# Shunt trip emergency disconnects



## butcher733 (Aug 4, 2012)

not code afaik, local ordinance?


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## longrf01 (Jan 31, 2015)

butcher733 said:


> not code afaik, local ordinance?


That's my guess; the AHJ has a reputation for being very progressive. But I didn't want to pay the bucks to buy a copy of their local code book.


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## hardworkingstiff (Jan 22, 2007)

Am I the only one that thinks using a shunt trip breaker for an EPO is silly because if you lose your control power the EPO won't work and you won't know it until you need it. I guess you can install components that will trip the shunt trip breaker if the control power drops out, but I don't believe it's taken to that level of complexity.


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## Bad Electrician (May 20, 2014)

Speaking strictly about experience in Data Centers in 40 years of working in Data Centers and Telco facilities I have seen the EPO hit maybe 8 - 10 times NEVER FOR AN EMERGENCY always some dork screwing up, crashing the data center.

When we did cellular work a Florida Cell Tech told me they had someone using a piece of conduit to trip sites off line reaching through the fences to hit the EPO.


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## jcjourneyman84 (Jan 24, 2015)

hardworkingstiff said:


> Am I the only one that thinks using a shunt trip breaker for an EPO is silly because if you lose your control power the EPO won't work and you won't know it until you need it. I guess you can install components that will trip the shunt trip breaker if the control power drops out, but I don't believe it's taken to that level of complexity.


Most power distribution systems configured with shunt trip controls have 125 vdc battery banks if they have a power outage can still operate trip coils especially in the power industry. The company I currently work for has Battery banks to operate the trip coils on the SF6 Breakers that power our ring buss


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## longrf01 (Jan 31, 2015)

Bad Electrician said:


> Speaking strictly about experience in Data Centers in 40 years of working in Data Centers and Telco facilities I have seen the EPO hit maybe 8 - 10 times NEVER FOR AN EMERGENCY always some dork screwing up, crashing the data center.
> 
> When we did cellular work a Florida Cell Tech told me they had someone using a piece of conduit to trip sites off line reaching through the fences to hit the EPO.


1. As a data center geek, I know what you mean. Last EPO activation was triggered by the fire alarm. A refrigerant leak developed in an CRAC unit and tripped both the VESDA and Photo detectors (cross zoned) resulting an EPO and FM-200 release. $$$$$

2. Now for that conduit, was it rigid or PVC? Rigid would be "more safer". There has to be a section in the 2014 NEC which specifically addresses which to use for vandalism. :laughing:


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## hardworkingstiff (Jan 22, 2007)

jcjourneyman84 said:


> Most power distribution systems configured with shunt trip controls have 125 vdc battery banks if they have a power outage can still operate trip coils especially in the power industry. The company I currently work for has Battery banks to operate the trip coils on the SF6 Breakers that power our ring buss


Isn't the OP talking about every commercial building? That's the way I read his post (I may be wrong). That's a lot different than what I think you are talking about and I would bet $100 that those commercial EPO's don't have the battery banks. 

In the jobs you are discussing, I bet there are some PMs and checks of the EPO system for functionality on a regular basis. I wonder if the jurisdiction in the OP's situation checks that?


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## longrf01 (Jan 31, 2015)

hardworkingstiff said:


> Isn't the OP talking about every commercial building? That's the way I read his post (I may be wrong). That's a lot different than what I think you are talking about and I would bet $100 that those commercial EPO's don't have the battery banks.
> 
> In the jobs you are discussing, I bet there are some PMs and checks of the EPO system for functionality on a regular basis. I wonder if the jurisdiction in the OP's situation checks that?


Yes - it's commercial not utility.

IIRC, The main breaker used a 120V trip which was supplied (via the 'panic' button) from a dedicated branch circuit on the same panel. In theory, the only time the shunt won't trip is when there's no power on the panel (or that specific branch circuit was disabled for maintenance.)

Knowing what I do about the particular AHJ, yes they likely require annual testing.


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## hardworkingstiff (Jan 22, 2007)

A normally open contactor held closed with an electrical voltage feeding a coil will fail (loss of control circuit) in the off position.

A shunt rip breaker will stay closed if the control circuit is lost.

That is the main reason I think shunt trips (while functional and cost effective) are inferior to an electrically held contactor (which costs more, considerably more as amperage goes up).


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## manchestersparky (Mar 25, 2007)

I know of a jurisdiction that requires a shunt button to disconnect the building power if the main service disconnect is not in a room with an exterior door.
( direct grade access). The button is located at the front door by the fire alarm annunciator.
This is a fire department requirement.


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## micromind (Aug 11, 2007)

hardworkingstiff said:


> A shunt rip breaker will stay closed if the control circuit is lost.


