Toyotomi FB-38N Operation And Maintenance Instructions page 28

SEMI-CLOSED / CLOSED EXPANSION TANK SELECTION
NOTE: The Semi-closed Expansion Tank (optional) should be selected in accordance with the
total water volume contained in the hot water piping system.
NOTE: Refer to the formula below or the manufacturer's formula when selecting the closed
expansion tank.
(When the discharge pressure of he Pressure Relief Valve on the hot water pipe indicates 95 kPa)
V: Capacity of Closed Expansion Tank (lit.)
V : Total water volume contained in hot water piping system (lit.)
0
ε:
Circulation water expansion rate
P : Air injection pressure of Expansion Tank (kPa)
1
The air injection pressure should be selected at the pressure, which is 10 to 20 kPa
greater than the maximum static pressure that is applied on the Expansion Tank
(maximum value between Expansion Tank and radiator).
P : Discharge Pressure of Pressure Relief Valve (kPa)
2
V (lit.) = Heat exchanger capacity of Water Heater + retained water volume in radiator +
0
retained water volume in pipe (see the following table.)
Retained Nominal
water volume Diameter
in copper
Retained water
pipe per 1m
volume (lit./ m)
Retained Nominal diameter
water volume
in city water
Retained
pipe per 1m
volume (lit./m)
Expansion rate of
Antifreeze Solution
(0~80°C)
[Calculation formula for Closed Expansion Tank]
V = {(P + 100) / (P
2
φ8
(8A)
0.040 0.050
1/2
(15A)
water
0.20
Mix proportion
Antifreeze Solution
Expansion rate ε
– P )} x 1.1 ε V
2 1
1/4 3/8 1/2
(10A) (15A)
0.103 0.165
3/4 1
(20A) (25A)
0.37 0.60
of
40%
0.042
9
0
3/4 1 1-1/4
(20A) (25A) (32A)
0.334 0.565 0.844
1-1/4 1-1/2
(32A) (40A)
1.10 1.36
50%
0.045
1-1/2
(40A)
1.183