Bulletin 30-034.009
Copyright © 2022 Unico Inc.
Page 6
Insulate all metal ducting with 1.5-inch (38-mm)
minimum fiberglass insulation. For round duct, use
either sleeve insulation or foil-faced duct wrap. For
square duct use either fiberglass duct board or foil-faced
duct wrap. Tape all seams to prevent air leaks.
High Humidity.
When the furnace is installed in high
humidity areas, such as an unconditioned attic or
crawlspace, there is a possibility of condensation
forming on the furnace cabinet during the cooling
mode. To prevent condensation, cover the furnace with
1-inch (25mm) foil faced fiberglass insulation or duct
board. Be sure to allow access to the control box cover
for servicing (Figure 9).
Tape all seams with UL 181-
A-P aluminum tape.
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Insulate exterior cabinet except the control panel
in high humidity areas with a minimum of 1.0" [25mm]
thick fiberglass or foam rubber
Figure 9. High humidity applications.
WIRING
All electrical wiring must comply with all local codes
and ordinances.
Connect power supply to a main disconnect per local
codes. The power connects to the line input terminals as
shown on the electrical wiring diagrams. For single
phase these are labeled: L1, L2 and for three phase these
are labeled: L1, L2, L3. Refer to the label on the control
box lid for specific wire sizes and amperage. Connect a
ground wire to the ground lug labeled G.
Note: The circuit breakers installed in this device
provide short-circuit protection of internal wiring and
DO NOT provide over current protection of the
supply wiring.
Separate power supply.
The electric furnace is
equipped with several circuit breakers, including a
circuit breaker for the blower (M1, M2). The blower
circuit breaker provides a convenient disconnect for the
blower motor for service. For single phase furnaces the
blower circuit breaker is separate from the heater circuit
breakers. Turning off the heater circuit breaker will not
disconnect the blower power. For three phase furnaces,
the blower circuit breaker is in line with the heater
circuit breaker. Turning off the heater will shut off the
motor
.
Figure 10. Separate heater and motor circuits
Combining the motor and heater loads (single phase
heaters only).
All single phase furnaces include a 4-
pole jumper bar (P/N: A01241-001) to combine the
blower motor circuit breaker and one of the heater
circuit breakers (Figure 11). The combined load can be
powered by one fused main circuit sized for both the
heater and motor loads. Remove the
jumper bars if
using a separate power supply for motor and electric
furnace as in Figure 10.
Figure 11. Combined blower motor and one heater
circuit wiring (single phase furnaces only) (10kW
and below)
The 15 and 20 kW single phase heaters have two heater
circuit breakers because most residential codes limit
Use separate fused
main power supply for
each circuit.
L1
L2
Heater
Circuit
Breaker 1
240V
M1
M2
Motor
Circuit
Breaker
240V
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L1
L2
Heater
Circuit
Breaker 2
240V
L1
L2
Heater
Circuit
Breaker 1
M1
M2
240V
Motor
Circuit
Breaker
4-pole jumper bar included with furnace
