York Furnace - 3 Weeks & No Heat - What Parts?

mattmia2 · February 8

use where the pressure switch connects. + or minus is fine, it will just change the sign. read in inches of water (h2o). you are checking the pressure of the gas supply from the regulator at the tank or house

if the gas valve has an inlet pressure tap you can use that too.

I can't help with adjusting the valve itself, i don't know how to do that.

Ironman · February 8

York has a history of problems with that LP pressure switch. I just took one off a couple of weeks ago for the same reason.

As others have mentioned, it’s just there to confirm that there’s sufficient pressure coming in from the tank and that it’s not empty.

I’m not aware of any other manufacturer that uses that setup except on some very old furnaces with a White Rogers valve that had a mercury vapor thermal couple from over 40 years ago.

The flame rectification safety system on your furnace really negates the need for that switch, but since the manufacturer put it in the kit, I can’t officially recommend removing it.

LegendsCreek · February 8

I believe it's possible that my service provider wasn't even using it on my system. I forgot to take pictures when all of the problems started so I don't know for sure that it was disconnected always, but I found the purple wires and pressure switch disconnected when I took over the repair.

I just went down and hooked up my manometer to the port where the pressure switch threads into. I'm attaching 2 photos. The first photo shows the manometer with just propane filled in the tube and the furnace not being fired, and the second photo shows the WC while the furnace is firing. No idea what to make of it though, or if it helps solve any further issues.

mattmia2 · February 8

the pressure switch is way out of calibration if it is supposed to be 6" wc cut in.

mattmia2 · February 8

one more thing. i'd look at where that brass nipple screws in to the pressure switch and make sure they didn't plug up the inlet to the diaphragm with dope or tape. make sure however it vents to the atmosphere is clear too, there may be some sort of intention restriction on it to limit the amount of gas that can leak if the diaphragm breaks.

pecmsg · February 8

DO NOT Blow into low pressure switches. Nothing to measure with and you can damage them!

LegendsCreek · February 8

https://forum.heatinghelp.com/discussion/comment/1841362#Comment_1841362

These measurements were with no pressure switch installed. The pressure switch was removed for me to put the nipple on for the manometer reading, so the manometer shows the WC between the manometer and the propane tanks.

mattmia2 · February 8

yes. and the pressure it was seeing is far above where it should be closed when it is installed

LegendsCreek · February 9

https://forum.heatinghelp.com/discussion/comment/1841394#Comment_1841394

How would I reduce the pressure prior to the low pressure switch? There's no components between that switch other than a union and a shut off valve. Thanks!

mattmia2 · February 9

you don't want the pressure reduced. the switch is there to measure if the pressure from the tank is too low and keep the furnace from firing. since your pressure is where it should be, the switch should be closed when it is installed in the manifold and the furnace is on. something is wrong with the switch.

pedmec · February 9

So the furnace staying running with the pressure switch jumped out? did it run a full cycle?

LegendsCreek · February 9

https://forum.heatinghelp.com/discussion/comment/1841425#Comment_1841425

With the pressure switch installed, but not powered or connected to any electronics, the furnace runs normal. When I wire the low pressure cut off switch to the flame sensor, it fires for 5 or 6 seconds and then shuts off the cycle. This is after replacing my gas valve, and prior to that my propane company replaced the inducer fan. It's been one thing after the other. I was hoping to confirm that the switch is bad before spending $100 on it, but for now I am running the furnace without it wired (which didn't work before replacing the gas valve).

109A_5 · February 9

Assuming the low pressure gas cut off switch tests OK with a multi-meter and closes above 6 inches of Water Column (the diaphragm did not get stiff or something odd) and there is 6 inches of Water Column or greater of gas pressure at the low pressure gas cut off switch assembly inlet.

I suspect there is an electrical leakage path between the switch assembly and ground (the gas piping). The flame detection signal is very small and weak, it would not take much to compromise it with almost invisible debris or some coating compromising the switch assembly.

I would also simply measure the flame detection current in various places (with and without the switch in circuit) to confirm the switch is messing with the flame detection signal circuit.

If it was me I would just replace the micro-switch if I could get it out of the plastic mounting assembly. I would actually try to remove the switch from the the plastic mounting assembly and wash the plastic mounting assembly and rinse it well. I would also wipe down the micro-switch assembly with a clean tissue lightly saturated with 91% isopropyl alcohol and see if it makes any difference.

The micro-switch without the rest of the assembly is available as I posted above assuming you can remove it from the plastic assembly. Much less expensive.

LegendsCreek · February 9

https://forum.heatinghelp.com/discussion/comment/1841442#Comment_1841442

Thank you! I did see the micro switch part you posted previously, but after examine my switch with it disconnected from the nipple I can't for the life of me figure out how to remove it from the plastic housing. When looking at each point on it, I so see a very tiny set screw on it, but I assumed that was to adjust the pressure and I didn't want to mess with it. So you know how these might be removed from the housing? I think they're $5, which would save a lot of cash for sure!

mattmia2 · February 9

https://forum.heatinghelp.com/discussion/comment/1841446#Comment_1841446

the switch tested fine when you blew in to it, right? it is that it isn't closing when there is 10" wc on it.

Ironman · February 9

https://forum.heatinghelp.com/discussion/comment/1841431#Comment_1841431

The switch does NOT go in the flame sensing circuit. It goes in the circuit to the gas valve.

109A_5 · February 9

https://forum.heatinghelp.com/discussion/comment/1841450#Comment_1841450

Not according to the instruction sheet. See earlier posting.

