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Sizing the Combustion Air Intake Ductwork
The combustion air flow rate requirements per boiler model are summarized in 3.4.3. When sizing the
combustion air intake ductwork, the pressure drop through this ductwork MUST NOT exceed 0.22"
W.C. as described in the table below:
®
P-K SONIC
Boiler Model
SC-1500, SC-2000,
SC-3000, SC-4000
SC-1500, SC-2000,
SC-3000, SC-4000
If the combustion air intake ductwork and the exhaust vent terminate on the same wall of
NOTE:
the building, they must utilize the same type of termination fitting.
Harsco Industrial Patterson-Kelley recommends including a motorized combustion air
NOTE:
damper in each appliance's air intake ductwork. Refer to
Motorized Combustion Air Dampers
Harsco Industrial Patterson-Kelley recommends,
and most installation codes require, the use of
motorized combustion air dampers with end limit
switches installed in the combustion air intake
ductwork upstream of each appliance. This
damper isolates the combustion air supply when
the appliance is in standby. Once the appliance
receives a call for heat, the motorized combustion
air damper opens and the end limit switch must
close before the appliance can proceed to ignition.
Harsco Industrial Patterson-Kelley offers motorized
combustion air dampers with built-in end limits
switches for sale, which are summarized in the
table below:
Table of Recommended Motorized Combustion Air Dampers
Combustion Air Ductwork
Size
12"
14"
These normally-closed motorized combustion air dampers operate on 120 VAC and feature a built in
end limit switch which must be wired to the appliances' Air Damper Interlock circuit. Upon a call for
heat, the boiler's Air Damper Relay energizes, which drives the damper motor open. Once the damper
reaches the fully-open position, the end limit switch makes contact and closes the Air Damper Interlock
circuit, allowing the appliance to proceed to ignition. The diagram on the next page shows the wiring
necessary to install the normally-closed motorized damper.
Revised: June 2, 2017
Released: June 2, 2017
Flue Vent Category
II
IV
Normally-Closed
Motorized Damper
10-0490-6946
10-0490-6989
HARSCO Industrial, Patterson-Kelley 2017
All Rights Reserved.
P-K SONIC
Technical Service 1.877.728.5351
Maximum Allowable
Pressure Drop
through Combustion
Air Ductwork
0.22" W.C.
0.22" W.C.
3.4.5
below for
more information.
A
B
12"
12"
14"
14"
1004905978 P-K SONIC NURO Installation and
Owners Manual (Rev F Jun-2017).docx
®
Gas Fired Boiler
Allowable Vent
Pressure
-0.01" W.C. to
-0.05" W.C.
+0.01" W.C. to
+0.22" W.C.
C
D
15"
4.38"
17"
5.5"
Page 25
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