Mich. Admin. Code R. 408.4272 - Minimum capacity of closed-type tank
Rule 272. The minimum capacity of the closed-type expansion tank may be determined from tables 272A and 272B or from the following formula where the necessary information is available.
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Where: Vt = minimum volume of tanks, gallons
Vs = volume of system, not including tanks, gallons
T = average operating temperature, degrees Fahrenheit
Pa = atmospheric pressure, psia
Pf = fill pressure, psia
Po = maximum operating pressure, psia
Expansion Tank Capacity for Gravity Hot Water Systems Based on 2-pipe system with average operating water temperature 170 degrees Faherenheit, using cast iron column radiation with heat emission rate 150 Btu per hour square foot equivalent direct radiation.
|Square Feet of Installed Equivalent Direct Radiation 1||Tank Capacity Gallons|
|Up to 350||18|
|Up to 450||21|
|Up to 650||24|
|Up to 900||30|
|Up to 1,100||35|
|Up to 1,400||40|
|Up to 1,600||2 - 30|
|Up to 1,800||2 - 30|
|Up to 2,000||2 - 35|
|Up to 2,400||2 - 40|
1 For systems with more than 2,400 square feet of installed equivalent direct water radiation, the required capacity of the cushion tank shall be increased on the basis of 1 gallon tank capacity per 33 square feet of additional equivalent direct radiation.
Expansion Tank Capacities for Forced Hot Water Systems Based on average operating water temperature 195 degrees Fahrenheit, a fill pressure 12 psig and maximum operating pressure 30 psig.
|System Volume, Gallons 1||Tank Capacity, Gallons|
1 Includes volume water in boiler, radiation, and piping, not including expansion tank.
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