LegendsCreek · February 9

https://forum.heatinghelp.com/discussion/comment/1841448#Comment_1841448

I can't say that it tested fine. I just blew into it and heard a click. There was no way for me to measure at what WC the click was made, because I was blowing into the nipple. There is no other port on it for me to hook up a manometer.

109A_5 · February 9

Well if the gas valve does not have an input pressure service port, you could just get a Tee and a nipple to insert between the gas pipe and the low pressure gas switch assembly pipe. Connect the manometer and the barb adapter to to the Tee to monitor the switch's change of state with the continuity test of the multi-meter. Open the manual gas shut off valve very slowly so you can see the change.

PeteA · February 9

@LegendsCreek

I know youre interested is saving a couple of bucks by just swapping the microswitch but the whole component does work together and it could be an issue with the diaphragm below the micro switch having debris or something else keeping it from rising up with that gas pressure that you have in the system which should be more than enough to make it work.

But if you really do want to inspect the microswitch closer it looks like there are actually just 2 little tabs that hold the switch in place (one side is shown below). You would use something like a toothpick to spread it on each side and slide the switch out of the plastic holder.

I would depressurize the gas line first so that the diaphragm relaxes, slide out the microswitch and check for any dust or debris in the plastic holder or the switch front. If you don't see anything or the testing of the switch doesn't yield any different results then reinstall it back into the plastic chassis and repressurize your gas and continue running the way you are and order a replacement for a permanent repair.

The parts are available and its a small price to pay for a long term reliable repair. The switch is not sold separately, it's going to come with a bunch of small parts that you do not need because your unit is already converted to run off propane so that's the main reason the kit costs as much as it does.

LegendsCreek · February 9

Thanks for the additional info everyone. I'll order a replacement tomorrow, and I'll get the entire piece. Hopefully it will be here on Tuesday, and I'll keep my fingers crossed that it will work properly once installed

Ironman · February 10

https://forum.heatinghelp.com/discussion/comment/1841453#Comment_1841453

Um, I beg your pardon, but the diagram clearly shows it in the circuit to the gas valve and every one of these that I’ve worked on had it there.

EdTheHeaterMan · February 10

https://forum.heatinghelp.com/discussion/comment/1841669#Comment_1841669

I doctored that diagram. The diagram on the furnace does not have the low gas pressure switch at all.

I added the purple part because I knew that it would work properly if placed there, but in the manual for the LP kit it clearly states that the purple wire from the flame sensor is to be interrupted by the low gas pressure switch.

I made the diagram because I could see from the conversations that @LegendsCreek was not understanding some of the terms we were using and guessing incorrectly what was needed. I'm sorry for the misunderstanding. I know that it will work but I didn't read the LP kit instructions which clearly wants to break the flame signal circuit.

I believe you will get the same result by breaking the limit circuit or breaking the circuit from the control to the gas valve. But the electrical circuit for the flame signal will put much less current thru the micro switch contacts. That should make the switch last much longer.

109A_5 · February 10

For what ever reason the instructions with the kit clearly states

And even they made the wire insulation colors match (kind of a clue in my book).

Apparently the engineers had their reasons, right or wrong, and they did not bother to explain it to the rest of us.

Also clearly the OP and others seem to have issues with this hook up or a failed switch assembly. I'm not there to come to my own electrical conclusions.

I would imagine the micro-switch should handle the current of the gas valve and the low gas pressure switch may or may not actually overall function better (and more reliably) if connected to the gas valve. And for all I know there is different instruction revisions with that kit over the years, I did not do and endless search.

Another example; Boiler I/O manuals usually clearly show how to build out the near boiler piping, so why is there so many amazing incorrect near boiler piping versions out there ???

mattmia2 · February 10

I suspect the reason is that the ignition control has a delay between loss of flame and turning off the main valve so if there is an issue with the pipe sizing or the responsiveness of the regulator if the pressure drops for a fraction of a second it doesn't close and reopen the main valve.

109A_5 · February 10

What mattmia2 stated does make some sense since propane is heaver than air and would not go up the flue as easy as natural gas, although I believe this unit has an inducer. So shutting of the gas valve or interrupting the flame detection circuit may have the same result. Although the flame fail post-purge and subsequent restart pre-purge may be a lot longer time delay than the gas valve going off then back on, so a safer method.

This low gas pressure switch may not have been specifically designed for this unit, but was an 'off the shelf ' addition by the factory as at least something to mitigate the propane fuel situation.

LegendsCreek · February 13

I received the the replacement low pressure cut off switch from SupplyHouse today. It came with a new wiring harness, and the switch itself looked a bit different from the one I had installed (the diaphragm inside the nipple was recessed on the new one, and on the old one it has closer to the end of the nipple). I got it swapped out, and wired it in series with the flame sensor. It works again! I plan on keeping it wired to the flame sensor, rather than the gas valve as discussed above, unless you guys tell me otherwise. I see that there was some back and forth and disagreements about where it should go, but I have it on the flame sensor for now. Thanks to everyone who helped, as always. As of today the propane company has still not called me back to come fix it, and I don't expect them to.

ratio · February 13

There should've been an installation manual with the new kit, do what it says.

PeteA · February 13

great job

I think that even with the back and forth that the color matched wires and the instructions included with the conversion valve points to the flame sensor being the location that York want it installed so you should be good to go.

York Furnace - 3 Weeks & No Heat - What Parts?

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