Nat Gas required BTU's for whole house Gen plus the house appliances

USMC3105

Hello,

A continuation from Gas Meter Size Thread. I am having a whole house gen (Generic 22Kw) installed by a local electric co (location is NJ. 50 miles SW of Newark). I had to call up the Gas Co. to see if my meter needed to be upgraded. The Gas Co tells me based off the max demand BTUs of my gas appliances I need to upgrade the line coming in the from the street to the house from a 1/2 inch pipe to a 3/4 inch for $5500.00 My meter is AC-250 with a max BTU of 390k. There are 2 other whole gens on the same street as me. Both are just two housed down from me. A 3rd one whole house gen is on the next block over. They all called the same Gas Co and they only had to upgrade their meter. And yes we did go over appliances Btu requirements. As of now, I need 383k BTU for the appliances. I am replacing the tank-less hot water heater for a tank. That will drop my BTU requirement (without Gen requirement) to 250k. Gas Co say still not good enough. Home Gen is Generic 22k with 327k BTU required at max use.

Two things they won't answer:

1. How much BTU's for the house will require a line upgrade? I was told by them, they can't tell me that number until they punch in the numbers to the computer. Really? I don't believe it.

2. Why am I the only one who needs to upgrade the line from the street to the house, yet not the other homes on the street? They say, because of your required demand. They even go as far as upping the requirement for the stove top/oven from 83k BTU's to 114k BTU's. Fighting with them on that this Monday.

Does anyone know if you can figure out the BTU's before to have to upgrade the line?

Thanks all for you help. They wife thinks I am going over the edge on this. Its the Marine in me that won't surrender just as the fight begins.


Mike

SlamDunk

Seems to me permits would have to be pulled. Let the electric co. Deal with gas co. You shouldnt worry it about until permit is denied to the installer.

Solid_Fuel_Man

Do you want to use the generator to run Air Conditioning? I'm a master electrician and we put in 11kw generators for houses. Generally speaking an 8kw will run an entire house with gas appliances.

Why is your gas load so high? 383,000 btu/hr? Can you list out your individual appliances and their BTU requirement.

Typical slide in range 60,000
Clothes dryer 30,000
Boiler/furnace 80,000
Etc.

ChrisJ

I'll confused how a meter rated for 250 SCFH is good for 390k btuh.

Isn't 250 SCFH typically considered good for 250,000 btuh?

mattmia2

The capacity of the service pipe is a function of its size, effective length, the pressure at the main and the pressure required at the house.

1. The other services may have been renewed with a larger pipe. .5" seems unusually small for a gas service line. My service was 1.25" iron and was renewed with 1" polyethylene when it developed a pinhole.

2. The other services could be closer to the main or have fewer bends. iron/steel fittings add a lot more effective length than a bend in polyethylene.

3. The other houses could be closer to the supply point of the main and the utility is figuring for pressure drop in the main.

4. If you requested a 2 psig service they need to still have enough pressure at the house to regulate down to 2 psig. If it is a standard 7" wc service they have more allowable drop over the service line.

5. The other houses may have electric appliances and the service is only serving central heating equipment and the generator.

an ac-250 is a 250 ft^3/hr meter which would be 250,000 btu/hr at 6.5" wc to the house with methane.

Both 83,000 and 113,000 btu/hr seem like a lot for a range but i suppose it is possible for a range with more than 4 surface burners and dual ovens.

Zman

If you want to play with the math yourself, you can plug the numbers into this https://www.engineeringtoolbox.com/natural-gas-pipe-calculator-d_1042.html

The .622 ID is probably close enough, the gas company probably does not want to allow more than 27" (1 PSI) pressure drop on a 2 PSI line. The max that is physically possible is ~ 35"-42" depending on the drop through the meter and regulator.

If the gas company only has 2# at the street, this is not going to happen on a 1/2" pipe. There will be too much pressure drop when everything is running.

USMC3105

Slam: All permits pulled by the installation co.

Solid Fuel: it will run an A/C. I'm in a two zone house. But only one A/C at a time. My Dryer is 20K, Furn 70,300, Tank-less hot water heater is 180K. (I'm replacing it with a tank HW heater. I hate the thing). My range/over is a LG 5 burner/double over. The specs say 83K total. Gas Co says over rated it to 114K..

ChrisJ: Most gas meters are higher then shown. Gas Co said it can go to 390K

Matt: That is some great intel. I need to research that info on my block.

