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Nat Gas H2O Heater: Burner Kills Pilot (Also Combustion "Whoosh" & Burnt Smell?)

Nat Gas H2O Heater: Burner Kills Pilot (Also Combustion "Whoosh" & Burnt Smell?)

Old 08-08-11, 05:15 AM
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Nat Gas H2O Heater: Burner Kills Pilot (Also Combustion "Whoosh" & Burnt Smell?)

I've been struggling for a couple years now with what I'm convinced is a lemon Kenmore natural gas water heater. I just don't have the money to replace it right now and have been trying to diagnose/fix the problem(s) myself.

Over the course of a couple years, the thermocouple has been replaced by a plumbing/heating guy. The gas pressure was checked by PG&E. I was advised to clean out the filter underneath with a refrigerator coil brush and had been doing that twice a year.

For the past 6-9 months, I had been having a problem where the water wasn't getting very hot even at the highest setting. It would get "just hot enough" and then the burner and pilot would go out. So I had to lower the temp control to get the burner and pilot to stay lit. Its temperature threshold has steadily declined to the point of it now not even wanting to stay going at the lowest temp setting.

In my observations, I noticed that the burner flame has been erratic and seems to be taking the pilot flame out.

I was willing to replace the thermocouple again, but a couple of nights with the temp set all the way down but the pilot on, I noticed the pilot would stay on steadily. As far as I know, a bad thermocouple would knock out the pilot no matter what. But the pilot is steady as long as the burner is off. Burner on, the flames jump all over the place, pilot goes out, followed by the gas cutting off.

I have been researching two possible causes for this: A dirty pilot orifice and possibly a blocked vent. I've read how to check and clear out the pilot orifice, but have no idea about checking the vent. I have held a snuffed out candle up to the "hat" while the burner was on and it seemed to be drawn up. But what about the venting in the center of the water heater? How do I check that?
(My water heater is in a closet in the kitchen...about 8 feet away from the dryer, with a refrigerator in between. The dryer vents outside. So I don't think there's a massive amount of lint being sucked up in there.)

My last question is about something that happened the other night: I was testing/observing the water heater. The flames jumped around, took out the pilot and the burner flame went out. But I heard the gas still going for a bit. I didn't want gas to build up in there so I didn't wait and turned the control knob down to cut the gas. After I stood up, I head a "foom!" noise like something suddenly catching fire and I smelled a burnt smell. As if something had been lit on fire. This worried me because I wondered if maybe my vent is clogged/blocked, could the blockage (lint?) have ignited? Further research/thinking about it made me think that it was just the accumulated gas in the combustion chamber flaming out. But it worried me and now I'm nervous to experiment any further with it.

I'm not really comfortable around gas appliances, but my money situation dictates that I try everything I can do myself. Any and all advice appreciated. Thank you.
Old 08-08-11, 05:46 AM
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I would make a bet that the burner is sealed. There is a little window down at the bottom to see the pilot?

IMO the unit is starving for air. The air intake screen/screens are clogged with lint. These can be found and possibly vacuumed. Its part of the new FVIR technology. Eliminates or reduced the chance of the water heater igniting flammible vapors.

The second part is tou have low hot water yeild. This sounds like a dip tub issue. And turning the water heater t stat up when the unit is starving for air is no help. Because of low or no air in the combustion area(flames dancing) the temperature in the chamber rise and trip a saftey device that turns the gas off. Pilot and all. When the unit cools you will be able to relight, but this process will continue.

Because you have two ongoing issues my advice would be to replace.

Since this is a DIY site you would need to:

1. Remove/check/and or replace dip tube.
2. Find the FVIR air intake screen/screens and clean then. This might include remove burner from the HWH.
( I recommend a pro be called for the gas work )

depending what route you go, you may find replacement will be the cheaper option.

Let us know.

Mike NJ

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