Shunt trip with multiple push button

[john37]

I'm not totally sure how to wire a shunt trip breaker with multiple power cut off push buttons. There are 3 different push buttons in 3 different rooms for a MRI room. Please see attached diagram and let me know if I wired the push buttons correctly. Thanks.

 

[augie47]

does not appear that you did.
The buttons need to be wired in parallel.,,.,A "HOT" and a load to each button..load to ST (along with a neutral) and hot to line

 

[Dennis Alwon]

I don't have an answer but this may help others view it.

 

[480sparky]

I can't see how it would work other than if all 3 buttons were pushed at the same time. Then I see the 120v control wiring being short-circuited.

 

[iwire]

does not appear that you did.
The buttons need to be wired in parallel.,,.,A "HOT" and a load to each button..load to ST (along with a neutral) and hot to line

I agree with Mr 47. :smile:

 

[gar]

090308-1434 EST

john37:

First, you need a definition of a shunt trip breaker, and how it works.

Consider this definition from:
http://www.iccsafe.org/ubb/Forum11/HTML/000741.html

Answer by Stormywyo

SHUNT TRIP
Some times it is advantageous to turn a breaker off from a remote location. To facilitate this task, an accessory called a shunt trip feature is installed by the manufacture inside of the breaker. This device consists of an electro-magnetic trip coil that is connected in series with an external field wired switch. When the switch contacts are closed, power is passed to the shunt trip coil causing the breaker?s mechanical latch to move to the open position. Re-closing the breaker is done by physically going to the breaker and manually moving the operating handle to the on?closed position.

When opened by use of the shunt trip coil, the breaker?s operating handle moves to the off (maximum handle travel) and not the tripped (short of full handle travel) position. Knowing this can help when trying to determine if the breaker tripped off due to an overcurrent condition or was remotely turned off.

What does this definition tell you? It says there is a conventional breaker with the addition of an auxiliary electromechanical trip coil that will force the breaker to the fully off position when momentarily energized.

You will have to determine for your breaker if the two trip coil wires are isolated and brought out to their own terminals (or wire pair). If two isolated terminals, then you need to supply external power. Also you have to determine if AC will work.

To the logic part of the problem. If you are working with the assumption of positive logic, and you want any one or more inputs to produce a true output, then you would use normally open push to close with spring return pushbuttons connected in parallel. This wiring of the switches produces a positive logic inclusive OR circuit. Between the two terminals of the paralleled buttons the circuit is open if no buttons are pushed. Pushing any one or more buttons causes a closed circuit that is maintained while at least button is pushed.

Put this parallel combination in series with the hot line to the trip coil and supply neutral (opposite side of the power source) to the other side of the coil.

Latch your breaker. All pushbuttons are open. No power to the unlatch coil and the breaker remains latched. As soon as any one or more of the buttons are pressed the breaker is tripped as if you had manually turned the breaker off. The breaker remains off until manually relatched.

.

 

[ohmhead]

Well we agree with 480 the drawn is not correct the 120 volts will blow up the buttons when pushed even if you push all three at the same time which is not the way this is to work .Each button should have a hot each button should be in parallel to turn on the shunt trip coil in that 150 amp brk, with any button pushed . rule one= series for multi STOPS parallel for multi STARTS a neutral for that shunt trip coil is needed but gos directly to one side of that trip coil not thur the button contacts .best to ya

 

[john37]

Thanks guys...Looks like I was totally off base. Appreciate your help.

 

[gar]

090308-1613 EST

The series string of normally closed contacts that ohmhead mentioned that would be used in the holding circuit of a relay is also a logical OR circuit, but using negative logic.

In a positive logic circuit a CLOSED contact corresponds to TRUE and an OPEN contact to FALSE. In negative logic these two definitions are reversed.

The true false logical truth tables are

for OR
F F = F
F T = T
T F = T
T T = T

for AND
F F = F
F T = F
T F = F
T T = T

for NOR
F F = T
F T = F
T F = F
T T = F

for NAND
F F = T
F T = T
T F = T
T T = F

for XOR (exclusive OR)
F F = F
F T = T
T F = T
T T = F

for NOT
F = T
T = F

for all except XOR and NOT the number inputs can be increased.

.

 

[cadpoint]

Isn't the wrong symbol used in the emergency panic line, isn't it to engage in a panic but it always to break a circuit, the "t" should be sitting hot till panic, the operator pushs down to and releases the service! (?)

