How to tap into propane (iron pipe) line

[plowhog]

Are you sure about the btu for that generator??? ... Most modern larger units take between 225,000-325,000 btu.

You are exactly correct. My earlier info on btu's was wrong, plus an extra-large unit was supplied (same price) because others are out of stock. I just checked and it is a whopping 355,000 btu's. 24kw generator.

This size generator is overkill, but is already delivered. Now, I need to check pipe size first, and determine if the existing 3/4" is adequate or if a new dedicated gas pipe is needed. Can anyone help with how to calculate that? Here are my specs:

Location from 300gal tank to generator- 60 ft. Existing 3/4" gas pipe from tank to generator location.
Generator location is outside. It is the first gas appliance.
T at the generator location-- going into house using 3/4" pipe. Call it 15 feet to the water heater.

Finally, if feasible, I'd like a future option to add a gas range in the residence. (Not part of this work.)

 

[plowhog]

largest was a 426 Hemi nicknamed Elephant

Surprised to hear you have that engine running on propane. I have the same engine in a muscle car and it gets 4mpg .... but I don't drive it gently.

 

[plowhog]

Though I have done my own propane hook up, it was entirely planned, supervised, and inspected before the final source connection was made.

A direction I am likely headed in. If I need to trench for bigger pipe, it will involve permits, inspectors, the propane company, probably half the neighborhood and maybe an article in the local newspaper before its done.

btw I checked on permit cost. Based on county website info, about $2,100 in permits and inspections to run a new gas line, connect a generator, and connect a 2SER wire to a transfer switch. This project would trigger 3 permits-- earthwork, plumbing, and electrical. 2 inspections for the trench.

Labor, equipment, materials, contractors, etc. is on top of that cost.

 

[workinonit]

When I did my mom's standby I had the gas company install a seperate tank just for the generator. Heck, here you set the generator and stub out the gas line then they deliver the tank, run the line and hook it up.

 

[rScotty]

I've never done gas pipe work before, so anything you can contribute will be appreciated. Thanks!

I've done a few systems. My tendency is to work to code and if questions I work toward the code's intent.
The diameter of the pipe seems right for your job. Conservative, if anything.

1. Should I use gas rated pipe dope on the threads instead of yellow gas tape?
I have gone away from gas tape and am now using pipe dope. I get better joints and they seal well. All the name brands of dope seem to work about the same. I take the time to clean & wirebrush the threads and deburr the ends.

2. When I extend the gas pipe, it will be unsupported. What is a recommended way, and what materials, are used for support?
I always run the pipe to and along a wall. I sometimes put wood blocks onto the wall for spacing. When the pipe leaves the wall to go to the appliance is where I put my low pressure regulator and then I go another foot of rigid and insert the flexible section. The flex section (comes with most generators) is especially important when connecting to anything that vibrates.
3. I presume a drip leg is needed. (None present for the spa heater.) Do you use a standard T with a nipple (4"?) pointing down?
YES
4. Where do you install the fitting to allow for a pressure test? Does that require another T, and does that test device stay in the system permanently? (I read you should pressurize with air to 25 lbs for 24 hours to check for leaks?)
Instead of a T for the drip leg use a cross. Drip leg goes down, pressure test fitting (1/4" npt) goes up. You can leave the gauge or just use a bore plug to close the 1/4" threaded opening.
YES. That is how I pressure test. Turn off the propane at the tank for the test.
5. Do you pressure test all of the pipe including back to the tank and to the water heater? I presume I should test all of it since I have to undo/redo fittings "upstream" of the shutoff to the generator.
You should test all of the pipe back all the way back to the high pressure regulator outlet on the tank. Turn off the tank.
6. After a successful pressure test, what is the process to bring in the gas to fire up the generator and re-fire the water heater?
No special procedure. If you want, you can leave one of the last connections loose until you smell propane and then tighten it. I consider that to be best practice and always do so. Don't worry about a little air.
I've noticed that most heaters (Rennai etc.) will purge themselves and recycle the start a few times until they light. Generators may have to crank for awhile....but basically they will all purge themselves. Still, I give them a helping hand as I've said. Best done with two people.
Good Luck,
rScotty

 

[grsthegreat]

You may not need a larger underground pipe from tank. You might just need to tee off before existing house secondary regulator and add another regulator for generator. But you need to have your propane supplier or heating contractor look at setup. They need complete list of all gas appliances max btu for house and generator. With this info they can estimate pipe sizing. The gas coming from tank primary regulator is probably 10 psi. You can move alot of gas at 10psi.

where i usually ran into issues is the houses up here are generally only supplied with 1/2” line from propane tank. If yours is really a 3/4” line, you may be ok.

