My furnace blower is rather loud and runs at one speed. I wish to have the blower run at a slower speed to mix the air in the house when the heat is not called for. I see some furnaces have variable speed blowers, which may also solve this issue if I run at high speed when the flame is ON and low speed when OFF.

Can I retrofit my Payne PG8UAA furnace with a two-speed or variable speed blower?

There are no other issues with the furnace, so I do not wish to replace the whole unit.

Thank you

  • I'm guessing not, but if it's actually possible it will be by a manufacturer who specifically markets an after-market blower for your furnace. Home-grown would NOT be the way to go here. Commented Dec 13, 2015 at 0:37

2 Answers 2


According to the manufacturer's documentation, your furnace should have a 3 or 4 speed blower motor. The problem is, the furnace control module doesn't use a separate speed when the unit is running in continuous FAN mode.

When the R-G circuit is made, the blower motor operates on heating speed.

The control module only uses two speeds, one for COOL, and one for HEAT/FAN.

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You could run the blower at a slower speed during both HEAT and FAN calls. But you'd have to insure that the blower is maintaining adequate flow during heating, otherwise you will damage the system. This is not recommended, as you could damage the system, and void the warranty.

You might be able to swap out the control module, but you'd have to contact the manufacturer to determine if there's a compatible replacement.

The other option is to build your own control circuitry, but that's beyond the scope of this site. And will likely void the warranty on the unit.

  • Thank you for the response. I see that the newer furnaces have two stage burners that do well with variable speeds. My simple goal would be to keep the fan running at a slow speed when no flame is present. The A/C function does run the blower at a slower speed. If I could get that to kick on as a circulator to mix the air in the house to provide more even temperatures throughout the house during the heating season, I would be halfway there. Thank you for the insight into my furnace system. I am still thinking about solutions.
    – Larry
    Commented Dec 10, 2015 at 2:22
  • I stated the speeds backward. The A/C runs at "HI" and the heater runs at "Med Lo" speed. Swapping the RED wire to the Heat lug will slow down the blower when the heater is ON, but is the airflow sufficient for safety reasons? This I do not know. I would hope that an overtemp condition from too slow a speed would cut off the furnace, but who knows. More food for thought.
    – Larry
    Commented Dec 10, 2015 at 2:31
  • The furnace should shutdown if it overheats, but frequent overheating can damage the system. It may be possible to run the blower at a slower speed, but as it sounds like you're not that familiar with HVAC systems I wouldn't recommend it.
    – Tester101
    Commented Dec 10, 2015 at 3:31
  • I have a call into a local service provider and Payne dealer to see if there is a retrofit available for this model of furnace. Thanks for the feedback. This is an interesting website.
    – Larry
    Commented Dec 11, 2015 at 2:52

yes. however, it requires a lot of electronics and process control components. if you don't understand this stuff, then no.

1) swap motor out for a dc synchronous drive motor or you may be able to get a sine controller for a motor that small (1st way is better - they last forever). this may require machining interface parts, mounts, etc.

2) you need to decide on a control protocol for the speed switching - pressure or temp triggered. whichever, then you need a proportional sensor for same.

3) use a plc, arduino or beaglebone to take all the i/o's and pop the sc driver.


  • I have built systems using PLCs at my job, but they were not for home heating systems. I do not want to create a situation where there is an increased risk of damaging the furnace with insufficient airflow when the flame is ON. This is all food for thought though. Thank you for your response.
    – Larry
    Commented Dec 10, 2015 at 2:25

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