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MaineScoot 12-16-2012 03:40 PM

Gas water heater help
 
I have a ten year old gas water heater, a State Select 40 gallon PR640NOVT. I use it to heat my workshop. So it was turned off for the summer. When I turned it on and lit the pilot a few weeks ago it ran fine at first but the next day when I was in the shop I noticed it was trying to fire up but couldn't. The power vent would come on for a couple of seconds but the burner didn't light and it shut down. Then it would try to fire up again... Repeat.
So I turned it off but a week later turned it on and it fired right up. Later I noticed it wasn't firing up again. I guess it is some kind of safety switch malfunctioning, what do you think?
The pilot stays lit, what should I check/replace first?

honsfun 12-16-2012 03:51 PM

replace the thermocouple

MaineScoot 12-16-2012 05:07 PM

Quote:

Originally Posted by honsfun (Post 20264165)
replace the thermocouple

The one down by the pilot light? I think that is fine, if it were bad the pilot wouldn't stay lit.

D.T. 12-16-2012 05:52 PM

Water heater to heat the workshop? How does that work? Like cirulation to a heat register?

Anyway, I assume the main burner is not coming on? It has a power vent too? I'd make sure all the things are working in the order that they are supposed to. You can try and clean the thermocouple first with sand paper.

KeithinSC 12-16-2012 06:09 PM

+1 on sanding the thermocouple. Its job is to sense the main burner, if it is dirty/damaged, it won't signal the main valve to open.

Also, how is the gas supply line coming to the unit? Often, air will get into the system and can be a SOB to purge. Until it is purged, it will work like you describe. Run, then die and not refire.
I've also had spider webs up in the burners in units that sat unused for a spell. Get some compressed air and clean out the cobwebs.

Keep us posted.

MaineScoot 12-16-2012 06:59 PM

Quote:

Originally Posted by D.T. (Post 20265001)
Water heater to heat the workshop? How does that work? Like cirulation to a heat register?

Anyway, I assume the main burner is not coming on? It has a power vent too? I'd make sure all the things are working in the order that they are supposed to. You can try and clean the thermocouple first with sand paper.

There is a circulator pumping the hot water through three 200' loops of hepex (cross linked polyethylene) buried in the concrete floor. There is a radiant barrier under the concrete.


So are there two thermocouples? One for the pilot light and another for the main burner?
The gas supply is good or the pilot wouldn't stay lit.

arcanum 12-16-2012 07:55 PM

On gas appliances with power vents, the unit wants proof that the power vent is sucking a vacuum before it lets the main burner come on. Some place on the vent fan housing,there should be a flexible hose of maybe 1/8 to1/4 of an inch. This hose will go to a vacuum switch that allows the main burner to come on. First,check the hose for cracks where it fits over the barb fitting. Then check the barb fitting itself. I have seen them get crudded up with dirt and deposits. A little drill bit turned in your fingers usually will clear them. Spiders love the 'gas smell' and will build little blockages in dormant gas appliances. You can also check the vacuum switch with a continuity tester to see if it works if all else fails. Make sure that the discharge pipe or chimney is not plugged as well
Any time I have had problems,a cleaning solves them with no parts needing replaced. Hope this helps, and please tell us how it goes for you.

Beezer 12-17-2012 03:06 AM

hmmmm... if there is a pilot light that is usually the lockout, but I know on other types of burners there is a sensor that looks for the main heat... you may or may not have that. anyway, when the start cycle begins, the burner fires maybe 10 -15 seconds... if the sensor does not detect heat, it shuts the main gas off because it thinks the main did not light. is that what you have?

otherwise the last post on the power vent is pretty right on...thats where I would look

lowflyer43 12-17-2012 08:17 PM

Quote:

Originally Posted by arcanum (Post 20265840)
on gas appliances with power vents, the unit wants proof that the power vent is sucking a vacuum before it lets the main burner come on. Some place on the vent fan housing,there should be a flexible hose of maybe 1/8 to1/4 of an inch. This hose will go to a vacuum switch that allows the main burner to come on. First,check the hose for cracks where it fits over the barb fitting. Then check the barb fitting itself. I have seen them get crudded up with dirt and deposits. A little drill bit turned in your fingers usually will clear them. Spiders love the 'gas smell' and will build little blockages in dormant gas appliances. You can also check the vacuum switch with a continuity tester to see if it works if all else fails. Make sure that the discharge pipe or chimney is not plugged as well
any time i have had problems,a cleaning solves them with no parts needing replaced. Hope this helps, and please tell us how it goes for you.


+1

sb955i 12-20-2012 12:56 PM

Air intake clogged? My home furnace locks out whenever I get snow accumulated in the intake vent. Doesn't take much, but I guess it senses the minor vacuum and locks out.

azcagiva 12-20-2012 01:54 PM

Post up a picture of your water heater if you could.

I am not sure but it sounds to me like it could be either the flame sensor is corroded (fire conducts some electricity) or the pressure switch is not working (which could be bad draft motor or bad switch).

-John

MaineScoot 01-04-2013 05:50 AM

Thanks, you guys. I think it must be the pressure switch. I emailed State but haven't heard back from them. I will give them a call. I disconnected the tube that runs into the power vent and cleaned it out with a pipecleaner. But it's still doing the same thing. It's annoying that it runs fine if I turn it on cold. And runs fine until it's up to temp. But the next time it calls for heat it hangs up.

DUNDERHEAD 01-04-2013 11:04 AM

Are you using Propane ? I had the same problem in my shop. Wall mount boiler. Start up fine, then shut down. Went round and round trying to figure it out. Someone mentioned water in the propane. Called the gas company, they came out and replaced the regulator on the side of the barn , low pressure regulator. They opened the regulator after removal and it was frozen solid with ice. Enough gas would push by overnight to fire in the morning , but not enough flow to maintain burn. Propane company driver told me they need to add methanol ( ? ) each load to prevent freezing in the winter. Some drivers can't be bothered. Changed the Propane supplier and all is fine for the last 6 years.

rakad 01-04-2013 11:28 AM

Appliance Guru . Com
 
Mmmmm - hot H2O heat in the floor - my favorite!

I have had good luck finding water heater and other appliance repair ideas on

http://applianceguru.com/forum26/23724.html

Let us know what the problem turns out to be.

MaineScoot 01-04-2013 01:40 PM

I talked to a nice guy at State today. He was able to send me a PDF of the correct service manual. I found the pressure switch and cleaned the other end of the hose. And I tapped on the regulator like he told me. I think it's doing ok. I'll keep an eye on it. They had tried to email me earlier but got one letter wrong on the address.


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