BTU Numbers For Gas Line Sizing

31b

I'm switching to gas, and will be having gas lines put in soon. From there I'll be having the furnace put in this summer, and then replace the elec hot water heater with a tankless gas one around winter, then next year do the range/dryer too.

Obviously I need to give the plumber the BTU numbers for the furnace and hot water heater, but I don't have any models selected for the dryer and range yet, I'll deal with those later.

I would think the loads on those would be pretty standard right, and the plumber could just estimate that without a specific number? i mean for most common models that is.

SLSTech

I know for Propane - 3/4" min. for a tankless
Range varies based on style & BTU requried
Dryer can be a 1/2"

Not sure on Naturual Gas - but I think it would be the same

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KillerToiletSpider

You need an 1-1/4 main line to the first fixture, it can reduce to 1" from there.

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ARealplumber

What he needs to do is find out if he has high pressure natural gas or low pressure...that would determine what size pipe to run. You cant size the line properly until you know the service pressure. We do 2lb gas systems and 1 1/4" pipe would run a few normal houses at that pressure and would be over-kill.........WAKE UP

fabdraftdesign

FIRST, you have to get the highest--it COULD be dual-stage--INPUT rating in BTU/Hrs. For a water heater it should be less than 200K or 200MBTUH. Check the (submitted, signed and sealed) P.E. drawing or (published) manufacturers spec.s.

If it's 200K or more, then it's not a "water heater" but rather a "boiler" and a whole, more-strict set of codes apply. Get the total for ALL the appliances.

THEN, figure out the length, the total length (main, run-outs, risers, etc.,) of ALL pipe from the meter to the device(s).

THEN, check the gas pipe sizing chart in the A.S.H.R.A.E. Fundamentals book... I forgot the section, just find it in the index in the back.

THAT chart will tell you the minimum size (in I.D. diameter) of pipe you need to handle a certain MBTUH input. Size yer pipe for THAT, the "branch-offs" to any device can be sized the same way; subtract the loss from the "main" and downsize (reduce) accordingly.

For LP ask the manufacturer about equivalents.

Get the range of delivery pressure from the P.E. or manufacturer(s), and tell the utility company what you need.

Et voila! ANOTHER satisfied customer! Now go collect that check!

31b

sorry meant to reply on this earlier, did the plans up a while back and submitted for the permit, got it back approved the next day. I'll post some pics of the install soon too.

Had lots of fun using a friends Ridgid tripod and electric threader.

This is the plan:

Leadworker

Hey what city are you from. I sized your drawing and turn out to be a 1" line for the main from the meter. Did you convert your btu's into cubic feet per hour.

31b

yeah I oversized it a bit, didn't want to have any problems with starving the tankless water heater, also eventually I may add another "T" between the first and second "T", branching off to the right side of the house to a permanent grill outside in a masonry type of enclosure.

no meters incidentally, it's for propane.

Leadworker

In that case. It'ill be fine.