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gas line sizing

Paul S_3
Paul S_3 Member Posts: 1,257
i recently installed a rheem tankless water heater(199,000 btu).....my boss told me to tap into the existing 1" gas line....now here is what is hooked up to this gas line....1" gas line 50 ft (= 245,000btuh) there are two warm air furnaces (1) 120k btu (1) 88,000 btu....and there is a dryer and stove on the line .....heating and water heater units are at the 50 ft mark....and the stove and dryer are about the 25' to 30' mark after the meter.....oh and gas meter is a 250cph.....i explained all this to my boss and he said he never had a problem with installing a tankless heater "as long as there is 3/4" line going to the unit"....i told him he would need a bigger gas meter and a 1" dedicated gas line to the tankless heater....he just brushed it off like they always do....my question is whenever i install a gas appliance on the side i always use a gas line sizing chart....when i install tankless heaters i run 1" gas lines from gas meters...hence i make less on the job...and i have lost some jobs due to charging extra for the dedicated gas line or upsizing meter/line....what is going on that these units are operating without any problems with undersized gas lines/meters....is it really that important....on paper to my customers it just looks like there paying more than they have too.....Paul S
ASM Mechanical Company
Located in Staten Island NY
Servicing all 5 boroughs of NYC.
[email protected]


  • Paul48
    Paul48 Member Posts: 4,469

    When the customer can't get hot water out of that heater, because the furnaces are running, it will become very clear that it is important.

  • Steamhead
    Steamhead Member Posts: 16,454
    Your boss

    apparently can't do basic math. 
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
  • Alx
    Alx Member Posts: 3

    As a consulting engineer, you are correct in properly sizing the gas piping as you have described as per good engineering practice. Although there is diversity in the system, and at times you may get away with running  a gas line as per your boss, there may be times where the equipment will not fire during the cold winter months  where HVAC equipment is energized,
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