Gas regulator and valve questions

Problems related to residential installations.

Gas regulator and valve questions

Postby michaelg » Mon Feb 17, 2014 11:14 am

I have a Carrier model 58PAV. It's been having an intermittent ignition problem and occasional flame outs for a few seconds. A service technician diagnosed the problem to being too much gas of 15" coming from the regulator which was adjusted to 6". After the adjustment it still was intermittent for a few lighting tries, but then it started working every time. The service tech said the regulator pressure may have caused the valve to go bad. I'm wondering if it just takes some time to normalize after the pressure adjustment? The valve part install is a little spendy so I don't want to replace it if I don't need to. Another symptom is once in a while the flames will drop out for a few seconds and then come back again on their own. I'm thinking that would be from the regulator being bad and not the valve. A valve to me would be open or shut while a regulator more likely to be fluctuating the level especially if it is bad. In the meantime while I decide on repairs they are trying to sell me a new furnace. I'm wondering if I should just get the regulator replaced or if the valve is also part of the problem..
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- Gas regulator and valve questions

Postby Freon » Mon Feb 17, 2014 12:41 pm

Is the furnace natural gas or propane? I am having a hard time with an adjustment of pressure from 15" to 6". I am assuming you're talking about the regulator at the gas valve/meter to the house or at the propane tank, not the regulator at the furnace gas valve. Did the tech measure the pressure on the manifold side of the gas valve? It should be 3.5" w.c according to the installation -
w w w .xpedio.carrier.c o m/idc/groups/public/documents/techlit/58pa-10si.pdf (remove spaces as necessary)

A gas valve is a simple valve except it is opened and closed by a solenoid. What can happen is something interrupts the current to the gas valve and it will close. I would try and watch the furnace in hopes of seeing the flames extinguish and relight. At that time you want to carefully listen for any metallic clicking noise indicating the gas valve did, in fact, close briefly.

Since you say the flames extinguish then relight, I would check your filters and make sure every register and return are open and clear. If the furnace overheats it will shut off the flame until the heat exchanger temp is back to normal and then relight the burners.

I would make sure the power to your thermostat is solid. If you have batteries only, replace them. A weak thermostat can cause interruption to the heating cycle.
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- Gas regulator and valve questions

Postby michaelg » Mon Feb 17, 2014 2:19 pm

It's a natural gas furnace. I believe when he was referring to a regulator he was indicating just outside the furnace. It appears to be flat and round with a protruding flathead screw adjustment. The heating checklist the tech left does list high fire gas pressure 3.5. I'll try listening for clicking noise. I'm assuming you mean something a lot softer than the ignitor click. The alkaline batteries in the thermostat are on their second winter. I do have a couple of registers closed so I can open those up. Thanks for your input!
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- Gas regulator and valve questions

Postby Freon » Tue Feb 18, 2014 1:54 pm

Is the furnace your only gas appliance? Usually the main pressure regulator is at the meter, outside the house where the piping enters the house. As long as you know the pressure to the burners is 3.5" w.c. all is good.

I would change the batteries to the thermostat. Also check for a common (C) wire connection which would indicate the thermostat is powered from the 24 volts at the furnace.

Listening carefully you can tell when the gas valve opens/closes. With the registers open, returns clear and new filters, you have made the airflow through the furnace as good as can be. If the cause was overheating, it should go away. Check the main (circulates air in the house) blower motor and squirrel cage to be sure all spins freely and quietly and that the squirrel cage is not dirty.
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- Gas regulator and valve questions

Postby michaelg » Tue Feb 18, 2014 11:34 pm

The gas regulator is inline with the water heater, dryer, range and furnace. This is what was adjusted from 15" to 6". At the moment it seems like the more the furnace runs, the easier it starts up again. If I turn the thermostat down a ways and let it rest a few hours then it may take three tries to light up again. More than three it shuts down until power cycled. When it struggles to light there usually is blue flame for a moment and then it blows out. I can't really detect a valve opening noise over the hum of the furnace, but can clearly hear the whoosh of the flame when it starts or lack thereof. The service tech is coming back tomorrow so will see what he thinks. Any other thoughts are appreciated. Thanks again..
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- Gas regulator and valve questions

Postby Freon » Wed Feb 19, 2014 2:31 pm

Let the furnace cool down so you increase the chances it won't start. Now have someone call for heat and you watch. Does the hot surface ignitor (HSI) glow very red to white hot? Does the HSI stay glowing for a few seconds after the burners light?

If you're hearing the whoosh as the gas valve opens and that sound remains for a few seconds just before the flame extinguishes, it seems the gas valve is OK.

I would have the tech clean and check the position of the flame sensor. I think the flame gets established but the flame sensor is not detecting it every time and then closing off the gas valve due to lack of flame. A flame sensor relies on a very small current to prove there is a flame. Bad electrical connections, a dirty surface or not being placed properly in the flame can all make the small current less that is necessary for detection.
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- Gas regulator and valve questions

Postby michaelg » Wed Feb 19, 2014 10:56 pm

The flame sensor was removed and cleaned. The tech was seeing that sometimes even though the test port pressure reads 3.5" on the valve the solenoid wasn't opening it when it should. He went ahead and replaced the valve. I replaced the thermostat batteries too. Now will watch and see. If still having flame issues it could be circuit board related too I'm told...Hopefully not.
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- Gas regulator and valve questions

Postby Freon » Thu Feb 20, 2014 2:46 pm

The possibility of circuit board problem is due to the flame sensing circuit. It is possible the circuit board is incorrectly saying there is no flame when there is flame.

Some manufacturers put their control circuit boards where they can get hot as the furnace operates. Heat is the worst enemy of integrated circuits and will age them quickly.

You saw flame and then the flame disappeared. Seeing flame tells me the gas valve solenoid did open. The question is did the solenoid close (no flame) for the reason of a bad gas valve or did it close due to the flame sensing circuit giving incorrect data (no flame when there was flame).

I hope all is well now.
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- Gas regulator and valve questions

Postby michaelg » Thu Feb 20, 2014 11:16 pm

So far so good. I was shown how the flame sensor was showing good current of 2.7 MA. I was having times where there would be no flame as well and that's what I meant in my initial post referencing intermittent ignition. The flame outs were the strange part of it as if the valve was partially working. Seems to be lighting forcefully every time and staying lit now so I'm thinking this is resolved. Thanks again for all your contributions. I'm glad to know more about how the system works.
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