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Bad gas control valve?  Rating:  Rating
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 Posted: Fri Mar 23rd, 2012 12:50 am
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CraigFlowers
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I have a 1987 State Censible 510e (85 gal) that will not stay lit. I have had the thermocouple replaced and the gas oriface cleaned. The pilot lights and the burner fires but it stays lint for less than 10 minutes and then the pilot goes out with the flame. The pilot will not stay lit.

I've read the Basics on thgis site and can rule out a vent issue. The flame chamber looks good (no rust, no condensation).

Could this be a bad gas control valve? Is there anything else I can try?

Thanks.

-cf

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 Posted: Fri Mar 23rd, 2012 06:12 am
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eleent
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Hello:  I'll guess it's a 75 gallon heater.  Both the 75 and 100 gallon units have 75,000 BTU burners, which are big and need lots of air.  You say the pilot lights and then that it doesn't stay lit, so I'm a touch confused, like normal ;) 

What I'd look at first is how well the pilot flame hits the thermocouple.  It should heat up the tip of the thermocouple to a dark red.  Next, as it runs for about ten minutes and goes out, I'd look at the shape of the main burner flame.  Is it a lazy yellow flame?  Does it lift off the burner?  Does it try to roll out of the combustion chamber?  Inadequate combustion air or poor draft up the flue may be a problem.  Is there spillage from the draft hood when it first fires up?  How long does it spill out (if at all)?  These sorts of things will help define the problem. 

Gas controls do fail, but it's rare.

Yours,  Larry

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 Posted: Fri Mar 23rd, 2012 01:35 pm
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CraigFlowers
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Yes, it's the 75 gal. model. Thanks for the input.

The pilot flame looks normal. No lifting, no yellow. It contacts the thermocouple just fine. The pilot lights once and then the burner fires. When the burner goes out (within 10 minutes), the pilot light goes out too. Then I cannot re-light the pilot until it is cool again.

There's a good draft up the flue. There's no spillage from the draft hood when it fires.

It has a new thermo-coupler.

I could not light the pilot at all this morning. I am going to weigh a new control valve (as rare as it is that they fail) vs a new water heater.

-cf

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 Posted: Fri Mar 23rd, 2012 02:52 pm
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eleent
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Hello:  I agree, it sounds like the control.  If you can pull the anode and have a look, it will help you to decide what course to take.  If the anode is totally gone, get a new heater.  If, somehow there is still something left of the anode, replace the control ;)

Yours,  Larry

ps.  Is there ANY chance a drip of condensation is falling on the thermocouple?  If this happens, it will look just like what you see happening.  One drip shuts off the heater!

Last edited on Fri Mar 23rd, 2012 02:54 pm by eleent

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 Posted: Fri Mar 23rd, 2012 08:17 pm
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CraigFlowers
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A new replacement water heater (75 gal) installed was going to be $1780 and the gas control valve installed ran me about $200. I used a local company for the original service call starting Sunday through the valve replacement. I have been very happy with their service and advice. I'm sure I could have found someone cheaper but I think they are competitive. Most of the cost would have been the 75 gal heater. We have a Jacuzzi tub which, from my understanding, requires larger hot water supply.

The new control valve is in and the water heater has stayed lit. My water is smoking hot! (Not really smoking. I'm just exagerating.)

The company followed up already and the installer left his cell number so I can reach him direct. Very nice service.

I appreciate being able to learn from this site. It helped me appreciate the costs and work involved and allowed me to confirm what I was being told.

-cf

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 Posted: Sat Mar 24th, 2012 05:22 am
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eleent
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Hello:  I'm glad it really was the control.  Two more things.  I'm sure you need a new magnesium anode and I'd go ahead and replace or at least test the relief valve.  That way you wind up with a working, safe and long-lived heater.  It's happily ever after :cool:

Yours,  Larry

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