Need Help Figuring Out Pipe Size NG for Generator

[Danny504]

Hello, I am trying to figure out everything I need and correct sizing to run a portable generator off of natural gas.

My gas meter is located 70ft from the spot where I would like to have a dual - quick connect valve, one side of the quick connect to plug my portable natural gas generator during emergencies and the other side to plug my Weber Genesis grill.

The manual for my generator has this information:

Natural Gas Feature: 6900 Starting Watts, 5500 Running Watts; 439cc engine.

Natural Gas Pressure Range: 7-11 inches water column (0.25-0.40 psi) (13-20mm mercury) (1.7-2.7 kpa)

Natural Gas Fuel Consumption: No Load = 72 cubic feet/hr; Half Load = 86 cubic feet/hr; Full Load 101 cubic feet/hr

My generator has a 3/8th inch male connector on it.

Here are my questions:

What size pipe should I have a plumber run from my meter to the spot with the dual quick connect that will supply a sufficient amount of gas?
What size should the quick connect connectors be?
What size hose should I use from the quick connect to my generator?
Will I need any adapters to going from a larger size to a smaller size?

I am a total novice at all of this so my terminology may be wrong. Try to break it down for me on kindergarten level lol!

Thank you for your help!

 

[Twowaxhack]

First things first. What is the gas pressure at the outlet of your meter and what appliances do you currently have on gas ?

If I had to give you an answer without anymore info, I’d say 3/4” pipe for the 70’ run.

You’ll need bell reducers to reduce the pipe size from 3/4” to the size of your connecting hoses.

Consult your generator book or hose maker for the BTU rating of the desired length of flex hose. I’m assuming neither will stay connected all the time.

1 cubic ft is approx 1,000 BTU’s
Example 72 CU FT is approx 72,000 BTU’s

 

[Danny504]

Here are some pics of my meter. Does this have the information you need?

As far as the hose, I was looking at this one on amazon, it is a 1/2 inch hose with 3/8th's connection, but I'm not sure if this is the correct hose to buy.

https://www.amazon.com/GASPRO-Natur...b03-ba62-d51dbcadf055&pd_rd_i=B07RBPR5LQ&th=1

 

[Danny504]

My stove top, clothes dryer, and on demand water heater are on gas. It's possible that gas is also tied into my central air and heat but I'm not positive on that.

 

[Twowaxhack]

My stove top, clothes dryer, and on demand water heater are on gas. It's possible that gas is also tied into my central air and heat but I'm not positive on that.

You might need a meter upgrade from your gas company.

 

[Danny504]

Ok thanks. As far as the meter upgrade, if I call the utility, what amount of gas do you recommend I should tell them I need an upgrade to?

 

[Twowaxhack]

Based on the size of your meter and the appliances you’ve listed that you’re running the meter is probably large enough. Based on the size pipe at the meter it’s probably low pressure, 8” w.c. Pressure.

You could add up all the listed BTU requirements of your gas appliances. There’s a tag someplace on each appliance telling you how much gas it uses.

I’d run 3/4” pipe most likely.

The hose you listed would be fine for the grill. I doubt it would be big enough for the generator, but it might be, it’s close.

When I posted you may need a meter upgrade, I hadn’t looked at the pics you posted. That’s a pretty big meter. That’s good.

 

[Danny504]

Thanks. Based on my meter size, and let's just say all other gas appliances are turned off, approximatley how many BTU's will my meter deliver in the 3/4ths pipe you are suggesting at the end of the 70ft run?

 

[Twowaxhack]

Thanks. Based on my meter size, and let's just say all other gas appliances are turned off, approximatley how many BTU's will my meter deliver in the 3/4ths pipe you are suggesting at the end of the 70ft run?

That depends on what pressure you’re starting with, what type pipe you use, how many fittings you install.

What type pipe will you be using ? We will figure the pressure is regular 8” W.C.

 

[Twowaxhack]

For steel pipe with a starting pressure of 8” WC you could run approx 100,000 BTU’s and only drop .3” WC. in pressure. With 3/4” 70’ of pipe or equivalent.

That basically means you could run 100,000 BTU’s and still maintain that 8” of WC you started with. 7.7” WC actually.

