Goodman furnace keeps breaking gas valves

airflo mech

Is it 90% furnace?..check for crackes in heat exchanger.also check for co.i would suspect circuit board in blower compartment.change it...

weelbaro

Goodman furnace keeps breaking gas valves

I have a new goodman furnace. It is converted to LP and on a neighborhood LP loop where no neighbors are having any furnace issues. These are spec homes. Everybody has the same furnace, installed by the same people as me. I'm the only one w/ a problem.

The last step in furnace startup, after all tests have been passed is 24 volts to the gas vavle to open the valve. The valve gets 24 volts every time. It doesn't open. Gas pressure on inlet is a proper 12". Gas pressure on the outlet side is zero. It's not opening. A LP hotwater heater has been working flawlessly right next to the furnace for months.

The thing to do is replace the gas valve. Its faulty. The problem is the same thing has happened to two previous gas valves in the past couple of weeks. This isn't coincidence. What's frying my gas valves?

Brian_24

If it is a 90% check the hose on the pressure switch. If it can trap water it will give you fits.

Unknown

You may have an

intermittent break in the ground side of the 24 volt circuit to the gas valve. Replace that connection just in case.

Are you possibly at the end of the LP loop in your neighborhood? If so the quality of LP may be causing impurities to get into the valve and cause the valve to stick closed. Have your LP provider check for this possiblity.

I would also drop the inlet gas pressure to 10" or 11" W.C. as 12 is too high.

lchmb

one other thought

Has anyone checked to see what the lockup is on the gas pressure's? If your starting at 12" and the regulator is not functioning properly it could be to much pressure is damaging the gas valve (or a sign of undersized lines).

Home Depot Employee

With the pressure drop of 1-1.5" W.C. through the gas valve, you can't drop the pressure much or you won't get the 10" on the manifold side. Unless you wish to derate the furnace and risk firing back at the orifices. The pressure of 12" is perfect especially on a colder day.

Now for the problem, do you have your own regulator servicing your house/appliances? If not, you may be seeing spikes that may be locking up the gas valve as previously mentioned. Gas piping, being closest or end of the line on the supply pipeline may be the variable that causes only you to see the spikes in pressure, taking out your gas valve.

Unknown

The pressure of 12\"

is not correct as the lockup on the second stage regulator is around 12.8" W.C.

As for the 1" to 1.5" drop through the gas valve that does not really happen unless you are firing the gas valve at its maximum BTU which is not likely. In fact all the gas valves I know of the maximum allowable is 1" W.C. not 1.5". So lets say the valve is rated for 250,000 BTU's and you are firing it at 80,000 BTU's the pressure drop through the valve is less than 1/2" W.C. and of no concern. There are actually graphs for the graduated pressure drop as per BTU Capacity.

It would help to know the make and model number of the gas valve. Gas Valves are designed to work without lockup at 14" W.C. and below. My testing however has found that valves can actually still operate at almost 16" to 17" W.C.

How many houses are on this loop and what size is the main supply tank? What is your location on the loop?

Has anyone checked the gas valves you have removed to see if they are actually bad?

Home Depot Employee

Good Point Tim
I know you know what you are talking about