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#171877 12/07/07 04:54 PM
Joined: Sep 2003
Posts: 114
I've been working for a retailer for a few years on electrical odd jobs. Most of the time it involves replacing circuit breakers. It is a commercial store front that sells running shoes. Apparently, when it was built the lighting circuitry was designed to turn on/off with breakers only. The breakers are failing regularly and I'm feeling guilty charging him $80 a visit to replace a breaker. One solution would be to install a light switch below the panel and just re-route the wires. Any other suggestions?


Joined: Jul 2002
Posts: 8,443
Likes: 3
Would installing a lighting circuit, without a switch in your area contravene the Code?.
Personally what I would do if the lighting load is that large, is install a contactor in the panel, if there is room and like you said install a Master switch near the Panel.
I've never liked the idea of using a CB as a switch as they are designed to stay closed under normal conditions.
This topic did come up in the Non-US area a wee while back.
It is of my opinion that a CB is only designed as a circuit breaker, not an isolator, the increased operation of the mechanism may cause it an early death.

Joined: Jul 2001
Posts: 599
JBD Offline
Originally Posted by Trumpy
I've never liked the idea of using a CB as a switch as they are designed to stay closed under normal conditions.

A circuit breaker that is UL listed as SWD has passed the same test procedures (including mechanical operations)as any standard light switch for tungsten and fluorescent loads. To my knowledge this Switching Duty rating is only available on 1-pole 15 & 20A breakers. There is a similar HID rating on larger ampacities and multi-pole breakers.

Many, if not most, commerical grade breakers (like the SQD QO and C-H CH) are SWD listed.

Joined: Jul 2002
Posts: 8,443
Likes: 3
Originally Posted by Trumpy

It is of my opinion that a CB is only designed as a circuit breaker, not an isolator, the increased operation of the mechanism may cause it an early death.

I just want to qualify what I said above.
I don't think that a CB should be used to break full-load amps un-necessarily that is what switches and contactors are made for.
I like the idea of the contactor because all you then need is a simple control circuit and that the switch only carries the control circuit current.
Contactors also handle inductive load currents a lot better than any switch, as long as they have a certain safety margin applied to them.
Just wanted to clarify my thinking at that idea.

Last edited by Trumpy; 12/07/07 07:21 PM. Reason: Typo
Joined: Jul 2007
Posts: 265
this is standard procedure in my area, no switches just swd rated breakers. Sometimes a dishonest contractor can get away without installing swd breakers. I do not know why though, cost for these breakers is usually close to the same. I have a Dollar store customer with a Cutler Hammer
CH panel with the wrong (non swd rated) breakers in it, so I go every few months and replace a breaker and send a bill for $80.00 I have suggested replacing them all at once, but the management is fine with the service call every so often, so who am I to argue?


Life is tough, Life is tougher when you are stupid
Joined: Jul 2004
Posts: 9,822
Likes: 20
I agree with JB, SWD breakers should handle this. If you are just replacing the non-SWD breakers with SWD and the new ones are working OK your customer is in a "pay me now or pay me later" situation.
If new SWDs are failing you have another problem.

Greg Fretwell
Joined: Jul 2007
Posts: 1,335
According to Square D pubs and UL listing, SWD rated breakers can only switch fluoresent lighting loads. The only other thing I can think of is the ambient temperture in the panel. Breakers stamped with "40 degeees C" indicate that it is rated for continious duty. If it is not stamped "40 degrees C" then the circuit needs derating. Breakers espically lighting panels can get really warm. Even if the air outside the pane may be normal, inside a closed metal box, it can get really warm. If you are switching HID lighting, then the breaker must be HID rated.

I have flipped SWD breakers that were old yet outside of the linkage having a worn feeling to them, there were nothing wrong with them.

"Live Awesome!" - Kevin Carosa
Joined: Jan 2005
Posts: 5,389
Likes: 1
Cat Servant
A slight example of bad grammar in the UL white book on the meaning of the markings.

What they 'meant' to say was:
"SWD" means that the breakers can switch the worst, most demanding type of lighting that existed at the time: fluorescent. They can switch 'ordinary' lights as well. When lighting companies then went out and made an even worse type of light (HPS, the MH) ... we had to come up with the "HID" rating to cover those. Praise heaven that the latest lighting innovations (cold-cathode, LED, etc) are less demanding than nasty fluorescents and HID's, or we'd have to come up with yet another rating!"

Joined: Jul 2002
Posts: 680
I can't seem to find a part # for SQ D HID QO breakers. Anyone have a link?? I see them mentioned on SQ D page but when I search for them I get nothing

Joined: Jun 2007
Posts: 301
The breakers are not the issue. It is the load applied when repeatedly switching of the lighting load. It is correct that most breakers are suitable for switching, but like any switch, will eventually fail.
I have found that switching on a lighting contactor is the best way to go. If you use just a switch, you will be replacing them as you are the breakers. same service call different device.
Just use a good quality snap switch and have it close the contactor.

Last edited by JValdes; 12/09/07 01:05 PM.
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