MG3P Installation Manual

19
cap to maintain air tightness in the furnace. Measurements for
hole locations on MG3 series furnaces are shown in Figure 44
(page 36).
Inducer Assembly Rotation
WARNING:
Inducer rotation must be completed before
the furnace is connected to gas and electric. If
both utilities have been connected, follow the
shutdown procedures printed on the furnace
label and disconnect the electrical supply.
CAUTION:
It is good practice to label all wires prior to
disconnection. Wiring errors can cause improper
and dangerous operation.
1. Disconnect the electrical harness from the inducer assembly.
2. Remove the inducer assembly ground wire from the blower
deck.
3. Remove three screws securing the inducer assembly to the
header box.
4. Rotate the inducer assembly to its new position.
5. Secure the inducer assembly to the header box by reinstalling
the three screws. If the inducer assembly is rotated to the left
or right side of the furnace, use the extra screw provided in
the parts package.
6. Remove the cabinet plug from side of furnace and reinstall in
hole on opposite side of cabinet. NOTE: The cabinet plug must
always be used to close the hole in the side of the furnace
when rotating the inducer.
7. Install in-line drain assembly and tubing.
8. If applicable, install the condensate drain lines. For MG3P
series see Figure 54. For MG3S series see Figure 55.
9. Reconnect the electrical harness to the inducer assembly.
10. Reconnect the inducer assembly ground wire to the blower
deck or door.
11. Verify operation as detailed on the furnace label.
Pressure Switch Tubing
Figure 24 (page 19) & Figure 25 (page 19) display the proper
routing of pressure switch tubing for MG3 Series furnaces. All
upflow (MG3P) furnaces have two switches, one connected
to the static tap on the inducer assembly and the other to the
collector box. Downflow (MG3S) furnaces require only one switch
connected to the inducer’s static tap as shown in Figure 25.
Alternate Pressure Switch Location
In some inducer orientations, the inducer pressure switch may
interfere with gas pipe installation. Check the side of the cabinet
the gas pipe will enter and determine if the inducer pressure
switch needs to be moved. If the switch interferes with gas pipe
installation, please follow these instructions for relocating it to
the alternate location:
1. Shut off any electrical power to the furnace.
2. Label and disconnect the tubing and wires from the pressure
switch.
3. Remove two screws securing the pressure switch to the
inducer housing.
4. Remove the pressure switch from the mounts on the inducer
housing and relocate it to the other set of mounts 90° from
previous location. See Figure 26.
5. Secure the pressure switch with two screws.
6. Reconnect the tubes and wires to the pressure switch.
Figure 24. Pressure Switch Tubing for Upflow
Furnaces (Models: MG3P-054 & MG3P-090)
FACTORY INSTALLED
LOCATION
ALTERNATE
LOCATION
Figure 26. Alternate Pressure Switch Location
Figure 25. Pressure Switch Tubing for Downflow
Furnaces (Model: MG3S-080)