Zman: I will try that link out. I need something to compare the Gas Co numbers to mine.

Thank you all for the help.
Mike

Solid_Fuel_Man

If you can live w/o A/C then you can use a much smaller generator and likely have enough capacity now.

EBEBRATT-Ed

@USMC3105

The gas utility has complete control over the piping up to the house and the meter. Any work downstream of the meter is your local plumber/gasfitters job. I suspect you will have no luck with the gas utility.

Every state and location has different rules. In MA. where I am we are required to get a "letter of availability" from the gas utility when changing any equipment that puts the gas service into question. Takes care of any issues before the install.

The gas utility can size the pipe and meter any way they want and pretty much make any rules they want.

Once you put in a tank type water heater your load would be about 216,000.

I think the over riding issue is the size of your generator 22k is a lot of generator and its going to require a lot of gas. Do you really need one that big? Thats 91 amps at 240 volt and 180 amps at 120 volt

You mention other whole house generator installs...where they large generators as well??

Consider this option: keep the existing gas service as is for the existing appliances. Put the generator (if already purchased and installed) on propane and have a propane tank installed.

Some locations prohibit propane and natural gas in the same building (MA. is one) but will allow it with special permission. In this case where all the propane is outside (gen & Tank) special permission may not be required even if your state had a restriction.

SlamDunk

I'm surprised you have a measly 1/2" line to your meter. That is pretty small for any kind of distance, with pressure drops, and all. Your area must run higher pressures.

How many power outages do you have in your neighborhood? And how long do they last?

A few of my coworkers purchased wh gens because they live in rural NC but I dont think anybody has had to use them yet in the past two years and we have hurricanes or tropical storms here annually!

ChrisJ

I have a 1/2" plastic line coming in and 50 psi.

Plenty of gas for all your needs and maybe a few neighbors.

However it is bottle necked by the same AC-250 the op has.

USMC3105

SlamDunk, we have had 5 since we bought the house in July. The longest is 4 hours. I travel for a living and have a two small kids and a wife to worry about when it goes out. Plus we have well water..

I have trouble believing we have just a 1/2 also. But you never know it, it is NJ..

Solid_Fuel_Man

As @ChrisJ said it's all about the pressure. 1/2 at a few PSI is a lot of fast at the inches of WC pressure we use.

I like LP for generators, fuel is on site and therefore 100% ready. NG is still subject to the gasco.

SlamDunk

Well water could be a game changer and I used to travel myself so I understand your concern.

I know what gens go for. I would be danged if I tacked on an extra 6k for a larger gas line for a four hour, or even a four day black out. I'd get one for just the essentials: water, refrigerator, a couple lights and heat.

Jean-David Beyer

I'm surprised you have a measly 1/2" line to your meter. That is pretty small for any kind of distance, with pressure drops, and all. Your area must run higher pressures.

How many power outages do you have in your neighborhood? And how long do they last?

I live in New Jersey Natural Gas territory, and some years ago they got tired of digging up local streets several times a year to fix leaking 70 year black pipe mains that were leaking. Supposedly, the pressure was 15 psi, but when I saw them meter it, it was closer to 8 psi. At the street. A little before I converted from oil to natural gas heat, they replaced all that with a larger size plastic pipe that ran at 50 psi (that I also saw them meter). They installed a new drop pipe (also plastic) to my house that was 3/4 inch or one inch. I told them I was going to have an 80,000 BTU/hr boiler installed. Just before the meter, the regulator drops the 50psi to about 7 inches water gauge pressure.

When I wanted to install a 12 KW natural gas backup generator, I had to call the gas company for permission. They just said it would be OK: they did not even bother to come and look.

The generator company finished the installation in early summer in the middle of the week. On that Saturday, the power went off for a couple of hours. What inspired me to get that generator was that the power went out for 6 1/2 days during tropical storm Sandy. I could not shower, cook, heat my house or hot water. The cold leaked out of my refrigerator and freezer. A bad time was had by all.

