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Old 11-05-13, 01:47 PM   #1
pinballlooking
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Default HVAC Blower motor.

I noticed that my blower motor is old and not very efficient. I was wondering if anyone has tried one of these blower motors?

http://www.davidonindustries.com/stu...20Brochure.pdf

The Green Motor - SNTech


SNTech Green Motor Indoor 1/2HP PSC Replacement Motor - GI10750G

With the new mini splits we will probably using just fan more but the current blower motor uses more power than my small Mini split.

My current motor is 1/2 hp two speed but the wireing shows it is set up with heat, cool, and just fan. High for cooling med heat/fan
That looks like it would work good with this motor.


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Last edited by pinballlooking; 11-15-13 at 03:26 PM..
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Old 11-05-13, 04:47 PM   #2
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If it's a really old unit, you'll be better off replacing the whole thing.
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Old 11-05-13, 05:22 PM   #3
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It is part of my gas heat and that is still good. Since I have added mini splits I am not really wanting to replace the whole thing.

Last edited by pinballlooking; 11-05-13 at 07:17 PM..
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Old 11-05-13, 06:43 PM   #4
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Is one of your new mini-split units going to be near a return air vent? If so, running just the fan should work rather well. If not, where does the return air come from? Hmmmm.....

The fan motor you linked to is awesome. Five speeds to choose from, all at high efficiency. Carrier and Trane are installing these types of motors in their new variable speed, variable capacity split systems (both indoors and outdoors). If it fits your existing blower, it should save much energy over a shaded pole motor and some energy over a split capacitor motor. At $250, not a bad price for a new motor. However, it could take many years to pay its cost back in energy savings. The more it runs, the more it saves.

I figured Mike would like it, it has FOC. They call it speed defined torque control.

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Old 11-05-13, 07:14 PM   #5
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Yes two of the mini splits return to the central return air vent. The other one is returns close to it.
It would be nice if I could run fan only and send some of the mini split heat to the kid’s rooms.
The current motor will not work very well for that.

I will not get to netzero but I would like to get close.
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Old 11-05-13, 07:55 PM   #6
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You can rig most (if not all) industry-standard blowers to run whenever, at whatever speed, you want them to, rather easily. Granted, a dimmer switch isn't quite as efficient as an ECM control, but 75 Watts is still less than 750 Watts. So what if I lose 15 RPM in translation?

Don't tell my landlord, but I tied into the LOW speed wire that the furnace manufacturer had no spot for on their control board. It was just begging me to be connected to something. I couldn't just ignore it, now, could I?
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Old 11-05-13, 09:51 PM   #7
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I'm surprised it doesn't have continuously variable speed via some standard interface like 5V PWM or 0-10V. Who would buy a CVT that could only operate in 5 predefined ratios?

What might work is a 3 phase motor connected to a VFD. Efficiency might not be quite as good as a permanent magnet motor but if you get those items off the surplus market, you can come way ahead on cost.
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Old 11-06-13, 08:00 AM   #8
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I don’t think a CVT will work for a retro fit. I only have three speeds cool, heat and fan only.
I am not changing out the old equipment so they still need about the same air flow.
I would like it to use less energy and have a very efficient low quite fan only mode.
What 3 phase motor and VFD would you recommend? I am an old navy electronics technician but a novice when it comes to HVAC.
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Old 11-06-13, 01:35 PM   #9
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Just find a 3 phase motor that would fit in the unit (with the same or greater HP rating) and any surplus VFD with compatible voltage and power ratings.

There's also a hack to run a single phase motor from a common VFD. Don't expect as much control range and you'll need a somewhat larger VFD (still small as far as VFDs go), but not having to replace the motor cuts costs.


And you can indeed make use of variable speed. For cooling, slow it down to enhance dehumidification or speed it up for better EER. For heating, it's generally best to run it such that the discharge air just feels warm, with a gradual ramp up as soon as the burners are lit so that it can purge the cold air out of the ducts. (That can take some trial and error to get it right.) For ventilation, you'll have to again use trial and error to find the right point.

BTW, multi speed motors (used conventionally) have an efficiency penalty as low speeds cause excessive slip and high speeds only use part of the winding. But with a VFD, there's a trick to using the entire winding. With the motor unloaded, run it on the highest speed and measure voltage from the lowest speed tap to common. Divide that by 60Hz and that's the value to use for the V/Hz parameter in the VFD. (You'll probably need, for example, a 208V VFD and a voltage doubler to run a 120V motor that way.) Also replace the run cap with a higher voltage version if needed (440V rating for a 120V motor should be good).
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Old 11-07-13, 07:43 AM   #10
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added a relay to my hp to switch to lower speed on fan when do not need immediate heat - motor power on fan is cube of speed

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