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Shunt Trip Breaker Wiring

Posted By: bot540

Shunt Trip Breaker Wiring - 12/09/07 01:42 AM

I need to install a few shunt trip Square D QOB breakers and was wondering how exactly are these things are wired. Off the ansul system I have three wires yellow, brown, and blue. I believe that the yellow is the common and the blue is the normally closed contact, which make the brown the normally open contact.
I am assuming you hook the breaker up to the normally open contact. Is this correct?
Posted By: leland

Re: Shunt Trip Breaker Wiring - 12/09/07 03:36 AM

Yellow should be common,brown N/O.
Dedicate a ckt from a NON-shunted panel to this contact. then to the ST brkr/brkrs.On activation the relay closes and shunts the brkr. Panel down.
The exhaust fan/s should not be shunted on deployment.
Posted By: leland

Re: Shunt Trip Breaker Wiring - 12/09/07 03:59 AM

====The exhaust fan/s should not be shunted on deployment. ==

I'll retract this, untill I can quote the art.
It is common practice, I just can't find it rght now.
Posted By: leland

Re: Shunt Trip Breaker Wiring - 12/09/07 04:24 AM


NFPA-17A-
4.4.3.5-- Exhaust fans do not need to be shut down on deployment of the wet system.


But in 5.6.2.2- all fuel and heat sources MUST be shut down.
easy to shunt trip the panel.
4.4.3.4- solid fuel- needs no shut down.Fancy Pizza joint--(Joint mmmm)
4.4.3.7- requires all shut down devices need a manual reset.
shunt trip brkr, coverd.
Posted By: bot540

Re: Shunt Trip Breaker Wiring - 12/09/07 11:47 AM

So the breaker needs a 120 volt signal to trip?
Posted By: walrus

Re: Shunt Trip Breaker Wiring - 12/09/07 12:51 PM

The shunt trips I've wired need 120v signal to trip
Posted By: electure

Re: Shunt Trip Breaker Wiring - 12/09/07 01:26 PM

I much prefer using a contactor instead of shunt trip breakers.
They don't take up valuable space in the panel (shunt trips take an extra pole space for the trip), and are more economical.
Posted By: leland

Re: Shunt Trip Breaker Wiring - 12/09/07 02:12 PM

Agree, if you only have a few peices of equipment to shut down, contactor may be more economic.
Most gas equip. will have a mechanicle gas valve shut off.

Only the equipment in the protected area (hazard) needs to be dumped. Check your local codes and follow specs.
Posted By: SteveFehr

Re: Shunt Trip Breaker Wiring - 12/09/07 03:00 PM

Originally Posted by walrus
The shunt trips I've wired need 120v signal to trip
I've seen some with 24VDC and 48VDC shunt trip- you'd need to check the specs on the breaker as to what it needs.

Should be OK to feed shunt-trip from this panel. After all, it will have power TO shunt trip, and after shunt trip... you don't really need power anymore!

Also, you might want to note somewhere on the panel that it's configured to shunt trip. We had one go off once over lunch when a contractor working sprinklers in another part of the building opened a valve just outside a data center to bleed the system and a flow sensor shunt-tripped the main breaker and killed power to the data center. DOH! None of the ITs had any clue what had happened or how to recover, and were running around trying to figure out why the generator hadn't started. - NOTHING was labeled, neither the panel nor the sprinkler. It's labeled now.
Posted By: leland

Re: Shunt Trip Breaker Wiring - 12/09/07 03:43 PM

I've done that! Wow,they don't like it much.
Coz everybody looses 10, mil$ a minute. Just ask them.
Posted By: renosteinke

Re: Shunt Trip Breaker Wiring - 12/09/07 05:53 PM

It has been a while since I put in a shunt-trip ... but if I recall correctly ...

The breaker took up three spaces. Two had large lugs, and were clearly for the panel feed. The third had a much smaller lug, and was for the wire to the 'kill' switch. The other side of the switch went to the neutral buss.

I was under the impression that closing the switch created a dead short, tripping the breaker. It sure sounded that way! I have since been corrected, and that there actually is a mechanism inside that operates ... a 'load,' as it were.
Posted By: electure

Re: Shunt Trip Breaker Wiring - 12/09/07 07:59 PM

Shunt trip circuit breakers work because of a small magnet coil that operates the magnetic trip mechanism.

Large (not molded case) breakers can be field modified with a kit that contains a coil with leads on it and installation instructions.

It's amusing to see how small a coil it takes to trip a big circuit breaker.



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