Shunt Trip??

[jahilliard]

I was called today to address an issue at a commercial kitchen. The problem is that with even the slightest little blink of a power outage (which in swfl happens constantly this time of year) all the shunted breakers trip...in turn they have lost several hundreds of dollars in frozen food over a weekend etc. There's the obvious of relocating freezers and equipment not necessarily required to be shunted BUT how could I prevent this from happening? I'm assuming there's a NC contact that even with the slightest loss of power closes and trips everything. Seems there would be a simple fix seeing that not every commercial kitchen does this upon a loss of power but I can't seem to wrap my head around it. Any help

 

[iwire]

Pretty tough from here without seeing it.

Is there just an ansul panel controlling the trip or is there a listed hood control panel involved as well?

Is there a gas sensor in the mix?

It is just that there are so many ways it can be wired and so much equipment that could be connected that from here we would be guessing.

I am sure you are right that there is a contact that is opening or closing for a quick second but if it happens to be in a listed control panel you really can't mess with it.


I would get the refrigerator stuff off the shunts, that is weird and not needed.

 

[jahilliard]

I haven't seen it in person either yet. I'm familiar with the facility but not exactly how this is installed, the questions are great places to start...but I haven't ever heard of this happening on ANY installation so it would seem something has been added that isn't necessary or is incorrect. Does this scenario sound familiar at all? Also, how exactly can the gas sensor cause this...I'm assuming this is a sensor that senses the presence of gas and could be shunting or something??

 

[templdl]

I was called today to address an issue at a commercial kitchen. The problem is that with even the slightest little blink of a power outage (which in swfl happens constantly this time of year) all the shunted breakers trip...in turn they have lost several hundreds of dollars in frozen food over a weekend etc. There's the obvious of relocating freezers and equipment not necessarily required to be shunted BUT how could I prevent this from happening? I'm assuming there's a NC contact that even with the slightest loss of power closes and trips everything. Seems there would be a simple fix seeing that not every commercial kitchen does this upon a loss of power but I can't seem to wrap my head around it. Any help

You used the term slightest which seems to infer brief. How about considering a time delay such that a time delay could be set to tried out any brief power outages before the STs are activated.
But, just how are the shunt trips activated if the power is lost? A shunt trip needs power in order for the ST coil to be energized to trip the breaker. The are 2 things that would trip a breaker with no power available. Using a capacitive trip device or an under voltage trip device.
As such a ST will not work with the absence of power.

 

[domnic]

Shunt trip

Shunt trip

On all the shunt breakers i have dealt with the shunt lug or screw must have voltage applied to it to trip the breaker it is not a holding relay it is momentary contact.

 

[gadfly56]

On all the shunt breakers i have dealt with the shunt lug or screw must have voltage applied to it to trip the breaker it is not a holding relay it is momentary contact.

What he said. Are you sure you're not dealing with a contactor which has to be energized to keep power on? And why on earth would anyone put freezer(s) on a contactor or shunt trip breaker?? The stupid, it burns.

 

[templdl]

What he said. Are you sure you're not dealing with a contactor which has to be energized to keep power on? And why on earth would anyone put freezer(s) on a contactor or shunt trip breaker?? The stupid, it burns.

Yes, it seems strange. I don't believe we're getting the correct description. It's almost as though we're shooting at shadows.

 

[iwire]

What he said. Are you sure you're not dealing with a contactor which has to be energized to keep power on? And why on earth would anyone put freezer(s) on a contactor or shunt trip breaker?? The stupid, it burns.

Yes I agree shunts need power applied to trip them. But in the control wiring there could very well be normally closed relays that drop out and do not reopen before the shunts trip.

Or maybe some one used the wrong shunts and got under voltage shunt trip breakers.

 

[iwire]

Also, how exactly can the gas sensor cause this...I'm assuming this is a sensor that senses the presence of gas and could be shunting or something??

Around here we have recently been installing gas sensors that will shut down the equipment under the hood.

The gas sensors contact is closed until you put power to the unit, than it does a self test and opens the dry contact you would use for a shunt.

So it could go like this, power failure > power restored > shunts drop out > gas sensor self tests > gas sensor resets > breakers now open.

 

[Jraef]

Yes I agree shunts need power applied to trip them. But in the control wiring there could very well be normally closed relays that drop out and do not reopen before the shunts trip.

Or maybe some one used the wrong shunts and got under voltage shunt trip breakers.

I agree, it sounds more like they have used Under Voltage trips in lieu of Shunt Trips. It's hard to tell from the outside, the difference is only in how they work. A UV trip must have power applied to it all the times, so any "blip" in the incoming power will cause it to release and the breaker trips.

Before investigating a strategy, I would confirm EXACTLY what those breakers have in them. Often times people will have a single phasing event, lose a bunch of motors, and someone will come up with the idea of putting in UV trips on everything, thinking that is the solution. They don't think through all the other possible consequences, then later on they leave and the next guys have no idea why the UV trips are there any more, but they are afraid to change them.

 

[jteel3]

The shade of gray that satisfies was taken from a 1911 book by Cutter Electric, the inventors of the I-T-E (inverse time element) circuit breaker.

“Where conditions are likely to arise in the use of electric motors rendering it desirable to open the circuit at will, independent of the load, the I-T-E Shunt Trip Feature should be employed in conjunction with the Circuit Breaker. It consists of a tripping magnet, having a high resistance coil normally out of circuit, adapted to be brought into circuit either automatically upon the occurrence of any predetermined mechanical condition, or by hand as necessity may arise.”

james-electrical enthusiast

 

[roger]

This thread is 7 years old so I am closing it, if you would like to start another thread please feel free to do so.

Roger