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Re: RE: Loss of Btu's Converting From Natural Gas To Propane (Reply to this comment)
by transgenik
Wow :) Thanks a lot, the_gas_man, your precise explanations are clear and useful!
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Mar 20 '02
7:12 pm PST
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RE: Loss of Btu's Converting From Natural Gas To Propane (Reply to this comment)
by the_gas_man
The only time I have seen this happen is when the orifice sizes do not match exactly between propane and natural gas. Gas jets or orifices are what regulate the flow of gas to the burners.
For example, on natural gas a number 47 orifice drill size will allow approximately 19 cubic feet per hour of gas to flow, at a manifold pressure of 3.5" water column (w.c.) which is roughly equal to 19,000 Btu's at sea level.
While the closest drill size for propane which is usually operating at 11" w.c. will require a smaller orifice size such as a #56 will deliver approximately 17,000 Btu's the next size up is a #55 orifice drill, which would deliver a little over 21,000 Btu's. The higher the number of the orifice drill, the smaller the hole size.
So you can see in the above example the required 19,000 is not available with standard orifice drill sizes and a gasfitter would tend to put in the smaller one to be on the safe side, rather than risk over-firing the appliance.
Usually, however, there is an orifice drill size that is very close to the specified input rate. This orifice sizes are specified by the manufacturer in their instruction manual and are certified with those sizes.
I hope this helped to answer your question about losing "power" when converting from natural gas to propane. Generally, there is little to no difference in Btu input rates between the two gases.
Regards,
The Gasman
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Mar 19 '02
1:20 pm PST
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