Bonneville America Forums Forums Off Topic Discussion Forums Lounge Any HVAC experts out there?

I have a friend whose furnace just quit. It's a very old gas type. The valve that is operated electrically by the thermostat no long opens. The pilot light is separate from the valve and the valve is seperate from, and outside of, the furnace. My question is this. Will any "universal" 24V 1/2 pressure furnace gas valve work as a replacement? Are there any other considerations? I've installed dozens of water heaters and hundreds of gas stoves but never a furnace or furnace valve and I'd hate to screw this up.

Pilot light works... valve clicks when thermostat moved to heat but no flame? Have you checked the thermo coupler?

To Answer your question on the gas valve replacement Not all gas valves are interchangeable, there are many different variables to concider. I would only replace with a "Like Valve" I would Not recomend taking a Chance with Gas!!

"very old gas furnace" has anybody checked the heat exchanger?? and depending on the fittings and the rate at which the valve opens and closes...see to many veriables. it might be time for a new one, some antiques are hard to find parts for. but if the valve fits and has the same operating specs, you might be alright. maybe he should call a specialist to look the system over for leaks and other near future problems?? what has me concerned most is "very old"

Very old isn't always bad sometimes they are better made...usually they are better made. My oil burner is about 40 yrs old and works like a dream. Just had weatherization people out here to go over my whole house and they said it couldn't work anybetter. but like was said above DO NOT TAKE ANY CHANCES WITH GAS!!!! GAS GOES BOOM!!!!!! One thing to consider is the number of hrs on the unit. If it has been run alot it maybe time to replace I saw good advice above... have a qualified tech look it over for near future problems no sense in fixing one thing just to have another break!! And check for leaks...match works well!! LOL JOKING DON"T DO IT!! LOL I have never been comfortable with gas I had a close call once when a gas line was leaking behind my stove. turned dishwasher on and had a minor explosion...no damage but very close to a major fire I saw the gas burn back up inside the wall where the line came through!!! Thankfully it went out butr don't play with it better to spend a few bucks and be safe!!!

I agree with Chy, Sounds like A bad thermo coupler.It's only a 6 to 8 dollar item easy to take off.If its newer it will have a flame sensor rod that is sticking into the piolt flame, dose the same thing wont let main valve open thill it proves piolt.

No idea,but Happy Birthday,Chy!! Ride safe,Charlie.

I'd have the heat exchanger checked as well. If your buddy has his buddy look at it, chances are he's never had a regular service/inspection done. If the heat exchanger has little holes in it, carbon monoxide can get into living area. Enough of that and it wouldn't be called living area any more.

Usually there are 2 thinks that go bad on a furnace, the thermocoupler and the blower (fan). On newer units there are printed circuit cards that can go bad, but that shows up pretty soon after install.

Someone mentioned that older furnaces are built better, that's crap. They're built heavier which isn't better. You most likely should buy a modern efficent unit, in the long run you'll save tons of cash.

I checked the thermocouple and it is fine. The 45-50 year old valve is not opening. It is a single solenoid valve with just down the line from a small regulator. What I'm trying to find out is if the valve has to be replaced with a identical valve or if I can use a more modern universal replacement valve that operates at the same pressure and fits the same pipe.

Quote:

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a more modern universal replacement valve that operates at the same pressure and fits the same pipe.

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I think that would be all that matters Larry. That and if the solenoid is part of the valve that it is the same voltage.

HVAC over 25 years.

New gas valves are proprietary, old ones are not 'usually'.
Still, if you don't know, you shouldn't be working on it. It also make a difference whether it is propane or Natural Gas.
Knowing you will work on it anyhow...

1) Make sure gas and electric is shut off
2) remove gas valve and thermocouples
3) cap off gas lines DO NOT LEAVE THEM OPEN
4) take gas valve, thermocouple, and all the data on the furnace to an HVAC supplier and get a replacement. Note Propane or NG and voltage. Some gas valves are universal replacements and need to be further set up in the field per requirements. Also note - most will not sell to you if you don't know what you are doing.
5) Install suitable replacement reversing the procedure using gas teflon tape (yellow) and only black pipe (No galvanized)
6) clean the heat exchanger and check for leaks (soap bubbles on the joints)
7) check for back drafts (usually indicates a leaky heat exchanger) - a cheap and dirt way is see if cigar smoke sucks up the chimney from the burner area with the fan running
8) adjust/check flame using air intake to each burner - flames should burn blue with the tips licking yellow
9) adjust/check thermocouple flame - flame should surround couple tip, if not the orifice may need cleaning and/or pilot gas pressure adjusted
10) once you are absolutely sure everything is back where it was when you started WITH NO LEAKS, fire it up.
11) MOST IMPORTANT skip steps 1 through 10 and hire somebody.
12) clean the filter and oil the motor

PS many high efficiency furnace do not last. Only 80% of Natural Gas you buy is actually combustible. To make a 90% furnace you must burn part of the inert 20% - some of that is air (oxygen) and hydrogen. When you oxidize hydrogen, you guessed it, you get acidic water which is corrosive. I've taken high efficiency furnaces apart where the combustion fan had completely disappeared! I personally believe in middle efficiency for this reason. If you do buy a new furnace, buy the name brand with the least number of proprietary parts. Most brands are made by one of about four or five companies.