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Gas Meter Sizing - max CFH

Brad White
Brad White Member Posts: 2,398
and what utility you use, your low-pressure situation is all too common. No idea where you are, but in Boston in many downtown areas and even outlying neighborhoods, Keyspan will only guarantee 4.0 to 4.5 inches at the meter. That is not enough to launch a photon torpedo.

You said that 'they should have a minimum pressure', and by golly, they do.

The infrastructure is old and the piping is wrought iron from the gaslight days is one reason I was told. Larger commercial projects can justify a gas booster but for a residence the cost would be in my opinion, prohibitive, tens of thousands of dollars.

Your meter is nominally rated at 0.50 inches WC pressure drop. Find out if you increase flow what the capacity would be and also if you can accept a drop in appliance performance at a lower pressure. Provided the unit will work within range, a drop in capacity should be expected.

I gather that your capacity assessment took into account non-winter use such as the outdoor grille (real men grill year round :)

My suggestion is that you may want to forget the tankless (high input, no storage) and go with an indirect (or immersion coil and storage tank) off your steam boiler and use the appliances you now have.
"If you do not know the answer, say, "I do not know the answer", and you will be correct!"

-Ernie White, my Dad


  • Capt K
    Capt K Member Posts: 1
    Tankless HWH - limited by gas main pressure?

    I plan to install a Rinnai Tankless hot water heater. This will replace current gas fired HWH. Also a steam boiler/radiator system that works fine. I calculate my gas consumption will increase from 245,000 BTUH to 385,000 BTU once the new Rinnai HWH, steam boiler, gas stove and dryer and outside grill are factored in. I also estimated the max CFH could be 300 CFH.
    The current gas meter is rated at 275 CFH with MAOP = 5 psi. All gas lines to appliances will be sized right including a new 1 inch gas line run from meter direct to Rinnai HWH.
    Question: when I called my local gas co re. installation of Rinnai HWH they mentioned the natural gas pressure in my area might not be sufficient to support the addition of the new tankless HWH. I find this hard to believe and think they could just install a larger flow rate gas meter. The gas main press in the street should have a min pressure to ensure all homes in the area could run their heating systems maxed out and not run short of gas press. Appreciate feedback since think I did not reach the right contact at gas company. Would a larger meter do the trick to run the tankless HWH?
  • Dave Yates (GrandPAH)_1
    pool heaters

    Our local gas co used to respond & change the meter when we hooked up pool heaters. Same CFH meters as you're mentioning. My thinking was that adding a 450K pool heater, by itself, would overload the meter and starve the home's gas appliances.

    They've since decided they don't need to install a new meter! The claim is that the pool heater's line joins at the meter's outlet and that the meter can handle the load by virtue of such a short 1" run until the home/pool loads split off.

    Sounds like trouble brewing to me & we have a disclaimer in our quotes for pool heater gas lines.

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