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Navien 240e NG Recirc Pumps

addohm Member Posts: 25
Two weeks ago we had our house converted from oil heat to gas. Since then, the house has not been able to keep warm. Originally, using the outside thermometer to set the naviens heat curve, the house would never get above 60. The plumber argued all day that the problem was our house, our plumbing. Of course my counter argument was that the "less efficient" heating system was heating out house just fine at the same outdoor temperatures of (at that time) 0-15F. Anyway, eventually I ended up calling navian and they said to disable the temp sensor and crank the heat setting up to 194 (max). Before doing that I had to replace the sched 40 exhaust pipe to sched 80 to support the higher output temps. It worked, sort of. The house is warm(er). Now, it's -1F outside, and our house is at 63-64. The boiler is working full time, literally 24/7 to achieve this. Can't wait to get my first gas bill.

My previous oil boiler baseboard heating system consisted of three Taco 007-F5 pumps. These pumps have a max output of 25gpm according to the data sheet. The pumps the plumber chose to replace them with, when designing the new NG gas boiler system are Taco 007e-2F2 which have a max output of 16gpm. Today when I got home from working in NY, my wife was complaining about the temps again. I've sort of had it at this point. I'd rather have the more expensive and less efficient system at this point. Of course, I had to do more investigation, because the house cooled down since I left on Wednesday. 4-6 degrees in fact. Needless to say, the pump differences jumped out at me.

Do you guys think this is the actual source of the newfound heating problems? If so, what can I replace the new pumps with, that would be a direct swap at the higher flow rate?


  • addohm
    addohm Member Posts: 25
    Comparing the dimensions, it seems the two pumps are pretty much the same. Is there any reason I shouldn't swap the new pumps back to the old pumps?
  • Paul48
    Paul48 Member Posts: 4,469
    edited January 2018
    Try this first... https://hvactechhangout.com/home/system-measurements/how-to-clock-a-gas-meter/ Don't worry about pilot lights, if you have any. Obviously you don't want a gas dryer or stove running, or other major gas appliance running. What is the supply temperature of the boiler?
  • neilc
    neilc Member Posts: 1,805
    and pictures of the boiler with piping and pumps
    known to beat dead horses
  • addohm
    addohm Member Posts: 25
    It was the pump. I had them put the appropriate size pump on that zone and all is well.