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Active Contributor

Join Date: May 2009
Posts: 13

A valid formula for calculating a customer's usage factor for natural gas???

05/12/2009 1:28 PM

My gas company has explained that this is the formula they use to calculate my natural gas usage factor (meaning my meter reads "Meter Usage :94" "Billed Usage: 151"). Every HVAC tech and regulator tech keeps saying, "This doesn't make sense. Your usage is your usage, regardless of delivery pressure!".

I am looking for someone to either legitimize this calculation so I feel a little better or offer reasoning why it can't be correct. The gas company is being sued in several states over billing matters. I am also currently fighting to have my line pressure decreased from 10 to 5 seeing as my property doesn't need 10lbs of pressure!!

USAGE FACTOR CALCULATION =

((Local Atmospheric Pressure+Set Pressure)/Absolute Pressure))*BTU Factor

Example based on the meter of: MELANIE VANDEVANTER

Local Atmos Pressure

Set Pressure

Absolute Pressure*

BTU Factor**

Usage Factor

12.22

+

10

=

22.22

/

14.73

=

1.508486

*

1.064

=

1.61

(this Usage Factor is what they are multiplying my ACTUAL USAGE by in order to get the amount of gas for which they bill me. It is insane some months!)

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Pathfinder Tags: calculations formula gas natural gas usage factor
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Guru
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Join Date: Jun 2006
Location: San Diego
Posts: 2637
Good Answers: 61
#1

Re: A valid formula for calculating a customer's usage factor for natural gas???

05/12/2009 1:48 PM

Basically the best place to go is your local Public Utilities Commission (or similar name) as they regulate what little control over pricing still exists.

http://www.sourcegas.com/choicegas-wyoming-bill_howto.aspx

Usage Factor
The natural gas meter at your address measures your consumption in hundreds of cubic feet (CCF). KMI converts this volume based measurement into a heat value measurement called Therms. Therms are measures of the energy content in natural gas. The impact of this heat content and the delivery pressure is reflected in the "Usage Factor" displayed on your bill. The CCF volume, shown in the "Metered Difference" portion of your bill, is multiplied by the "Usage Factor" to determine the number of Therms used. The "Billed Usage" amount on your bill therefore reflects the units of energy consumed rather than the volume of gas delivered

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Guru

Join Date: Jul 2005
Location: Stoke-on-Trent, UK
Posts: 2416
Good Answers: 63
#2

Re: A valid formula for calculating a customer's usage factor for natural gas???

05/12/2009 4:56 PM

Hello Melanie

I don't see much wrong with that. I think your HVAC tech and regulator tech are wrong. Your gas meter almost certainly measures actual volume of gas used at the pressure/temperature of supply. So if the nominal CV is based on 14.73 psia, and your supply pressure is 10 psig = 22.22 psia where you are, need to multiply your reading by 22.22/14.73 to get equivalent volume at 14.73 psia.

Changing to 5 psig won't help - for a given amount of heat produced (and given gas volume corrected to 14.73 psia), your meter reading will increase, but the conversion factor will fall to (12.22 + 5)/14.73 = 1.17 leaving your bill unchanged.

Cheers..........Codey

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Associate

Join Date: Jul 2008
Location: Clover, SC
Posts: 27
#3

Re: A valid formula for calculating a customer's usage factor for natural gas???

05/13/2009 5:13 PM

Another writer's comment about the use of "therms" to calculate a cost for the gas you use is probably correct. As far as the 10 psi, I have been designing fuel gas systems for close to 30 years. In that time, I have probably designed two 5 psi systems. As I recall, one system provided fuel for a replacemnt boiler in a rather dated School building northeast of Washington, DC. There were not funds for energy conserving measures, only for the replacement of the heat source. Another 5 PSI installation I recall was for a 650,000 square foot covered mall in Northern VA; and in that case the fuel gas pipe went up the side of the building to the roof and then across the roof to supply several rooftop heating units. I commonly design 2 psi systems for facilities with high gas demand such as a school or office building with a cafeteria.

I suspect that your gas supply pressure is 10" W.C. not 10 pounds per square inch. To put that in perspective, 14" WC is a half a PSI.

For all you techies out there, I deliberately skipped over gauge pressure vs absolute pressure in the interest of making a point.

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Active Contributor

Join Date: May 2009
Posts: 13
#4
In reply to #3

Re: A valid formula for calculating a customer's usage factor for natural gas???

05/13/2009 5:36 PM

I can only go off what the gas company tells me. They said my meter pressure is 10psi. They say it has to be this high due to the three buildings on my property and potential load pull. My neighbor's pressure is .25psi and mine is 10psi based on their calcs.

The meter set up is this...My neighbor's and my meters are side by side. His meter supplies his 8200 sqft home, mine supplies my house( 2600sqft), a barn (8000 sqft) and a mother-in-law house(1000sqft). The barn and side house are "locked out" so no gas is used but they say they still need a meter set up for potential future use. From my meter there is a straight pipeline going to my main house (5-8.5inwc regulator), there is a T in the middle, one to a barn (6-15inwc regulator), and one to a side house (5-16incwc regulator). TOTAL DISTANCE FROM MAIN METER TO DWELLINGS IS 1300 feet. If there are any elbows, they are very slight. We walked the line with a sensor it was a straight shot. (piping:1" schedule 40 black…steel) The gas company is claiming my usage is increased so high due to the set pressure, of 10#, in the line, a pressure they claim it must remain at due to the "larger meter". I have blogged with enough mechanical engineers at this point to realize their formula is fine, it is my meter configuration that is off and can potentially me changed to a more efficient set-up. Thanks for your help!

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Associate

Join Date: Jul 2008
Location: Clover, SC
Posts: 27
#5
In reply to #4

Re: A valid formula for calculating a customer's usage factor for natural gas???

05/13/2009 7:28 PM

Thank you. That is a heap more info than I had before; due to friction loss in that long run of pipe, the pressure needs to be high to get an adequate volume of gas to the appliances.

One chart I looked at (and there are several used to size fuel gas pipe) shows that for 1" outside diameter (OD) schedule 40 black steel pipe (1.049" inside diameter) having a total equivalent length of 2000 feet (That is the 1300 feet times a 1.5 factor for losses thru fittings + 50 feet) the volume of gas that can be moved thru that pipe at 10 PSI with a 10% pressure drop goes from 3259 cubic feet 100 feet from the beginning down to 443 cubic feet at 2000 feet from the beginning. I don't know all the details (As in I haven't seen a sketch).

So YOU pay the gas company for them to get the gas to your house. I see your point. So, the gas company's philosophy (Apparently) is that once the gas pipe passes your property line, the gas in that pipe becomes yours, and you are responsible for the economic impact of the forces of nature/physics on the gas in that pipe.

I can see their point as well. One improvement for your costs would derive from moving the meter up to the house.

Good luck!

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