So the burner on this rooftop unit keeps cutting in and out when it first starts. I inspected the heat exchanger for any holes but didn't see any; although the style of heat exchanger makes it difficult to fully inspect.
As soon as the flame drops out the ignitor fires again and the burner lights so the flame sensor is working correctly. Voltage is continuous to the gas valve through all of this so its not the ignition module.
I put my manometer on the outlet of the gas valve but naturally I couldn't reproduce the problem at that point. The customer says the unit will run for a while and then lockout and then eventually come back on.
Im wondering if the flame is getting blown out by something (the building is on the shore of Lake Ontario and its been very bad weather lately) or if the gas valve is having trouble staying open despite proper voltage.
Might want to change your photobucket settings to "private"
Its a Grandville actually. Same thing though. I haven't used that photobucket account in ages hence all the BS in there.
Every time I connect a manometer I cant reproduce the problem. It appears if the flame is going out, then the flame sensor is seeing it and restarting the ignitor and not the other way around which means the flame is going out from an outside source, so to speak, rather than being shut off from flame failure.
I guess i'll have to start changing some parts if i can't get the gas pressure to check out.
You said you checked the voltage to the gas valve while this is happening. Did the voltage fluctuate when this was happening? I'm wondering if the gas valve coil is bad and dropping in and out. If so, you should see a voltage fluctuation. If the gas valve is good I would suspect something is disrupting the flame. HX, inducer, wind sheer.....etc. You said the weather has been bad. Perhaps something temperature related.
"The bitterness of poor quality remains long after the sweetness of low price is forgotten". --Benjamin Franklin
"Don't argue with an idiot, they will drag you down to their level and beat you with experience". --Mark Twain http://www.campbellmechanical.com
You said you checked the voltage to the gas valve while this is happening. Did the voltage fluctuate when this was happening? I'm wondering if the gas valve coil is bad and dropping in and out. If so, you should see a voltage fluctuation. If the gas valve is good I would suspect something is disrupting the flame. HX, inducer, wind sheer.....etc. You said the weather has been bad. Perhaps something temperature related.
I didn't really see voltage fluctuation but it happens so quick and my meter doesn't respond instantly, especially in -25C. There is no pilot on this so it just opens the valve and starts the ignitor when it sees flame failure and its only a fraction of a second between dropout and reignition so its really hard to figure out where its coming from. I think i'll just see about switching the gas valve out with something I have laying around to eliminate that possibility.
I didn't really see voltage fluctuation but it happens so quick and my meter doesn't respond instantly, especially in -25C. There is no pilot on this so it just opens the valve and starts the ignitor when it sees flame failure and its only a fraction of a second between dropout and reignition so its really hard to figure out where its coming from. I think i'll just see about switching the gas valve out with something I have laying around to eliminate that possibility.
Try tapping on the valve to see if you can duplicate the problem.
"The bitterness of poor quality remains long after the sweetness of low price is forgotten". --Benjamin Franklin
"Don't argue with an idiot, they will drag you down to their level and beat you with experience". --Mark Twain http://www.campbellmechanical.com
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Originally Posted by 2sac
