Shunt-trip breaker - help with connections

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LarryFine

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
I was asked to troubleshoot a supposedly non-functioning electrical cut-off situation in a restaurant fire-suppression system. I traced the wiring to an ITE load-center panel, where a 200a or 225a breaker feeds a panel in an adjoining section.

There are three black wires and one white wire emerging from the back of the breaker. Two of the black wires are taped off, and the third black and the white wires land on a 2-section barrier strip. I measure 120v between the black and white wires.

The complaint is from the fire marshal, that the electrical equipment does not de-energize when the system is tripped. The white is grounded, while the black is hot, returning from the fire suppression system. Here is my question:

Do all shunt-trip breakers trip when 120v is fed into the breaker, or do some trip when the 120v is removed? When I disconnected the wire returning from the system control box, nothing happens. Why are there four wires out of the breaker?

As always, any info is welcome. :smile: Danke!
 
Larry can you remove the breaker and open it up?

A lot of larger breakers can be opened up and closed back up with out effecting the calibration.

If you can get the lid off I bet you could figure out what you have for connections.

I have never seen a 4 wire set up, usually two black wires, one goes to neutral and the other is powered to trip the breaker.

Good luck. :)
 
Shunt trip breakers usually require 5ma to 45ma and 120volts to trip (usually).
It could be that the shunt trip signal is not enough to trip the shunt trip within the breaker.
You may need to contact the breaker manufacturer, their technical services group can give you this information.
And then frind out what the output in "ma" the shut trip signal actually is.
Just my $.02
 
Larry -

All the shunt trip CBs I've seen take power to trip. I'd guess the other two black wires are an aux contact, either "trip" or "open".

Best I could suggest would be to get the cat number and call the mfg.

Now for the guessing part: Bad news. The trip coil is burned out or the disconnector contact is stuck open. If the trip coil is burned out, it is from the disconnector contacts stuck shut.

Reasoning: Most of the shunt trips I've seen have the trip coil in series with a disconnector contact that opens when the CB opens. This keeps a continuously applied trip signal from burning up the trip coil.

This is interesting. Let us know what you find. It will add another point to the troubleshootong database.

carl
 
Larry many shunt trips will have a range of trip voltage 120-240 VAC. A shunt is nothing but a coil, energize the coil the lever moves to trip the CB.

This could also be undervoltage release, energized all the time, take power way and it trips.

If this is a factory install device it is most likely listed on the CB, shunt trip or UV release, with operating voltage.

If you have a variac you can ramp up the voltage and see if it trips, though the Shunt trip voltage can be 24 VDC, 120 VDC, 24 VAC, 120 VAC 240 VAC 0r 120-240 VAC.

Lastly it may be a multi voltage relay with taps (unlikely in my expierence) or the additionally conductors could be coil clearing leads, contacts that open to take power off the coil. Some shunts are designed to be energized for a short period of time. Energize tthe device to trip and the clearing contacts remove power from coil after the CB opens.


So you have a variety of options.
 
coulter said:
Larry -

Most of the shunt trips I've seen have the trip coil in series with a disconnector contact that opens when the CB opens. This keeps a continuously applied trip signal from burning up the trip coil.



carl
Click to expand...

At least one manufacturer (I don't recall) has a trip coil seperate from the breaker which you install in the field. If you don't align it properly it will supply voltage continuously.
 
I have seen these things a few ways, most common would be 'powered' (Shunt) to trip, and it's buddy, 'no power' (Under-voltage) to trip. (At various voltages) I have not seen one with both, but for a breaker that size anything is possible. (I often see the Shunt module that goes into the space next to the shunted breaker - they have a tab that sticks into the breaker - but it doesnt sound like you have one of those.)

ITE is Seimens - I think.... And they may be simular any way... Look at around page 30 here... I'm only assuming its a J or F -frame?
 
davidr43229 said:
Shunt trip breakers usually require 5ma to 45ma and 120volts to trip (usually).
Click to expand...


You can get shunt trips in about any voltage you want, AC or DC. So I wouldn't really say they are usually 120V. If possible, you should verify the part number is for a 120VAC shunt trip.

I agree with the other posters, the other two wires are probably an alarm contact. You should be able to use an ohmmeter to find the two wires that go to the shunt trip coil. Look for a low (but not quite zero) resistance between two wires. That should be the coil.

Also look for zero ohms between two wires with the breaker closed, that goes away when you turn the breaker off. If you have that, those two wires are probably an aux. contact.

