Gas meter size??

ChrisJ

Hi all,

I need some input on how gas meters are sized because I think mine is technically undersized for the load.

My meter says it's rated for 250 CFH @ 0.5" diff.

My current loads are :

WH : 40
Boiler : 125
Clothes dryer : 30
Kitchen range : 50 (5 burners + oven)
Weber grill : 37

I come up with a total of 282.

I'm hoping to add a generator soon that needs 162 so that'll put me at a total of 444.


Generator aside, do I need a bigger meter already or is this "close enough"?

What is the next larger size meter typically used?

Zman

You are a bit undersized as it stands. Those 250's are pretty common, affordable meters, I have seen quite a few of them that are sized like yours. If you get curious, you could turn everything on and clock the meter.

CTOilHeat

Yeah, you're technically a smidge undersized but if you weren't going to be adding a generator I'd say "close enough". The chances of you running everything at max load at the same time is pretty low.

If you are going to increase your potential load you should get the ball rolling ahead of time on the meter. It can take the utility-depending on who you have- a LONG while to upgrade.

DZoro

Contact gas Co. Around my area they can put on a 2psi regulator, not sure if they change out the entire meter.

Gilmorrie

Your present meter is fine, considering load diversity - which the gas utility will undoubtedly say. Ask yourself how likely it is that all those loads will running simultaneously.

HVACNUT

@ChrisJ
If you dont already have one.

EBEBRATT-Ed

So if you ran everything at once which is doubtful your meter would be undersized. The pressure drop would increase above the standard .5" of wc, gas pressure in the house would have a very slight drop.

The last one I did was adding a large pool heater that needed 250,000btus. The gas utility upsized the meter. Not sure the next size around 500-600cfh I think

MikeJ

Have the same meter in my house and very old and wise heating help member ask if my meter was big enough.

If you go to a 2lb system its good for 600, I have 2lbs

EBEBRATT-Ed

so it will give you 250cfh with only 7"wc inlet pressure

Gordy

You have to ask yourself can this scenario happen often.

Wifey is doing laundry so water heater may fire, and gas drier is running. It’s winter time boiler is firing, and wifey is preparing a huge meal with all five cook top burners going, and the oven. Chris decides he’s going to cook a beef brisket on the grill also.

Then the power goes out, and the generator comes on.

What are the odds that everything fires simultaneously? The only constant loads would be cook top burners, generator, and grill.

Steamhead

It only takes one time for something to go wrong. Too-low gas pressure can cause atmospheric burners to "blow back" i.e. the flame passing from the burner head into the tube. Under certain conditions this can cause a fire.

This is why gas meters should be sized to handle the entire connected load.

JUGHNE

Mike, was the meter very old or the other HH member simply wise and not very old?

Tinman

The rare times I diagnosed a problem at the meter or it's regulator, there was always an issue with a gas appliance in the building that got me there. I would think that if you fired all the appliances up, checked gas pressure at each, and clocked the meter individually for each, you'd know if there's a problem with the meter or line sizes.

Solid_Fuel_Man

Gas ranges always make me laugh, I bet not even on Thanksgiving morning will every burner and the oven be on HI simultaneously.

How many gas (propane) guys have seen a 30 foot long 3/8" copper tubing feeding a full slide-in gas range which states its total load at somewhere 60,000 btu/hr? With no signs of under pressure and it's been there for 40 years.

ratio

I personally have found, in an actual install, a 7" system with over 7" per 100' of pressure drop. Now, it's true that since the equivalent length was only ±50 feet I got somewhat over the 4" minimum necessary to operate; nonetheless I think that's excessive. The only saving grace was that it only served one appliance (250K BTUh duct heater), so it wasn't underfired—as long as the inlet to the regulator didn't sag noticeably.

Where sizing things for greatest pressure drop gets you into trouble is if there are more than one appliance on the regulator, especially if one or more are large loads. Think of regulators as a manually adjusted resistance to reduce the supply voltage. Now imagine the load current changing. What's going to happen to the voltage? The same thing happens to the appliance gas pressure.

Solid_Fuel_Man

I like to pipe gas with manifolds. Run black iron into house to an accessible location (boiler room) and then make a valved manifold out of iron T's. Then each branch can be sized according to the individual load served. I am strictly propane so supply pressure sag is not an issue like it is (I read here) with NG. Having on-site fuel supply with all the variables in your control simplifies things! The only meter job I've piped was an appartment complex with a large UG tank, each appartment was individually metered.

ChrisJ

@Stephen Minnich said:
> The rare times I diagnosed a problem at the meter or it's regulator, there was always an issue with a gas appliance in the building that got me there. I would think that if you fired all the appliances up, checked gas pressure at each, and clocked the meter individually for each, you'd know if there's a problem with the meter or line sizes.

There isn't a problem, yet.
I have fired everything, and everything was happy.

But, the generator I want to add needs 162CFH at full output, 80 at 1/2 output.

I'm just trying to get all my ducks in a row before I start going down this road.


