Weil McLain Cga Gold flame error SOLVED

mark2025

Hello everyone, I’m hoping to gain some insight into an issue we have with our Wel McLain CGa series 2 boiler. This boiler has three zones each with its own control valve. 2 zones are for baseboard heat and one zone is for indirect water tank. This may have been an issue for years but we never noticed it until we had a baby and tried to keep the house warmer.

Problem: Boiler only works properly when it starts a cycle and both zones for baseboard are calling for heat. When both baseboard zones are calling for heat, the system fires normally and continues to cycle normally. The other day I turned up both thermostats to observe and watched 17 start cycles occur and fire the boiler. The moment one of the two thermostats reached temp, the zone valve for that unit would close. The call for heat would continue from the other thermostat still trying to get to temp. At this point, the boiler would attempt to cycle on and fail to light. This is where it enters in to a lockout and eventually resets. By the time (1hr) it resets, both thermostats are calling for heat again and it runs fine. I can also reset it immediately by turning power off to boiler and turning it back on immediately. At this time, it will light the burners on first cycle, but fail on the 2nd or 3rd if both baseboard heat thermostats are not calling for heat. The error happens like clockwork. It doesn’t appear to matter which thermostat is satisfied and which one is calling for heat. The error happens shortly after a good cycle ends and it wants to run the next cycle.
When the error happens, the lights on control module are as follows:

Power: solid light

TSAT: solid light

Limit: solid light

Damper: solid light

Flame: blinking after failure. At the time damper light goes off as well.

When the failure happens, I’ve observed the spark pilot light, and then go out immediately. Burners never fire.

This one really has me scratching my head. The boiler can do unlimited cycles when both thermostats call for heat but fails when one is satisfied and the other calls for heat.

Boiler was installed back in 2016. We have a 3rd Gen Nest for both thermostats. One thermostat has heating and cooling and the other is set for heating only. The heating only was previously an old mercury thermostat. Both are using two wire line for heat. Red/white. When we upgraded the heat only thermostat, our electrician added a transformer for C. (March 2024). I thought this addition may have caused the issue so I reverted back to a basic 2 wire thermostat. Issue still persists. Like I said above, this issue may have been happening since original install but never noticed it until we had a baby and kept the house comfortable for her versus mid 60’s before. It’s more noticeable on cold days because temp drops faster before boiler is reset with power off/on or resets itself.

Thank you for your thoughts and let me know if you need any more info.

Solution here 1/17/2025

SOLUTION RIB relay installed between boiler control module and wiring. As suspected by the many great people on here, re-wiring did not solve the problem. With the freezing temps coming next week, I kept the appointment for today. I’m slammed at work this week and night time I didn’t feel comfortable running tests. After the re-wire failed, HVAC guy was puzzled and broke out the multimeter and placed a call to Weil Mclain. I believe this is one of the tests someone here asked to perform. Weil Mclain was told the problem and immediately knew the issue. I may get this not perfect but bear with me. While on phone, Weil Mclain said to test voltage coming in to boiler. It should have read zero when calling for heat or something. Instead it was showing a couple of volts. Weil Mclain said it was likely there was some induced voltage happening somewhere in the circuit. Other than tracing it back to something, the fix would be to install the RIB relay. It’s been running for about 2 hours now with no failures or both thermostats calling for heat. I was told that there were no safety concerns related to this solution. The end to all of this may not be perfect but now I have very clean wiring, labeled, etc. and a system that seems to be working now. As part of the re-wire, the low water cut off was removed from the thermostat line and done straight in to boiler. All in all, the total cost was probably higher than it should have been but as father of 1 year old that wakes up if too cold at night, I’m glad it’s now fixed. The re-wire was surprisingly fast and efficient. All in all, across three visits here, it was about 4.5 hours of which 3+ hours was today. Pic of new relay attached as well as new wiring. 
I guess my only lingering question would be: should what seems to be a very experienced HVAC technician caught this on visit one or two? Is this truly an oddity / rare thing. Thank you to all that chipped in with ideas. If it wasn’t for the deep freeze coming, I may have eventually found this by Sunday. My cousin suggested to me to install a zone relay box. That probably would have solved it though I wouldn’t know the issue at that point.

Mark

HVACNUT

Any ice build up on the regulator. That will lower lockup pressure. But it's sporadic so likely not the issue.