I have quite a few short failures (an hour or a little more) every year, and even more that are only a few seconds. They do not matter much as my computer and related stuff goes through a way oversized APC SmartUPS that can easily coast through a 10 second drop-out. Actually, it is big enough to run my computer stuff for an hour or two.

ch4man

service capacity is not determined by meter size, its the pressure drop across the regulator orifice. yes the meter still needs to be sized right' but it's sized to much more than just demand. i believe the ac250 is rated for 250CFH at 1" wc delta P that you'd find on a low pressure system; 1/4 LB out at the street. a 1/2" line from the street is much higher pressure than that

ChrisJ

> @ch4man said:
> service capacity is not determined by meter size, its the pressure drop across the regulator orifice. yes the meter still needs to be sized right' but it's sized to much more than just demand. i believe the ac250 is rated for 250CFH at 1" wc delta P that you'd find on a low pressure system; 1/4 LB out at the street. a 1/2" line from the street is much higher pressure than that

But the regulator is at the input of the meter, so doesn't it still behave the same as if the entire system was 1/4 psi?

ChrisJ

> @Solid_Fuel_Man said:
> As @ChrisJ said it's all about the pressure. 1/2 at a few PSI is a lot of fast at the inches of WC pressure we use.
>
> I like LP for generators, fuel is on site and therefore 100% ready. NG is still subject to the gasco.

LP has it's own issues that do not exist with NG such as low temperature considerations. For example natural gas will behave completely normal when it's -20F out and even substantially colder. -100F? no problem. Will an LPG generator start when it's -40 out? There are many areas that actually see these temperatures.

That being said, many of us live in areas where the natural gas is extremely reliable. The objective, at least for me, is to deal with what is most likely, not Armageddon.

In my situation, even during Sandy and other bad storms where the power goes out natural gas is not effected. I'm betting @Jean-David Beyer has a similar experience with NG reliability that I do.

Perhaps in some areas natural gas is less reliable and that should be taken into consideration.

mattmia2

The draw rate at a given ambient is part of lpg tank sizing. There are also systems that deliver liquid to handle cases where that would result in an impractical tank size.

the natural gas utility goes to great lengths to make sure service is never interrupted because if it is, they can't just turn it back on, they need to do a startup on every customer affected.

STEVEusaPA

If you have to drop and extra 5-6k just to get gas, maybe the extra cost for a diesel gen may be the way to go. Just get a tank that gives you a 3-4 day run time, as no one is putting trucks on the road if there's an ice storm.

ChrisJ

> @STEVEusaPA said:
> If you have to drop and extra 5-6k just to get gas, maybe the extra cost for a diesel gen may be the way to go. Just get a tank that gives you a 3-4 day run time, as no one is putting trucks on the road if there's an ice storm.

How long does a tank of Diesel last sitting?

Jamie Hall

ChrisJ said:

> @STEVEusaPA said:

> If you have to drop and extra 5-6k just to get gas, maybe the extra cost for a diesel gen may be the way to go. Just get a tank that gives you a 3-4 day run time, as no one is putting trucks on the road if there's an ice storm.



How long does a tank of Diesel last sitting?

Not that long -- a month or two, perhaps. Further, you should have a winter blend (if you have cold weather) and perhaps an anti-ice treatment if your supplier doesn't provide it (automotive fuel stations do, automatically). But the life of gasoline is about the same. If you're getting biodiesel, it's shorter. If you have ethanol blended gasoline (hard to not have that, anymore) you should be adding an additive such as Sta-Bil to combat the ill effects of the ethanol.

That said, you should run your generator -- any fuel -- at least once a week, under some kind of load, long enough to at least warm it up.

SlamDunk

Maybe it is a volume thing but I have 12000 gallons of diesel at work that takes three years to burn through less than half. Just added 4000 gallons. Still viable.

Like @Jamie Hall said, you should run once a week. Add fresh fuel every three months. I think natural gas is the way to go. I would work within my gas capacity limits- only because my expendable cash is limited

STEVEusaPA

I fuel diesel generators all the time. The fuel can sit a while, but I'd avoid bio blends. But you should also have a good generator company for service. They will own a fuel polisher. I don't know their recommendation for polishing but if the gen is hardly ever used, maybe every 2 years? I'm sure they would (should) test it.

All of that being said, I have a whole house 20kw Kohler nat gas generator, 200amp auto-transfer. I own an oil company, so I'd get the fuel at wholesale cost. The deciding factor was location of install and size. Had to be almost 150' from the street so I wouldn't be able to fuel it easily, and the thought of dragging that much hose in high snow, during a blizzard/ice storm (uphill-not both ways ), plus the large size (footprint) of a diesel gen with a tank with 3 day run time, was the deciding factor.