 

[RickB]

Depending on your ambient temperatures and the shape of the tank it may not have sufficient liquid surface area to volatize enough vapor to meet the generator's peak fuel demand.

Propane Tank Sizing - Tarantin Industries

www.tarantin.com

 

[LD1]

Since op didn't ask for help sizing the gas line or opinions on whether he should install his generator I trust he has that part covered. For crowd that insist's on kicking it around,here's something you can stir into the pot. I've been running irrigation pumps,generators and farm tractors on propane since the 50s. Although non of the engines were rated in BTUs,all had horsepower ratings prominatly displayed. The smallest was a 22 hp 9N,the largest was a 426 Hemi nicknamed Elephant but I'll talk about one that has been on our farm since new in 1958 because it's the one I've owned,used,repaired and maintained the longest. 841 Ford rated at 62 horsepower. I seriously doubt the engine on OPs gen is even close and this old girl has been happy with a 1/2" line now going on 65 years. You can aurgue it must not have been loaded heavy else it would have starved and suffered damage that required repair. Maybe not,but it has been loaded heavy enough to bring the governer in at full throttle.
I'm looking foward to istallation of transfer switch. "EVERYBODY" on TBN are experts when it come's to electricity so it should turn out to be fun,fun,fun.

Not that its relevant to the OP's question on pipe sizing.....but there is a BIG difference in a LP engine for a tractor or forklift and a home generator.

The propane tanks made for LP engines have a suction tube and they are actually drawing LIQUID propane. Not propane gas. And regulator is the wrong term that was mentioned earlier...but the engine will have a vaporizer on it that converts the liquid propane to gas.

A 1/2" line 10' long will flow about 7gpm of LP....which roughly translates to over 35 million BTU worth of propane. Which is a little more than a 10' piece of 4" gas line if flowing the vapor.

Most all gas pipe sizing charts assume gas flowing in gas form....not liquid. Because liquid form of propane is not really common outside a few old tractors and LP forklifts.

 

[4570Man]

You are exactly correct. My earlier info on btu's was wrong, plus an extra-large unit was supplied (same price) because others are out of stock. I just checked and it is a whopping 355,000 btu's. 24kw generator.

This size generator is overkill, but is already delivered. Now, I need to check pipe size first, and determine if the existing 3/4" is adequate or if a new dedicated gas pipe is needed. Can anyone help with how to calculate that? Here are my specs:

Location from 300gal tank to generator- 60 ft. Existing 3/4" gas pipe from tank to generator location.
Generator location is outside. It is the first gas appliance.
T at the generator location-- going into house using 3/4" pipe. Call it 15 feet to the water heater.

Finally, if feasible, I'd like a future option to add a gas range in the residence. (Not part of this work.)

75 feet of 3/4 line definitely won’t support 355k btu if it’s at the typical supply pressure of 2-3 psi. If you can bump the supply pressure up it might work.

 

[ultrarunner]

Neighbor bought a 10k duel fuel generator at Christmas and was unpacking it over the weekend.

He bought it because it is Propane rated and plans to use his small BBQ propane tank.

No doubt it will run on propane but I don't think it is going to work as planned.

I ran into problem at a small medical clinic where I maintained the natural gas generator for the medication refrigerators.

A tree damaged the utility meter and utility was replacing with a much smaller meter... and generator simply would not put out.

That was a long weekend as the nearest appropriate gas meter was in a service yard 100 miles away.

About the only time I have found existing homeowner service ok is when it was sized for large pool gas heater.

Very interesting thread.