# Gas Valve?



## sansanity (Jan 31, 2012)

Howdy,

Troubleshooting old day & night furnace and its not cooperating. Pilot on and blue but wont ignite burners. Gettin voltage at gas valve and no resistance at limit switch. My main HVAC colleauge looked at it and told me to rewire it as wiring was a little old and brittle. All new wiring and still no ignition to burners. Can it be anything besides the valve?


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## user84377 (Jan 7, 2012)

sansanity said:


> Howdy,
> 
> Troubleshooting old day & night furnace and its not cooperating. Pilot on and blue but wont ignite burners. Gettin voltage at gas valve and no resistance at limit switch. My main HVAC colleauge looked at it and told me to rewire it as wiring was a little old and brittle. All new wiring and still no ignition to burners. Can it be anything besides the valve?


If your pilot is burning properly w/o having to continually hold in the pilot gas "button" on a thermocouple set up OR if the pilot is burning properly on a re-ignition style pilot system....

AND...

you have the proper voltage on the proper Main Gas Valve terminal....then there will be gas going to the main burners. 

Before simply condemning the gas valve check for proper gas pressure on the outlet side of the valve (manifold side).

If you are unsure of any of the above safe yourself a disaster and possibly a ticked off customer and call a qualified service tech.


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## Dr Heat (Dec 25, 2008)

Power to it nothing through it throw it away


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## user84377 (Jan 7, 2012)

Dr Heat said:


> Power to it nothing through it throw it away


Incorrect.

1) You check for outlet/manifold gas pressure. Too low...check for inlet gas pressure. 
2) Too low of inlet.....locate supply gas pressure problem and have fixed. 
3) Inlet correct but outlet too low...check internal regulator. 
4) Inlet & Outlet right...check burner ports (spuds).
5) If all the above checks out and the pilot sensor (whatever style) is proving the pilot and sending the proper voltage to the proper main gas valve terminal THEN you can replace the gas valve.

Don't be part changer...take the time to solve the problem...only then will you have confidence that your diagnosis is right. It's great that you are working to figure it out rather than walking away. Good sign of a good tech.


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## Dr Heat (Dec 25, 2008)

CAS said:


> Incorrect.
> 
> 1) You check for outlet/manifold gas pressure. Too low...check for inlet gas pressure.
> 2) Too low of inlet.....locate supply gas pressure problem and have fixed.
> ...


If the Gas valve is not opening how do you check outlet pressure
How do you check the internal regulator?
How do I check pilot sensor is proving pilot if the pilot is not lit and no burner.

We most likely need additional info from the OP but if you have power to the PV or MV and the gas valve is not opening put in a new gas valve. 
I am making a few assumptions here:

1). At one point in history this was a working furnace
2). The OP has checked that there is gas in the building
3). The OP is from earth
4). etc.

Now it is nice that you got question 239 correct "take the time to solve the problem...only then will you have confidence that your diagnosis is right." 
:no:But insinuating that because I can diagnose a bad gas valve without checking to see if the correct burner orifices (spuds) have been installed makes me a parts changer is just rude. :whistling

Sorry had to edit as I saw something in the OPs that changed my response. If I read the OP correctly this is a standing pilot furnace and the pilot is staying lit. So. power to it nothing through it throw it away. An old Day Night will likly need a V800 valve. But I need more info to confirm that.

But what do I know I'm just a parts changer.


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## flashheatingand (May 3, 2008)

OP could have "dropped" the common. That could explain why 24v at the valve but no fire.


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## user84377 (Jan 7, 2012)

Dr Heat said:


> *If the Gas valve is not opening how do you check outlet pressure
> How do you check the internal regulator?
> How do I check pilot sensor is proving pilot if the pilot is not lit and no burner.*
> We most likely need additional info from the OP but if you have power to the PV or MV and the gas valve is not opening put in a new gas valve.
> ...


