# Using mechanically held contacts with SPST timer switch



## BleedingLungsMurphy (10 mo ago)

A mechanically held (lighting) contactor being controlled by a switch??!!??!!!!!!!! 


Jdog921 said:


> How can I make this work??


I don't know, sir, you better contact an engineer for this one. Have you tried sending Elon Musk a tweet?

/sarcasm

How long have you been an electrician for, anyway? Do you know how to wire a 3 way light switch to a contactor coil? Switch leg on one side of the coil. Neutral on the other side. EZ-PZ.


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## Jdog921 (6 mo ago)

BleedingLungsMurphy said:


> Do you know how to wire a 3 way light switch to a contactor coil? Switch leg on one side of the coil. Neutral on the other side. EZ-PZ.


Right…so I then when I need to unlatch and turn the lights off with the same timer switch, then what? Would an added relay suffice?


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## Wirenuting (Sep 12, 2010)

8903LX AC Lighting Contactors Installation and User Guide | Schneider Electric


This user manual provides installation and operation instructions for multi-pole mechanically held AC lighting contactors, Class 8903, Type LX, Series B.




www.se.com


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## sundogusa (Jan 22, 2007)

You need a pulse ON signal and pulse OFF signal. Some timers have the pulse setting as an option. The other switches could be momentary on-center off- momentary on toggle switches.


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## SWDweller (Dec 9, 2020)

Have you ever worked with the GE RR9 relays? 
Others have said this before you need a momentary signal for open and close. However I would not be using line voltage for the coil. Makes things a bit harder in my opinion. 
Electrically held will last a few years the mechinical contactor will last decades.
LV wiring can be typically run with out conduit. Your not clear about the timer, so you may be better off using an ice cube timer, 24v coil, and using 120v to power it, keeping the coil at 120v.
keeping the timer and the contactor in the same cabinet. Out of sight and out of prying hands.


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## gpop (May 14, 2018)

Siemens you can send power all the time as the contractor will disconnect power to the coil once it has made the switch (makes it easy to install a relay using a N/O and N/C set of contacts). Not sure about the SQ-D with out reading the manual.


Sorry re-read the original post. 
Do you require override on or off or both


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## Almost Retired (Sep 14, 2021)

Jdog921 said:


> I have a Square D 8903LXO40 mechanically held contactor that I’m trying to use as you would normally with an electrically held contactor. It would be controlled by a simple 120v SPST timer switch that goes into a single gang box.
> They also need to be wired with 2 override switches at 2 separate entrances. How can I make this work?? I never wired mechanically held contractors for this scenario before? I would like to think there’s an easy way to do this with getting some kind of conversion kit or swapping out the contactor for an electrically held one. Any insight on this would be helpful.


as i understand it ... you want lights to come on when ppl are there, and either time out or get overridden by a switch by the door ?
all of what you mentioned sounds entirely too complicated

may be a better option would be occupancy sensors?

explain what results you want
not how you are trying to do it
we will either tell you that is the best way, or we will tell you a better way


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## Almost Retired (Sep 14, 2021)

well he hasnt been back in 10 days ,, guess i wasted my time


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