If you have 8”wc and went 70’ with 3/4 you could run 130,000 BTU with a .5” wc pressure drop. That would put you at 7.5”Wc with 130 btu being consumed.

If you had 8”wc and went 70’ with 3/4 and your appliance had a minimum inlet pressure of 5”wc, a 3” pressure drop, you could run 330,000 BTU’s. But your generator requires at least 7”wc and lucky it doesn’t require near 330,000 btu.

That’s for steel pipe……every other pipe has much better flow.

Figure each 90 degree ell as 2’ of equivalent pipe run.

 

[Danny504]

I was thinking galvanized pipe to match the pipe that is coming out of the meter now, but I can use whatever pipe you recommend would be best. As far as fittings, it is a straight run down the side of my house from my meter to the spot at the end of the 70ft where I want the dual quick connect. There may be one rain gutter the pipe needs to work around but that's it.

 

[Twowaxhack]

If use this pipe for the run underground
https://www.supplyhouse.com/Oil-Cre...Medium-Density-PE-2708-Gas-Pipe-150-Ft-SDR-11
I’d use galvanize or copper to come out of the ground with. 3’ on the horizontal before you come vertical out of the ground has to be metal pipe. In my area, any type metal basically. We use galvanize, copper and stainless.

Transition fittings are made to transition from plastic to the metal pipe.

 

[Twowaxhack]

Here are what the transition fittings look like.

If you use copper to transition out of the ground you should use a brass nipple between the copper and the tradition fitting.

Those black caps are thread protectors. That’s 3/4” MIP pipe threads under the cap.

 

[Danny504]

The whole 70ft run is over paved concrete, so I was thinking I would have a plumber run a pipe above ground and bolted along the side of my house. Is the pipe your recommended good for this scenario?

 

[Twowaxhack]

The whole 70ft run is over paved concrete, so I was thinking I would have a plumber run a pipe above ground and bolted along the side of my house. Is the pipe your recommended good for this scenario?

Not the plastic, no. Here I could use copper, galvanize or stainless. Or that flexible track pipe crap.

 

[Danny504]

Another question is about the size of the hose from the quick connect to the generator. The input on the generator where you connect the natural gas hose to is 3/8ths.

Some hoses are 3/8ths diameter, and some hoses are 1/2 diameter with a 3/8ths flare connector. Should I go with a 3/8th diameter hose to connect to the 3/8ths input connection on the generator, or go with the larger 1/2 in diameter hose with the 3/8ths flare connector?

 

[Twowaxhack]

Another question is about the size of the hose from the quick connect to the generator. The input on the generator where you connect the natural gas hose to is 3/8ths.

Some hoses are 3/8ths diameter, and some hoses are 1/2 diameter with a 3/8ths flare connector. Should I go with a 3/8th diameter hose to connect to the 3/8ths input connection on the generator, or go with the larger 1/2 in diameter hose with the 3/8ths flare connector?

For the generator get the 1/2” hose. For the grill get the 3/8” hose.

You want a bigger hose then reduce at the generator if need be.
The hose you linked from Amazon has a 1/2” flare x 3/8” fip fitting that will screw over the male 3/8” mip of your generator.

You could just get two 1/2” hoses so you had a spare that would work with either the generator or the grill. The 3/8 hose wouldn’t run the generator.

 

[Danny504]

Ok, so if I have a dual female quick connect attached at the end of the 70ft run of 3/4ths inch pipe, one side of the dual connection will have an adapter that goes from 3/4ths to 3/8ths and the other side will go from 3/4ths to 1/2 inch. Does this sound correct?

 

[Twowaxhack]

Ok, so if I have a dual female quick connect attached at the end of the 70ft run of 3/4ths inch pipe, one side of the dual connection will have an adapter that goes from 3/4ths to 3/8ths and the other side will go from 3/4ths to 1/2 inch. Does this sound correct?

Yes. You must either use a reducing tee or bell reducers. No bushings.

Or use 2- 1/2” hoses. Then use a 1/2 x1/2 x 3/4” tee and two 1/2”nipples to screw your quick connects onto.

 

[Danny504]

Great! Now, how can I figure out what my starting WC pressure is? I think you made an assumption we were starting at 8 inches. What's the best way to confirm what I am starting with?