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#184845 02/23/09 09:13 PM
Joined: Apr 2005
Posts: 33
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Need some help. Are there voltage ranges for a coil? I have a 3 phase 208 volt 3 hp motor with a NEMA Size 1 contactor with a 208 volt coil and a start/stop built in.
After the initial smoking of the coil, it had a 24volt coil instead of the 208 volt varity the box label stated. Lesson learned...
Anyway, I now have the correct coil but it won't pull in, it chatters. I read the voltage to actually be about 225 volts between phases which is not something I have come across much in this neighborhood.
Is there a "range" that the coil should work in? This started as a simple "favor" for a friend and it is turning into more of a time consuming problem.
Any input is appreciated.


Joined: May 2005
Posts: 984
G
Member
Chattering is often the result of installing a DC coil on an AC control circuit.
When the drops to zero (before reversing polarity) the coil loses its field and the contactor starts to spring back open.


Ghost307
Joined: Jul 2004
Posts: 9,663
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Is this the type with a pick and hold coil, selected by a side switch? You may be wired to the hold side.


Greg Fretwell
Joined: Apr 2001
Posts: 41
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i am experiencing the same problem with a set of contactors that control heating elements for a water heater.they keep chattering .even after replacement.i am now in the process of replacing them with a larger contactor 70a instead of 50a .i am thinking that the load is to much for the contactor.im not sure if this is helpful to you.im not sure if the higher voltage would effect the contacts inside the contactor.

Joined: Jul 2001
Posts: 599
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Load does not affect the contactor sealing in.

The three most common reasons that contactors make noise are:
Low coil voltage. Most coils will pull in at 85% and drop out at 65%.
Jammed mechanism from dust or worn slides.
And probably the most common; rust, dirt, or scratches on the magnet poles faces which prevent them from mating correctly.

JBD #184860 02/24/09 10:02 AM
Joined: Mar 2005
Posts: 1,213
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It could simply be defective from the factory. We ran into a few defective chattering contactor solenoids last year in an application where problems like that are unheard of (high-end UPS systems).

It can be hard to tell the difference between a wrong part and a defective one, especially if you're pulling the replacements from the same defective batch.

Joined: Jul 2001
Posts: 599
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One more question.

You say it does not pull in, it just chatters.
Do you mean that it chatters while you hold the Start button in and then it drops out when you release the button?
Not holding in would be caused by a bad holding circuit contact or a wiring error.
Chattering, like rapid pickup then dropout, could be a wiring error where a contact from the starter is actually turning the circuit off instead of holding the circuit on.

JBD #184880 02/24/09 10:24 PM
Joined: May 2008
Posts: 4
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Most contactors are equiped with a shaded pole. This shaded pole holds the contactor shut while the AC current crosses the zero point. If it is chattering, this is the first thing that I would look for...

Joined: Jul 2004
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got my attention...


Greg Fretwell
Joined: Mar 2005
Posts: 1,213
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Originally Posted by mb95307
Most contactors are equiped with a shaded pole. This shaded pole holds the contactor shut while the AC current crosses the zero point. If it is chattering, this is the first thing that I would look for...
How does that work, are there two solenoids in the contactor, one with a straight winding and one with a shaded pole?

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