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4 Water connections
28
Boiler circulator requirements
This is a low mass, high efficiency hot water boiler which
must have adequate flow for quiet, efficient operation. Pump
selection is critical to achieve proper operation. A pump should
be selected to achieve proper system design water temperature
rise. Pipe diameter and length are critical to ensure proper flow
through the boiler. A System Temperature Rise Chart (Table 4B
on page 30) is provided to assist in proper pump selection. This
table provides GPM and boiler head-loss at various temperature
rises for each model based on Btu/hr input. Temperature rise
is the difference in boiler inlet temperature and boiler outlet
temperature while the boiler is firing at full rate.
Example: The boiler inlet temperature is 160°F (71.1°C) and
the boiler outlet temperature is 180°F (82.2°C). This means that
there is a 20°F (11.1°C) temperature rise across the boiler. The
boiler temperature rise is visible in the Operator Interface on the
boiler’s front control panel.
Circulator pump specifications
1. Maximum operating pressure for the pump must exceed
system operating pressure.
2. Maximum water temperature should not exceed the
nameplate rating.
3. Cast iron circulators may be used for closed loop systems.
4. A properly sized expansion tank must be installed near the
boiler and on the suction side of the pump.
FLOW IN GALLONS PER MINUTE
PRESSURE DROP IN FEET HEAD
Pressure Drop Chart
Models 497 - 747
80
75
70
65
60
55
50
45
40
30
20
10
0
2
4
6
8
10
12
MODELS 987 - 2067
Figure 4-4_Heat exchanger pressure drop chart_
Models 987 - 2067
Figure 4-3_Heat exchanger pressure drop chart_
Models 497- 747
Installation & Service Manual
Circulator pump operation (heating boilers only)
The boiler pump must run when the boiler is firing. Separate
supply circuits can be provided or the two circuits (pump
and controls) can be combined for connection to one circuit,
properly sized for both.
Pump delay operation
A pump delay operation feature is provided. The boiler’s
circulating pump will cycle on at each call for heat, before the
burner fires. The pump will continue to operate while the
burner is firing. The pump will run for a minimum 30 second
period after the temperature set point is satisfied. This timing
will remove any of the residual heat from the combustion
chamber before turning the pump off. See the wiring diagram
in Section 10 of this manual.
Water connections (heating boilers only)
Inlet and outlet water connections on Models 497 - 747
have 2'' NPT and on Models 987 - 2067 the inlet and outlet
connections are 2 1/2'' NPT.
ƽ CAUTION
Field installed reducing bushings must not
be used to reduce below the pipe diameters
of the models listed above.
Any reduction in pipe size may decrease flow resulting in high
water temperatures, boiler noise, flashing to steam, and non-
warrantable heat exchanger damage.
The boiler may be installed with a primary/secondary piping
system provided to the boiler. It is important to guarantee that
adequate flow is provided to properly dissipate heat from the
boiler and also ensure that flow through the boiler does not
exceed the maximum recommended flow rate of 55 GPM for
Models 497 - 747 and 90 GPM for Models 987 - 2067 for a boiler
equipped with a copper heat exchanger.