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LP gas pressure drop

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kcopp
kcopp Member Posts: 4,443
Installing a Combi boiler in a home today.
Fire up the unit and gas pressure is @ 11.1 in wc.
Goes into high fire and it drops to 8.5" wc.
I don't do a huge amount of LP work but that sounds excessive?

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  • lchmb
    lchmb Member Posts: 2,997
    edited October 2016
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    yes...sounds like either your piping is undersized or an issue with the regulator. (wouldnt want more than .5" drop in pressure)
    kcopp
  • kcopp
    kcopp Member Posts: 4,443
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    Piping is 25' on 1/2" should be fine for 125K....
  • njtommy
    njtommy Member Posts: 1,105
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    Whats the min max range say in the manual?
  • kcopp
    kcopp Member Posts: 4,443
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    7-14 at start... only 1-2" drop.
    NFPA refers to only a 1/2" pressure drop in all the LP stuff.
  • Jamie Hall
    Jamie Hall Member Posts: 23,450
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    How big is the boiler and how big is the tank? Any possibility that evaporation rate in the tank is being exceeded by the demand?
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • kcopp
    kcopp Member Posts: 4,443
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    Boiler is 125K in. Tank is huge... Its a condo w a meter.
  • Zman
    Zman Member Posts: 7,575
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    I had a similar problem that drove me nuts for a while. The pressure would drop to 4" to the whole house when the boiler fired up. Any other load would not drop the pressure at all.
    I swapped out the house regulator and it was fixed.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
    delta T
  • delta T
    delta T Member Posts: 884
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    My money is on the reg. Usually the first thing I go to anymore when I see this problem on LP.

    25' of 1/2 should be plenty for 125k, so you should be seeing a drop of less than .5"