I was just surprised I had already exceeded the meters capacity. Technically.


The gas co had told me back in 2011 they would gladly give me a bigger meter for free if I ever needed it. I just don't know what they would require to do so.

Danny Scully

I would think all you would need is a pressure test certificate @ChrisJ

Shane_2

In my area, we add a lot of gas appliances. Gas company only needs list of appliances and inputs. They have no problem upgrading a meter at no cost to the customer.

Just call them, you have the info already.

adambnyc

@ChrisJ having been to this rodeo myself, don’t forget that depending on how you are hooking up that generator, you might have to repipe you main gas pipes for your house for larger diameter pipes. I had to go from 3/4th to 1 1/4” to accommodate my tankless.

If your going to tap into the gas line for the generator right after the meter, then you should be OK leaving your existing gas pipes. If you are going to go , say out of the other side of your home and the generator needs to go thru your in house gas piping, then your looking at a repipe here also.

USMC3105

Get info. Very late to the game. A couple of questions..

Trying to install a home Gen. The Gas company telling me i need to upgrade line from street to house from 1/2 inch to 3/4 inch. They say unable to tell me how much BTU's required for mandatory upgrade of line? Seems like BS? Are they correct?

My max demand now is 383k BTU.I can reduce it to 243k btu by replacing tankless water heater with the traditional water. My meter is rated to 250 btu. The Gen would add a 329k btu. I see info about a 2 lb line upping the total load to 600k btus. Anyone have more info on that 2 lb line. Can't find anything online about it.

Thanks,
Mike

Steamhead

The gas pressure in the street is higher already. There should be a regulator in front of the meter which drops the gas pressure to less than 1 PSI before it goes thru the meter and out to the appliances. That's how they can get away with such small service lines.

This is not the same as 2-pound gas inside the house. For this you would need an additional regulator before each appliance to drop the pressure to a level it can use. Since, from your description, the rest of your system is set up for low pressure (7" water column or so, which is roughly 1/3 PSI) it makes sense to stay with that pressure. You would just need a bigger pipe between the meter and the generator, once the meter and service line are upgraded.

Last but not least: Gas piping is NOT a DIY thing. You need a knowledgeable, licensed pro to do this work. Where are you located?

HVACNUT

@USMC3105
You might be better off starting a new thread.
Click on the Pencil.

mattmia2

i wanted to get a 2psi service so i could replace the 70 year old piping that had been trough a fire and put a regulator where the appliances were. i found out there was only 2psi in the street.

Since propane is about 3 x the energy content per volume of methane and is usually regulated at a bit higher than 7 " wc, isn't 3/8 copper tube usually perfectly adequate to supply the full output of a range?

It seems the utility uses the 1/2 psi drop table when sizing services and that is very conservative, if you have 2psig at the street you can drop at least 1 psi, probably 1.5 psi and still have plenty of pressure to regulate down to 7" wc.

ChrisJ

> @mattmia2 said:
> i wanted to get a 2psi service so i could replace the 70 year old piping that had been trough a fire and put a regulator where the appliances were. i found out there was only 2psi in the street.
>
> Since propane is about 3 x the energy content per volume of methane and is usually regulated at a bit higher than 7 " wc, isn't 3/8 copper tube usually perfectly adequate to supply the full output of a range?
>
> It seems the utility uses the 1/2 psi drop table when sizing services and that is very conservative, if you have 2psig at the street you can drop at least 1 psi, probably 1.5 psi and still have plenty of pressure to regulate down to 7" wc.

I'm completely confused.
Did you convert from NG to LPG? Or did you go to a 2 psi NG system? Or did you not change anything?

If you're replacing your piping why not just install the proper size for 6-7 " wc NG?

mattmia2

The lpg comment was about an earlier comment about ranges being fed by 3/8 copper tube.

If i converted to 2 psig i could feed it all with a single 3/4" pipe which is easy to work with hand tools. If I was working with 6.5" wc i would have needed several 1" or at least 2 1.25" or 1 or 2 1.5". At the time I was looking at a tankless and a separate gas heater in my garage along with a grill and a cooktop and a gas furnace and dryer. It was about 550 ft^3/hr. the existing piping was in an existing hard ceiling. getting a single 3/4" through below the ceiling was easy(either to be regulated and distributed at the appliance that were all in about the same area or what ultimately turned out to be only for the grill), getting multiple larger pipes through would have been difficult.

USMC3105

I started a new thread titled: Nat Gas required BTU's for whole house Gen plus the house appliances..

Thanks for all the help.

mattmia2

If they upsize the meter to 500 or 600 ft^3 per hour, can the regulator typically handle that or does it also need to be upsized?

USMC3105

Mattmia2, I didn't know they made home meters that big. I thought 375 was the biggest. I am not sure about the regulator. I have learned alot about this stuff from this thread/webpage. I can't wait to talk to the Gas co about it tomorrow.

rick in Alaska

I would have to check with our gas supplier to verify this, but it sure seems like our 250's are good for something like 425,000btu's. Not sure how they figure it though.
Rick