Lockup and manifold pressures need to be checked.

During the failed ignition attempts, there should be 24 volts between A and C for the pilot, then once pilot is proven, 24 volts between A and B for the main valve. Can you verify?

109A_5

Hello mark2025,

Does your system have a zone valve control module or just zone valves ? System pictures help us help you.

If I understand your description correctly, when both thermostats are calling everything works fine, then when one thermostat drops out and the other is still calling the boiler starts to act up, is that correct ? If things are wired correctly the boiler should never see that transition, electrically speaking.

I would disconnect both thermostats where they are connect to the system and temporarily mimic the thermostat activity with jumper wires (if needed). See if the boiler still acts up or it acts normal.

mark2025

@hvacnut No ice build up on the regulator.

I can give that test a try between A & B. I was home today and monitored the activity. I’m 100% confident that the issue only happens when only 1 of 2 thermostats call for heat. I can reproduce the failure at and time by going from 2 simultaneous calls to only 1.

I did read the manual and one of the faults that can lead to this lockout was labeled as “line polarity is reversed”. I’m not in this trade and talked to an engineering friend of mine. He asked me to take a look at the transformer. He said that the red should be connected to R and the white to C. In my case it is the opposite. The red is connected to C and the white is connected to R. I haven’t done anything with this information yet. Could this be causing the misfire? I traced the red back to module and it is going in to the TSAT port labeled as R in the manual. I’m a little reluctant to think this is the issue because it does fire correctly when two thermostats call for heat but fails when only one calls. I’m not an expert by any means. That’s why I came here. If it by some chance is the cause, it has probably been like that since the beginning. Like I said, we never noticed it because we kept the house pretty cold. I do recall it occurring but never paid attention as when I reset the main power it would kick on because house got cold and both thermostats were calling for heat. Here is a picture of transformer.

109A_5

Yes, typically the Red colored wire is connected to the 'R' terminal, often it does not matter, but it maintains uniformity. In your case with zone valves and NEST thermostats, the wire orientation may be an issue and it all should be review, especially if the boiler works correctly with jumpers as temporary thermostat substitutes.

HVACNUT

If you're using zone valves, which the third party transformer indicates, and if there's a third wire at the Nest, the Common can be connected.

I hate to blame Nest again, but if it truly is happening with only one zone, then...

R could be possibly landing on W at the Nest? we need more pics. Zone valves and thermostat sub base wiring.

mark2025

Yes, using three zone valves. One thing I want to clarify is that the nest in the 2nd level is being fed from two different sets of wire. The AC in attic space is sending a five wire bundle to the nest with 4 of the 5 wires connected at the nest. Y, G, Rc, and C. Inside the wall there is a two wire bundle coming from boiler that is R and W. The other day I checked behind the backing plate to ensure that the R and W feeding from the two wire cable were properly in the Nest Rh and W. They were. Pictures below. The ground level thermostat is currently run by a Honeywell battery powered. I went back to basic thinking it would be a solution and it did not solve the problem. The transformer that powers the zone valves also is connected to the low water sensor (pic also included).

mark2025

I have an extra heat only thermostat. I was thinking of swapping the last nest and having both thermostats be basic to see if things work normally. I’ll report back tomorrow. The house was originally wired for basic thermostats.

tcassano87

following curious to see what the issue ends up being. It feels like it’s 100% a wiring issue with either the zone valve wiring or the thermostats

Jamie Hall

Probably overkill, but…

What I think I would plan on doing is use a pair of RIB relays to isolate the thermostats completely from the zone valves and controller and the boiler. Each thermostat R and W would be connected to its relay coil, and the normally open contacts of the relay would go to the corresponding zone control.

The beauty of this is that it removes and possible power supply connection and phasing complications from the picture, and it seems very likely to me that this is what we are seeing here…

mark2025

Hello all, here is the update as of today. I ended having HVAC company come this morning after explaining the issue of failure only when 1 thermostat was calling for heat and the other was satisfied. They initially believed it could be a bad zone valve and checked them for continuity. Both zone valves had continuity verified. They the completely isolated thermostat wiring from boiler and manually fired it up numerous times. No issue. I mentioned the piece about the reversing of wires at transformer but he said that shouldn’t be an issue because the zone valves don’t care about polarity. He suggested that the Nest could be the cause and told me to remove it and and add the basic. If the issue persists, it must be bad wiring and would provide an estimate for re wiring. I’m going to swap out the nest this afternoon and do that test. I’ll will post back an update. Thanks everyone for the suggestions.

