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Old 11-20-2011, 08:43 AM   #1
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Adjusting blower speed wiring


I live in an unconventional loft style home with a fully exposed HVAC heat pump system. The air handler is a Nordyne B5BM-T42K-B system as described on this Nordyne web site. The wiring diagrams for the air handler and motor can be seen here. I know a little about electrical systems, but I'd like confirmation as to whether my reading of these diagrams is correct.

I have been wondering if I could reduce the fan speed on my system to make it quieter and run continuously during winter months. According to the Nordyne web site, this system can be configured for multiple speeds. Mine appears to be capable of three speeds. The motor wiring diagram shows six connections with numbers 4, 5 and 6 controlling motor speed. I looked at the blower motor plug on my unit and saw red and black wires connected to 6, and nothing connected to 4 and 5. That leads me to believe my fan is already configured to run at its lowest speed. If that is the case, then I assume there is little more I can do.

Does anyone see this different from me? Does anyone have any solid ideas for reducing the fan speed on this system?
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Old 11-20-2011, 09:17 AM   #2
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Adjusting blower speed wiring


Thats as low as it can go. If you ever did get it lower then it may overheat the heat pump or electric strips and cause damage. They have high end airhandlers nowadays with ECM variable speed energy saving motors which you can run at a lower speed for circ but you would have to buy one and they are not cheap. Still would have to get a tech from the heat pump co to set it up for proper flows but you could have a much lower quieter circ speed. Don't ask about the cost as it depends on what your local contractors charge.

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Old 11-20-2011, 11:29 AM   #3
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Adjusting blower speed wiring


if it is s tand alone along a perimeter wall might consider boxing it like a old fashion radiator with a grilled op and and open bottom for the return....
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Old 11-20-2011, 01:02 PM   #4
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Adjusting blower speed wiring


Probably another over sized unit, with under sized duct work. What size is the trunk line.
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Old 11-20-2011, 08:07 PM   #5
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Adjusting blower speed wiring


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Probably another over sized unit, with under sized duct work. What size is the trunk line.
Because of the loft setting, the air handler is in the center of the room feeding symmetrical duct work on either side. Each run of ducting is arrow straight with outlets roughly every 7'. The first 22' of ducting on each side is 12" in diameter. The last 10' of ducting is 10" in diameter.
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Old 11-20-2011, 08:30 PM   #6
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Adjusting blower speed wiring


Border line size on the trunk. And with only 8 supplies, if they aren't all 7", they are too small also. And give you noise problems.

What is the return like.
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Old 11-20-2011, 08:52 PM   #7
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Border line size on the trunk. And with only 8 supplies, if they aren't all 7", they are too small also. And give you noise problems.

What is the return like.
Return air goes directly into the air handler via two 16" x 20" louvered openings.

I assume much of the sound is due to the fact that there is nothing between the exterior of the HVAC unit and ducting and the rest of the room. But my main interest was in running the fan continuously, but at a lower speed for more even heating. The ceiling in this loft style structure is about thirteen feet high at its peak, and the HVAC unit is near the ceiling. I wanted the fan to keep the air circulating so the warm air wouldn't all end up pooling at the ceiling.
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Old 11-20-2011, 09:03 PM   #8
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Adjusting blower speed wiring


Might be able to use pleated air filters to minimize the noise.
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Old 11-21-2011, 05:29 AM   #9
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Adjusting blower speed wiring


blade type variable speed ceiling fan would work. but the best one you can afford. the cheap ones get noisy and howl if you put a speed control on them.

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Last edited by yuri; 11-21-2011 at 05:31 AM.
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