The p/n 903091 2-wire and p/n 902987 A/C
Heat Pump (4 to 7 wire) Relay Boxes install with
current models of the E2 and current models of
the E(1,2) electric furnaces. The 2-wire Relay Box
has control switches that are operable through an
opening in the furnace door, where applicable.
IMPORTANT INFORMATION
Read all instructions carefully before starting the
installation. Specifications or designs are subject
to change or to discontinuance without notice
and without incurring obligations.
WARNING:
Improper installation may damage
equipment, can create a hazard, and
will void the warranty.
2 Wire: For models E2E(H,B) Series
4-7 Wire: For models E(1,2)EH Series
Electric Furnace - Relay
WARNING:
Shut off electrical supply to the furnace
at the household breaker box to
prevent electrical shock which could
cause personal injury.
These instructions are primarily intended to
assist qualified individuals experienced in
the proper installation of heating and/or air
conditioning appliances. Some local codes
require licensed installation/service personnel
for this type of equipment. Read all instructions
carefully before starting the installation.
INSTALLATION INSTRUCTIONS
2
Circuit
Breakers
Relay Box
Wiring Harness
plugs here on
Furnace Control
Panel
Blower
and
Relay
Decorative
Door Insert
Door Control
Frame (used w/
2 wire relay box)
Furnace
Door
Wiring
Harness
Low Voltage
Wiring
Blower
Connector
Connects
Here
Connect
8 Pin
Connector
on Wiring
Harness
Here
Blower
Connector
(Connect to
Relay Box)
Wiring Harness
Connect
to Relay
Box
Connect
to Furnace
Control Panel
Figure 1. E1E(-) Series Electric Furnace
Figure 2a. E2E(-) Series Electric Furnace, manufactured prior to 1999
Connect Blower
Connector Here
Blower Connector
(Connect to Relay Box)
Circuit
Breakers
Relay Box
Wiring Harness
plugs here on
Furnace Control
Panel
Blower
and
Relay
Nameplate
Insert
Door Control
Frame (used w/
2 wire relay box)
Furnace
Door
Wiring
Harness
Low Voltage
Wiring
Connect 8 Pin
Connector on
Wiring Harness
Here
Circuit
Breakers
Relay Box
Wiring Harness
plugs here on
Furnace Control
Panel
Blower
and
Relay
Furnace
Door
Wiring
Harness
Low Voltage
Wiring
Figure 2. E2E(-) Series Electric Furnace, manufactured 1999 or later
Connect Blower
Connector Here
Blower Connector
(Connect to Relay Box)
Connect 8 Pin
Connector on
Wiring Harness
Here
3
INSTALLATION SEQUENCE FOR
MODELS E(1,2) E(H,B) SERIES
ELECTRIC FURNACE (SEE FIGURE 1,
2, OR 2A)
Prior to installing a relay box in the furnace, be
sure to install the correct A/C system equipment
as outlined on the furnace options label.
Remove the furnace door by pulling outward
either from the top or the top side of the door.
Switch the circuit breaker(s) to the OFF position.
(See Figure 1, 2, or 2a for the circuit breaker
location.)
Before installing the relay box remove the blower
and install the cabinet insulation kit for furnaces
that are not factory equipped with this package.
Refer to the instructions supplied with the kit for
proper installation.
E(1,2)EH Models: All E(1,2)EH models require
a relay box when adding an air conditioner or
heat pump.
E2EB Models: E2EB models using a 2-wire
thermostat require a relay box (2-wire) when
adding an air conditioner.
Blower Selection: See the furnace Installation
Instructions for the correct air conditioning or heat
pump available with the factory installed furnace
blower. Change out the blower when needed.
Remove the cover from the relay box by removing
the screw from each side.
Blower Speed Selection:
• HEATING - Move the orange wire on the circuit
board to one of the four quick-connects labeled
with heating blower speeds.
• COOLING - Move the violet wire on the circuit
board to one of the three quick-connects
labeled with cooling blower speeds.
• TWO SPEED BLOWER - Connect the orange
wire (heating) to the L (low) quick-connect for
low speed. Connect the violet wire (cooling)
to the ML (medium low) quick-connect for high
speed.
• THREE OR FOUR SPEED BLOWER - See
Table 1 for the appropriate speed connections
for E1E(-) models & Table 2 for E2E(-) models.
Reattach the relay box cover using the two screws
previously removed.
IMPORTANT: For the 2-wire relay box (only after
the cover has been reattached):
a. Attach two red caps (provided in plastic bag)
to the switches that stick through the bezel on
the sheet metal cover (see Figure 3, items 7
and 8).
b. (E1 & E2 furnace models manufactured prior to
1999 only): Attach the appropriate brand label
to the sheet metal cover so that it may be seen
through the door control frame (see Figure 2)
in the furnace door when it is replaced.
c. (E1 & E2 furnace models manufactured prior
to 1999 only): Attach the foam “standoff” to the
bottom corner on the back side of the relay
box opposite the side where the bracket is
attached (See Figure 2b). This standoff will
Table 1. E1E(-) Heating & Cooling Speed Setting Positions – 4 Speed Blower
Furnace Operation (Orange Wire)
Furnace
Model #
-10,
-012
-015, -017,
-020, -023
Relay Box Speed
Terminal (min.)
