ECN Forum Forums General Topics of the Trade General Discussion Area contactors/ lighting versus definate purpose

would someone explain the difference between the 2? i know the lighting contactors have latching mechanisms
that require an impulse of some sort to open the switch. but what other differences might there be? i am
building a lighting control that will be actuated by a photoeye. it will control various h.i.d. fixtures, a couple
flourescents and some l.e.d signs. the lighting contactors are 4- 5 times the cost of a definate purpose, to do
the same thing. any input will be appreciated. thanks

The primary difference is in the contacts.

Definite purpose contactors have general duty contacts. They are rated for motors and resistance loads. If they carry a rating for lighting it is propably only for incandescent types.

Lighting contactors contacts are specifically designed and tested for the inrush currents associated with Tungsten, Fluorescent, and HID ballasts and lamps. Also lighting contactors are not always "latching" types.

General use contactors are rated for typical inrush currents of 6 times full load, lighting contacts are often designed as high as 12 times. The lighting inrush also tends to last longer than general inrush currents.


While the NEC requires switches (and breakers used as switches) to be listed for the type of lighting they control, there is no such requirement for contactors.

So in answer, yes you could use non-lighting contacts if they can be sized correctly for the inrush of the load, but in the long run why bother.

One can buy a lighting contactor in a listed enclosure that is intended to be installed as a listed, complete assembly. Not sure that is the case with a "definite-purpose" version. The second item is available as a repair part, and not enclosed or intended for use as a standalone assembly, right?

Lighting contactors do come in electrically held as well as mechanically latching types.
Out here in SoCA, if the DP contactors are used, an electrical inspector will very often cite 110-3 Examination, Identification, Installation and Use of Equipment as a basis for turning them down (via their powers in 90-4).
Also, plans many times use the wording "Lighting Contactor", which precludes the use of the DP contactors.
The combination inspectors usually don't know what they're looking at anyway (a box full of wires and little square things), and approve them without a second thought.
S

Looks like JBD, Bj, electure have you covered on the differences. I will add that if you are going to use the latching type, and control it with a PE cell, or time clock, then, you will need to get a "two wire control module". Otherwise, it won't work correctly. Don't ask me how I know.
By the way, when I was in the Navy, a JBD was a Jet Blast Deflector. JBD, do you resemble that, or am I mistaken?

Regards,
Doc

thanks for all the replies.
my local supplier (only one for in a 30 mile radius) isn't much help in differentiating between equipment. all they sell is cutler hammer, and the catalog isn't very descript either.
i'm concerned with the price of the l.c., but need to make sure i build a reliable unit.
i may have to make a few calls to other suppliers to find a better priced brand of l.c..

bjarney,
Yes, you can get definite purpose devices in their own enclosures.

WattDoc,
I spent some time growing up as a Navy Brat, but this is the first I've heard of a JBD. As I get older it's getting harder, but so far I don't resemble one (well not too much at least).

JBD,
In case you're not familiar with what they are, watch the "cheesy" movie "Top Gun". At the opening of the movie when all the flight ops are being shown, you will see an F-14 go into afterburn just before launch. If I remember correctly, they show the JBD's lifting out of the deck. There are big deflectors used to keep the flight deck crew from being blown overboard.

Regards,
Doc

danger: It's sounds from what you are trying to control that you would probably get away with a derated definite purpose contactor. If you see any with two ratings, use the smaller. If you where trying to light up Tiger stadium, it would be a different story. I've got a couple of DP contactors in lighting control, they are sized up quite a bit. (15amp of current, used 25 amp inductive rated contactor)

For what it's worth.

Trainwire

Ooops, JBD--I'm way out of the loop, I guess. "...definite purpose devices in their own enclosures."




[This message has been edited by Bjarney (edited 08-06-2002).]