Gas meter sizing

snakej200

New member 1st time post -
I have just upgraded a few appliances in my house and also added a portable generator which I converted to run on natural gas (or gasoline) during an outage. Here is what my house HAD before the past few months that was running just fine for years-
120k btu furnace, 50 gallon conventional tank water heater (40k btu), gas dryer (30k btu), gas stove (10k btu). I recently replaced my furnace with a 100k btu unit and my water heater with a tankless unit rated at 199k btu. I am not too concerned about the generator since I could run that off gasoline if needed and could also manage the load if needed during an outage - I only lose power 24-48 hours a year so I can make that work. I'm more concerned with the furnace, water heater, dryer, and stove working at the same time as while it is a slim possibility, it could happen. My meter is rated at 275cfh and I did call my gas company about upgrading the meter however they would want to replace the main which would entail ripping up my entire front yard which I'm not really looking forward to doing and would like to avoid if possible. I found an article stating that 275 cfh units can actually handle up to 385cfh

https://jmcinspections.com/is-your-gas-meter-too-small/

I'm not sure if that's an accurate statement or not but I guess I'll find out once I get the tankless water heater installed, it's currently sitting on the floor in the basement - should have it in by the end of this month. I'm going to try running the furnace, dryer, and stove at the same time and then see if the water heater will run - I believe these tankless units will throw an error if there's not enough fuel.

Wondering if anyone has ever run into this before and should I be concerned? Also the generator I'm running is a 713cc 22hp engine, I'm not entirely sure how many btu's that will draw since I converted it?

mattmia2

You have to check the pressure on all of the appliances with all of them firing to test if the supply is adequate experimentally, just seeing if you get an error is not sufficient.

ChrisJ

snakej200 said:

New member 1st time post -
I have just upgraded a few appliances in my house and also added a portable generator which I converted to run on natural gas (or gasoline) during an outage. Here is what my house HAD before the past few months that was running just fine for years-
120k btu furnace, 50 gallon conventional tank water heater (40k btu), gas dryer (30k btu), gas stove (10k btu). I recently replaced my furnace with a 100k btu unit and my water heater with a tankless unit rated at 199k btu. I am not too concerned about the generator since I could run that off gasoline if needed and could also manage the load if needed during an outage - I only lose power 24-48 hours a year so I can make that work. I'm more concerned with the furnace, water heater, dryer, and stove working at the same time as while it is a slim possibility, it could happen. My meter is rated at 275cfh and I did call my gas company about upgrading the meter however they would want to replace the main which would entail ripping up my entire front yard which I'm not really looking forward to doing and would like to avoid if possible. I found an article stating that 275 cfh units can actually handle up to 385cfh

https://jmcinspections.com/is-your-gas-meter-too-small/

I'm not sure if that's an accurate statement or not but I guess I'll find out once I get the tankless water heater installed, it's currently sitting on the floor in the basement - should have it in by the end of this month. I'm going to try running the furnace, dryer, and stove at the same time and then see if the water heater will run - I believe these tankless units will throw an error if there's not enough fuel.

Wondering if anyone has ever run into this before and should I be concerned? Also the generator I'm running is a 713cc 22hp engine, I'm not entirely sure how many btu's that will draw since I converted it?

Just a guess, but I'd bet the generator can use between 150-200,000 btu/h.

How much you can run through the meter depends on a lot of things.
My meter is rated for 250 and at around 285 the pressure drop through the meter becomes enough that it could be an issue because my gas company only gives us 6"WC. Because of this 1" of drop is a lot under those conditions.

Some places run 7" and I've heard some run even higher so with that you could get by with more drop across the meter and maybe the line running in.

snakej200

thanks for the response - I was figuring the generator to be in that range as well. I'm not sure about the pressure, I'm still new to this and learning the terms. On the plate on my main regulator it says 6-8 IWC. I'm gonna hope I'm closer to 8" I guess. Judging by your experience then sounds like you can't get much more out of these meters than what they're rated for? I will post my experiences after I get the tankless water heater installed.

ScottSecor

We've witnessed about twenty percent more can pass through a residential type gas meter than the rating without a significant pressure drop (275 x 1.2 +330,000 BTU). That being said, most utility companies will gladly install larger meter if required.

