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#36809 04/15/04 11:07 AM
Joined: Feb 2004
Posts: 17
I understand the purpose behind shunt trips but i have never installed one.

How many wires do the have typically? and how are they installed? Can you make any breaker a shunt trip breaker? Do some breakers have the shunt trip internalized within the breaker frame?

thanks, -andrew

#36810 04/15/04 11:29 AM
Joined: Apr 2002
Posts: 2,527
For an example of a shunt-trip accessory used in smaller industrial-frame molded-case circuit breakers, see page 15 of

#36811 04/15/04 12:04 PM
Joined: Jul 2002
Posts: 680
I've only used a one brand, Sq D and it was a QO style breaker with a unit on the side which required a neutral and a hot from a switch. In my case a panic button that shut a whole panel down. Pretty simple to install. I doubt you can make a regular breaker into a shunt trip. This breaker went bad, 100 amp 3 pole and it cost 300 bucks,used, [Linked Image], had to have it overnighted from California. It was the only thing my supplier could find at 4 pm in the afternoon and we needed it yesterday [Linked Image]

#36812 04/15/04 03:37 PM
Joined: Jan 2003
Posts: 4,391
We install a lot of these, typically the ones we install look like a standard breaker with two black 16 AWGs sticking out of it somewhere.

Hook one to the neutral bar and power the other one when you want to shunt the breaker.

The most common application we use these for is shutting down power under commercial kitchen hoods or sometimes a feed to a Article 645 room (computer room).

Bob Badger
Construction & Maintenance Electrician
#36813 04/15/04 03:40 PM
Joined: Jan 2003
Posts: 4,391
I forgot, smaller size breakers you have to buy as shunt trip breakers, larger frame size breakers you can often buy the shunt trip as an accessory.

If you do field install the shunt unit I recommend doing it in a clean and swept area, there are a lot of small screws, springs and small pieces to get lost when you open up breakers. [Linked Image]

Bob Badger
Construction & Maintenance Electrician
#36814 04/15/04 09:16 PM
Joined: Apr 2001
Posts: 507
Shunt trips are also used to shunt down the feeder for elevators. Heat dectectors with a 120v contact is usually used to switch the shunt trip.

#36815 04/16/04 05:25 AM
Joined: Jan 2003
Posts: 4,391
I would have mentioned that but I believe that practice has stopped.

We have had to go to jobs here in MA and disable the elevator shunt trips under the direction of the elevator inspectors.

It may be just a local thing though.


[This message has been edited by iwire (edited 04-16-2004).]

Bob Badger
Construction & Maintenance Electrician
#36816 04/16/04 07:38 AM
Joined: Dec 2000
Posts: 4,294
I'm not a big fan of shunt trips, as they require power to operate. In the small, molded-case breakers, they require another pole space in the panel, which could usually be better utilized.
The field installed trip units are just a little magnet coil, with short leads, that "coerce" the C/B's magnetic trip.

Like Bob says, I haven't seen them used on elevators recently.

(What would happen if Ella Fitzgerald married Darth Vader?? She'd become Ella Vader)
Let the boos and rotten tomatoes fly.

#36817 04/16/04 10:05 AM
On the elevator issue. NFPA 70 and 72 tell us "if" your going to do it here is how it needs to be done. In my area the last call has always been left to the elevator inspector. My first call is to the elevator inspector for any given jurisdiction to see what he says regardless of what the F.A. drawings say on new installs. I have never liked the idea of shunting the power since it could leave people in the car between floors. To me that has always seemed to be a major life safety issue.

#36818 04/16/04 04:17 PM
Joined: Feb 2003
Posts: 939
there is the other area i use the shunt breakers is the gas staion area. [ this is more common with older system ] and anyone hit the e stop button aka panic button it will shut off the gas pumps off [that have seperate breaker box for it or add shunt breakers as needed],

as far for the elevators, i know few place did have shunt trips. but as far i work on it i haven't deal with it for quite a while so i dont know if the local codes have diffrent addmentdent[changes] over the state and national codes .

and the other area i try to think they use the shunt trips is commercal kitchen they use that too . when the Fire Alarm go off or someone hit the trip button it will shut few appliances off.

for other area i have no idea but maybe other members maybe have some idea here too.

merci, marc

Pas de problme,il marche n'est-ce pas?"(No problem, it works doesn't it?)

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