Mark

mark2025

update: removed the nest and put in basic Honeywell. Failed once one zone was satisfied and the other called for heat.

Will keep all updated.

mark2025

Flipped red / white wire on external transformer as well. As someone mentioned, polarity shouldn’t be an issue. It was not as it still failed when one thermostat was satisfied.

Re-Wire supposed to happen on Friday.

I did come across this thread and it feels like my issue. I mentioned it to the HVAC gentleman and he shrugged it off. The thread attached had similar issues and discussed faulty zone valves that triggered the relay when multiple called for heat but failed when one called. I guess I’ll know more Friday morning. Here is the similar issue I found on here.

https://forum.heatinghelp.com/discussion/178801/honeywell-zone-valve-end-switches-damaged-but-not-destroyed-by-surge-difficult-to-troubleshoot

mark2025

the reason I think it could potentially be the zone valve is because about 1.5 years ago we came home to a inoperable nest after a power outage. Could just be coincidence.

EBEBRATT-Ed

Not sure rewiring is the fix. Before I would rewire I would check that the wiring is done right and that you have continuity on all wires.

Once that is done, I would run it and see if the problem persists, then look at the zone valves.

Why spend $$ on something you don't need?

Question for the Nest experts.

If Rh is from the heat transformer and RC is from the cool transformer where do you get Common from heat trans or cool trans? Since common is on the heat side of the stat I would assume you get it from the heat transformer.

Jamie Hall

Oh good grief. You didn't mention that we were fighting a Nest…

We are not suggesting that you need to run new wires — so long, that is, that you have at least 5 wires to each thermostat. What we are thinking is that (particularly when doing battle with a Nest) we — and you — need to have a very clear understanding as to what wire (NOT colour — the physical wire) is connected to what.

mark2025

If it helps, I disconnected both nests and hooked up basic heat only thermostat and heat/cool thermostats connected to Rh and W. Both activated zone valve when calling for heat, but system failed once one stopped calling for heat.

mark2025

@EBEBRATT-Ed HVAC gentlemen went straight to calling for a rewire. From my limited understanding, the yellows on zone valves were all connected to the wires leading to 24v transformer. The reds were connected to line that went to thermostat connection in boiler. So, to a newb, they looked ok. I’m still guessing zone valve. HVAC checked end switch for continuity and said both were good. The article I pinned talked about resistance.

tcassano87

maybe this was said, but does only one zone fail after the other is satisfied or does it also happen in reverse?
Also do both thermostats individually turn on the boiler and let it run until the boiler is at temperature or the thermostat is satisfied on their own?

mark2025

@tcassano87

It happens in reverse. It doesn’t matter which thermostat is satisfied first. I’ve done it both ways and watched for failure.

I’m not sure I follow the second part. All Yellows on zone valves are connected to individual thermostats then spliced together to go into the boiler.

Mark

tcassano87

https://forum.heatinghelp.com/discussion/comment/1835101#Comment_1835101

what I meant was when you turn the two thermostats individually, each one turns the boiler on by itself without the other one being turned on?

EBEBRATT-Ed

The point is NO one can walk in there and tell you you need rewiring, unless the old wiring is badly deteriorated, or you don't have enough conductors in the cable to wire it properly.

They should be testing to find where the failure point is. This can be done without rewiring by using a test meter and some jumper wires. If at the end of that something needs rewiring, then so be it.

What will they do if they rewire, and it doesn't work?

They will come back and tell you they need mor $$$ to replace or add parts.

Jamie Hall

Back to basics.

First, label all your wires as to which one is connected to what terminal — because you are going to take them all off and want to be able to restore them. Take all the wires off except the common power return to the zone valves.

Second, jumper from T to T at the boiler. Does the boiler fire? I hope.

