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Air supply question for Bradford-White 40gal NG, Hot Water tank Installed 9/2011

Air supply question for Bradford-White 40gal NG, Hot Water tank Installed 9/2011


  #1  
Old 08-17-16, 06:17 AM
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Air supply question for Bradford-White 40gal NG, Hot Water tank Installed 9/2011

Last couple of nights storms came through and with winds rain gets blown into the hot water tank vent pipe, putting out the pilot light.
Yesterday, I was able to get the hot water tank restarted but this morning I had to take off the front burner-cover plate to put a propane torch to the thermocouple for 15-30 seconds so that the piezo-igniter would work.

Funny thing was, when I went to fasten the front burner-cover plate back on, the lit burners started to die out. Once I opened the plate up a crack - the burners stayed lit normally. I tried a couple times more with the same results. If I fastened the outside access plate down, the burners would flame-out.

The last couple of water heaters we've bought had this similar 'sealed burner' designed and I wondered Where the air-supply came from. I assumed it was from the top area around the exhaust pipe hole - but why would it suddenly start now.
I thought maybe there was an air supply vent on the bottom of the hot water tank. I didn't find anything like an air-supply vent but did find a small nylon plug that went up into the burner area. When I removed it, the water that had collected in the bottom of the tank drained out.

I'm wondering if the air supply is from the top, that the rain blowing in through the vent pipe has caused some kind of restriction to the air flow, supplying air to the burners.
If anyone knows, I would appreciate your advice and insight.
greynold99
 
  #2  
Old 08-17-16, 09:25 AM
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Residential gas-fired water heaters have used a system called FVIR (Flammable Vapor Ignition Resistant) since about 2003. Some models have a filter that eventually can become clogged with dust and dirt, severely restricting the incoming combustion air.

Google FVIR for more information.
 
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Old 08-18-16, 08:40 AM
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Thanks Furd,
I came across the FVIR acronym on the Bradford-White manual for my water tank but didn't know what it meant.
I'll check it out in more detail - there is some dust on the top of the hot water tank near the exhaust vent but I'm wondering if the water getting into the combustion chamber could've clogged the FVIR filter to the point of not allowing air to flow?
If so, I'll have to test to see if I can eventually tighten the inside-combustion chamber cover down once everything dries out.
Thanks for the help,
greynold99
 
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Old 08-19-16, 11:45 AM
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It looks like the FVIR system on the Bradford-White water tank allows the air flow up from the bottom though what appears to be some kind of metal-mesh or screen. Looks like I might've accidentally did the right thing by removing the small (less than a 1/4 inch diameter) nylon drain plug from bottom of the outside cover, allowing the water that had collected in the bottom up to the level of the screen (thereby blocking the air flow for combustion). I've had the second, internal access cover plate to the combustion chamber propped open on one side to allow for the required air for the burners. Over the weekend I'll seal everything back up and check to make sure the air flow through the bottom screen allows the burners to fire up.

That also probably explains why I couldn't get the piezo igniter to light the pilot light as well - since there was probably no oxygen to support even the pilot light at that point.
 
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Old 08-22-16, 06:28 AM
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I was able to replace the sealing cover plate panel and fasten it down - and the tank burners were supplied with air.
I'm going to leave the small nylon plug I removed from the bottom of the HW tank as we periodically get water blowing in down through the exhaust vent from time to time... and, I don't think that small an opening would allow much flammable vapors into the combustion area if ever there was some kind of spill.
I didn't mention before that I installed my hot water tank on 12" concrete blocks according to the old recommendations before they had developed FVIR systems and combustion air was pulled in directly from slot-openings in the base of the HW tank.

thanks again Furd.
greynold99
 
 

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