Installation Sequence - Nordyne MGHA Series Installation Instructions Manual

INSTALLATION SEQUENCE

1. Remove the furnace door. Shut off power to the fur-
nace.
For MGHA and MMHA Furnaces:
For a 2-wire relay box application, remove the door insert
from the furnace door and replace it with the door control
frame provided with the relay box (see Figure 1).
2. See Table 1 to determine whether the factory installed
blower is acceptable for use with the selected cooling
application.
For MGHA and MMHA Furnaces:
To change out the furnace blower, unplug the motor plug
from the furnace. Remove the two screws on the top of
the blower deck, one on each side of the blower (see
Figure 1), and slide the blower out of the furnace. Slide
the new blower into the blower mounting guides. Do not
yet secure with the screws previously removed.
For M1 Furnaces Only:
To change out furnace blower, unplug the motor plug
from the furnace. Remove the screws on the left side
of the blower (see Figure 2) and lift the blower out of
the furnace. Place the new blower into the mounting
guides.
3. 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.
• ONE SPEED BLOWER - Both the orange wire (heating)
and the violet wire (cooling) must be connected to the
H(high) quick-connect.
• TWO SPEED BLOWER - See Table 2 for the appropriate
speed connections.
• THREE SPEED BLOWER - See Table 2 for the appropri-
ate speed connections.
• FOUR SPEED BLOWER - See Table 2 for the appropriate
speed connections
For M1 Furnaces Only:
Discard the brackets and remove the relay box cover.
Mount the relay box on the top side of the blower using
the two self-tapping screws provided. The thermostat
terminations should be towards the top of the furnace.
The furnace door should not interfere with the relay box.
Reattach the relay box cover.
2
IMPORTANT: For the 2-Wire Relay Box (only after the
cover has been reattached), now attach two red caps
(provided in plastic bag) to the switches that stick through
the bezel on the sheet metal cover (see Figure 5, Items
6 and 7).
4. For MGHA and MMHA Furnaces Only:
If not already completed, remove the two screws on the
top of the blower deck, one on each side of the blower.
(See Figure 1) Slide the blower partially out of the furnace.
Attach the relay box bracket(s) to the blower as shown
in Figure 3 using the screws provided. Next, attach the
relay box to the brackets as shown in Figure 3 using the
remaining screws provided. Slide the blower back into
the furnace and secure with the two screws previously
removed.
5. Unplug the blower plug from the furnace control box
and disconnect the fi eld installed thermostat wires from
the furnace. Remove the label from the yellow furnace
thermostat wire and strip it about 3/8". (For M1, this is
the grey wire.)
Find the 6-wire harness supplied with the relay box.
Connect its 8 circuit in-line connector into the side of
the relay box. Connect the 6 circuit matrix connector on
the other end of the harness into the furnace where the
blower was plugged. Wire nut the remaining harness
wires to the furnace thermostat wires (see Figure 4).
For Furnace Models MGHA & MMHA
Cool Capacity (Tons)
1.5-2.0
2.0-3.5
2.0-4.0
*The blower shipped with the furnace can be used for this
cooling capacity.
Table 1. Blower Selection - MGHA & MMHA
For Furnace Models M1
Cool Capacity (Tons)
2.0 or 2.5
2.0-3.0
2.0-4.0
2.0-5.0
*The blower shipped with the 056 furnace can be used
for 2.0 tons, the blower shipped with the 070 furnace can
be used for 2.5 tons.
Table 1A. Blower Selection - M1
Blower Kit No.
Standard
902809
902810
Blower Kit No.
Standard*
903412
903413
903414