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16
shipped loose. The full open position is appropriate for
most systems, and ensures adequate flow through the
boiler.
If system flow is inadequate, (indicated by excessive
temperature drop through the system) the bypass
valve can be throttled slightly. Care must be taken
against over-throttling which may lead to inadequate
flow through the boiler and boiler harmonics (a hum-
ming sound from the heat exchanger).
If adequate system flow cannot be obtained without
causing harmonics, an additional pump is required.
The factory-mounted circulator will provide adequate
water flow for systems designed at a 20°F temperature
drop, and system pressure drop or head not exceed-
ing that which is shown in Table J.
When the total system head exceeds the available
head pressures, a primary/secondary pumping system
is recommended.
The minimum boiler operating temperature should be
105°F. When operating at low temperature applica-
tions, ∆T (temperature rise) must be 20°F or less.
Propylene glycol solution is commonly used in the
heating system when freeze protection is required.
This will affect the system design and pump perform-
ance. As a rule of thumb, 50% solution of propylene
glycol will require the system flow (gpm) to increase by
14%, and the system head (ft/WC) by 23% in order to
maintain the same heat transfer load.
Model No.
System Flow
(gpm)
Max. System
Head (ft/WC)
H-0042 3.5 8.0
H-0066 5.3 8.5
H-0090 7.3 6.5
H-0135 11.0 10.0
H-0180 14.6 7.0
Table J: System Pressure Drop
Systems with multiple zones may require an addition-
al circulator. Consult manufacturer's data for valve
pressure drops. When an indirect water heating sys-
tem is used, it is recommended that a separate
circulator be installed to meet the required flow and
pressure drop conditions of the indirect water heater.
We recommend that the make-up water from the cold
water line have a check valve, gate valve, and feedwa-
ter regulator set at 12 psi. Install unions and gate or
ball valves at inlet and outlet connections at the boiler
to facilitate servicing.
The pressure relief valve is mounted on the boiler and
must be piped to a drain. We recommend that all high
points be vented and that purge valves be installed. A
boiler installed above radiation level must be provided
with a low water cut-off device. See page 27 for wiring
hook-up.
The boiler, when used in connection with a refrigera-
tion system, must be installed so that the chilled
medium is piped in parallel with the boiler with appro-
priate valves to prevent the chilled medium from
entering the boiler.
The boiler piping system of a hot water heating boiler,
that is connected to heating coils located in air han-
dling units where they may be exposed to refrigerated
air circulation, must be equipped with flow control
valves or other automatic means to prevent gravity cir-
culation of the boiler water during the cooling cycle.
A diaphragm expansion tank should be installed in the
return line. A typical 8"-diameter expansion tank can
be used on models H-0042, and H-0066, and an 11"-
diameter expansion tank can be used on models
H-0090, H-0135 and H-0180. Consult tank manufac-
turer for correct sizing.