Changing the blower speed on furnace

Old 05-02-07, 09:45 PM
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Changing the blower speed on furnace

I have heard that by swapping a couple of wires on a furnace blower will change the speed. I am looking to increase the blower speed on my furnace because the air velocity at the registers does not seem to be adequate. It would be great if I can simply change the wiring configuration but if this is not possible I may need to purchase a new, more powerful blower.
Old 05-03-07, 04:46 PM
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You could make improvement if say your furnace had a steady temperature rise during heating.

But if your goal is to try to make more heat at the registers by increasing the air flow, I believe the opposite will occur, and you will get a temperature drop instead, because you will be sending more room-temperature air through the heat exchanger that only is emitting the same given amount of heat. There will be a dilution.

If your furnace is running hot and the blower speed seems slow, then yes, if you already have a multi-speed motor (has many colored wires on it besides say a black a white and two browns if it has an external capacitor), you can switch one of the wires.

You might tell everyone here what you have,... and if you have a multi-speed blower, look at the motor plate and see what rpm's they list for the speeds and corrolating colored wire. I think they are like 950, 1050 and 1150...something like that.
Old 05-03-07, 05:57 PM
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Fan speed

All furnaces have a specification as to the temperature increase between the incoming & outgoing air. This spec is refered to as "temperature rise" or sometimes as "delta T". The temperature rise should be on the data plate or in the installation manual if you have it. A temperature rise which is either too high or too low, can damage the furnace. Unless you can measure the temperatures, I don't suggest messing with the fan speed.

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