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BTU/hr for Cubic feet per hour

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Brad White_200
Brad White_200 Member Posts: 148
in
Steve, the actual BTU content of the gas varies day to day. Your bill will have an adjustment factor for the average BTU content over the billing period.

It can vary from 950 to 1050 BTUs per CF depending on what is added or favored beyond methane which usually constitutes about 95% of NG heat value. Sometimes pentane, butane, propane and other "anes" (Rogaine?) are added based on availability and advantageous spot market prices. Most people use 1,000 and, at least in my experience, less often 1,050 BTUH per cubic foot as a base assumption.

Clocking gas flow from the gas meter meter, for as accurate as they are, is like flying a jet and using a calendar for an airspeed indicator.

If you are counting 159 CFH and are aiming for 152 MBH, less than 5 percent difference, the burner technician can adjust within reason but it may not reflect actual heat content used, nor how well it is used. That five percent could as easily be absorbed in the heat content differential.

The entire boiler and steam distribution is a <i>system</i>; you may well need the extra CFH at whatever heat content, to make steam at a rate which works for you.

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  • Steve Garson_2
    Steve Garson_2 Member Posts: 712
    BTU/hr for Cubic feet per hour

    I just timed the gas meter while firing a new EZ-Gas conversion burner. The rate works out to 159 cubic feet per hour. I don't want to fire over 152,000 BTU, which is what the boiler is rated for (1.1 GPH oil).

    Is 159 cubic feet equivalent to 159,000 BTU/hr for Keyspan gas, or do I need a precise conversion number for BTU per foot? Do I need a smaller orifice hole and therefore a new orifice pipe? The hole drilled should be firing at the right rate. Or can the pressure be reduced on the gas valve to reduce the BTU output? I have a pro coming tomorrow AM to tune things and wonder if I need to reschedule so he has the parts needed.
    Steve from Denver, CO
  • Unknown
    Unknown
    Steve most of us

    in the gas industry use 1050 BTU's as a measure of the heat content of a cubic foot of gas. We use this to size orifices on gas equipment using charts available and also gas pressure along with the specific gravity of the gas. As Brad pointed out the daily send out is usually less than that. It is reflected somewhere on your bill as a cost per CCF or therm and will be maybe 1023, 1025 ,1027 it varies, it is the average send out for the particular billing period you just received a bill for.

    If a combustion analysis was properly done by your installer and the readings support good combustion with under 100 PPM for CO then you are safe and enjoy your new system, leave it alone as you will not get much more out of it.

    What were the combustion figures for your installation? That will help us to figure out if things are good. To answer your other post the differnt diffuser whould not be a problem as your are within the firing rate of your system. A professional gas combustion technician which I assume you have had install and set up your system will have brought everything to its maximum eff and operation.
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