1)You do not know that the gas valve is not opening without checking the outlet or manifold gas pressure. 
2)The internal regulator will allow adjustments in outlet gas pressure if working correctly.
3)The pilot is lit.
4)The purpose of checking the spuds is not to verify correct size but rather whether they are clogged. Certain insects native to certain areas will actually clog them up...among other almost inexplainable debri/dirt/whatever.
5)In regards to parts changer. I was informing the OP not to be a parts changer but rather take the time to figure it out. My compliments to the OP as his thread shows he is working towards figuring it out.


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## Dr Heat (Dec 25, 2008)

flashheatingand said:


> OP could have "dropped" the common. That could explain why 24v at the valve but no fire.


This is true.

Cas I'm just having fun with you. But the Op is not without some common sense. 

Its gonna be a gas valve. Or the dropped neutral. Or it could be something else :whistling But its gonna be a gas valve


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## Doc Holliday (Jan 2, 2012)

Kids, go to your room.


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## flashheatingand (May 3, 2008)

CAS said:


> 1)You do not know that the gas valve is not opening without checking the outlet or manifold gas pressure.
> 2)The internal regulator will allow adjustments in outlet gas pressure if working correctly.
> 3)The pilot is lit.
> 4)The purpose of checking the spuds is not to verify correct size but rather whether they are clogged. Certain insects native to certain areas will actually clog them up...among other almost inexplainable debri/dirt/whatever.
> 5)In regards to parts changer. I was informing the OP not to be a parts changer but rather take the time to figure it out. My compliments to the OP as his thread shows he is working towards figuring it out.


Ok, you know enough to be dangerous, the valve may be the problem. But nobody wants to spend the hundy+, unless necessary. For the moment, lets bypass the safety proclamations. How are you going to verify the valve is bad, without a manometer? As safely as possible...


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## Doc Holliday (Jan 2, 2012)

Had one today that was receiving a near 38 volts (stemming from a completely silent transformer, mind you) that without testing pressure I could tell it was a low pressure issue. Rheem Criterion with vertical orifices. Ignitor on top, flame sensor on bottom. Top two orifices would slightly (began low and then lit) ignite but by the time they did the lack of flame sense would cut it off from down below. I did make certain the orifices were clear before adjusting gas.

I adjusted the pressure and wham, goOd to go. All orifices lit up.

All I needed to know that the valve was good was the click and the flame trying to ingite. Of course I did check voltage as well. 

Eh.


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## user84377 (Jan 7, 2012)

flashheatingand said:


> Ok, you know enough to be dangerous, the valve may be the problem. But nobody wants to spend the hundy+, unless necessary. For the moment, lets bypass the safety proclamations. *How are you going to verify the valve is bad, without a manometer? * As safely as possible...


Service tech should always have one....U-tube preferrably. If one doesn't happen to be on the van...need to go get one.

In terms of by-passing safety....should never do so.

Obviously...gas, natural or LP, has an odor that one should smell if the gas valve is opening...but this would not allow one to know if the WC was right for combustion. Also some of the older burners have a carry over rail that if damaged or improperly re-installed after a cleaning could cause ignition problems.


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## flashheatingand (May 3, 2008)

I wasn't talking about us. Come on man, That's not how I operate on a professional basis. I am just having some fun to see what others those who know what they are getting into, would do


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## Dr Heat (Dec 25, 2008)

user84377 said:


> Service tech should always have one....U-tube preferrably. If one doesn't happen to be on the van...need to go get one.
> 
> In terms of by-passing safety....should never do so.
> 
> Obviously...gas, natural or LP, has an odor that one should smell if the gas valve is opening...but this would not allow one to know if the WC was right for combustion. Also some of the older burners have a carry over rail that if damaged or improperly re-installed after a cleaning could cause ignition problems.


The OP is A GC Not a HT so wtf would he have a U-tube I think he might have a video on U-tube. 

Trasformers Hum.:laughing:


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