Another Gas pipe/meter size question.

Paul_H

We are considering adding a 54,000btu gas cooktop, 22,000btu dryer and a 50,000btu BBQ grill to our existing system. We currently have a 70,000btu boiler and a 199,000btu tankless HWH; for a total of 395,000 btu.
There currently is a 250 cfh meter and 1" supply into the house.
The cooktop will be the furthest appliance, at approximately 70' from the meter.
We've received two estimates/proposals. The first wants to tee off the existing 1" line and running 3/4 to supply the three new appliances.
Number two told us our current meter is too small as well as the 1" supply. He says we need to increase supply to 1.25" to the boiler and HWH, with the rest of the piping following "longest run method" and upgrade meter to 400 cfh.
Now my question: is the meter sized to max btu load? What is the likelihood of max load happening?

Thanks...

Paul S_3

doesn't matter of the likelihood....gas piping and meter has to be sized for max load....you need the 400cfh meter go with second plumber...1st one is probably lowest bidder

Rich_49

Even taking into account what some call diversity factors you require the bigger meter . Pipe sizing recommended by Contractor 1 may be fine but contractor 2 is correct about the meter sizing issue .

Tim McElwain

Is the gas pressure coming to this house from the street high pressure or low pressure?

Using the longest run method with an allowable .3" W.C. loss the size for 395,000 is 1 1/2" as it will allow 552.000 while an 1 1/4" will only allow 368,000.

The other sizes using 70 feet as the longest run method:

Cooktop 3/4 "
Dryer 1/2"
Grill 3/4"
Boiler 3/4"
Tankless 1 1/4"

That is using Table 6.2a from the National Fuel Gas Code NFPA 54/ANSI Z223.1

There are other methods such as Branch Length Method or the Summation Method which will give different numbers.

The longest run method depends on what you are using for an allowable loss .3 will give the largest pipe size but as you increase what you will use for an allowable loss the sizes of pipe decrease.

Paul_H

Thanks for the responses, I figured I was looking at changing the meter and supply, just wanted to make sure that it is required to size to max load.

Here is additional info from the meter.
Street pressure - Metal tag on the regulator says 60psi. (High pressure I assume?)
Regulator output is 6 IWC.
Meter is stamped 250 / 195 cfh @ 1/2" WC.

Gordy

The combination exists that you will be doing laundry using hot water, and the dryer. While also cooking supper on the cook top, and BBQing steaks in the middle of winter with a call for heat.

All the while the wife is complaining the cook top takes for ever to boil potatoes, etc etc...

Rich_49

At the point where the listed meter capacity is exceeded the pressure drop through the meter increases . This will in most cases not deliver enough pressure ( " w.c ) to the fixtures and the possibility exists that none of them will operate properly .

As you have shown , stamped right on the meter is the pressure drop through it at listed cfh .

Tim McElwain

Because of the allowable loss through the meter of a 1/2" W.C. plus the .3 in the code for piping sizing on the outlet side is critical. Keep in mind those losses are allowable and are for calculating purposes. Testing in our meter shop at the gas company where I worked showed actual losses through the meter depended on whether you were on the low end of the capacity of the meter or the high end. So on 250 meter you would anticipate that loss at a demand close to 250,000 BTU's.