Viessmann Vitocrossal 300 CU3A Application Manual page 62

Application Rules & Formulas
Universal Hydronics Formula:
BTUH
GPM=
500 x ΔT
Piping & Tubing Properties
Steel/Wrought Iron Pipe
Content/ft
Size
(gal)
1/2" .016
3/4" .028
1" .045
1-1/4" .078
1-1/2" .106
2" .174
*Based on a velocity of 4fpm
*Based on 20°F ΔT
Pex Tubing
Content/ft
Size
(gal)
1/2" .009
5/8" .013
3/4" .018
1" .030
1-1/4" .046
1-1/2" .105
*Based on a velocity of 4fpm
*Based on 20°F ΔT
Copper Tubing (Type L)
Content/ft
Size
(gal)
3/8" .007
1/2" .012
3/4" .025
1" .043
1-1/4" .065
1-1/2" .092
2" .161
*Based on a velocity of 4fpm
*Based on 20°F ΔT
58
BTUH= GPM x 500 x ΔT
Max Flow Rate 1 Max Heat Carrying
(GPM) Capability (BTUH)
4
7
12
20 200,000
28 280,000
44 440,000
Max Flow Rate 1 Max Heat Carrying
(GPM) Capability (BTUH)
2.3
3.3
4.6
7 .5
11.2
15.6
Max Flow Rate 1 Max Heat Carrying
(GPM) Capability (BTUH)
2
3.2
6.5
10.9
16.3
22.9 229,000
39.6 396,000
2
40,000
70,000
120,000
2
23,000
33,000
46,000
75,000
112,000
156,000
Quick Pipe Resistance Calculation:
2
1. Measure longest run of pipe
2. Add 50% for fittings
20,000
3. Multiply by .04
32,000
= A rough calculation on the feet of
65,000
head the pump needs to overcome
109,000
for that circuit.
163,000