Tjernlund DB-2 Duct Booster 8504030 Rev B 09/00 - Manual (Page 4)

OPERATION
The DUCT BOOSTER® can be operated and controlled in several manners:
1. By means of a standard ON/OFF switch.
2. By wiring the DUCT BOOSTER® in parallel with a gas or oil fired central furnace
blower motor.
3. By using the optional Tjernlund Products, Inc. Model PS1503 DUCT AIRSTAT pressure
switch, sold separately. The DUCT AIRSTAT will automatically control the operation of
the DUCT BOOSTER® in both heating and cooling systems. When the air handler
supplies warm or cool air, the DUCT AIRSTAT senses positive pressure and starts the
DUCT BOOSTER®.
ELECTRICAL WRING
NOTE: All wiring must be appropriate Class 1 wiring as follows: installed in rigid metal
conduit, intermediate conduit, rigid non-metallic conduit, electrical tubing, Type MI Cable,
Type MC Cable or be otherwise suitably protected from physical damage.
CAUTION: When wiring DUCT BOOSTER® in parallel to a gas or oil fired central fur-
nace blower motor the following conditions must be fulfilled.
In addition, the DUCT BOOSTER® cannot be wired into both the low (heating) and high
(air conditioning/fan “on”) contacts of the blower relay. Doing so will short out the blower
motor.
A. The gas or oil-fired central furnace may include refrigerant cooling coils, however, it
must be equipped with 120 VAC single phase blower motors. The DUCT BOOSTER®
SHOULD NOT BE WIRED IN PARALLEL WITH 240 VAC BLOWER MOTORS.
B. The basic furnace wiring and components should not be disturbed except for wiring
interconnection of the DUCT BOOSTER® and furnace blower motor at a splice box in
the furnace.
C. The rating of furnace blower motor controller must be adequate to control blower
motor and the DUCT BOOSTER® motor. The DUCT BOOSTER® motor is rated 0.5
amps.
NOTE: Blower motor controller should not be a variable speed tap type, solid
state speed control or any other type not suitable for dual motor control.
D. The existing short circuit and ground fault protection for the furnace blower motor
should be of a size and type which will adequately protect the DUCT BOOSTER®
motor. Refer to Section 430-53 of the National Electrical Code.
E. The wiring from the furnace to the DUCT BOOSTER® must be 14 AWG and the
furnace should be protected by over-current protection (fuses or circuit breakers) rated
at 15 amperes or less, (as applicable for 14 AWG conductors).
F. IMPORTANT: Refer to Section 430-53 (d) and Table 310-16 of the National Electrical
Code for additional limitations.