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Member Posts: 61
open to corrections from those more in the know...

40 ft of FIN, assuming 800btu/ft @ 190F E.W.T. + 24 Hour operation. (highly unlikley, shouldn't degree days come into formula?)

800 btu/hr x 24 hours = 768,000 btu/day
100,000 btu = 1 therm
7.68 Therms per day @ \$0.67 per therm = \$5.14 per Day or \$156.34 Monthly (extrapulated over 12 months)

How close was I ??, come on wallys.

EIN

• Member Posts: 3,262

My customer is in an apartment over a restaurant sharing a gas bill. The lanlord wants him to pay for gas in the winter without adding a meter.

The apartment has 40' of fin-tube installed. The boiler runs at about 190f. The utility charges \$0.67 per therm. Assume the boiler never shuts off.

Can someone help me with a formula?

P.S. It was much warmer in the Carribean last week.

JohnNY

Contact John "JohnNY" Cataneo, NYC Master Plumber, Lic 1784
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Heating in NYC or NJ.
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• Member Posts: 610
what's the firing rate

of the boiler in hundred cubic feet/hour?

1 Therm, by definition = 100,000 BTU Assume the boiler runs 24 hrs a day (your assumption) divide the input rate in BTU/hr by 100,000 BTU/therm, giving you the firing rate in Therms/hr. Multiply this by the number of hours it runs to get the cost of the gas used.

for a 60,000 BTU/hr input boiler run continuously for a 30 day billing period: (60,000 BTU/hr)/(100,000 BTU/Therm) = 0.6 Therms/hr. (30 days)*(24 hrs/day)= 720 hours, so (720 hours)*(0.6 Therms/hr)=432 Therms. Since a Therm costs \$0.67 the cost is (432 Therms)*(\$0.67/Therm)=\$289.44 for the 30 day billing period.

Two observations:
1. the gas is dirt cheap where he lives (assuming US dollars)
2. Clearly the boiler doesn't run 24 hours/day -- if you had a time meter on it you could meter it that way. Say it averaged 16 hours a day that month. then the time would be (16hrs/24hrs)*(720 hours/billing period)=480 running hours and the bill becomes (480hrs)*(0.6 therms/hr)*(\$0.67/Therm)=\$192.96

• Member Posts: 610
so you figure

32,000 BTU input (and 32,000 output, for 100% efficiency), but say we call it 80% efficiency, then input is 40,000 BTU/hr and bill is \$192.75 for a 30 day billing period.

I'm quessing he planned to divide the result by the actual boiler on percentage, as it wouldn't run continuously in the real world.

Very close to my guess of a 60,000 BTU input boiler running 2/3'rds duty cycle -- but that is just coinidence.
• Member Posts: 2,542
Why...

won't the LL allow a gas meter? Sounds like he plans on making money off the enrgy, which is illegal unless you're registered as a "utility purveyor".

Gas meters are around \$150.00.

ME
• Member Posts: 3,262
It has to be a legal 2-family....

It has to be a legal 2-family, which it is not....
Then we would need another boiler.....
This, believe it or not, is common practice 'round these parts.

Contact John "JohnNY" Cataneo, NYC Master Plumber, Lic 1784
Consulting & Troubleshooting
Heating in NYC or NJ.
Classes
• Member Posts: 299
BTU Meter

What about using a btu meter?

Never used one but I might considder it in this application.