And when power returns, it will trip. 

Around here, it's a fire dept. requirement. And the shunt trip needs to be fed from a circuit it controls.


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## panelbuilder (Jul 12, 2013)

manchestersparky said:


> I know of a jurisdiction that requires a shunt button to disconnect the building power if the main service disconnect is not in a room with an exterior door.
> ( direct grade access). The button is located at the front door by the fire alarm annunciator.
> This is a fire department requirement.


Here's hoping it's a keyed button!


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## hardworkingstiff (Jan 22, 2007)

micromind said:


> And when power returns, it will trip.


I think you missed my point. I'm not talking about losing power to the building, just to the control circuit. Could be a breaker tripped for some unknown reason or someone turned it off w/out knowing what it is for or some handy man hack disconnected it by "accident". 

The point is if the control circuit fails, the shunt trip breaker continues to deliver power.


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## hardworkingstiff (Jan 22, 2007)

micromind said:


> And the shunt trip needs to be fed from a circuit it controls.


So if you have an 800-amp shunt trip main breaker, your going to send power to the EPO button directly from the load side of the 800-amp main?


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## micromind (Aug 11, 2007)

hardworkingstiff said:


> So if you have an 800-amp shunt trip main breaker, your going to send power to the EPO button directly from the load side of the 800-amp main?


Of course not, it simply needs to be downstream of the breaker it controls. Anywhere downstream is ok, and yes; I missed your original point. If the control circuit is not energized, the shunt trip will not trip the breaker. One of the first things a fire inspector will look at is the breaker that feeds the shunt trip. It it is off.........trouble..........

Often, a building will have a generator, in which case it will have two shunt trips. the one for normal power needs to be fed from a normal power panel, the one for gen power needs to be fed from a gen power panel.


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## Zog (Apr 15, 2009)

A shunt trip is an accessory, not a type of breaker. It's like calling a car with A/C an "Air conditioning car"

Regarding the OP, Reedy Creek has all kinds of weird local rules with emphasis on safety so that requirement does not surprise me at all.


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## Zog (Apr 15, 2009)

hardworkingstiff said:


> Am I the only one that thinks using a shunt trip breaker for an EPO is silly because if you lose your control power the EPO won't work and you won't know it until you need it. I guess you can install components that will trip the shunt trip breaker if the control power drops out, but I don't believe it's taken to that level of complexity.


The breaker will still work (Assuming this is a LV breaker) if you lose control power, you just won't be able to trip it remotely via the shunt trip.


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## glen1971 (Oct 10, 2012)

Bad Electrician said:


> Speaking strictly about experience in Data Centers in 40 years of working in Data Centers and Telco facilities I have seen the EPO hit maybe 8 - 10 times NEVER FOR AN EMERGENCY always some dork screwing up, crashing the data center.
> 
> When we did cellular work a Florida Cell Tech told me they had someone using a piece of conduit to trip sites off line reaching through the fences to hit the EPO.


Without knowing all of the specs, wouldn't making the buttons a "pull to shut down" create a more "vandal proof" scenario? I've seen quite a few ESD buttons that are pull to operate and are adequately labelled as such... Prevents accidental shutdowns...


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## hardworkingstiff (Jan 22, 2007)

Zog said:


> The breaker will still work (Assuming this is a LV breaker) if you lose control power, *you just won't be able to trip it remotely via the shunt trip*.


That is my point, along with no one will know it unless there is active functionality testing.

I got on this kick a long time ago because I used to wire gas stations, and would never install a shunt trip breaker because in case of an emergency, I want the EPO to work and if someone alters the wiring of the EPO system or it loses power, the gas system will not work and someone will have to find out why.


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## bobelectric (Feb 24, 2007)

On new jobs I've been on they have been using those clear tamper covers over fire pull stations. Lift them and they start screaming. But you still need to activate the pull station. I wonder if there have been cases of confusion during a fire, people thinking the alarm is activated.


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## Bad Electrician (May 20, 2014)

bobelectric said:


> On new jobs I've been on they have been using those clear tamper covers over fire pull stations. Lift them and they start screaming. But you still need to activate the pull station. I wonder if there have been cases of confusion during a fire, people thinking the alarm is activated.


I have seen EPO's mistaken

For Light Switches
Fire Alarm Pull Stations (several times during a test of the FA system)
Door release buttons
Had the EPO cut and trip the critical loads

Wired a bizarre way and cause problem in general when trying to expand or verify wiring.
and General Stupidity.


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## bobelectric (Feb 24, 2007)

Wasn't on this job but in a computer room a smoke under the floor went off (dirty) and the hero security chief went to silence it and hit the activate button on the pull station and released the 200 charge. There was no count down just a big windstorm they said.


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