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Gas Furnaces - Blower & Relay
Installation Instructions
For MGHA and MMHA Series, Models -05 only, and M1 Series Furnaces
The p/n 903092A 2-wire and p/n 902898A A/C Heat Pump (4 to 7 wire) Relay Boxes install with cur-
rent M1, MGHA and MMHA models of NORDYNE gas furnaces with the new standardized blower
assembly. The 2-wire Relay Box has control switches which are operable through an opening in the
furnace door on MGHA and MMHA furnaces.
Read all instructions carefully before starting the installation. Specifi cations 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 war-
ranty.
Blower
Screws
Field Installed
Thermostat Wires
Furnace
System Switch
Furnace
Thermostat Wires
Furnace
Control Box
Figure 1. MGHA and MMHA Series Gas Furnace
These instructions are primarily intended to assist qualifi ed 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 instruc-
tions carefully before starting the installation.
IMPORTANT INFORMATION
Additional
Nameplate Insert
(on older models)
Decorative
Nameplate
Insert
Blower
Plug
Door Control
Frame
DANGER:
!
Shut off electrical supply to the furnace at
the household breaker box to prevent electri-
cal shock which could cause personal injury.
Blower
Screw
Relay
Box
Field Installed
Thermostat
Wires
Blower
Plug
Thermostat
Leads
Fan On/Auto
Switch
(on Heating
only Models)
Fig 2. M1* Furnace
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Table of Contents
Related Manuals for Nordyne MGHA Series
Summary of Contents for Nordyne MGHA Series
-
Page 1: Installation Instructions
The p/n 903092A 2-wire and p/n 902898A A/C Heat Pump (4 to 7 wire) Relay Boxes install with cur- rent M1, MGHA and MMHA models of NORDYNE gas furnaces with the new standardized blower assembly. The 2-wire Relay Box has control switches which are operable through an opening in the furnace door on MGHA and MMHA furnaces. -
Page 2: Installation Sequence
INSTALLATION SEQUENCE IMPORTANT: For the 2-Wire Relay Box (only after the cover has been reattached), now attach two red caps 1. Remove the furnace door. Shut off power to the fur- (provided in plastic bag) to the switches that stick through nace. -
Page 3: Relay Box Installation
Blower Speed Selection Chart For use with Blower Kit No. 902809 Cooling Speed/ Evap Coil Heating Furnace Input Speed 042, 046 & 024, 030 Setting Bracket -Right 070, 075, 077 056, 066, 070 *MH on Relay Box circuit board. **ML on Relay Box circuit board. Blower Speed Selection Chart Bracket - Relay Box... -
Page 4: System Operation
Find the 4-wire harness supplied with the relay box. Connect its 6 circuit matrix connector to the blower plug Wire Nut to and connect its 6 circuit in-line connector to the bottom Low Voltage Wiring Furnace of the relay box (see Figure 4). Thermostat Wires (Red to Red;... -
Page 5: Wire Relay Box Exploded View
Model p/n 903092A Figure 5. 2-Wire Relay Box Exploded View Model p/n 902898A Figure 6. A/C Heat Pump Relay Box Exploded View... -
Page 6: System Wiring
Figure 7. System Wiring... -
Page 7: Wiring Schematics
2 Wire Circuit Board (used in relay box 903092A) 2 Wire Circuit Board (used in relay box 902898A) Figure 8. Wiring Schematics... - Page 8 707893A (Replaces 70789300) ¢707893P¤ Specifi cations and illustrations subject to change without notice and without incurring obligations. 707893A O'Fallon, MO Printed in U.S.A. (06/09)