ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
ShoutChat Box
Recent Posts
From an outsider- How does tipping work?
by NORCAL - 01/17/21 05:26 AM
Can I ask for your input?
by electure - 01/16/21 07:04 PM
Ground fault remover :-)
by NORCAL - 01/16/21 10:29 AM
Photo Editing Software?
by grich - 01/13/21 11:18 AM
Happy New Year Folks!!!
by Trumpy - 01/04/21 05:46 AM
New in the Gallery:
Facebook follies, bad wiring
FPE in Germany pt.2
Who's Online Now
1 registered members (Scott35), 15 guests, and 8 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
Contactor #54169 07/21/05 09:44 AM
Joined: Apr 2002
Posts: 156
kinetic Offline OP
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?

Work Gear for Electricians and the Trades
Re: Contactor #54170 07/21/05 12:32 PM
Joined: Apr 2004
Posts: 349
Radar Offline
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.


There are 10 types of people. Those who know binary, and those who don't.
Re: Contactor #54171 07/21/05 02:03 PM
Joined: Dec 2003
Posts: 751
earlydean Offline
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.

Re: Contactor #54172 07/21/05 02:09 PM
Joined: Dec 2003
Posts: 751
earlydean Offline
just checked out the grainger site. There is a 120 volt coil kit you can purchase for $64.

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

Re: Contactor #54174 07/21/05 10:13 PM
Joined: Apr 2002
Posts: 156
kinetic Offline OP
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.

Re: Contactor #54175 07/21/05 10:16 PM
Joined: Jan 2005
Posts: 5,316
renosteinke Offline
Cat Servant
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...:-)

Re: Contactor #54176 07/22/05 10:03 AM
Joined: Apr 2002
Posts: 156
kinetic Offline OP
Member trying to give me ideas? This guy has a pretty good sense of humor. He might actually like that.

Re: Contactor #54177 07/22/05 10:23 AM
Joined: Mar 2005
Posts: 1,803
Alan Belson Offline
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?

Wood work but can't!


2020 National Electrical Code
2020 National Electrical
Code (NEC)

* * * * * * *

2020 Master Electrician Exam Preparation Combos
2020 NEC Electrician
Exam Prep Combos:
Master / Journeyman


Member Spotlight
Levittown, PA
Posts: 810
Joined: April 2004
Show All Member Profiles 
Top Posters(30 Days)
Trumpy 15
Popular Topics(Views)
273,971 Are you busy
207,724 Re: Forum
195,435 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.7.3