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Furnace and hot water heater keep going off

Amy1 Member Posts: 2
Please help. We have a furnace and hot water heater in the same room. We have lived in our house for 4 years. The first two years we had no problems with either. Last winter the hot water heater pilot was going out periodically. We had the thermocouple replaced which did not fix the problem but it was the end of the season and didn't have problems. This winter we started having problems again. Anytime the temperature drops below 30 the hot water heater pilot goes out. However, now, in addition to that the furnace will not kick on. We had a different guy come and replaced the thermocouple on the hot water heater again and the gas valve on the furnace. It worked for a week and then once the temp got cold again both continue to go out. Yesterday with one of the experts here we thought we had the problem figured out, that there was not enough oxygen getting into the room so last night we left the doors to the furnace room open. Again, woke up with no heat or hot water. Then we thought that the exhaust pipe is getting cold when the furnace goes off and there is a down draft preventing the furnace from kicking on and also blowing out the pilot on the water heater. However, today the pilot on the water heater stayed on and the furnace would still not go on. Then, we brought a chimney sweeper out and he blew soot out of the chimney hoping this would help. Again tonight the pilot light was still on yet the furnace wouldn't start. Finally, on the third attempt the furnace started but the pilot light on the Water heater went out. We have had 3 professionals and a chimney sweep out and no one can seem to figure out the issue. Both the water heater and the furnace are vented through the same main vent (b-vent maybe but I might be wrong in my terminology). There is no outside air source for the room but again this has only been a problem the past 2 years. We are really hoping someone can help provide some

Insight into what we might be missing.


  • Zman
    Zman Member Posts: 7,607

    Has anyone tested the gas pressure? They should watch the pressure as the different appliances fire.It would be best to do it when it is cold outside.

    A good gas contractor should also be able to do a combustion  analysis on the appliances and check the draft in the chimney.

    The guys you have had look at it are making pretty good guesses. You need someone to thoroughly check the entire system.

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • Tinman
    Tinman Member Posts: 2,808
    Type of gas?

    Do you have natural gas or LP?
    Steve Minnich
  • Gordy
    Gordy Member Posts: 9,546
    Gas pressure

    And gas supply piping size.

    How many gas appliances in the home? Dryer? Stove top? Oven? Besides water heater, and furnace.

    If the meter size, and supply piping is not the correct size the appliances will not get the proper amount of gas. The more of the gas appliances running at the same time the worse it will get.
  • Amy1
    Amy1 Member Posts: 2
    Furnace and hot water heater (continued saga)

    Thank you all for your quick responses. It is natural gas. We have a dryer and gas stovetop neither of which have been running in the evenings when the furnace and heater go off. Also, they have measured the gas coming in with a some sort of monitor they hooked up to the furnace. I am guessing this is what you are talking about. The numbers were all where they were supposed to be.
  • Ironman
    Ironman Member Posts: 7,399

    Can you post some pics?

    Does the furnace have a standing pilot or electronic ignition?
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • Tinman
    Tinman Member Posts: 2,808
    Cold weather

    The fact that the issue is only happening in really cold weather would lead me to look at the regulator at the meter. Is the main meter and regulator outdoors?
    Steve Minnich
  • Gordy
    Gordy Member Posts: 9,546
    edited December 2013

    With the problem not occurring for the first two years, 3rd year water heater this year furnace and water heater. Tin man may be correct about the meter regulator failing.

    Is there any changes to the home in the last two years. Exhaust fans installed that did not exist, high exhaust range hood? Insulation weather sealing upgrades to the structure?

    Is the water heater natural draft or a power vent?

    Is the furnace high efficiency? Exhaust pipe is plastic vented through the sidewall of the


    What is the btu input of the furnace, water heater, cook top, and dryer?

    The total of these should not be more than the meter rating which is on the gas meter.

    Also the gas piping needs to be sized correctly for the total btu rating of all the appliances added together.

    It is quite possible that all appliances could run at the same time.
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