L ML
NOTE: See furnace installation instructions for nominal air deliveries.
Air Conditioning / Heat Pump Operation
(Violet Wire)
Air Conditioning
Model #
-024 -030, -036
-042, -046,
-048
Heat Pump Model # -018 -030
-036, -042,
-048
Relay Box Speed
Terminal (min.)
ML MH H
Table 2. E2E(-) Heating & Cooling Speed Setting Positions – 3 or 4 Speed Blower
Furnace Operation (Orange Wire)
Furnace
Model #
-10, -012 -015,
-017, -020, -023
Relay Box Speed
Terminal (min.)
L-3 Spd ML-4Spd
NOTE: See furnace installation instructions for nominal air deliveries.
Air Conditioning / Heat Pump
Operation (Violet Wire)
SEE FURNACE BLOWER LABEL OR
FURNACE INSTALLATION INSTRUCTIONS
FOR APPROPRIATE SPEED CONNECTIONS
4
prevent movement of the relay box when the
homeowner adjusts the switches.
Relay Box Attachment
(See Figure 1, 2, or 2a)
Attach the mounting bracket to the appropriate
side of the relay box. Attach the relay box to
the side of the blower housing. For E2 furnaces
manufactured 1999 or later, bracket should be
attached by self tapping 2 screws into the side
of the blower housing approximately 1/2” back
from the mounting holes.
Insert the relay/blower assembly into the furnace
by sliding it into the furnace and under the
mounting tabs. Secure the blower in place by
using the blower screws previously removed.
Relay Box Connection (See Figure 1, 2, or 2a):
• Unplug the blower connector and the
thermostat pigtail leads connector from the
furnace control panel.
• Plug the two different 6-circuit connectors
on the relay box wiring harness into their
corresponding locations on the furnace control
panel (where the blower and thermostat leads
connectors were just removed).
• Plugthe8-circuitconnectorontheotherendof
the wiring harness into the side of the relay box.
• Plugthe6-circuitblower connector into the
bottom of the relay box.
Low Voltage Wiring
(See Figure 1, 2, or 2a)
Bring in the low voltage field wires from the
thermostat and air conditioning or heat pump
unit and attach them to the screw terminals
located at the top of the relay box. See Figure 5
for System Wiring.
Switch the circuit breaker(s) to the ON position.
The unit is now ready for operation.
SYSTEM OPERATION
For the AC/Heat Pump Relay Box
Heating: Set the furnace system switch to AUTO
(where applicable), the thermostat system switch
to HEAT, and the thermostat fan switch to AUTO.
Cooling: Set the furnace system switch to AUTO
(where applicable), the thermostat system switch
to COOL, and the thermostat fan switch to AUTO.
Emergency Heat: (Used with a heat pump only.)
Set the furnace system switch to AUTO (where
applicable), the thermostat system switch to
EMERGENCY HEAT, and the thermostat fan
switch to AUTO.
Continuous Air Circulation: Set the thermostat
fan switch to ON.
Shut off System: Set the thermostat system
switch to OFF and set it to the lowest temperature
setting. Set the furnace system switch to OFF
and shut off all power to the air conditioner.
For the 2-Wire Relay Box
Heating: Set the furnace system switch to AUTO
(where applicable), the temperature switch (on
the relay box) to HEAT, and the fan switch (on
the relay box) to AUTO.
Cooling: Set the furnace system switch to AUTO
(where applicable), the temperature switch (on
the relay box) to COOL, and the fan switch (on
the relay box) to AUTO.
Continuous Air Circulation: Set the fan switch
(on the relay box) to ON.
Shut off System: Set the temperature switch (on
the relay box) to OFF and set the thermostat to
the lowest temperature setting. Set the furnace
system switch to OFF and shut off all power to
the air conditioner.
