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Huge gas bill something is wrong with my furnace

John_54 Member Posts: 17
I have a 4 floor apartment building with hot water heat. I have 2 identical gas furnaces in parallel. One lead and the other comes in at 20F outside temp. Something went wrong last month based on the gas bill. I checked the furnaces and one was taking twice as long to bring the water up to temperature and using the same gas per minute based on the meter. The flame is blue but looking a bit lazy in places. I thought it must be dirty and took the top off and cleaned it. There was a lot of carbon around the fins which I removed with a brush and vacuum. I expected that to fix it but it still takes twice as long to heat up as the other one. Nothing else has changed. It is further from the chimney and closer to the fresh air supply. There is a new carbon monoxide alarm in the room which has not gone off. Can anyone offer me any advice?
The furnaces are 25 or more years old. Gaz industries 400,000 input.

Thanks John



  • Steve Minnich
    Steve Minnich Member Posts: 2,673
    You need to have a professional clean the boilers, check gas pressure, and do a combustion analysis on each. The soot is an indication of a much bigger problem but is also slowing down the heat transfer from fire to water.
    Steve Minnich
    Minnich Hydronic Consulting & Design, LLC
    [email protected]
  • Gordy
    Gordy Member Posts: 9,514
    Time to make the other boiler the lead boiler, and get that one fixed. like Stephen suggested.
  • John_54
    John_54 Member Posts: 17
    Thanks for the help. I called a professional and the gas pressure on one furnace was a lot higher than the other. I don't know how that happened as it wasn't adjusted in at least the last 8 years.
  • lchmb
    lchmb Member Posts: 2,997
    I would suggest a yearly inspection to verify all safeties are functioning properly and at that time they can clean and test the price for safety...
  • Zman
    Zman Member Posts: 6,965
    edited February 2016
    The advise about the servicing is absolutely correct.
    The control strategy you describe is unconventional at best.
    Typically a 2 boiler system would be set up so that the boilers auto rotate lead/lag to assure equal run times between the 2 appliances. Normally the boilers are staged based on the amount of energy needed to maintain the required water temp, not just on/off based on outdoor temp.
    You would likely save a significant amount of money by installing a multiple boiler controller with outdoor reset.
    A product like the Tekmar 274 might be appropriate.
    When looking for contractors, make sure they know you are looking for someone that specializes in Boilers rather than Furnaces, there is a difference.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • captainco
    captainco Member Posts: 502
    Sounds like no combustion test was taken. How can you adjust fuel when you have no clue how much air you have and it keeps changing? Could that one have had the right amount of fuel but not enough air and the other and the other one not enough fuel?
  • deadmansghost
    deadmansghost Member Posts: 32
    When the tech came in and found the gas pressures were incorrect, what was the combustion readings of the fires at that time? Did he leave a printed slip from the test equipment?