Third, take that basic heat only thermostat and hook it as one zone. Find the corresponding wires and hook one up to power (this should be a red wire, but if not, label both ends "red") and the other (should be white; if not label both ends "white") to the corresponding zone valve control terminal. Take a pair of wires and connect them to T-T on the boiler and the end switch on the zone valve. Turn up the thermostat. The zone valve should open and, when it does, the boiler should fire. If so, that set of wires and zone valve control connection are good. Add labels to mark them at both ends. If the zone valve doesn't open, jumper the control terminals on the zone valve. Does it open and the boiler fire now? Then the problem is in the wires or the thermostat. Otherwise the problem is in the zone valve end switch. If this test shows a problem in the wires or thermostat, go to the thermostat and connect the two wires together. If the zone valve doesn't open and the boiler run, the problem is in the wires — either one or the other is open or they aren't, in fact, the same wires at each end. Wouldn't be the first time… If something fails along the way in here, fix the problem before proceeding.

Fourth, do exactly the same thing with the other zone.

At this point you should be able to say that a basic thermostat on either zone will open its zone valve and fire the boiler.

Now call for heat from the zone with that thermostat. That zone valve should open. Now connect the identified thermostat wires from the other zone together. The boiler should keep firing and both zones should be open. Discontinue the call for heat from the thermostat. The other zone should continue open and firing, but the first zone valve should close.

You should now have a pair of wires at each thermostat which you know will open the proper zone valve, and you have just shown that the system will behave with basic thermostats.

You can stop there (get another basic thermostat) or you can now proceed to play with the Nests. You will need a third wire for each thermostat. This is "C", and the other end of each one will be attached to the same power supply terminal as the return wires from the zone valve control terminals. If you have a multimeter, check that you have 24 volts AC between the wire labelled "red" and C at each thermostat. If not, the wire labelled "red" isn't red. Try the wire labelled "white" instead. If that one gives you 24 VAC, the labels are switched. Fix it.

Now connect up the Nest. It should show it has power — and it should turn on the zone.

Sorry if this isn't clearer…

109A_5

The HVAC guy probably does not want to deal with someone else's wiring mess. IMO, he as with most others want to make their own mess an get paid for it, it is rare to see a nice wiring job. Will it fix your problem, time will tell.

If the thermostats, zone valves and boiler are wired correctly the boiler as far as a thermostat call should not even be aware that one thermostat was satisfied and drops out. The boiler and circulator may 'feel' the difference since now the heat load is different and the water flow characteristic may change too.

Does the HVAC guy for the money you are paying guarantee that a rewire will fix your issue ?

" The call for heat would continue from the other thermostat still trying to get to temp. At this point, the boiler would attempt to cycle on and fail to light. This is where it enters in to a lockout and eventually resets. "

Normally the boiler should just continue on running with no interruption, and no attempt to cycle and fail to light. To me this may be a boiler or system issue, since the zone valve end switches should be in parallel and electrically speaking the boiler does not know which zone is calling or how many. Maybe the zone valve wiring is really messed up and you are lucky it works at all. Or the boiler shuts down on a high temp limit and just has a hard time firing back up when the boiler's water temperature drops.

Hopefully the HVAC guy is prepared to resolve the issue even if it is not a thermostat wiring issue.

I'll review the other thread.

109A_5

OK, I read the other original post, good find. Micro-switches fail all the time and can have erratic closed resistance so two in parallel may act different than just one. Rewiring your system would not solve that type of problem, since a Micro-switch is not a wire. Someone that can take voltage measurements and understand what they mean when the system is acting up should be able to prove what the circuit defect is fairly quickly. Using a jumper wire to bypass the end switch is another diagnostic technique.

mark2025

https://forum.heatinghelp.com/discussion/comment/1835117#Comment_1835117

yes. Each thermostat can turn on boiler individually. If both are off and I turn one up, it will kick boiler on. The problem is that it will fail after a cycle or two. It only runs smoothly if both thermostats call at same time.

mark2025

That is what I’m worried about exactly.

mark2025

Thank you. Everything you say makes sense and I feel the same way. The wires are messy but I’m a newb and after some reading I can trace them all and they look good. Not a clean wiring but looks correct.

mark2025

@109A_5 thanks for the review. I mentioned this to the HVAC guy and he wasnt having it or I didn’t explain it correctly. I am going to try to test the resistance tomorrow, just so slammed at work and I don’t want to mess with it at night with temps in 20’s. Just in case I bungle something up. My cousin is an electrician and explained to me how to test resistance today. I’ll give it a shot. Hardest part is untangling the mess of wires to get to them. I’ll report back.

