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# Clocking NG Boiler off gas meter

Member Posts: 9,537
Tim,

I noticed on the gas meter plate that it was tested at 60* ambient. Is there a correction factor to use when clocking an appliance when its cold outside say single digits?

Reason I asked I clocked my boiler. IT has a rating of 210000 btu input. Clocked at 214000 input. Could this difference be because of the density of gas in colder weather, or the cold affecting the metering mechanisms in the meter?

Thank you

Gordy

• Member Posts: 4,555
Gordy, the 60° is the temperature

compensation in the meter which means it measures as though the temperature is 60 at all times so it is accurate in measuring. I typically will clock a burner 3 times and then average the readings, many things can cause you to be off actual design input such as varying BTU on the gas being sent to you or specific gravity not quite .6 all the time. Did you clock with a sweep second hand on a wrist watch or did you use an actual digital stop watch (Preferred method)?

You can also check gas pressure and match up with orifice sizes on the burners. If some one did a combustion test on the boiler they may have adjusted the pressure to get the unit to the maximum design firing rate which may mean it will perhaps clock a little high. What do you use for a value of BTU per cubic foot? If you use 1050 it may cause you to be high in your calculations. Check your last gas bill and see what value they give per CCf it is typically around 1023 to 1027 from most utilities unless you are out in Denver Colorado in Eatherton land.
• Member Posts: 9,537
edited January 2012
Tim

Clocked with stop watch using 1/2 cu ft, and 2 cu ft. Few times each. Always came up 17 sec per cu ft.  Btu value is 1011 per gas bill. Not a huge difference from actual to theoretical input that's why I was wondering if there was a correction factor for cold weather.

Thanks Tim for clarification on the meaning of the 60* plate on the meter.

Gordy
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