# shunt trip breaker



## Salvatoreg02 (Feb 26, 2011)

spider said:


> I am having a brain cramp, do you connect one lead to the nutrual bar.


Does it have a neutral?

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## spider (Apr 4, 2011)

No just the two black leads


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## BBQ (Nov 16, 2010)

If you are sure the trip unit is 120 volts then yes one black lead needs to go to the neutral bar.


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## spider (Apr 4, 2011)

Yes it 120 or 240


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## BBQ (Nov 16, 2010)

spider said:


> Yes it 120 or 240


Well now I am lost because I have never seen a shunt with just two leads rated 120 or 240.


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## raider1 (Jan 22, 2007)

BBQ said:


> Well now I am lost because I have never seen a shunt with just two leads rated 120 or 240.


Agreed, all the shunt trip devices that I have seen are typically 1 voltage.

Chris


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## Salvatoreg02 (Feb 26, 2011)

spider said:


> I am having a brain cramp, do you connect one lead to the nutrual bar.


Did you Install a push button switch also?

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## spider (Apr 4, 2011)

Sorry for the delay but this shut has dual voltage 120 to 240 first time I have come across this but I will treat it like a 120 application.


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## MDShunk (Jan 7, 2007)

spider said:


> Sorry for the delay but this shut has dual voltage 120 to 240 first time I have come across this but I will treat it like a 120 application.


I'm not so sure I'd hook it to the neutral bar if this was a 277/480 panel. I'd probably also not hook it to the neutral bar if your control power comes from someplace else. Use that "someplace else" neutral.


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## MDShunk (Jan 7, 2007)

spider said:


> Sorry for the delay but this shut has dual voltage 120 to 240 first time I have come across this but I will treat it like a 120 application.


Is there a terminal you need to move around on the accessory, inside the breaker? Got a manufacturer and part number for this rascal? I'm curious. I've never seen a dual voltage unit with only two leads either.


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## spider (Apr 4, 2011)

The shut trip breaker is a GE 3 pole thbq


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## Mike_586 (Mar 24, 2009)

BBQ said:


> Well now I am lost because I have never seen a shunt with just two leads rated 120 or 240.


Funny, my experience has been the exact opposite :laughing:

Almost all the shunt trips I've seen can handle more than one voltage and need a separate circuit to feed the shunt coil and make the breaker trip.

(I'm using SquareD numbers here because that's what I have been mainly using and have the numbers handy on my phone)

The coil ratings on the ones I've seen are 12 to 24 volts. Those I see in a lot of car washes inside control cabinets. They can handle AC or DC voltages.
12V - 60VA
24V - 168VA

and the coils on the others I more commonly run into are 120 to 240 volt. I see them all the time in gas stations and started running into them a lot more the last few years. AC voltage only on the coils.
120V - 72VA
208V - 228VA
240V - 288VA


Normally the shunt coils are fed with a separate circuit and wired at 120V around here. One side of the coil goes to neutral and the other needs a hot to complete the circuit. Liven up the shunt coil and it trips the breaker. 

I've been using big red mushroom switches that need to be manually pulled up, but breakers are rated to accept momentary contacts. Once tripped the breakers have to be manually reset, and if the contact to feed the shunt is a maintaining contact, it has to be opened. That confused the hell out of me the first time I ever saw one, not realizing I had to go across the building and pull up a mushroom switch.

The ones I've used take an extra breaker space, so a single pole 15A breaker shunt trip breaker takes the same space as a 2 pole breaker, a 2 pole takes the space of a 3 pole and so on.

Also, in the applications I use them for, the breaker with the circuit that feeds the shunt coils are normally locked on so they can't be turned off accidentally as their operation serves important safety/security measures.


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## spider (Apr 4, 2011)

Thanks it work on a 120 input off fire alarm system, works great passed inspection


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## Smoke (Feb 25, 2011)

BBQ said:


> If you are sure the trip unit is 120 volts then yes one black lead needs to go to the neutral bar.


thats not entirely correct, he is likely working on an elevator shunt (doesnt matter though). the neutral comes from the source, rarely the panel the shunt is located, but possible. 

unrelated to quote, hot on one wire neutral on the other, color doesnt matter.
i put 2 red wires off the shunt here this weekend, i like it to be obvious the shunt circuit is there and not fed from the panel (277/480 in my case).
its a coil, polarity is irrelevant.


