Weil-McLain boiler won’t fire
So first the boiler is a PFG6SPN Series 6, single zone.
yesterday we turned on the boiler for the first time this season and it seemed to be working fine, today however it’s not firing. At first I thought it was the thermostat, and I wanted an excuse to replace that anyway so I got a Honeywell Pro non programable one, now when it’s set to heat it just clicks and flashes the temp and a code of 10 n.
I’m thinking issue is in the boiler it self, the pilot is lit, and I can hear the relay clicking, I checked with a multi meter and I have a reading with each click from the relay but it doesn’t fire. Also while I can see it jump, I’m not sure of which contacts I should be testing and what reading to look for.
I don’t want to throw parts at it, as the gas valve alone is $740, so I’m just trying make sure I can eliminate all other possibilities before swapping it. My knowledge is limited to millivolt steam systems so the wiring in this is not my comfort zone.
something else I noticed is there is a wire spliced into the thermostat wire and then zip tied to the gas line with 2 little jumper things (photo) that then connect to each other, I don’t think it’s that, but I don’t know what it is, the diagram indicates it’s for multi zone but this is a single zone set up.
Any suggestions on how to test components or common issues with these would be great, so I can get back to hunting camp.
(Also I posed this an hour ago but accidentally deleted it when I was editing a typo)
Comments
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Do you have a multimeter or amprobe? something to perform electrical control test?
That device with the yellow spade connector looks like the spill switch but if that's is it it's definitely in the wrong location. it has a manual reset switch in the middle. You can reset it by pressing that. But then you need to figure out why its there and make sure that you are drafting. something is not right with that set up
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There are a number of safety switches in series with the gas valve. If any of them are open, they will keep the gas valve from opening. The relay you hear clicking is probably the relay controlled by the thermostat ("CR" on the ladder diagram), so that is OK. What you need to verify is that you are getting 24 volts to the gas valve when the thermostat is calling — and if not, figure out what is open.
Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
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you’re talking about those little round things on the gas line?
I didn’t know what they were, but they are wired in with the thermostat. Is that the spill switch? They have buttons on them, but they don’t depress. Not sure if they are stuck but if I use anymore force it feels like they would break (photo)
I have a cheap harbor freight multimeter, the issue is the read out is there and gone with the relay clicks before it can really display a value, with the multi meter set to ACV 200, I get readings of 202 to 2.4, but judging by the display I’m guessing it just slow to show the reading so not sure exactly how accurate it is.
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Forgot
the photo
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Is there a way to manually feed the valve the power to open? I’m getting a reading on the terminals at the valve (TR and TH) but my multimeter isn’t great and I don’t know if the brief flash it’s showing me is accurate or not.
I’d just do that to confirm if it’s the valve or something else, not to actually run the unit.
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Based on the wiring diagram you can eliminate many of the safety to test the gas valve with a quick test. use a jumper wire and connect the Y to the R on the transformer. if the valve operates, then the valve is not your problem. First you need to know if the transformer has power and is making ~24 VAC at R to C with a meter.
I have highlighted the path the power from the transformer takes in Red on both the ladder diagram and the Schematic diagram. the return path from the gas valve to C on the transformer is in Blue. This test eliminates the thermostat and the relay. if the gas valve opens, then the thermostat or the relay is the problem..
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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Saying this for your benefit, but I think that you are over your head over here. There are a lot of important safety things there, that are there to protect your life. If you don't really know what any of them are, you probably should not be working with them. Don't take this the wrong way.
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thanks for that it was a huge help, I jumped Y to R and the valve opened and ignited.
Does that mean the issue is in the relay/ transformer unit or should I be lookIng elsewhere?
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The part that is hanging out in nowhere that you are holding on to is supposed to be attached to a hot section of the boiler or the supply pipe as close to the boiler as possible.
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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OK that means that the thermostat is defective, the wire from the thermostat to the boiler is defective or the relay is defective. the transformer is working because it opened the gas valve.
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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I appreciate the concern, I’m not trying to bypass anything other than to test functionality of the parts. When I get to what part is malfunctioning, I’m just going to replace it with new parts in the same configuration.
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to test the thermostat and wiring to the thermostat you place the jumper between Y and G on the transformer
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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so one follow up on that, the thermostat is new (I can they can still be bad from the factory) but when the Thermostat is signaling the boiler to fire I can ear the relay in the boiler clicking, if I turn the thermostat off it stops the clicking at the boiler.
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Or one of the safeties is open, probably because whatever it is protecting from happened.
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could these potentially be the problem? Do they go bad?
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the only item I can see that would be a safety are the 2 buttons someone zip tied to the gas line (assuming that isn’t the correct location) I wasn’t really considering them to potentially be an issue only because they are spliced into the thermostat wire and the relay is clicking when it gets the call from the thermostat.
if they could be an issue can I bypass them to test, then replace them in the proper location?0 -
I can't quite tell form the pictures if it is hot water or steam. I'm thinking steam because of how the returns tie together, but it should have a low water cutoff if it is steam or an aquastat if it is hot water and it might have a vent damper switch on either.
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no it’s hot water, I miss the simplicity of my old millivolt single pipe steam system in my old house.
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SEE EDIT BELOW
" because they are spliced into the thermostat wire and the relay is clicking when it gets the call from the thermostat."
Then the thermostat circuit is operating properly. The clicking is the relay coil making that clicking noise. That means that the circuit with the thermostat to the relay back to the common is not defective. To be clear The thermostat calls for heat and the relay clicks once (not off and on multiple times) and when the thermostat call is satisfied (turned down) the relay clicks once to the off position.
We have determined that the circuit R with green jumper to Y to Limit to Gas Valve with return path from Gas valve to C is working when the gas valve operated and lit the burner.
We have determines that the R to the thermostat back the G to the relay coil and the return path back to C is working by the clicking of the relay coil.
That leaves the actual CR1 contacts in the relay and the wires that connect those contacts to the R and the Y terminls are the part of the circuit that is not working.
You can replace that relay with this part. https://www.supplyhouse.com/Jard-92340-DPDT-24V-Power-Power-Relay but I would check to see if the wires are broken off somewhere first. But we are zeroing in on the problem now. The relay is less expensive than the gas valve.
If that part is defective (the plate with the relay socket), then you can get the plate with the socket and transformer and relay for a lower price than the gas valve
This is a lower cost than the Weil McLain OEM part but it has everything you need plus a few more wires that you don't need. Just compare the old part to the new part when you get both in front of you and determine what wires are not necessary and cap them off individually. (don't wire nut several unused wires together because they may make a connection that you don't want connected.)
The Weil McLain OEM part number for your part is this 510-312-167 and is triple the cost for the same thing from White Rogers. The wire colors may have been changed to protect the innocent. (that last line is a Jack Webb reference)
EDIT Take a picture of the wires under that 4x4 plate to see how they are connected to make your replacement easier. then you can do the comparison. you want the wires that are in the same place on the relay socket, not necessarily the same color wire.
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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