Lighting contactor terminology.

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rrc14

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Anchorage, AK
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Engineer
I am having problems understanding what is meant by a 3,4,5-pole lighting contactor. Are these the number of poles(circuits) feeding the lighting contactor or is it the number of circuits that the lighting contactor switches on the output?

Is it typical to have the same number of poles feeding the lighting contactor as there are poles being switched?

Can anyone help me understand this lighting contactor terminolgy?

Thanks in advance!!!
 

augie47

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Tennessee
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State Electrical Inspector (Retired)
each "pole" is a switch. the number of circuits can vary depending on conditions. 208, 240 and 480 v lighting might use 2 or 3 poles per circuit.
120 and 277 v lighting commonly is one pole per circuit.
does that help or confuse it more ?
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
I am having problems understanding what is meant by a 3,4,5-pole lighting contactor.
It's the quantity of contacts (or, more properly, 'contact sets'), each one opening and closing one conductor. How many circuits or loads it switches depends on how you wire it, as explained above.

For example, a 3-pole contactor can control one 3-pole load (such as a 3-phase load), a 2-pole (line-to-line) and a single-pole load (line-to-neutral, or three 1-phase (line-to-neutral) loads.

It's not always required to open every hot conductor of a given load for controlling purposes, but it's a good idea.
 

nakulak

Senior Member
the poles are just as in a switch, a 1 pole contactor is like a 1 pole switch. a 2 pole is like a 2 pole switch, etc. how you use the poles is just like how you use poles on a switch. two at a time, 1 at a time, etc. a 10 pole contactor would be like 10 single pole switches banked together to switch at one time, but not electronically connected otherwise. so you could have some two pole ckts as well as some single pole ckts all being switched at same time. coil voltage is always specified so whatever you use to switch it could be a separate switching ckt at 120, 277, or whatever the coil voltage is specified at. hope this helps.
 

cadpoint

Senior Member
Location
Durham, NC
I am having problems understanding what is meant by a 3,4,5-pole lighting contactor.

Until you wire one there even tough to understand, MO

Are these the number of poles(circuits) feeding the lighting contactor or is it the number of circuits that the lighting contactor switches on the output?

Yes, in answer to your question but there several different types
(wiring methods) and applications (both series and parellel). What you might or might not know, (as you as you asked your question) the classic wiring method is a Master/Slave relationship, all circuits come from the panel through a contactor and out to an application, these are slaves to a master switch, once throw it'll open or close all!

Is it typical to have the same number of poles feeding the lighting contactor as there are poles being switched?
Yes

Use Google and once with-in Image type in diagram contactor or contactor schematic

or

go to your favorite lage manufacturer's web site and type the same.
 

hillbilly1

Senior Member
Location
North Georgia mountains
Occupation
Owner/electrical contractor
There are also two types of lighting contactors, magnetically held, and latching (also known as mechanically held). Magnetically held requires a constant voltage source to keep the contacts closed (on a normally open contactor) while a mechanically held contactor only needs a pulse to close or open. Many have clearing contacts that remove power to the coil once the contacts change state.
 

infinity

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Location
New Jersey
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Journeyman Electrician
Here's a photo of a 12 pole, mechanically held, lighting contactor from ASCO.

917as.gif
 

infinity

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Location
New Jersey
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Journeyman Electrician
Those are famous for the coil melting and jamming, nice compact design though. Asco also makes them for Siemens, type CLM, GE, and I also have seen Square D's name on them too.

