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Need help with Warm Morning lp gas space heater

CRCgoodguy Member Posts: 3
I have a warm morning v30 vented gas space heater. It is vented to an existing chimney. My problem is that the vent spill switch trips. I have attached a diagram of the space heater showing the combustion chamber. I have measured the temperature at the spill switch and it gets over the 230 degrees and trips as it should. I checked the vent and it is not blocked. I noticed I do have a down draft coming down from the chimney into the vent pipe. When I first turn it on, works fine but after about 15 to 20 minutes, it shuts off. I noticed that the vent pipe is not too hot while the rear of the heater near the vent switch is over 240 degrees, I have had no problems with this heater before this year.
Any suggestions?
Thank you,


  • Jamie Hall
    Jamie Hall Member Posts: 22,162
    What changed? If you have a downdraught in the chimney, that air has to be going somewhere in the building and out. Any fans? Any exhauts? Kitchen fan? Bathroom fan?
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 6,753
    edited January 3
    The down draft is the problem. What has changed? as Jamie said.

    There are many reasons for a downdraft that never happened before. Did you add anything that will tighten up the home, Caulking, new windows, any other weatherization? Any new exhaust fans? Clothes dryer, oven range hood, or new bathroom vents?

    Have the outdoor conditions changed. A structure or roof line that can block the chimney? A tree that has grown higher than the chimney? I had a customer that had a 45 year old oil furnace that never had a problem. The property next door was able to build a 4 story condo complex within 5 ft of the property line. Right next to the 3 story chimney. When ever the wind blew from the south west the building next door acted like a big air scoop forcing a major down draft burning up the plastic oil burner motor coupling = no heat. Took me 3 couplings to figure this out, after 3 other techs gave up.

    Another customer had a pine tree grow to 15 feet above the chimney top with the same result.
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
  • CRCgoodguy
    CRCgoodguy Member Posts: 3
    You're right. The air has to be going somewhere. Okay, here's what changed the last couple of years. New windows but that would seal the house. We have a range vented to outside and bathroom vent but they were there for the past 30 years. I bet it's the radon mitigation system that was installed two years ago. It is supposed to suck the air under the basement slab and vent it above the roof. I can hear the air coming down the gas heater pipe when I stand next to it. The gas heater is in the basement.
    What can I do to correct this downdraft? I am not supposed to turn off the radon fan. Can I add a booster fan on the gas vent pipe to force the gas vent up the chimney?
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 6,753
    edited January 3
    This is how I fixed the problem on the house with the 4 story condo next door
    https://www.supplyhouse.com/Field-Controls-DI-1-DI-1-Draft-Inducer-for-3-6-Pipe. You will need too add a relay to operate the draft inducer from your thermostat. Then once the fan is on, the gas valve can be activated from that relay. It is not the best answer but it will get you where you want to be. Your system operates on millivolts. You need to get the 120V fan motor to operate before the millivolt gas valve opens.

    The best answer is very expensive to purchase and install because it goes on the top of the chimney. If you are interested in that Just ask me about it.
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics