Harsco Industrial 1004905923, Installation & Owner'S Manual

Page: 23 / 56

MODU-FIRE
®
Forced Draft Gas-Fired Boiler 2500-3000
23
3.7 B
OILER
W
ATER
P
IPING
3.7.1 Piping Design
3.7.1.1 Water Flow in System
Ideal operation of the
MODU-FIRE
®
Forced Draft
boiler would consist of a 20º F temperature differential across
the heat exchanger at high fire. Insufficient flow may result in excessive short cycling of the boiler and eventual
damage or premature failure of the equipment.
NOTICE! The closing of the flow switch does not prove that flow is adequate. It only indicates that some flow
is present. The proper water flow rate for the N2500 & N3000 MFD is 165-325 gpm.
Minimum Return Water
Temperature should be
greater than 130º F to avoid
problems of condensation
on the outside of the heat
exchanger or in the flue
passages.
Proper flow rates and
return water temperature
may be achieved through a
combination of primary and
secondary flow loops.
Multiple zones and pumps
may result in different flow
rates at different times.
Consideration must be
given to all possible
conditions and their
consequences.
3.7.1.2 Piping with Refrigeration Machines
When used with a refrigeration system, the boiler shall be installed so that chilled medium is piped in parallel with
the boiler. Valves should be installed to prevent chilled water from entering the boiler when the system is
operated in the cooling mode.
3.7.1.3 Piping with Air Handling Units
The boiler piping system of a hot water heating boiler connected to heating coils located in air handling units,
where they may be exposed to refrigerated air circulation, must be equipped with flow control valves or other
automatic means to prevent gravity circulation of the boiler water during the cooling cycle.
0
2
4
6
8
10
12
14
16
18
20
150 175 200 225 250 275 300 325
Flow (GPM)
P
re
s
s
ure
D
rop (
ft
of
he
a
d