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FORMULAS & FACTS
BTU (British Thermal Unit) is the heat required to raise 1 pound of water 1°F
1 BTU = 252 cal = 0.252 kcal
1 cal = 4.187 Joules
BTU X 1.055 = Kilo Joules
BTU divided by 3,413 = Kilowatt (1 KW)
One gallon of 120°F (49°C) water
weighs approximately 8.25 pounds.
Pounds x .45359 = Kilogram
Gallons x 3.7854 = Liters
% of hot water =
(Mixed Water Temp. – Cold Water
Temp.) divided by (Hot Water Temp.
– Cold Water Temp.)
% thermal efficiency =
(GPH recovery X 8.25 X temp. rise X
1.0) divided by BTU/H Input
BTU output (Gas) =
GPH recovery x 8.25 x temp. rise x 1.0
BTU output (Electric) =
BTU Input (Not exactly true due
to minimal flange heat loss.)
Capacity of a
cylindrical tank
– 1⁄2 diameter (in inches)
x 3.146 x length. (in inches)
Divide by 231 for gallons.
Doubling the diameter
of a pipe will increase its flow
capacity (approximately)
5.3 times.
Linear expansion of pipe
– in inches per 100 Ft.
Grain
– 1 grain per gallon = 17.1 Parts Per million
(measurement of water hardness)
FAHRENHEIT CENTIGRADE
32 0
41 5
60.8 16
120.2 49
140 60
180 82
212 100
To convert from Fahrenheit to Celsius:
(°F – 32) x 5/9 or .556 = °C.
TEMP °F RISE STEEL COPPER
50
°
0.38˝ 0.57˝
1
00
°
.076˝
1.14˝
125° .092˝ 1.40˝
150
°
1.15˝
1.75˝
TC-092
FORMULAS & FACTS