Steve
 
Steve,
Also look for zero ohms between two wires with the breaker closed, that goes away when you turn the breaker off. If you have that, those two wires are probably an aux. contact.
Click to expand...
Some aux contacts are "bell alarm" contacts and they only change state when the breaker is tripped, not when you turn it off or on.
Don
 
Virtually all the shunt trip breakers I have seen are energize to trip. I know you can get an under voltage relay attachment that will trip on lack of voltage, but I don't believe I have ever seen one.

As other posters have already said, one set of wires is probably the trip and the other set an alarm contact.
 
The shunt-trip mechanism usually has a Normally Closed Clearing Contact. It removes the trip circuit from the coil once the breaker is tripped. With 'two wires taped together', it was probably not used - which may explain why the coil is inoperative.
 
barclayd said:
The shunt-trip mechanism usually has a Normally Closed Clearing Contact. It removes the trip circuit from the coil once the breaker is tripped. With 'two wires taped together', it was probably not used - which may explain why the coil is inoperative.
Click to expand...

If the shunt trip has clearing contacts and they were not used and the CB was ever shunted, the shunt coil is now defective, MORE THAN LIKELY. As noted above shunts with clearing contacts are designed to remove power to protect the coil after opening the CB.
 
There should be a modification sticker on the breaker which states what accessories have been added and what those wires are. Otherwise, your shooting at shadows.
Common accessories include a simple shunt trip that has (2) wires. By applying a specific voltage to those wires causes the shunt trip to hit the trip bar of the breaker, tripping the breaker. When that occurs a cut-off switch located usually on the shunt trip immediately opens the shunt trip circuit removing power from the shunt trip coil.
The there is the flux transfer shunt trip that also has (2) wires and is used when very little power is available. It is held with a magnet which hold when the breaker is moved to the closed position. When a small amount of power is applied to the leads it is enough to weaken the magnets hold and release the flux transfer shunt trip to hit the trip bar and trip the breaker. Again, there is a cut-off switch to open the flux ransfer shunt trip circuit.
The there is the undervoltage release which also has (2) wires. A specified voltage must be applied to the UVR before closing the breaer. When the breaker is closed the breaker will remain closed untill the voltage is removed from the UVR coil at which time it hits the trip bar. For the breaker to stay closed the UVR must be continually energized.
The there are auxiliary and alarm switches which commonly consist of an A/B form 'C' contact with (3) wires. There will be a common wire and one to the A amd the other to the B. However, it is posible to have a sinble switch with (2) wires either to make or break when the breaker is openned or closed.
 
Okay, I finally got back to the restaurant and opened the panel. Here's what I found:

It is a Gould/ITE panel board, and the breaker in question is a Siemens Cat. # S01QJOR3 (first 0 is a digit, second O is a letter), but I found a connection label on it, so it doesn't matter, unless we need a replacement. :smile:

(Edited to add): I just found out that the above number is the shunt-trip accessory number; the breaker itself is a QJ23B225.

The breaker has four small wires coming out of the back. A black pair and a black and white pair. The black pair are labeled T and S, and connect to the trip coil. The black and white pair, A and C, connect to a pair of contacts.

The coil pair have 120v across them now, even with the system not tripped (unless there is a problem with the micro-switch wiring, which I have not been asked to address (yet)), and the contact pair are unconnected.

It sounds like Carl hit it with the burned-out coil theory, especially since the aux. contacts were taped off. There is one more possibility: removing power disables the breaker, but the wiring diagram doesn't bear that out.

I just did a search with the Cat. #, and under the heading that you-know-what happens, the only result was an eBay auction for that breaker ended on 3/13 for $50! If I had only known. :rolleyes: Here's a clickable image:



I'm going to call a local electrical surplus wholesaler. As Ahnold would say, "Ah'll be bahk!"
 
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Larry,
Your complete part number is QJ23B225, which are obsolete.
Breaker Breaker 1-800-233-0595 West coast $543.78 List $1,431.00
this is a complete new breaker w/ shunt trip and tested.
ask for Jack.
Breakers Unlimited = 1-800-875-3294 $260.00 in stock Ask for Stuart.

Just my $.02
 
It could be the the ST coil is separate from the cut-off switch which is closed when the breaker is closed and where by that switch should be connected in series with the ST coil. When the switch is closed power can be applied to the ST coil where by the breaker trips opening up the switch which immediately removes power from the ST coil pwhich prevents the ST coil form being fried.
Most Westinghouse/C-H breaker have that switch mounted and wired with the ST which makes it more fool proof by preventing wiring errors.
 
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