Janitrol gas valve voltage

[ParamountAir]

Issue with Janitrol furnace --

Goes through normal sequence on call for heat - inducer on, pressure switch closes, HSI glows, then gas valve doesnt open. Interesting that the valve has 15-16V consistently until board calls for main valve to open, then 26V at the valve for a few seconds. The 15-16v is to chassis ground and ground on the valve terminal.

I thought there would be no voltage on the valve until a call from the board, thoughts?

[pacnw]

safety or bad valve or loose connection or bad board or?

[Ductfisher]

What is your inlet gas pressure? LP or Natural? If you have good inlet gas pressure and no outlet pressure when there is 24 volts across the gas valve coil then the gas valve is bad.

[billg]

I think it's a bad valve.

[Joehvac25]

Double Check with the manometer the out let pressure. If you have 24v and no outlet pressure then well you get it. First verify you have inlet pressure though

[VTP99]

[QUOTE=ParamountAir;14929331]Issue with Janitrol furnace --

Interesting that the valve has 15-16V consistently until board calls for main valve to open, then 26V at the valve for a few seconds.


Something seems fishy here. Sounds like some kind of back feed. Are you sure your transformer is not weak ? I would think that the ignition board would not leak voltage till a call for the main valve. How many wires go to the valve ?

[Joehvac25]

[QUOTE=ParamountAir;14929331]Issue with Janitrol furnace --

Interesting that the valve has 15-16V consistently until board calls for main valve to open, then 26V at the valve for a few seconds.


Something seems fishy here. Sounds like some kind of back feed. Are you sure your transformer is not weak ? I would think that the ignition board would not leak voltage till a call for the main valve. How many wires go to the valve ?

I bet it's a false reading, one other thing is look for the cracks on top of hx

[billg]

The coil in the gas valve is open, once you change it the 15-16 volts will go away and it will function when it gets 24 volts.

[ParamountAir]

Yes, definitely something fishy. I must have measured it started the unit 10 times and measured voltage to make sure my readings were correct. There are 3 terminals on the valve, MV, PV (factory jumped) and C. Where could the 15 volts be coming from?

Thanks!

[craig1]

There are 3 terminals on the valve, MV, PV (factory jumped) and C. Where could the 15 volts be coming from?

Thanks!

the 15 volts is phantom voltage. When you have a wire connected to nothing (open relay on one end, broken gas valve on other) Voltage will be induced in it just by its proximity to other wires with current flowing in them.

If you put any kind of load on the wire its voltage will drop to 0

[chaard]

It's not uncommon to see the 24v split across the secondary of the transformer. 12v on one side to ground. 14v on other leg to ground. Together 26v when load is applied.

[billg]

On Goodman common side of 24 volt transformer winding is grounded to chassis.

[chaard]

I thought that after I posted. But it does happen, especially on 240v units.
I have come across 2 different units that was 120v to ground on secondary side with no load. 24v with load. Still have never figured that out.

[ParamountAir]

@ Ductfisher - 8.8 IWC inlet, nat gas 24V across coil.

[ParamountAir]

Thanks for the replys, I will pick up a valve in the AM

[hurtinhvac]

If your safeties are holding steady all the way thru to the HSI being energized (the pressure switch is the only one likely to drop out and cause issues at the beginning of a cycle, the rest would not permit any action at all), you have 24 volts across the gas valve for a couple seconds until trial for ignition fails, you hear no click of the valve, or even if it clicks (or chatters) and you smell no gas...

90% of the time it's a bad valve. Just make sure you have gas service. Ignore goofy low voltage readings, they serve no purpose unless you are in controls.

Not exactly a RSES SAM...but it's been my experience.

[Cosmicmuffin]

Great info... I made up a test 24v. Transformer.ext. cord to 115v / two jumper wires. Eliminates quessing board wiring! I have seen 24v to valve,but if its not grounded thru another switch it "wont" open! Note; clicking of valve is not always accurate either..Goodmans latest bulletin states both Hi And Low side power is needed to open gas valve in two stage models.an auditable noise is no longer a true test!

[Cosmicmuffin]

I have had two calls this year same thing.H.S.I would glow but NOT lite the Nat. Gas. I now always test with an open flame "Torch". Repositioning HSI...,or replacement have been my remedy.But to be honest...,not sure why! No call backs yet!

[VTP99]

[QUOTE=Cosmicmuffin;14933661] I now always test with an open flame "Torch".

Yes...This is a very good test to fool the board and check your gas valve. I would try this if you have not yet. Keep us posted with the outcome.

[hurtinhvac]

[QUOTE=Cosmicmuffin;14933661] I now always test with an open flame "Torch".

Yes...This is a very good test to fool the board and check your gas valve. I would try this if you have not yet. Keep us posted with the outcome.

Surely you jest...

[VTP99]

Surely you jest...

Nope....serious as a heart attack !

[Core_d]

Ever check if that 16v was comin outta the board?

[hurtinhvac]

Nope....serious as a heart attack !

{sigh}

[VTP99]

{sigh}

I also sometimes do this to bleed the air from the line if I had to open it for a repairs. Just last night I started up a 12 ton Carrier RTU. I had no air in the line up to the shut off valve. So the only trapped air was from that point to the burner. It took about 10 times of letting it work the air out before it lite. I was just getting ready to get my torch when it finally hit. Had I had my torch handy it would have been one time.

[timjimbob]

Modern digital volt meters use very little current. (loading the circuit)

Have you ohmed the gas valve coil? Open or bad winding would not load the GV circuit enough to bring voltage to zero.

[hurtinhvac]

Had I had my torch handy it would have been one time.

Got that right...one and done.

[ParamountAir]

Gas valve replaced....works perfect!