Changing Blower Speed


Old 10-18-06, 10:32 AM
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Changing Blower Speed

I recently installed a Miller M3RL-080 gas furnace. I live at 9600 feet and replaced with high altitude burner orifices. Checked the firing rate, within specs. However, the temperature rise is to low, so I need to lower the blower speed. The install manual provided the following in the wiring diagram: Red to Heat, Orange to M2, Blue to M1, Black to Cool, White to Common. Blower Motor wiring diagram shows Red-Low, Orange-Medium Low, Blue-Medium High, Black-High.

Furnace as delivered was:
Orange to M1, Red to M3, Blue to Heat. Black to Cool.

Notice on wiring diagram states:
Furnace Input 60,000 Wire Color Red,
Furnace Input 80,000 Wire Color Blue

I assume mine is set to Medium High for Heat, High for Cooling.
Do I just place the orange wire on the Heat terminal for Medium Low, or the Red wire on the Heat terminal for Low? What does the M1, M2 and M3 terminal represent? Do I just switch the wires? For example, If I want a medium low speed, remove the blue wire from the Heat terminal, and switch it with the orange wire on the M1 terminal. Unfortunately, the Install Manual didn't give much help other than the wiring diagram.

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Old 10-18-06, 10:54 AM
Ed Imeduc's Avatar
Join Date: Aug 2002
Location: Mountain Williams Missouri
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Id say put the orange wire to the heat. But look at the schematic. It should be on the blower door and see that thats how it goes.

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