Attach foam "standoff" here
Figure 2b. E2E(-) (Pre-1999 manufacture)
Electric Furnace w/2 wire Relay Box
5
1
2
3
4
6
7
8
Figure 3. 2 Wire Relay Box, Exploded View
Model P/N 903091
1
2
3
4
5
6
Figure 3. A/C Heat Pump Relay Box, Exploded View
Model p/n 902987
Table 3. Blower & Relay Replacement Parts List
ITEM # PART # DESCRIPTION 903091 902987
1
375952 Cover (2-Wire) 1 —
376431 Cover (AC/HP) — 1
2 378700 Box Relay 1 1
3
624567 2-Wire Relay Circuit Board 1 —
624625 AC/HP Relay Circuit board — 1
4 259200 Wire Harness 1 1
5 376050 Mounting Bracket, E1 — 1
6 380790 Mounting Bracket, E2 1 1
7 669084 Bezel 1 —
8 632278 Switch Cap 2 —
6
Figure 5. System Wiring
Blower
Motor
L
ML
MH
H
C
123456
123456
R Y W G
A/C O.D. Section
4 Wire A/C
T- Stat
8765
4
3
21
8765
43
21
Blower
Motor
R C Y O W
2
W/E G
L
ML
MH
H
C
Furnace With the AC/Heat Pump
Relay Box and a 4 Wire Thermostat
123456
123456
RC RH Y W G
A/C O.D. Section 5 Wire A/C
T- Stat
8765
4
3 21
Blower
Motor
R C Y O W
2 W/E G
L
ML
MH
H
C
Furnace With the AC/Heat Pump
Relay Box and a 5 Wire Thermostat
123456
123456
R W
A/C O.D. Section
2 Wire Heat
Only T- Stat
8765
43
21
8765
43
21
Y R C W
Furnace With the 2 Wire Relay
Box and a 2 Wire Thermostat
HEAT
COOL
OFF
ON
AUTO
FAN
123456
123456
H/P O.D. Section
H/P
T-Stat
Blower
Motor
R C Y O W2 W/E G
L
ML
MH
H
C
Furnace With the AC/Heat Pump
Relay Box and a Heat Pump
R C Y O E W2
R C Y O W2 E G
1 23456
1 23456
Powermiser
Compressor Section
Blower
Motor
R C Y O W2 W/E G
L
ML
MH
H
C
Furnace With the AC/Heat Pump Relay Box and a Powermiser
C W2 G R G Y W2 O P R
Powermiser
T-Stat
C W1 G Y E F O P R X
Fan Coil T-Stat
ODT
LEGEND
Field Wiring
Factory Wiring
Wire Harness Supplied with Relay Box
Wire Harness Supplied
with Relay Box
Wire Harness Supplied
with Relay Box
Wire Harness Supplied
with Relay Box
Wire Harness Supplied with Relay Box
Optional
Heat Pump
Interconnect
Cable
8765
4
321
8 765
4
321
8 765
4
321
8765
4
321
8765
4
321
3
2
1
6
5
4
3
2
1
6
5
4
6
5
4
3
2
1
6
5
4
3
2
1
Furnace
control panel
1: SEQ1 (W2)
2: SEQ2 (W2)
3: 24V COM
4: 24V HOT
5: G
6: OPEN
240V L2
240V L1
HIGH
MED-HIGH
MED-LOW
LOW
3
2
1
6
5
4
3
2
1
6
5
4
6
5
4
3
2
1
6
5
4
3
2
1
Furnace
control panel
1: SEQ1 (W2)
2: SEQ2 (W2)
3: 24V COM
4: 24V HOT
5: G
6: OPEN
240V L2
240V L1
HIGH
MED-HIGH
MED-LOW
LOW
3
2
1
6
5
4
3
2
1
6
5
4
6
5
4
3
2
1
6
5
4
3
2
1
Furnace
control panel
1: SEQ1 (W2)
2: SEQ2 (W2)
3: 24V COM
4: 24V HOT
5: G
6: OPEN
240V L2
240V L1
HIGH
MED-HIGH
MED-LOW
LOW
3
2
1
6
5
4
3
2
1
6
5
4
6
5
4
3
2
1
6
5
4
3
2
1
Furnace
control panel
1: SEQ1 (W2)
2: SEQ2 (W2)
3: 24V COM
4: 24V HOT
5: G
6: OPEN
240V L2
240V L1
HIGH
MED-HIGH
MED-LOW
LOW
3
2
1
6
5
4
3
2
1
6
5
4
6
5
4
3
2
1
6
5
4
3
2
1
Furnace
control panel
1: SEQ1 (W2)
2: SEQ2 (W2)
3: 24V COM
4: 24V HOT
5: G
6: OPEN
240V L2
240V L1
HIGH
MED-HIGH
MED-LOW
LOW
Figure 6. Wiring Schematics
P1
H(H)* MH(M)* ML(L)* L
COOL
HEAT
K1
K2
P2
K3
K3
K4
COOL
OFF
HEAT
AUTO
FAN ON
K1
Cooling Speed
Selector (violet wire)
Heating Speed
Selector
(orange wire)
K2
K4
Blower
Switch
Temperature
Switch
2 Wire Circuit Board (used in relay box 903091)
AC/Heat Pump Circuit Board (used in relay box 902987)
P2
K1
K2
P1
COOL
HEAT
K1
K2
Cooling Speed
Selector (violet wire)
Heating Speed
Selector
(orange wire)
65 4 3 2 1
65 4 3 2 1
6
5
4
3
2
1
7
8
6
5
4
3
2
1
7
8
YR C W
RC Y OW2 W/E G
* - 3 speed motor
* - 3 speed motor
H(H)* MH(M)* ML(L)* L
708802A (Replaces 7088020)
Specifications & illustrations subject to change
without notice or incurring obligations (05/15).
O’Fallon, MO, © Nortek Global HVAC LLC 2015.
All Rights Reserved.
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