Please help/ Gas line sizing

kevin_5

We installed a Lochinvar 300,000 BTU ouput LP boiler in a large new truck shop, and are having trouble with getting the recommended 13" WC pressure at the boiler. We don't want to soot the thing up.
There is approximately 200 feet of 1" gas pipe between the LP tank and boiler room. There is a second stage regulator at the boiler.
My supplier now says that the charts call for two inch pipe. Is there not a way to get the pressure we need by bumping up the pressure at the tank, through the one inch, all the way to our second stage regulator?

We used to bury a lot of HDPE gas line for the gas utility, and I know that you can feed a lot of houses from a two inch line. Of course, it's a relatively higher pressure, but not THAT high, and why wouldn't it work in this case?

As always, thanks for your time-tested counsel.
Kevin

Unknown

Kevin, what pressure

is in the line from the first stage regulator at the tank to the second stage at the building?

Is the second stage regulator outdoors?

Noel

Floyd

Looks like...

You should have 1 1/4" line at 10 psi and 1 psi drop.
Would think that 1" would do it, you would just have a higher pressure drop.
But.. how many ell's???
each ell adds 10 ft and that could change everything.

Floyd

Unknown

Is the second stage outside?

If not, the code might not allow 10 PSI inside the building.

Noel

Jackchips

Where are you

located. In Ma the maximum psi for gas is 14". To go higher requires an application to the State Board but I doubt they would allow it in the house. The gas supplier should be able to tell you if the first regulator can be moved inside the house adjacent to the boiler regulator. Have you taken a permit? What does the inspector say? You may have to bite the bullet and change the piping.

Unknown

Pipe Sizing

First you said 300,000 BTU output do you mean input??

If that is the case

Sizing Between Single or Second Stage(low pressure regulator) and Appliance.

As follows:

Assuming undiluted propane capacities based on 11" W.C. seting and a 0.5 " W.C. pressure drop.

200 feet of pipe Schedule 40

1" pipe will allow only 227,000 BTU's.

1 1/4" pipe will allow 465,000 BTU's

2" pipe will allow 1,343,000 BTU's

Sizing Between First Stage (High Pressure Regulator) and Second Stage (Low Pressure Regulator)

Maximum undiluted propane capacities listed are based on a 10 psig first stage setting and a 1 psig pressure drop

200 feet of schedule 40 1" pipe will allow 2,601,000 BTU's

kevin_5

extra info

This is in Nebraska. It is 300K OUTPUT not input.
There are two elbows and a combination ell/street ell in the piping. The second stage regulator is inside near the boiler, the first one is outside near the propane tank. Thanks for all your help. Anyone else have any ideas or experience with this?

Floyd_2

Sure you don't have.....

a bunch of sh.... I mean stuff blocking one of the regulators???
Did you get a actual pressure reading on the piping between the two regulators???

Paul_6

you need to do a little

more leg work. you need to determine the actual req. input, the maximum supply pressure, the min supply pressure needed for adjusment purposes, and the manifold operating pressure.you need to determine the actual pressure between the outside regulator and the inside regulator. if the 2nd regulator was supplied with the boiler what does it require for inlet pressure? inches of water or lbs? nfpa allows inside distributon systems to operate at up to 5psi, without any special considerations. it allows pressures over 5psi with restrictions that you don't want to get into. most propane co. set up for 2psi max press. inside blds. even at 2psi your 1" pipe is a little small. if you figure a 300,000 btu output at 80% eff. your input would be 540,000 and that is moving you into 5psi distribution when you correct the sizing charts in nfpa 54. hope you find this info usefull. paul.

[Deleted User]

Propane/Lochinvar

Kevin,

My handy dandy chart says the following w/ some extrapolating.

200' of 1 1/4" pipe (.70 specific gravity propane)w/ 14" pressure @ the tank regulator should deliver approx. 400 cfh to the burner regulator w/ a 1" pressure drop. The 1" drop should compensate for fittings. Lochinvar recommends 2" pipe. However, that is w/ a .50" pressure drop & .65 gravity gas.

I am guessing that you are working on a Copper-Fin. My book (somewhat dated) calls for 10" manifold pressure. That is on the 300-750 mbh input units. The recommended supply pressure to the gas valve is 11-14". But, you seem to have read the book.

Hope this helps.

Paul_6

yes that makes

sense, they want that low pressure drop so that you don't get high lock up pressure at shut down, and a big wumph at the next start cycle. Paul