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#54169 - 07/21/05 07:44 AM Contactor
kinetic Offline
Member

Registered: 04/06/02
Posts: 158
Loc: Phoenix, Arizona
I have a contactor supplied by a plumber for a misting system. It is a Square D 8910DPA. Basically a 3 phase/1 phase contactor with a 24 V coil. It didn't have a wiring diagram and I haven't dealt with contactors before. My question is how do I get the coil to fire? Do I need an external power source?

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#54170 - 07/21/05 10:32 AM Re: Contactor
Radar Offline
Member

Registered: 04/30/04
Posts: 349
Loc: Los Angeles, CA
Sounds like you need a 24V source to energize the coil, plus some way to control (ON/OFF) the 24V. You also need to confirm the 24V you're talking about is 24VAC as opposed to 24VDC. A 24VAC supply is pretty easy to provide, a 120V circuit feeding a 120V to 24V transformer. The 24V side of the transformer probably needs fuse protection sized to the transformer rating.

Radar
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#54171 - 07/21/05 12:03 PM Re: Contactor
earlydean Offline
Member

Registered: 12/22/03
Posts: 749
Loc: Griswold, CT, USA
You could also explore the possibility of swapping the coil out to the voltage you are controlling (208?, 480?). Most contactors will have interchanageable coils of many different voltages.
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Earl

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#54172 - 07/21/05 12:09 PM Re: Contactor
earlydean Offline
Member

Registered: 12/22/03
Posts: 749
Loc: Griswold, CT, USA
just checked out the grainger site. There is a 120 volt coil kit you can purchase for $64.
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Earl

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#54173 - 07/21/05 03:08 PM Re: Contactor
Rich R Offline
Member

Registered: 04/25/05
Posts: 29
Loc: Florida
Sometimes the controller/timer for the misting system or sprikler system will have a 24 volt output for the pump contactor.

You should find out how they plan on controlling this before spending any money on transformers etc.

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#54174 - 07/21/05 08:13 PM Re: Contactor
kinetic Offline
Member

Registered: 04/06/02
Posts: 158
Loc: Phoenix, Arizona
Thank you for the help. I thought I would need an external power source like you mentioned Radar. I didn't feel like experimenting with the contactor and risk blowing it up or causing bigger problems. The mister is 240V 1 phase and I was going to ask the plumber to get a different contactor with a 240V coil but he left town for vacation this week. Easier for me to get a simple multi-tap transformer and be done with it. The other misting systems I helped install all had internal controllers but for some reason this one did not.

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#54175 - 07/21/05 08:16 PM Re: Contactor
renosteinke Offline
Cat Servant
Member

Registered: 01/22/05
Posts: 5305
Loc: Blue Collar Country
One of my favorite new "Candid Camera" episodes showed what happened when they connected the misters at a supermarket produce case to a motion sensor. Customer approached produce, mister fired...:-)

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#54176 - 07/22/05 08:03 AM Re: Contactor
kinetic Offline
Member

Registered: 04/06/02
Posts: 158
Loc: Phoenix, Arizona
Hmmmmmm.....you trying to give me ideas? This guy has a pretty good sense of humor. He might actually like that.

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#54177 - 07/22/05 08:23 AM Re: Contactor
Alan Belson Offline
Member

Registered: 03/23/05
Posts: 1801
Loc: Mayenne N. France
The contactor needs to have the single phase Hot 'snaked' through the contacts to equalise the overload 'heaters' if fitted- see my question posed 04 26 2005 under 'Motor Starter' ( currently on p. 9 ) for the good advise I got. Will a 240-24V transformer, plus casing, be cheaper than a new 240v coil?
Alan
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