Heat Transfer MODCON VWH 300 LP Installation & Maintenance page 20

PART 5: BOILER PIPING
Fig. 5-1 below represents the combined flow rates
and pipe sizes when using multiple boilers to design
the manifold system for the primary circuit. To size,
simply add up the number of boilers and the required
flow rates for the system design temperature.
Flow rate 30 50 60
Pipe Dia. 2" 2½" 2½" 3"
7
6
5
4
3
2
1
0
0
Figure 5-1
The chart below represents the various system design temperature rise through the Mod Con along
with their respective flows and friction loss which will aid in circulator selection.
Model
Mod Con 300 VWH
Mod Con 500 VWH
Mod Con 850 VWH
90
80
70
60
50
40
30
20
10
0
2 4
Figure 5-2
19
GAS-FIRED HOT WATER SUPPLY BOILER
(CONTINUED)
MULTIPLE BOILER MANIFOLD PIPING
85 90 100 120 150 170 180 200 210 240 250 255 300 340 350 400 425 510 595 680
3" 3" 4" 4" 4"
Multiple Boiler Manifold Piping
100 200 300
Combined Boiler Water Flow (GPM)
SYSTEM TEMPERATURE RISE CHART
Friction Feet
19'
19'
35'
FRICTION IN FEET OF HEAD
MOD CON HEAT EXCHANGER PRESSURE DROP
6 8 10 12 14
FRICTION IN FEET OF HEAD
MODCON 300
Example: (5) Mod Con 300 Boilers with a design
of 30 degree temperature rise with each boiler
having an individual flow rate of 20 GPM. To cor-
rectly size the manifold feeding these (5) Mod
Con 300 Boilers you would need a pipe size of 3".
4" 4" 4" 5" 5" 5"
400 500
20°Δt
Flow G P M
30
50
85
16 18 20 22 24 26
MODCON 500 MODCON 850
Boiler Manual
5" 5" 5" 5" 5" 6"
600 700 800
25°Δt
Friction Feet Flow G P M
12'
11'
26'
28 30 32 34 36
LP-205-E Rev. 12/5/07
6" 6"
24
40
65