Author Topic: blower motor wiring help  (Read 1673 times)
Lumex120
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blower motor wiring help « on: September 20, 2016, 09:20:59 AM » Author: Lumex120
Yesterday I got this big NOS 1/2 HP 3450 RPM motor at a surplus store. I want to use it for a project because the specs are perfect and it has good bearings that spin forever when you spin the shaft. (the project is building an air raid siren if anyone is curious). I need to wire it up to 115v and it needs to spin at 3450 RPM. The motor has 7 wires, as seen in the pictures below:

The color of the wires are: Black, Red, White, Yellow, Blue, Brown, and Brown and black.
Can someone provide a diagram or just tell me what I need to wire so it runs on 115v and runs at 3450 RPM? I am pretty sure it needs a capacitor, but after that what do I need to connect?

Also, I need USEFUL answers on this, not just nonsense.
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Re: blower motor wiring help « Reply #1 on: September 20, 2016, 09:23:05 AM » Author: Lumex120
Pics:

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Re: blower motor wiring help « Reply #2 on: September 20, 2016, 10:40:57 AM » Author: Solanaceae
Uhhhh, have you tried looking up model numbers and specs? Maybe the wires had labels, but they fell off.
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Re: blower motor wiring help « Reply #3 on: September 20, 2016, 12:07:52 PM » Author: Lumex120
Uhhhh, have you tried looking up model numbers and specs? Maybe the wires had labels, but they fell off.
That's the problem. I can't find ANYTHING on google about this.
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Re: blower motor wiring help « Reply #4 on: September 20, 2016, 02:29:01 PM » Author: Ash
The RPM is somewhat below 3600. This means it is an Induction motor with one set of windings. This alone does not say whether the "set" is for single Phase or three Phase use

The fact there is a capacitor size stated, means that hopefully it is a single Phase. (3 Phase motor does not need start or run capacitor). Single Phase motors have a main and a shifted Phase (usually leading, with the capacitor) winding, so 4 wires. One end of them can be permanently connected together, then 3 wires

The motors that are rated for voltage X and voltage 2X (like 120V / 240V) have each coil split to 2 parts. So there are 2 parts of the main and 2 parts of the other coil. The concept is, each "part of coil" is meant to get 120V always, and it gives 1/2 of the required Magnetic field strength for the motor. They are always wired together, so provide the complete field. When connecting to 120V you wire them in parallel, when connecting to 240 you wire them in series, so each get 120V anyway. That is 8 wires for 4 coil parts. Again 2 of them may share one end, so 7 wires

That is what i'd expect to see there....

But it is possible that they did some other fancy stuff, like using the same starting coil for both 120V and 240V (then it is 5 or 6 wires), providing external wire to the centrifugal switch (so you can connect separate start and run capacitors) and such....

And finally one of the wires could be Earth for the chassis



Measure resistance between each 2 wires, and find if there is one connected to the chassis, so we can try to match the findings to the guessing
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Re: blower motor wiring help « Reply #5 on: September 20, 2016, 03:08:39 PM » Author: Lumex120
The RPM is somewhat below 3600. This means it is an Induction motor with one set of windings. This alone does not say whether the "set" is for single Phase or three Phase use

The fact there is a capacitor size stated, means that hopefully it is a single Phase. (3 Phase motor does not need start or run capacitor). Single Phase motors have a main and a shifted Phase (usually leading, with the capacitor) winding, so 4 wires. One end of them can be permanently connected together, then 3 wires

The motors that are rated for voltage X and voltage 2X (like 120V / 240V) have each coil split to 2 parts. So there are 2 parts of the main and 2 parts of the other coil. The concept is, each "part of coil" is meant to get 120V always, and it gives 1/2 of the required Magnetic field strength for the motor. They are always wired together, so provide the complete field. When connecting to 120V you wire them in parallel, when connecting to 240 you wire them in series, so each get 120V anyway. That is 8 wires for 4 coil parts. Again 2 of them may share one end, so 7 wires

That is what i'd expect to see there....

But it is possible that they did some other fancy stuff, like using the same starting coil for both 120V and 240V (then it is 5 or 6 wires), providing external wire to the centrifugal switch (so you can connect separate start and run capacitors) and such....

And finally one of the wires could be Earth for the chassis



Measure resistance between each 2 wires, and find if there is one connected to the chassis, so we can try to match the findings to the guessing
It says 1 phase on the sticker. 3 phase motors aren't usually used with this low of an HP rating in HVAC equipment (which this is for). I also think I found out what kind of capacitor I need to use. It says "25MFD 236vAC". The problem is that I can't find a capacitor with those same specs anywhere. The capacitor connects to the brown and black and brown wires, so that means there are 5 left. I think that this might actually be a 4 speed motor, in which case I have to find out which wire runs it at the highest speed. I have been looking at various stuff on Google about blower motors and I think this is the most likely case.
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Re: blower motor wiring help « Reply #6 on: September 20, 2016, 03:32:11 PM » Author: Ash
Sometimes one of the capacitor wires also connects to the Neutral or the like, so dont rule those two out from the other connections yet

I'd expect multiple speed ratings if it was multiple speed ?



Our Air Con blower and fan motors here (well, the older ones not the Chinese stuff) adhere to some convention, allthough it is not written in any standard. If i recall it correctly :

Black - Phase for max speed
Blue - Phase for mid speed
Red - Phase for low speed
White - Neutral
Brown ---- run capacitor (typically around 3 or 4 uF for small blower) ---- Neutral

This standard does look sorta American, but i would not bet that your motor is anywhere near the same wiring..
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Re: blower motor wiring help « Reply #7 on: September 20, 2016, 05:45:34 PM » Author: Medved
Are you able to check continuity between the different wires and post a drawing?
Try to find ends of the individual windings, the difference in resistances may suggest different voltages across individual windings, taps,...

My thinking (but it has some gaps):
I would guess there would be at least two 115V windings, which are supposed to be connected in parallel to 115V and in series to 230V.
Then there will be another winding to be connected via the capacitor, to form the auxiliary phase.
But all that would mean just 6 wires, not 7 (hence the gap...)

Or it could really be wound like a 3-phase motor, using the capacitor to form the 3-phases out of the single phase input (it works for a single, fixed load, what the blower is). To have all 3 phases formed from 2 sections to be series/parallel connected, it would need 10 wires (and not 7 - a gap as well).

Definitely if you will be able to get the windings, some extra playing with AC power source and V-meter may help to figure out the winding arrangement and from that should be, I think, possible to form a working wiring diagram...
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