One thing I noticed, you suggested 10K for your stove. Most "regular" stove/oven combinations I have seen are more like 65,000BTU or thereabouts. Stovetops are different as are some large Viking style stoves.

mattmia2

ScottSecor said:

One thing I noticed, you suggested 10K for your stove. Most "regular" stove/oven combinations I have seen are more like 65,000BTU or thereabouts. Stovetops are different as are some large Viking style stoves.

It also isn't clear to me in my reading of the code if a demand factor can be applied to the surface burners on a range or a cooktop since they won't all be firing on high at once unless you're trying to burn the place down.

Back to the original question, each appliance will have a minimum pressure on its ratings plate and that varies between 3.5-5.5 " wc depending on the appliance. If you can drop 1.5" wc over the meter and the piping there is a lot more capacity than if you only have .5" wc.

ChrisJ

mattmia2 said:

One thing I noticed, you suggested 10K for your stove. Most "regular" stove/oven combinations I have seen are more like 65,000BTU or thereabouts. Stovetops are different as are some large Viking style stoves.

It also isn't clear to me in my reading of the code if a demand factor can be applied to the surface burners on a range or a cooktop since they won't all be firing on high at once unless you're trying to burn the place down. Back to the original question, each appliance will have a minimum pressure on its ratings plate and that varies between 3.5-5.5 " wc depending on the appliance. If you can drop 1.5" wc over the meter and the piping there is a lot more capacity than if you only have .5" wc.

According to my gas company they don't have to size for the entire load because it won't be used all at once.

I thought it was nuts but whatever.

EBEBRATT-Ed

The gas company is a utility and can size there pipe and there meter any way they want. Will it work, who knows?

To get an accurate check on the gas pressure you would have to check it while your neighborhood is under full load.

I would not have installed a tankless water heater. nothing but trouble.

There is a location 30 miles from me where the gas company will allow no additional load and the gas co will tell you to expect 4-5" of wc during the winter

JakeCK

How many watts is that generator you converted rated for? It will be significantly less with NG(maybe 20%?) But that should give you an idea of btu usage when accounting for the efficiency of the generator.

ChrisJ

JakeCK said:

How many watts is that generator you converted rated for? It will be significantly less with NG(maybe 20%?) But that should give you an idea of btu usage when accounting for the efficiency of the generator.

22HP would be around 10-12KW.
On natural gas it'll be good for 8-9KW assuming it's running correctly.

mattmia2

EBEBRATT-Ed said:

There is a location 30 miles from me where the gas company will allow no additional load and the gas co will tell you to expect 4-5" of wc during the winter

So then does the customer's gas piping look like gravity hot water mains?

nicholas bonham-carter

Also to think about is the requirement for clean sine wave power from your generator, for the tankless water heater, as their electronics can be very finicky about the quality of power they receive.—NBC

JakeCK

nicholas bonham-carter said:

Also to think about is the requirement for clean sine wave power from your generator, for the tankless water heater, as their electronics can be very finicky about the quality of power they receive.—NBC

Good point. You want a THD less than 5% to keep electronics happy. Also a floating ground can also cause issues. 

mattmia2

JakeCK said:

nicholas bonham-carter said:

Also to think about is the requirement for clean sine wave power from your generator, for the tankless water heater, as their electronics can be very finicky about the quality of power they receive.—NBC

Good point. You want a THD less than 5% to keep electronics happy. Also a floating ground can also cause issues. 

I suspect some good high frequency filtering would make it happy since it is just going to rectify the incoming power and make a few low voltage dc power supplies if it is off a couple hz or has some low frequency harmonics it will get filtered out by the power supply but even a little bit of high frequency harmonics could make it through the filtering in the power supply and case problems with the microcontrollers.

EBEBRATT-Ed

@mattmia2

Pretty much. A 6" main coming in the building. They wanted to install a Munters dehumidification system and the unit needed 10"wc gas pressure. The gas utility said they may be as low as 4-5"wc in the winter. We had to install a 25K gas booster pump and a bunch of repiping the total was over 100K. This was a supermarket