W.C." to PSI conversions?

AntnyC

where can i find info on how to convert  PSI to Inches WC and vice-versa when talking about natural gas pressures? More specifically how to size supply lines with this difference in gas pressure. I'm  only familiar with sizing with the 4"-5" WC that our local utility Co guarantees. Whats the formula? Thanks for any help

kcopp

pretty sure....

that 1/2 psi equals 14" water col....  here is a link

http://wiki.answers.com/Q/How_do_i_convert_inches_of_water_to_psi

Tim McElwain

It is very

easy as 27.68" W.C. is equal to 1 PSI. The specific gravity is .6 for natural gas. The BTU content of a cubic foot of natural gas is between 975 to 1050 BTU's per cubic foot.



Pipe sizing is accomplished with piping tables contained in NFPA54/ANSI Z223.1 the National Fuel Gas Code. Use those tables for utility gas and all you have to then get from the local utility is what there allowable loss is us ally .3" W.C. or .5" W.C. that will get you to the correct chart.

AntnyC

??

OK. I got the gas code book in front of me but now I cant find the conversion from cubic ft/hr to BTU!This book makes my mind mush!

AntnyC

Let me be

a little more specific. Im trying to supply 970K BTU with a pipe run of 150'.  The manufacturer is insisting on line pressure of 2 PSI OR a WC between 8" -12" now to me those 2 values do not correspond.  2 PSI will give me a WC of approx 55".  With the use of a special regulator  I can get 2 PSI  from the utility Co. and with  1 1/4" pipe and  a pressure drop coefficient of 1.0 PSI i can obtain 2,817,00 BTU. I'm just wondering why the manufacturer requested this pressure and size pipe. Any thoughts are much appreciated.

Charlie from wmass

Is it Propane?

also there could be a typo. I would call the manufacturer directly and confirm the supply pressure.

AntnyC

No Typo

No typo and its natural gas. I talked with a rep and he was a typical clueless desk jockey "engineer". He was almost insulting as he repeatedly questioned my competence. Man he pissed me off! He tried to tell me 8" of WC  is the same as 2 PSI thats when we got "disconnected"

icesailor

W.C. to PSI

Sounds like some of the guys I've run into.

I would call the manufacturer of the equipment. Sounds kind of bogus to me.

VictoriaEnergy

2PSIG vs Inches service pressure

All residential gas appliances have a maximum allowable pressure of 14", aka 1/2 PSIG.



Your gas utility offers standard or 2PSIG gas service.  A 2PSIG service allows for a 2 stage system where you can run a much smaller pipe to a second stage regulator that then kicks the pressure down to standard 7" appliance input pressure.



Never connect an appliance directly to 2PSIG gas.



I don't have my code book at home tonight, but 1 000 000 BTUs @ 150 feet is about a 2" SCHED 40 pipe for an inches service, and easily done with 1" pipe for 2PSIG. 

Tim McElwain

The following calculated

from Schedule 40 Metallic Pipe tables:

Natural Gas at Specific gr of .6



Pressure 2 lbs



Pressure drop 1PSI



150 feet of pipe  3/4" will give 751,000

1" will give 1,370,00

1 1/4" will give 2,820,000



At the equipment use a Maxitrol pounds to inches regulator which can be adjusted for your 8 to 12" W.C. requirement. That regulator should be installed just before any of your gas controls. Also be sure to follow specifications of the equipment manufacturer and also the insurer for the system. Check all your CSD requirements.

Henry

12inch

Many make-up air units require 12 inch pressure, therefore we use 2 PSI lines. My spreadsheet program for pipe size gives me this for 150 feet at 2 PSI:

3/4 inch 768,000BTU

1 inch 1,447,000BTU

We use one cubic feet of gas at 1,000BTU as a standard. It makes everything simple.



Henry

AntnyC

Many Thanks

Thanks for all the feedback from all who took time to help!! 

Ex Maine Doug

"Sounds like some of the guys I've run into"

"I would call the manufacturer of the equipment. Sounds kind of bogus to me."

Are these the same guys having the discussions and spreading the myths about all that is bad about LNG?