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    gas line sizing (9 Posts)

  • Paul S Paul S @ 11:59 PM
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    gas line sizing

    hey everyone .....does anyone have a easy to use gas line sizing chart?....doing a oil to gas convo....boiler is 110000 btu.....there is 3/4" gas pipe near the boiler....meter is about 50 feet away.....gas line feeds 3 stoves and a 75 gl water heater.....should i increase to 1"???and gas meter is 250cph(how many btus can that do??)
    thanks PAUL S
  • JStar JStar @ 6:42 AM
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    Gas

    The burner instructions should have a gas sizing chart.

    In this situation, I always leave the existing gas line, and run a dedicated gas supply for the boiler. In your case, that would be a minimum of a 3/4" line. Better to go one size bigger, as it is borderline sufficient. Otherwise, you would have to increase the existing line to 1-1/4". The meter is also too small. 250CFH = 250,000BTUH.
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  • Paul S Paul S @ 7:11 AM
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    thanks

    Is the Meter really too small?...how many BTUs is the average stove?
  • Paul48 Paul48 @ 1:40 PM
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  • heatpro02920 heatpro02920 @ 9:28 AM
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    tons of them on the web...

    http://www.paragoninspects.com/images/Tankless_WH/gas-piping-sizes.jpg

    But if I were you I would run the boiler her own line, 1" is just as easy to thread and costs only a little more than 3/4" so I normally run 1" then drop from the ceiling 3/4" with a reducing elbow, then if your boiler has a 1/2" inlet {not sure what boiler you have} I would 3/4x1/2 tee to the unit... A sinlgle 3/4 depending how far you are will give you 110 all the way to almost 100' but once you start taking stoves and clothes dryers off of it, you run out fast... Plus the elbows add up your length pretty fast....

    Save your self some trouble and go 1" designated, you dont want to do it twice because when the boiler comes on and she is cooking the stove burner chases itself and rolls off...

    I factor stoves in at 50K BTU 80k btu for 80 gallon tank so if I were running 3 stoves, an 80ga tank, and a 110 btu boiler I would want 1 1/4 main {but I dont like threading and running 1 1/4 it sucks} so most likely they would get 1" feeding the boiler and water heater and the existing 3/4 would do the stoves...

    How much gas pipe is between the boiler and the meter and how many elbows? if its a nice straight shot with 3 elbows it will make a big difference vs. if its up and down and around and 70ft of pipe...
    This post was edited by an admin on February 26, 2013 9:41 AM.
  • RJ RJ @ 12:12 PM
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    line sizing

    here is some info
    RJ
  • RJ RJ @ 12:20 PM
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    sizing

    Sorry sent 001 twice    here is 1 more
    RJ
  • Paul S Paul S @ 7:10 PM
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    thank you guys

    thanks for all the help....the meter is 250 cph.....what is the next size up since its too small....????and do the utility company usually change it for NO charge or is there usually a fee....
    PAUL S
  • Tim McElwain Tim McElwain @ 7:58 PM
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    Paul S you can find

    everything you need in either the National Fuel Gas Code NFPA54/ANSI Z223.1 Chapter 5 & 6 and Annex "C" or the International Fuel Gas Code and others. You want to total up all the BTU inputs for all the equipment. On gas ranges you can figure 4 top burners 10,000 BTU's each plus the oven 25,000 so that is roughly 65,000 BTU's get the inputs for other equipment from the rating plate. There are tables in the code 6.2(a) through 6.2(v) for Natural gas and 6.3(a) through 6.3(m) for Propane. Annex "C' also contains Table C.3.2 Equivalent Lengths of Pipe Fittings and Valves. To use the tables you need to find out from the local gas utility what they use for an allowable pressure drop as you will need this to be able to get the correct table. Natural Gas uses a specific gravity of 0.60 and propane uses 1.50.

    Gas utility must not only size the meter correctly but the gas line into the building may also need enlarged. The AL 250 meter will pass roughly 250,000 BTU's.

    There are two methods for sizing shown in Annex "C" of NFPA 54 which are used The Longest Length Method which is conservative in its approach by applying the maximum operating conditions in the system as the norm for the system and by setting the length of pipe used to size any given part of the piping system to the maximum value. The other method is The Branch Length Method this sizing method reduces the amount of conservatism built into the traditional Longest Length Method.
    My Fundamentals of Gas Volume I illustrates with actual piping examples all of this.
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