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=VTP99;14930031]

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.