How sealed does a sealed combustion chamber have to be?


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Old 12-02-14, 10:46 AM
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How sealed does a sealed combustion chamber have to be?

GE SmartWater PG40T09AVG00 natural gas water heater.

Woke up yesterday to not hot water. A heating technician said it was likely the thermocouple, because the pilot light burns well while the red button is pressed down, but goes out as soon as the red button is let go. He replaced the thermocouple, and it now stays lit. But, I turned it off right after because I have the following safety concerns:

This unit uses a sealed combustion chamber. There are two grommets -- a rectangular one that goes around the access door, and a circular one about the size of a quarter where the three "wires" go through.

Question 1 - The label says any time the access door is removed, its grommet needs to be replaced. The tech said not to worry about that because the old grommet still seemed to be making a good seal. Is this OK, or does that grommet really need to be replaced? What risk is there if the sealed combustion chamber isn't 100% sealed?

Question 2 - When he pushed the new thermocouple through the quarter sized grommet, it split in half. The holes in it were just wide enough for the middle parts of the wires, but the thermocouple of course is wider at each end. He used aluminum tape to "patch up" the area. I have the same concern about whether this is improper.

 
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Old 12-02-14, 11:21 AM
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GE is saying the circular grommet should be flexible enough to "wiggle" the thermocouple through. Perhaps mine was brittle from being 10 years old and near the flame.

BUT, GE is saying they do not carry a replacement grommet all by itself. They're saying I can only get it as part of a $114 whole new pilot assembly.

Maybe there's some type of putty rated for usage here?...
 
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Old 12-02-14, 05:18 PM
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I just replaced the thermocouple myself and had the same problem. The grommet broke into 3-4 pieces. I tried putting them together and put duct tape over them. I just did this yesterday the tape did melt a little. I am thinking they may sell some kind of putty. The kind that you could use for a radiator. My only concern would be that the putty not be flammable. If anyone could help with any other suggestions, that would be great.
 
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Old 12-02-14, 06:25 PM
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Duct tape is a no no for sure. Try foil tape, the stuff they use on flue pipe.
 
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Old 12-03-14, 11:02 PM
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Found a 2700 degree F furnace cement, meant to fill gaps. 12oz container or so was only $4. If I have to replace another wire going through there, I'll have a job on my hands... But this is going to seal it up with no fire hazard for sure.
 
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Old 12-06-14, 01:41 PM
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Could you tell us what brand you used, and where you purchased it? I bought some tape which is supposed to hold up to 500F. I would like to cover it with the stuff that you used
 
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Old 12-15-14, 06:28 PM
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The water heater will heat water equally fine if the hatch is not properly sealed compared with being sealed, all other things equal such as the cleanliness of the actual air intake vent.

The purpose of sealing the hatch is to prevent vapors such as from spilled cleaning fluid on the floor nearby from being ignited outside of the water heater combustion chamber. The intake has a screen across it and only the amount of vapor that got into the combustion chamber will burn.
 
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Old 12-16-14, 05:20 PM
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Thank you so much your explanation helps to understand better.
 
 

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