The gas install went easy. Installing gen company always commissions a report from the gas company to make sure there will be enough gas. Meter/regulator changed, everything completely load tested. 20kw easily does two AC units, electric oven, electric dryer, boiler, a gazillion hihats, mostly incandescents (I change them out as they fail). I had everything running when commissioned. I also put the 2 AC units and electric oven each on their own load shedding switch.
The year before the gen went in we lost power I think 23 times.
With Sandy, 4 days. We're at the end of the run serving about 20 some houses thru the back yards, so were almost always the last to get turned back on. And if it's a tree down/line down, could be weeks as truck/bucket access is impossible.

Solid_Fuel_Man

We are all trying to figure out ways of helping the OP to not have to upgrade his gas service.

So that leaves 3 options for an automatic generator.

1. Install smaller generator on NG.

2. Install large generator on LP or Diesel (unlikely).

3. Get gas consumption low enough so that existing will handle generator or reasonable size.


FWIW, the power company in my area sizes their transformers on the pole to 5kva (kw) per hundred Amps of residential service. This isnt exactly apples to apples....as kva isnt the same as kw of generator capacity. I get a laugh out of people who want a 20kw generator "to run everything" when the transformer on their electric service is 5kva.

My neighbor and I share a transformer on the pole, his service is 200Amps and mine 100Amps, it's a 10kva. My LP recoil start generator is 3250 watt (3.25 kw) and runs my 3/4hp submersible well pump, all my lights, the boiler, and fridge simultaneously. I have LP dryer and range.

EDITED for fat finger typos...

Jamie Hall

All true, @Solid_Fuel_Man . Cedric's home is a farm, and we have a 16 KW generator which really will run everything, and pretty much all at once (except the kitchen stove -- got to be a bit fussy about that). There is such a thing as overkill...

mattmia2

The difference between a transformer and a generator is that the engine in a generator can output its maximum out put and that's it. the transformer can output probably 10x its rating for brief periods for things like starting motors. the generator has to have enough capacity to handle the starting current of any large motors involved.

ChrisJ

> @Solid_Fuel_Man said:
> We are all trying to figure out ways of helping the OP to not have to upgrade his gas service.
>
> So that leaves 3 options for an automatic generator.
>
> 1. Install smaller generator on NG.
>
> 2. Install large generator on LP or Diesel (unlikely).
>
> 3. Get gas consumption low enough so that existing will handle generator or reasonable size.
>
>
> FWIW, the power company in my area sizes their transformers on the pole to 5kva (kw) per hundred Amps of residential service. This isnt exactly apples to apples....as kva isnt the same as kw of generator capacity. I get a laugh out of people who want a 20kw generator "to run everything" when the transformer on their electric service is 5kva.
>
> My neighbor and I share a transformer on the pole, his service is 200Amps and mine 100Amps, it's a 10kva. My LP recoil start generator is 3250 watt (3.25 kw) and runs my 3/4hp submersible well pump, all my lights, the boiler, and fridge simultaneously. I have LP dryer and range.
>
> EDITED for fat finger typos...

The kva rating on pole pigs isn't exactly the same as the ratings on backup generators. One is grossly under rated and the other grossly over rated.

You do realize in reality 5000 va is 20 amps @ 240v.

A typical 8kw generator won't deliver enough current to start a 3 ton AC compressor and yet that 5kva transformer will effortlessly.

Solid_Fuel_Man

Yes, I'm very well aware of how transformers work. I didnt want to go into mich detail as its beyond the scope of this topic.

My point is that generators are grossly oversized for residential loads. Which is why I asked the OP if he wanted to run A/C load. The only other motors are fractional horse power like 1/2 or 3/4 hp water pump, 1/20 hp refrigerator etc.

If he can get bu without A/C the generator can be 1/2 the proposed size.

Solid_Fuel_Man

> @ChrisJ said:

>
> The kva rating on pole pigs isn't exactly the same as the ratings on backup generators. One is grossly under rated and the other grossly over rated.
>
> You do realize in reality 5000 va is 20 amps @ 240v.
>
> A typical 8kw generator won't deliver enough current to start a 3 ton AC compressor and yet that 5kva transformer will effortlessly.

Yes, 20 Amps. Most residential services rarely see draws over 20A @240V for more than 30 min. The POCo knows this. A typical oil filled can transformer can take 125% over its rating for approx 1 hour. Newer cans (pole transformers) have CSPs built in which is a circuit breaker on the secondary winding. So it will trip to protect the can from overheating and boiling over. Older cans, also called conventional cans or delta cans, have two primary bushings and have to be protected by a fuse known as a cutout.

I've spent many days up in the bucket.

