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#54169 - 07/21/05 10:44 AM Contactor  
kinetic  Offline
Joined: Apr 2002
Posts: 156
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 01:32 PM Re: Contactor  
Radar  Offline
Joined: Apr 2004
Posts: 349
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.


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#54171 - 07/21/05 03:03 PM Re: Contactor  
earlydean  Offline
Joined: Dec 2003
Posts: 751
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.


#54172 - 07/21/05 03:09 PM Re: Contactor  
earlydean  Offline
Joined: Dec 2003
Posts: 751
Griswold, CT, USA
just checked out the grainger site. There is a 120 volt coil kit you can purchase for $64.


#54173 - 07/21/05 06:08 PM Re: Contactor  
Rich R  Offline
Joined: Apr 2005
Posts: 27
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.

#54174 - 07/21/05 11:13 PM Re: Contactor  
kinetic  Offline
Joined: Apr 2002
Posts: 156
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.

#54175 - 07/21/05 11:16 PM Re: Contactor  
renosteinke  Offline
Cat Servant
Joined: Jan 2005
Posts: 5,316
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...:-)

#54176 - 07/22/05 11:03 AM Re: Contactor  
kinetic  Offline
Joined: Apr 2002
Posts: 156
Phoenix, Arizona trying to give me ideas? This guy has a pretty good sense of humor. He might actually like that.

#54177 - 07/22/05 11:23 AM Re: Contactor  
Alan Belson  Offline
Joined: Mar 2005
Posts: 1,803
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?

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