sized to handle much external load.

I had 3 wifi thermostat for a couple of years, and the last one, a nest, was added last fall, and been running ok. I just removed/disconnected the two Emerson thermostats, but unfortunately I am not able to see any difference.

> That schematic in that manual shows a control module.

> You don't have that..... or at least not shown in your picture.

are you referring to the Honeywell Continuous Re-try module in this picture?

https://photos.google.com/share/AF1Q...9iZzFBNFFtdWZ3
 
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Old 04-10-20, 11:18 AM
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The XX terminals should create a dead short when calling for the boiler.
Yes.... that is an ignition module. That manual shows a control module. Two different devices.
 
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Old 04-10-20, 12:37 PM
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thanks Pete. It seems that this control module is only available on the CGa gold module, and on my CG model, the picture is all I have - it does not have such control module. The Honeywell module does not have any LED, but I am happy to take a picture of the pins if it helps.

I just went and took another measurement of x-x terminal, yes, it is shorted when the LED is on (call for heat). resistance is 0 and VDC is 0. I previously measured it using the VAC mode in my pocket multimeter, and it always reads 10VAC for some reason. but I think that reading was incorrect.
 
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Old 04-10-20, 01:11 PM
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Ok.... well that eliminates the zone controller for problems.
When there is no call for heat there should be 24vAC on the XX terminals.

A powered damper was discussed. Do you have one ? Is it opening ?
There are a number of safeties in the XX switched line.
Look at the ignition module..... the yellow wire on TH gets 24vAC when the boiler should be firing.
Follow that yellow wire. It will go thru switches and it should end up going to one of the wires to the XX terminals. The idea is to find out what is opening that yellow wire. The damper also interrupts it.

I could tell you exactly if you were to post an actual diagram. The ones in the book are representative and that book is newer than your boiler. There is usually a diagram glued to a service door.
 
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Old 04-10-20, 01:31 PM
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thanks Pete, the circuit diagram of my boiler can be found in this photo

https://photos.google.com/share/AF1Q...9iZzFBNFFtdWZ3

for the damper, it seems to respond to the toggle switch in the back - it responds to switching from automatic to keep open, or the other way around, but it does not make turns when calls for heat. I switch it to "keep open", and it did open, and then turn on thermostat, but still no firing.

the xx terminal is not 24VAC. I got a few readings and still don't fully understand what it means.

1. when the boiler is off (switch toggled to off), the voltage between pairs of connectors in the relay are all 0, except xx, which gives me a 45VAC reading.

2. when the boiler is just turn on without heat calls, xx is 12VAC, but it is open circuit (large resistance)

3. when the boiler is on and there is a heat call, xx is 10VAC but resistance is 0, which means it is short.

don't know if this means anything to you. appreciated for your input again!
 
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Old 04-11-20, 05:40 AM
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Hi, circulator runs so that proves that the ARGO control is working, next step is to find out which safety is holding the module out, attach one lead of your meter to a ground point “C” terminal and work through the safety circuit Y-W - all the way through TH on the module .
Check all connections on the module especially the grounds make sure they are clean and tight.
Geo
 
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Old 04-11-20, 07:01 AM
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thanks a bunch @Geochurchi! I found where was the problem - following your suggestion, I measured voltage C to Y/W/R etc, and found that the C&Y is 24VAC, but C&W is always 0. So I trace the wires, and see it connects to a small black switch, i.e. the spill switch - for some reason, I thought spill switch is for water spill/pressure relief related, but did not expect it to be on the chimney.

(correction: I think it is the "roll-out switch", see this picture)

After pressing the red reset button on the pill switch, the boiler finally starts as usual! yee-hoo! after two cold nights, finally we can have heat back on again.

I have two more questions if you don't mind:

1. at some point, I thought the low water level was a culprit that holds the ignition, so I manually filled in more water by pushing up the lever on the regulator of the water inlet, but then when I slightly depress the pressure relief valve, it runs water out of the pipe, and I got about 8-10 gal water.

is this something that I should be worried before I turn it full on? will the expansion talk and the water relief valve takes care of excessive water? or it is dangerous - I wish I had replaced the pressure gauge so I can tell.

2. there is a device with a dial-shaped piece to the left of the control module - see this in the picture, on the top-left corner.
https://photos.google.com/share/AF1Q...9iZzFBNFFtdWZ3

it is in series to thermo-fuse, so from the circuit diagram, I assume it is a "limit" switch. I moved the dial slightly, I am wondering if I should move the dial to a certain point ? it was slightly point to the right of the middle pin.

thanks so much for many of your inputs! so happy it is working now
 

Last edited by Qianqian Fang; 04-11-20 at 08:32 AM.
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Old 04-11-20, 07:19 AM
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Hi, glad you found the problem, I would check to make sure your flue pipe is clear, not sure what the limit on the left is, is there a probe that goes into a well on the boiler? I wouldn’t be adjusting it until you know what it is, any mfg. or model # on it? really can’t help you much with the water situation, maybe one of the boiler guys on this site will jump in, I don’t believe I would be adding water unless I new what I was doing.
Geo
 
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Old 04-11-20, 08:41 AM
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I plugged all thermostats back, turned the boiler on, and all zones are heated up normally.

During my restarting process, I observed the relay rapid clicking again - I took a short video

https://photos.google.com/share/AF1Q...9iZzFBNFFtdWZ3

I suspected that it is again due to my faulty Emerson wifi thermostat (although both of which were set to "Off" but connected on the wall). I removed them from the wall, and the clicking disappeared. I reset the wifi connections for both thermostats, and plug them back, switch to Heat mode, so far so good.

Another thing I observed is the bubbling from one of the pressure relief valves, see this short video

https://photos.google.com/share/AF1Q...9iZzFBNFFtdWZ3

this only happened when the flame was one, and disappeared after a few heating cycles. I see the rust on that valve, so I assume this happened before. Is this expected?

anyways, thank you all for your help! it feels good to have the heat back after two cold nights.
 
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Old 04-11-20, 11:33 AM
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Hi, I would try removing the thermostat wires, one zone at a time from the terminals on that control and see how it behaves, is there any current rating on those stats ? Also you didn’t post any information on that other control on the left side.
You really should have a working pressure gauge on that boiler, it’s hard to tell what’s going on, is the temperature/pressure valve blowing off?
Check out this link, page 16 for relay chatter.
https://argocontrols.com/sites/defau...-AD4%20IOM.pdf
Geo
 
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Old 04-13-20, 07:53 AM
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thanks @Geochurchi. The boiler has been working fine since it fired again. I did not see the relay chatter again. But reading the relay manual you posted, it seems like my 4 wifi thermostat is too much for the relay to drive. I will switch the Emerson ones back to a non-wifi thermostat today to lower the load.

Regarding the gauge, it is rusted, and I dd not know if I could trust the readings, see a picture

https://photos.google.com/share/AF1Q...9iZzFBNFFtdWZ3

The water pressure is always close to 0, even I added water to the system. I will definitely look into replacing it (need to find a tutorial/video on how to do that safely and a compatible part).

Other than this, I noticed two minor things after the system restarted:

1. there is a rattling sound for two zones at the beginning when the boiler heats again, now they are quieter, but still can hear occasionally. If you turn on your audio, you can hear the noise from this video
https://photos.google.com/share/AF1Q...9iZzFBNFFtdWZ3

is this the so called "air hammer"? does that indicate there is air in the system or just pipe expansion?

2. One of the 4 zones has a slow circulation (2nd floor). Other zones take almost within 1 min to feel hot for the returning pipes, but this zone took over 10 min to feel warm. The pump is working, but seems there is high water resistance.
 
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