Gas water heater inlet/outlet plastic rings melted

alex532

<span>I installed a 40 gallon 36,000 BTU GE water heater in Feb of this year and last week I noticed the plastic rings around the inlet, outlet and anode rod were melted.  After reading another post on this topic I think that the issue could be related to the microwave vent fan and bathroom vent fan that I have, since it is likely that when they both run in my 1,000 sqft house that I am creating negative pressure which is drawing exhaust back into the house from my chimney.  To complicate the issue more, about a month ago I decided my central air system needed more return air than it was getting, so I added a return register in the basement where the water heater is located, but no output register.  My guess is that this is also contributing to the issue.

</span>

<span>I never had this issue during the winter when the furnace was on, so I’m pretty sure my recent change to the return duct is causing the issue, the question is, how do I correct this?  Should I just add an output from the duct work in the basement?

</span>

<span>Also, is it true that I need 2x the surface area for the central air return system as the output from the system?</span><span style="font-size:12pt">  </span>

Mark Eatherton

CAUTION, DANGER, WARNING!!!!

You have a VERY unsafe condition.



First you can NEVER have a return air connection in the same room as a gas fired appliance.



Second, ALL gas fired appliances REQUIRE their own source of outside air. Without it, it will consume the air inside, and if other devices are exhausting that air, the products of combustion WILL be drawn into the house.



Thirdly, you need to perform a worst case combustion air zone negative air pressure test. If is fails, you MUST correct this situation.



Your situation is exactly what causes people to die from carbon monoxide.



Get rid of the fan induced negative air pressure problem TODAY. If the microwaves exhaust fan is causing the problem, open a window near the fan to give it a source of relief air.



By all means, if you don't already own some, buy and install carbon monoxide detectors near all sleeping areas, TODAY.



You have a potentially deadly situation on your hands. Fix it before you find your or one of your family members name in the Obituaries...



Seriously.



ME

alex532

Point taken

1) I'll correct the return duct in the basement immediately. 

2) How do I get outside air for the water heater to use in the basement?

3) How do I perform this test, turn on everything and then what?

4) I have carbon monoxide detectors in the living area, but not in the basement, I will add one down there.

Thank You.

Mark Eatherton

Answers...

Outside air is generally introduced through an outside wall at a rate of 1 square inch per 4,000 btuH input. !/2 of the air should be within 6" of the ceiling and 1/2 within 6" of the floor.



It really depends upon which code you are dealing with, but the formula I gave has worked well for me for over 30 years.



A worst case CAZ test is done by closing up all windows/doors etc within the home, turning on all exhaust fans and then firing up the appliance. If there is spillage for more than a few minutes, as detected at the appliance draft relief hood. If spillage continues, you will have to perform further analysis. Possibly closing off (partially) some of the exhaust air?



You do not want to put the CO detector in the mechanical room or you will get nuisance alarms (per the manufacturers instructions) unless you are in a code jurisdiction that requires it (Massachusetts and a few others).



You are quite welcome.



ME

alex532

more questions

ok, I understand how to calculate the area of air I need to bring into the basement for combustion.  But, I have not seen this done before, in Ohio where it is hot in the summer and cold in the winter we normally seal everything up really well, what is the technique you normally use?  Do you just use a pipe in the diameter needed and have some sort of damper in it to prevent air from flowing out of the basement?  How close to the appliance does the duct need to be?  Do I need to insulate the duct?

Thank You.

Mark Eatherton

No dampers allowed...

unless they are safety interlocked into the appliances being served. Virtually impossible to do with a gas fired water heater. You could put a 5 gallon bucket beneath the low air and it will act as a cold air trap, and you could make a J bend for the upper air, but you are not allowed to block it off, Summer or Winter.



I believe the code states that it must be within the same room as the appliance, and have had inspectors ask me to keep it within 5 feet of the appliance.



Here in Coldorado, we don't usually insulate any combustion air pipes, but you're in another world with lots of mugidity...



ME