INSTALLATION INSTRUCTIONS
TrueZONE
®
Bypass (CPRD)
APPLICATION
The TrueZONE
®
Bypass constant pressure regulating
damper (CPRD) is a round static pressure relief damper. It
is used in forced-air bypass applications to relieve excess
static pressure when some of the zone dampers are
closed. The damper is installed in a duct that delivers air to
the return or a dump zone. The damper automatically
opens and closes to maintain a desired static pressure.
The CPRD uses a calibrated spring to regulate the bypass
air accurately when any number or combination of zones
is calling. Conventional, weighted arm, bypass dampers
may operate properly when one zone is calling; however,
when different combinations of zones are calling, they
bypass too much or too little. This can cause callbacks
when homeowners complain of air noise.
Selecting the Correct CPRD
1. Size the bypass damper by subtracting the cfm of
the smallest zone from the cfm of the system.
2. Consult Table 1 to determine the CPRD to use.
3. Example:
Bypass CFM = Total System CFM - Smallest Zone CFM
SPECIFICATIONS
Construction:
Galvanized steel, see Table 2
Temperature Range:
Ambient: 0–165 °F (-17–73 °C)
Storage: 30–150 °F (-1– 65 °C)
Table 1. Damper Sizing
Table 2. CPRD Dimensions.
Bypass
Damper
Replacement
Regulator Maximum Airflow
CPRD8 CPR8 600 CFM
CPRD10 CPR10 1000 CFM
CPRD12 CPR12 1400 CFM
CPRD14 CPR14 1700 CFM
Model
ABCDE
Gaugein mm in mm in mm in mm in mm
CPRD8 8 203.2 9.65 245 1.50 38 11.54 292.84 4.65 118 26
CPRD10 10 254 11.42 290 1.50 38 13.50 343 4.65 118 26
CPRD12 12 305 13.18 235 1.50 38 15.47 392.84 4.65 118 24
CPRD14 14 355 14.96 380 1.50 38 17.36 441 4.65 118 22
M34207
D
E
B
C
A
Regulator
Damper
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