It's funny I've seen them in office buildings that are 15 years old without any problems. I installed one in my own house for outdoor lighting and the coil only lasted 4 years. The replacement coil ($95) lasted only 2 years. Needless to say I disconnected the thing. :roll:
 

hillbilly1

Senior Member
Location
North Georgia mountains
Occupation
Owner/electrical contractor
It's funny I've seen them in office buildings that are 15 years old without any problems. I installed one in my own house for outdoor lighting and the coil only lasted 4 years. The replacement coil ($95) lasted only 2 years. Needless to say I disconnected the thing. :roll:

Surges seem to take them out easy, I think they have diodes to rectify the ac. I've replaced lots of them in Targets, and Home Depots. Usually the coils melt so bad they gum up the plunger, and your better off replacing the entire contactor. I do have one on my boss's house for his Christmas lights, eight circuits! It's been working for about six years now.
 

bobsherwood

Senior Member
Location
Dallas TX
I prefer mechanically held. Does not have that 60 cycle hum or buzz. Mercury contactors are nice too. I've got a few Mercury that so far have lasted 15 year. I've worked here 28 years and the mechanically held for the coliseum where ten years old when I started. I think we've replace two "un latching" coils in that time.
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
Here's a photo of a 12 pole, mechanically held, lighting contactor from ASCO.

917as.gif
I'd be willing to bet that three 4-pole or four 3-pole contactors cost a lot less than that beast. I usually use a 2- or 3-pole contactor to replace burned contacts in multi-pole lighting contactors.

The customers have invariably been pleased that I offer a less expensive option to direct replacement of a 12-pole contactor because of a couple of bad contacts, even if I need to add an enclosure.


I had to replace a mechanically-held 3-pole contactor in a K-mart a couple of months ago. They opted for the electrically-held contactor I offered at less than half the price of the direct replacement.

The controlling voltage was constant, and the original contactor itself opened the voltage after energization. The pull-in coil had burned, but it would stay on if manually operated (pushed in.)
 

hillbilly1

Senior Member
Location
North Georgia mountains
Occupation
Owner/electrical contractor
The blue box's use electrically held contactors, but the orange box uses mechanically held, as well as wally world, but have been using SOB's (solenoid operated breakers) for a while now. Square D had a motorized breaker that had high failure rates when they first came out back in late 80's or early 90's. Harder to troubleshoot those without a computer.
 

iwire

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Staff member
Location
Massachusetts
I had to replace a mechanically-held 3-pole contactor in a K-mart a couple of months ago. They opted for the electrically-held contactor I offered at less than half the price of the direct replacement.

I think that is a poor suggestion but if you insist on going electrically held for retail work at the very least set it up as a normally closed so a coil or control circuit failure put the store in the dark.

Another advantage of mechanically held contactors is they can almost always be quickly manualy operated if they fail in the off position.
 

hillbilly1

Senior Member
Location
North Georgia mountains
Occupation
Owner/electrical contractor
I think that is a poor suggestion but if you insist on going electrically held for retail work at the very least set it up as a normally closed so a coil or control circuit failure put the store in the dark.

Another advantage of mechanically held contactors is they can almost always be quickly manualy operated if they fail in the off position.

Also if there's a loss of control power there will not be a loss of lighting, that's one thing I do not like about the blue box's set up, if a coil shorts out, a minimum of one quarter of the store lights will go out. Also makes it hard to change out a contactor with out having to turn all of them off while the store is open. Power Box loops the wiring from contactor to contactor, with mechanically held you can kill the control circuit and safely remove the contactor from the circuit.
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
. . . set it up as a normally closed so a coil or control circuit failure put the store in the dark.
Also if there's a loss of control power there will not be a loss of lighting, . . .

The lighting is automated, and their controls do default to energized with control failure. I didn't go as far as finding a normally-closed contactor, though. If they lose power, there's no light anyway.
 

iwire

Moderator
Staff member
Location
Massachusetts
There's no such thing as a truly interruptible power supply, either. :cool:

No, but there is a reason the store you where at used a mechanically held contactor and you just made the lighting less reliable.

On another note if you working on a lighting contactor the controls egress lighting it had better default to 'on'
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
No, but there is a reason the store you where at used a mechanically held contactor and you just made the lighting less reliable.
I did explain the difference, and they opted for the lesser expense.

On another note if you working on a lighting contactor the controls egress lighting it had better default to 'on'
I agree.


I should add that this contactor controlled the parking-lot lighting, not interior lights.
 
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