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Joined: Jul 2004
Posts: 11
I just purchased a lighting contactor to control three 20A 277V circuits with fluorescent 2x4 lights. The name brand is ASCO and they call it a remote control switch. My problem is that the control terminations are L - Line, O - Open, and C - Close. What I was hoping to get (and what I asked for) was something that i could apply 120V to and close the contacts for the three circuits. Apparantly that is not how this contactor works. You apply 120 to the close and the contacts close, and if you apply 120 to the open the contacts open. I would imagine this would be done with some sort of pushbutton on/off switch. That is not how I want this to operate, and the ko's on the included cabinet have been knocked out so returning it and switching for a different contactor may not be an option. Anyway, here is my question. If I wire this up so voltage (120) switches from the open termination to the close termination, will it damage the contactor. I know it works, because i did it earlier by swapping out the three way switch that the switch leg (120V to operate contactor) was landed on with a four way, and adding another switch leg, thus swapping the voltage back and forth between the open and close contacts. I don't know however if the contactor is designed to have a voltage on one of those contacts at all times or if is just supposed to have voltage there long enough to throw the contact. If anyone knows how these contactors work any advice would be greatly appreciated. Sorry if this post is confusing, it's been a long day.

Thanks for any help,

Joined: Feb 2005
Posts: 693
Chris, I'd say you need to asl ASCO.

Larry Fine
Fine Electric Co.
Joined: Jan 2005
Posts: 109
That comntactor is a lock on/off the coil will not take control power all the time. I have usesd a ice cube relay to make them work on a toggle switch. Each time power is aplyed to the coil it opens or closes. Hope this helps. Rod

Joined: Apr 2002
Posts: 558
You purchased a mechanically held contactor but you need an electrically held contactor. I’m not sure if these coils will hold up being energized continuously since they are not designed for this purpose. Some mechanically held contactors have coil clearing contacts to de-energize each coil after it operates but I don’t believe your contactor does. ASCO does make a solid state module that mounts on the contactor and adapts them to 2 wire operation. It might be cheaper to just replace the contactor.


Curt Swartz
Joined: Oct 2000
Posts: 2,723
Likes: 1
Broom Pusher and

There are Two ways of doing this (well, 2 simple ways, that is!);


[*] Control the LC with a Single Pole Double Throw - Momentary Contact w/ Center position "off", type toggle switch - most common option,

[*] Use a typical "3-Way Switch" - most simplest.

The type of Contactor you have is a Mechanically Held (AKA "Latching") Contactor.
One Coil (the "C" Coil), will close the contacts and "Latch" them closed; while the other Coil (the "O" Coil), will "Unlatch" and open the contacts.

The "opposite function" Coil's leads will go through auxiliary contacts of their own - so the coil does not remain continuously energized
(if the Contactor is latched in the "Closed" position, the lead going to the "C" Coil is now opened via the interlocking contact, and the lead going to the "O" Coil will now be closed via interlocked contact - allowing the "O" Coil to be energized when needed).

Simply stated, once the contactor has latched into one position, that coil's circuit will be opened by the interlock contact. At the same time, the opposite function's coil circuit will be closed via the interlock contact.
This makes it possible to leave AC power on the control circuit, without frying the coil - or having a fight breakout between the Open and Close functions!
(Contactor would open and close over and over..... and over....and over.... like the Energizer Rabbit!!!).

Nearly all the Mech. Held LCs I have dealt with have interlocks - and the ASCO brand is no exception.

To verify if your's does have interlocks, energize one of the function coils and leave it hot (keep AC power on) after it latches, or unlatches the contacts.
Feel the coil, to see if it's "Humming".
If no "Hum", coil circuit is "Dead".

FYI: Coil leads =

"C" = "Close" Coil lead terminal,

"O" = "Open" Coil lead terminal,

"LINE" or "COM" = "Common" terminal for control circuitry
("other" ends of "C" and "O" coils)
For 120 VAC control circuitry, connect the Grounded "Neutral" Conductor to this terminal.

Good luck.


Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!
Joined: Jul 2004
Posts: 11
thanks for all of your replies, i will call asco in the morning


would i need an electrically held contactor if i swapped this out for a normally closed version of this contactor


could you explain to me how you would wire up the ice cube relay

this contactor was $250, so i would really like to get it working if at all possible

thanks again,

Joined: Jul 2004
Posts: 11
Thanks scott, you really answered all of my questions. What you said about using a three way is pretty much what i am doing except i am using a four way at the end of a three way set up instead of a three way and running up two switch legs. i am certainly glad to hear that i don't have a $250 contactor that i can't use. Thanks again for the informative reply

Joined: May 2003
Posts: 2,876
e57 Offline
If this is a multiple location SW requirement, and a latching contactor, i.e. it holds on its own, you can parralel momentary switches so your common to ON (close) is the same for all, and likewise for (open)OFF.

Leviton even makes a nice decora one I like to use.

Mark Heller
"Well - I oughta....." -Jackie Gleason
Joined: Oct 2001
Posts: 172
Get the momentary switch or switches,like e57 says you can use as many as you need, and use this contactor. It does not make the noise associated with the electrically held models. Since this is being used in a 2X4 enviornment, they may have done you a favor by providing this type. It should be an excellent application.

Joined: Jan 2005
Posts: 109
To use the ice cube just wire the NO contact to close and the NC contact to open. Rod

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