gravity conversion

R. Kalia

I read the article on gravity conversions and flow rates:

http://www.heatinghelp.com/newsletter.cfm?Id=125

But if I want ΔT=20, the flow rates listed for gravity conversions are way too high. I calculated this using the specific heat of water, see below and please check if possible.

My house was designed for around 160,000 BTU, so the chart says 25 gpm for a gravity conversion. Water specific is heat 8.34 BTU/gal/F. So heat delivered = 25*8 BTU/minute/F = 12,400BTU/hour/F. so [B]ΔT = 160,000/12,400 =13F[/B].

Further, for the [B]actual[/B] BTU needed on a design day (only 80,000 because of insulation), I would have ΔT=6.5, which is wasteful and would reduce efficiency in a condensing boiler.

The article says people have flow rates that are too high, but I claim the flow rates listed in the article are too high. The flow rates for 'modern' systems give a better number but it is still less than 20F. And as I said, if the actual BTU is much lower than the design BTU, the ΔT is even smaller.