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## Smoke (Feb 25, 2011)

spider said:


> The shut trip breaker is a GE 3 pole thbq


doesnt matter, its 2 wires to a shunt coil, only the voltage you need to trip it is relevant.


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## vos (Apr 1, 2010)

what's a shunt trip breaker?


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## micromind (Aug 11, 2007)

I've seen lots of shunt trip coils that were rated for more than one voltage. I'd say most of them I've seen recently. 

Two black wires, but the inrush is way more for the higher voltages. 

Remember, a shunt trip coil is energized only for a very short time; not long enough to cause the coil to heat up. 

The only ones I've seen that are single voltage are either 125 or 250 DC. Just about everything else has a range of voltages. 

One wire goes to the switch leg of whatever will cause the breaker to trip, the other wire goes to the return; often the neutral bus. Sometimes the grounded side of the control transformer. 

Rob


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## leland (Dec 28, 2007)

BBQ said:


> Well now I am lost because I have never seen a shunt with just two leads rated 120 or 240.



Never mind. I was gonna be a wise ass. But never mind.


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## dowmace (Jan 16, 2008)

vos said:


> what's a shunt trip breaker?



A breaker than can be remotely tripped by an outside voltage source. Thats the easiest description I can come up with.


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## leland (Dec 28, 2007)

vos said:


> what's a shunt trip breaker?



Basically- It is a breaker -can be of any voltage or # of poles.
It has a built in coil that for any number of reasons may be asked to open.

So essentially. when an event happens a signal/voltage is sent to the coil - built into the breaker- and that forces the breaker to open.

These breakers are usually found in kitchen panels associated with suppression systems, or in computer rooms with water suppression.

Or in a system where it is best to terminate power than to have a bad event.

http://www.cbs.state.or.us/bcd/programs/elevator/interps/shunt_trip_wiring.pdf


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## B4T (Feb 10, 2009)

vos said:


> what's a shunt trip breaker?


Example.. Fire Alarm is tripped by a smoke detector..

You don't want smoke circulating through the HVAC, so the Fire Alarm trips the circuit breaks that controls the HVAC units or anything else you want disconnected during a fire..


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## BBQ (Nov 16, 2010)

Smoke said:


> thats not entirely correct, he is likely working on an elevator shunt (doesnt matter though). the neutral comes from the source, rarely the panel the shunt is located, but possible.


 I assumed an EC would know to use the neutral from the source ...... almost all shunts I do are powered from the panel they are in.


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## BBQ (Nov 16, 2010)

vos said:


> what's a shunt trip breaker?


The other guys described them, they can be used for many shut down needs. I have used them a lot to shutdown kitchen equipment located under exhaust hoods, as mentioned eleveator shutdown is another common use.

They come in many kinds, some look exactly like a regaulr breaker, this one is a Square D I -Line shunt trip and other than the leads hanging from it looks just a normal I Line breaker.












On the other hand the OP said it was a GE THQB shunt, they do look different. They have what looks like and extra pole.

Here is a 3 pole THQB, the extra section does not connect to the bus at all and has the leads hanging out to trigger the shunt.











And when you get into breakers more like this










There are often terminals on it for remote trip.


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## Smoke (Feb 25, 2011)

BBQ said:


> I assumed an EC would know to use the neutral from the source ...... almost all shunts I do are powered from the panel they are in.


almost all i do are not,.... apples and oranges, both good but unique.
ive worked with too many that are too stupid to wire a simple coil.
i went up to the penthouse today to see one of my experienced jman had the ground from the primary on a 15kv xfmr on the xo. 
my perception of things is skewed by the retards my company hires....


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## leland (Dec 28, 2007)

BBQ said:


> I assumed an EC would know to use the neutral from the source ...... almost all shunts I do are powered from the panel they are in.


Remember- an FACP can not be fed from a shunted panel.
This is more geared to a suppression system that some like to feed from the room power panel.


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## raider1 (Jan 22, 2007)

leland said:


> Remember- an FACP can not be fed from a shunted panel.
> This is more geared to a suppression system that some like to feed from the room power panel.


Where in the NEC does it prohibit an FACP from being fed from a panel protected with a shunt trip?

760.121(B) prohibits the circuit supplying a power limited fire alarm equipment from being supplied through GFCI's or AFCI's but I don't see where it prohibits being supplied from a shunt trip panel.

Chris


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