Gas pipe sizing for heater

[tpothen]

Hey all - Seems like there's quite a few people here that know about gas line sizing so I'm hoping one of you can assist. I'm looking at installing a 45,000 BTU gas heater in my garage but need to figure out the pipe sizing. Currently I have an 1 1/4" pipe coming into the house that travels about 20' then a 1/2" pipe drops to the furnace and a second 1/2" drops to the water heater. At this point the pipe is reduced to 3/4" and travels about 15' where there's a T that has a 1/2" pipe to a gas dryer, the other side of the T stays at 3/4" and goes to another T with one side going to a stove. and the other is capped off.

Any input on if I can continue to the garage heater from the capped pipe and continue the 3/4" to the garage or will I starve the heater if the stove or dryer are used?

 

[LS6 Tommy]

It's not a yes or no question. You need to measure the runs, count the ells, tees and calculate equipment usage, then use a sizing chart for pressure drop to see if your planned size is OK with what you want to do.

Tommy

 

[HoosierBuddy]

Tommy is right, but I'm going to at least "lean towards" you should be OK with continuing 3/4" based on little more than a gut feeling.

In the immortal words of Lieutenant Columbo though, there is one thing that's bothering me and that's your 1 1/4" pipe. Odd size and not something you see in many houses...so please verify that it is in fact 1 1/4". If you're right, it should measure just a hair over 1 5/8" OD. If it measures between 1 1/4" and 1 3/8"...that is 1" pipe....and it does make a difference to the calculation. 1" would be a lot more common in residential construction than 1 1/4". Like 100 times more common.

A sketch with all of your line sizes should be sufficient to answer your question.

Phil

 

[sweetk30]

i have almost 200 ft total run of 1" from the meter on the house threw the house and then out to my shop and to the end of the shop were i have a 125,000 btu modine hot dawg . not a problem yet with flow or demand i can tell . it was all in here when i moved in 5 years ago .

the only upgrade i did was the modine heater inplace of the old already removed unit . and the inside of the house were the meter use to be years and years ago was choked down to 3/4" and back to the 1" . i removed the 3/4" section and installed 1" stuff for un restricted flow .

soapy water and no leaks . all has been good .

 

[Jim greengo]

1 1/4" is pretty common around here in older houses.

 

[D45]

3/4" will be fine

I have 3/4 pipe on a 70 foot run for a 75k heater

 

[mrobins297aaa]

Here's the method we used to size NG lines, IIRC it was even in the BOCA book.

Anyway it's pretty straight forward: you take the distance to the farthest appliance from the meter and use that column to sizes all the other appliances based on BTU's required.

In this example the farthest appliance is 150' from the meter so you would use that column.

 

[mrobins297aaa]

There's a big difference in the capacities between 1" and 1 1/4" pipe, 1 1/4" pipe is double.

 

[Ggg]

Another detail that is not mentioned; is this natural gas or LP?