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Discussion Starter · #1 ·
My Trane blower motor was running whenever it wanted so I had it professionally replaced. As the tech was leaving he told me he "adjusted the motor size to a larger one" so it would run stronger. I noticed the system does blow a heavier volume of air now but it is also noisier. What is the point of doing this and what are the ramifications (speed wise, efficiency, and cost wise)? Also, How do I return it to its previous setting?

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model number of the furnace?

The motor is limited to just under the synchronous rpm - so 1200 synchronous, rated speed 1075 rpm and unlikely to ever exceed 1100 rpm.

So running the motor under-loaded doesn't increase the speed much at all.

Using a lower speed tap weakens the motor but for it to slow down below normal high speed, the load has to exceed the strength of the motor on a specific speed tap.

So if your tech wired cooling for high and heating for medium high, probably running at same rpm in heating and cooling mode - resulting in more air volume in heating mode.

Over-sized motors use more electricity and some say have a shorter lifespan too. The speed range is more limited -> normally 4 speeds and medium low could be equivalent to high speed of the old motor.
 

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Discussion Starter · #4 ·
model number of the furnace?

The motor is limited to just under the synchronous rpm - so 1200 synchronous, rated speed 1075 rpm and unlikely to ever exceed 1100 rpm.

So running the motor under-loaded doesn't increase the speed much at all.

Using a lower speed tap weakens the motor but for it to slow down below normal high speed, the load has to exceed the strength of the motor on a specific speed tap.

So if your tech wired cooling for high and heating for medium high, probably running at same rpm in heating and cooling mode - resulting in more air volume in heating mode.

Over-sized motors use more electricity and some say have a shorter lifespan too. The speed range is more limited -> normally 4 speeds and medium low could be equivalent to high speed of the old motor.
Apparently you're much more versed than I am as to what he actually did. We are in South Florida and don't use the heater much. The motor would cut in and out and was not running when he came. Anyways it is a Trane Model number 4TEH3F42B1000AB. Can he actually adjust the air volume (as I stated it seems noisier now)?
 

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So you have an air handler.

Based on your description, the old motor probably was overheating due to failing bearing or other problem.

Yes - there are usually 3 or 4 speeds.

New larger motor on medium high could be equivalent to high of proper motor.

As stated before, there's the speed tap / motor strength that matches the load at 1075 rpm and rpm does not increase much at all bumping it up from there - so putting a large motor is not really beneficial.

The air handler is a 3.5 ton and if you have a 3.5 ton outdoor unit, it probably needs to be on maximum speed/rpm - old motor may have already been set to high and new equivalent is medium high or something.

Just keep in mind, failing motors can run slower than normal so you may have just gotten used to the lower speed and now it's normal.
 

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My Trane blower motor was running whenever it wanted so I had it professionally replaced. As the tech was leaving he told me he "adjusted the motor size to a larger one" so it would run stronger. I noticed the system does blow a heavier volume of air now but it is also noisier. What is the point of doing this and what are the ramifications (speed wise, efficiency, and cost wise)? Also, How do I return it to its previous setting?

Thanks
Could be that it was the only size motor he had on his truck. He didn't do you any favor though. The A/C now removes less moisture because its moving more air.

Mat be possible to set it to a lower speed/CFM.
 

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Discussion Starter · #8 ·
The model number on the motor was the same. All I did was replace the old failing motor to a new one that was exactly the same model number. He says he tuned it so it would blow higher. Can I readjust it myself?
 

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Yes, you can do it yourself, if you know how. There are usual several "taps" on the motor to which you connect one of the wires from the air handler for different speeds. You need to know what motor you have, what air handler you have in order to connect it up correctly. We may be able to help you here but why not just call the guy back and ask him to change the wire over to the original speed setting?
 

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Discussion Starter · #12 ·
Yes, you can do it yourself, if you know how. There are usual several "taps" on the motor to which you connect one of the wires from the air handler for different speeds. You need to know what motor you have, what air handler you have in order to connect it up correctly. We may be able to help you here but why not just call the guy back and ask him to change the wire over to the original speed setting?
That sounds like the answer, thanks.
 
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