109A_5

I'd leave the tangled mess alone for now, (maybe not in your case) moving things can temporarily mask intermittent issues. Also IMO you are much better off doing AC voltage measurements than resistance measurements in this case, you will be seeing how the system dynamically works with the normal system loads. With voltage measurements you don't have to disconnect anything. With resistance measurements you have to shut the power off and/or disconnect the device under test. Also with resistance measurements the current provided by the meter is much lower and DC which in some cases may give you misleading information.

Voltage measurements may be easier to understand logically. Power sources (a transformer) should have a constant nominal system voltage. Loads should have nominal system voltage when turned on and zero voltage when turned off. Switches should have near zero voltage across them when closed (on) and nominal system voltage across them when open (or off).

A closed switch (like a Zone Valve End Switch) that has 5 volts across or an erratic voltage, for example, it is bad.

Inspect for loose wires and poorly crimped wire connectors, if any.

mark2025

SOLUTION RIB relay installed between boiler control module and wiring. As suspected by the many great people on here, re-wiring did not solve the problem. With the freezing temps coming next week, I kept the appointment for today. I’m slammed at work this week and night time I didn’t feel comfortable running tests. After the re-wire failed, HVAC guy was puzzled and broke out the multimeter and placed a call to Weil Mclain. I believe this is one of the tests someone here asked to perform. Weil Mclain was told the problem and immediately knew the issue. I may get this not perfect but bear with me. While on phone, Weil Mclain said to test voltage coming in to boiler. It should have read zero when calling for heat or something. Instead it was showing a couple of volts. Weil Mclain said it was likely there was some induced voltage happening somewhere in the circuit. Other than tracing it back to something, the fix would be to install the RIB relay. It’s been running for about 2 hours now with no failures or both thermostats calling for heat. I was told that there were no safety concerns related to this solution. The end to all of this may not be perfect but now I have very clean wiring, labeled, etc. and a system that seems to be working now. As part of the re-wire, the low water cut off was removed from the thermostat line and done straight in to boiler. All in all, the total cost was probably higher than it should have been but as father of 1 year old that wakes up if too cold at night, I’m glad it’s now fixed. The re-wire was surprisingly fast and efficient. All in all, across three visits here, it was about 4.5 hours of which 3+ hours was today. Pic of new relay attached as well as new wiring.

I guess my only lingering question would be: should what seems to be a very experienced HVAC technician caught this on visit one or two? Is this truly an oddity / rare thing. Thank you to all that chipped in with ideas. If it wasn’t for the deep freeze coming, I may have eventually found this by Sunday. My cousin suggested to me to install a zone relay box. That probably would have solved it though I wouldn’t know the issue at that point.

mark2025

just to clarify, today was 3.5 hours of which rewire done in under and hour with rest being testing and diagnostics before the call to Weil Mclain. Last 20 or so minutes was routine boiler maintenance, testing, and cleaning.

EBEBRATT-Ed

As I posted above you probably didn't need the rewire. It ran before and could have been fixed without rewiring. Yes, they probably should have found the issue in one trip

That being said it looks like they did a decent job and peace of mind is worth something

They probably just looked at it and it was messy and said "rewire" knowing they would find the issue during the rewire.

I can't say that is the wrong approach either.

You paid some $$$ but its working and they left you in a better place …..except in the wallet.

Paying for hack work is one thing. Looks like they did it right.

mark2025

Yes I’m not mad to pay for the rewire. It was definitely hacked before this.

mark2025

heat running smoothly all day. No more cold feeling in babies room.

109A_5

I guess what bothers me about this situation is if the Zone Valve's End Switches are possibly becoming marginal or getting tired, since either one of them should be able to command the boiler to work correctly (even if the other drops out). Adding the relay appears to have remedied the problem, since the relay coil may be more tolerant of the situation. Although relays may provide many years of service and may be good for 10s of thousands of cycles it does add another point of failure to the system. If the integrity of the Zone Valve's End Switches are fading the problem or a similar one may return at some point, since it was not properly repaired.

" It should have read zero when calling for heat or something. Instead it was showing a couple of volts. "

IMO a better repair would be to find the reason for the presents of the "couple of volts" and repair that issue.

Also IMO measuring the voltage across an End Switch that is supposedly closed certainly would not take long and probably should be the second test after measuring the voltage at the boiler's T-T.

Just my opinion from here.