Discuss Quick motor wiring question, I hope! in the Electrical Forum area at ElectriciansForums.net

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S

sjm

I've just been to look at a job for a potential new customer.

He's just had a commercial kitchen extractor fan rewired/overhauled and would like me to wire it back in.
It would seem that the supply to the motor is single phase and the motor is three phase, ie live neutral and earth into junction box then 2 x 3 core out to motor.
He has marked the cables as they were before removal of the motor and the rewinders have marked the cables from the motor.
I have U, U2 and Z marked on the terminal block the cables appear to match but I have 1 cable from the motor that doesn't seem to be attached to any incoming cable.

Any help or ideas would be greatly appreciated.


Thanks in advance.
Steve.
 

IQ Electrical

Regular EF Member
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4,544
I've just been to look at a job for a potential new customer.

He's just had a commercial kitchen extractor fan rewired/overhauled and would like me to wire it back in.
It would seem that the supply to the motor is single phase and the motor is three phase, ie live neutral and earth into junction box then 2 x 3 core out to motor.
He has marked the cables as they were before removal of the motor and the rewinders have marked the cables from the motor.
I have U, U2 and Z marked on the terminal block the cables appear to match but I have 1 cable from the motor that doesn't seem to be attached to any incoming cable.

Any help or ideas would be greatly appreciated.


Thanks in advance.
Steve.
Is this not a single phase speed controlled fan?
 

stef

Regular EF Member
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Location
Gosport
Sounds like a single phase motor with capacitor U = line, U2. = N and z for the cap
to Line.
 
OP
S

sjm

Many thanks guys for the quick replies.

So 1 of the four conductors to the fan will have no connection, is that correct?
 
OP
D

DurhamSparky

seen as i cant see the job the extra cable may be a neutral..!!
 
OP
S

sjm

OK new information after looking at the job properly.

4 x cables to the motor, 2 x red marked Z1 and Z2, 2 x black marked U1 and U2.
Live and neutral in from the controller.
The capacitor is external to the motor.
So I'm thinking live in linked to either Z1 or Z2 and live to the capacitor.
Return from the capacitor linked to either Z1 or Z2, the 1 not already used.
Neutral in linked to U1 and U2.

Any help would be very appreciated.
Thanks in advance.
Steve.
 
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K

Knobhead

What's the capacitor conected to?

This is how it should be. The start winding will be higher resistance than the run
View attachment 14195
 
Last edited by a moderator:
OP
S

sjm

Hi Tony.
The capacitor is not connected to anything currently. It has 1 x conductor to it and 1 x conductor from it.
It's mounted externally to the motor. I'm thinking it goes in the line to the start winding Z1 or Z2.
I guess it possible that this capacitor is now redundant following the rewind of the motor, but I'm really not sure.

Thanks.
 
OP
K

Knobhead

I forgot it was variable speed, ignore the switch shown. The capacitor is conected in series with the start winding.
 
OP
S

sjm

Sorry to keep posting on this subject but------.

Wired fan as instructed and it sucks air in not out.
Wired as follows.
Line in to U2 and out through the capacitor back to Z2.
Neutral in to U1 and Z1.
Tried swapping U1 for U2 and Z1 for Z2 same result it sucks.

Just to be sure, before I tell the customer to remove the motor+blade and install it the other way round, would wiring it differently make a difference?

Thanks.
Steve
 
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S

sjm

Many thanks again Tony just the answer I was looking for!
 
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