ChrisJ

> @Solid_Fuel_Man said:
> > @ChrisJ said:
>
> >
> > The kva rating on pole pigs isn't exactly the same as the ratings on backup generators. One is grossly under rated and the other grossly over rated.
> >
> > You do realize in reality 5000 va is 20 amps @ 240v.
> >
> > A typical 8kw generator won't deliver enough current to start a 3 ton AC compressor and yet that 5kva transformer will effortlessly.
>
> Yes, 20 Amps. Most residential services rarely see draws over 20A @240V for more than 30 min. The POCo knows this. A typical oil filled can transformer can take 125% over its rating for approx 1 hour. Newer cans (pole transformers) have CSPs built in which is a circuit breaker on the secondary winding. So it will trip to protect the can from overheating and boiling over. Older cans, also called conventional cans or delta cans, have two primary bushings and have to be protected by a fuse known as a cutout.
>
> I've spent many days up in the bucket.
>

You don't have to yell...
Jeez.

USMC3105

@Jean-David: Taking what I learned here I called the gas co to ask a few question, the same person I have talked to twice on the phone and the rest in emails. All of the sudden they didn't know the answers to any questions. Even the ones that this person told me like, why they over estimating my stove/oven BTU's after I told them what I was reading and sent them the spec sheet.

When they were upgrading the lines in the ground, did they bore or dig?

Mike

Solid_Fuel_Man

Mike, thank you for your service to our country. Semper Fi

mattmia2

Usually they dig a hole at each end of the service line, attach polyethylene pipe to the old pipe or to a cable through the old pipe, and pull the new pipe through with a backhoe or winch. They can also pull polyethylene pipe with a vibratory plow.

Jean-David Beyer

When they were upgrading the lines in the ground, did they bore or dig?

The mains in the street: they dug.
For the drop from the street to my new meter (I did not have gas before), they dug where the meter was to go, and where the hookup in the street. They then got a gizmo they called a "mole" that basically pulled the plastic pipe from the street to the meter. I think that the mole was powered with compressed air, but I do not remember for sure.

ch4man

ChrisJ said:

> @ch4man said:

> service capacity is not determined by meter size, its the pressure drop across the regulator orifice. yes the meter still needs to be sized right' but it's sized to much more than just demand. i believe the ac250 is rated for 250CFH at 1" wc delta P that you'd find on a low pressure system; 1/4 LB out at the street. a 1/2" line from the street is much higher pressure than that



But the regulator is at the input of the meter, so doesn't it still behave the same as if the entire system was 1/4 psi?

as i said theres more to it than meets the eye. an AL250 is rated at 250 CFH but only when 1/4# flows through it. the 250 cfm will induce a 1" wc pressure drop.
however feed that same meter with 2 LB gas it will pass 600 CFH at a 2" wc pressure drop. the engineering charts dont spec a 1" drop but 390 cfh something sounds right.
many utilities around here use a 2 psi system to feed the house. that increases the capacity dramaticaly

study page 2
https://www.elster-americanmeter.com/assets/products/products_elster_files/EAM-DS3535.pdf

homeowner11111

Question please: last year my home needed 220K BTU for my appliances. I had an AC250, rated at 250K at .25psi line pressure and 1/2 wc pressure drop at the meter. All worked fine.

This year, I added a 200K on-demand water heater, and my max became 420K.

I assumed I would need to upgrade to an AC425 meter (425K BTU), but the gas company told me I could live with the AC250, because the AC250 is rated for 583K at 1psi and 2 wc pressure drop.

I'm trying to understand what that means, please. It sounds like I'd have to either increase the pressure going into the home (from .25psi to something higher) or accept a higher pressure drop at the meter.

If I increase the line pressure, I'm concerned some appliances might have too much pressure at their input. And if I accept a higher pressure drop I'm concerned some appliances may have too little pressure at their input. The easy way seems to be to resize the meter, so I can provide the additional capacity at the original .25psi line pressure setting.

Am I missing something or does this sound right?

Zman

Utilities will often decide is OK to overwork the meter. From your point of view, as long as the pressure drop is not an issue it should not be a problem. I would measure the static vs dynamic pressure at the farthest appliance with everything fired up and see how it looks.

EBEBRATT-Ed

@homeowner11111

It's called diversity. The gas co know that the likelehood of every gas appliance operating a 100% capacity is pretty rare. If you start having issues call them.

pecmsg

And during power outages it dropped even further.