Even more so cause your breaking a shunt trip.

I didn't take a photo : ? I just installed one!

The electrical sysmbol on the side of the breaker was:
A rectangular box with two wires out one end, dots wrapped the other three sides.
Break the shunt to that!

 

[cadpoint]

never mind wrong application on my part

What does this definition tell you? It says there is a conventional breaker with the addition of an auxiliary electromechanical trip coil that will force the breaker to the fully off position when momentarily energized.

Over posted!!!

 

[hillbilly1]

From the looks of the diagram, the first two pushbuttons do absolutly nothing, That's assuming that the wire shown below the switches is the hot continued. If the wire leaving the last pushbutton is connected to the shunt trip coil, it would be the only one that works. As augie47 replied, they need to be wired parralleled, not series.

 

[barshe3177]

the push buttons are not connected right. 1st time replying

 

[john37]

If some one could help me out with a diagram it sure would help me understand on how to tie all the pushbuttons together. I'm a little lost here...Thanks.

 

[augie47]

check p.m. s

 

[gar]

090309-0539 EST

john37:

Do you know what it means to connect two switches in parallel in contrast to two switches in series? Then can you extend this concept to more than two? Also what does a normally open contact mean in contrast to a normally close one?

.

 

[wasasparky]

check p.m. s

PMS? No thanks...:roll:

 

[ronaldrc]

Click here for diagram


Please copy this picture I am getting ready to change connections and will loose this FTP storage. Thanks

 

[ATSman]

Mis-information

Mis-information

090308-1434 EST

john37:

First, you need a definition of a shunt trip breaker, and how it works.

Consider this definition from:
http://www.iccsafe.org/ubb/Forum11/HTML/000741.html



What does this definition tell you? It says there is a conventional breaker with the addition of an auxiliary electromechanical trip coil that will force the breaker to the fully off position when momentarily energized.

You will have to determine for your breaker if the two trip coil wires are isolated and brought out to their own terminals (or wire pair). If two isolated terminals, then you need to supply external power. Also you have to determine if AC will work.

To the logic part of the problem. If you are working with the assumption of positive logic, and you want any one or more inputs to produce a true output, then you would use normally open push to close with spring return pushbuttons connected in parallel. This wiring of the switches produces a positive logic inclusive OR circuit. Between the two terminals of the paralleled buttons the circuit is open if no buttons are pushed. Pushing any one or more buttons causes a closed circuit that is maintained while at least button is pushed.

Put this parallel combination in series with the hot line to the trip coil and supply neutral (opposite side of the power source) to the other side of the coil.

Latch your breaker. All pushbuttons are open. No power to the unlatch coil and the breaker remains latched. As soon as any one or more of the buttons are pressed the breaker is tripped as if you had manually turned the breaker off. The breaker remains off until manually relatched.

.

Just for the record I would like to disagree with the Shunt Trip definition posted by GAR. The ST operation described in the quote is incorrect. When the ST coil energizes, the solenoid plunger operates the trip lever in the molded case breaker internal mechanism. The breaker main contacts open and the breaker handle moves to the middle (trip) position, not the off position as described. This is the same operation that occurs when the breaker trips on a fault where the thermal OC or magnetic trip device operates the same trip lever. The breaker handle then has to be moved to the off position to latch (reset) it before it can be moved to the on position to close the breaker. If the handle is moved from the trip position to the on position the breaker will not close. It has to be latched in the off position before it can be closed.
The operation described in the quote is that of a motor operator. This device is a motor (universal type) and worm gear mechanism that is mounted on to the front of the breaker that drives the breaker handle from the on to the off position (no tripping occurs.) The motor is then reversed to close the breaker. They are commonly used in automatic transfer schemes, load shed schemes, etc. Their advantage is that the breaker doesn't have to be reset to close it.
BTW, factory ST's come wired with an "a" auxiliary contact in series with the coil. This contact opens up after the breaker trips to de-energize the coil since they are not rated for continuous duty. So if you install it yourself make sure you include this contact or you may end up with a burnt ST coil :grin:

 

[gar]

090309-1830 EST

tonytonon:

That is a good description and makes logical sense. A good definition of what a devices is and how it works is important to properly apply the device.

ronaldrc:

Your diagram should be a big help to john37.

.