Shunt Trip Breaker Wiring

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Tommy Blackmon

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Auburn, GA. USA
I am getting ready it install a 480volt Siemens BQD Breaker with a Field Installed 120v Shunt Trip for a Boiler. The Shunt Trip is going to an E-Stop Button near the exit of the building. I have run a black(hot), red(return), white and green to the E-Stop from a 15amp 120v Breaker and into my 480volt panel.
I have not installed a Shunt Trip in years and am a little confused on the wiring. I may be overthinking it. Is it like wiring a switch? Line to one terminal and load to the other and the E-Stop when pressed sends the 120volts telling the Shunt to Trip the 480volt breaker?

Thanks in advance for the advise.
Tommy
 
No not like a switch. The two leads coming off the breaker are for the coil. Once you put 120 volts across the leads your breaker will open. So feed one lead with the control circuit neutral and the other with the hot conductor fed from the load side of the push button.


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Tommy Blackmon said:
I am getting ready it install a 480volt Siemens BQD Breaker with a Field Installed 120v Shunt Trip for a Boiler. The Shunt Trip is going to an E-Stop Button near the exit of the building. I have run a black(hot), red(return), white and green to the E-Stop from a 15amp 120v Breaker and into my 480volt panel.
I have not installed a Shunt Trip in years and am a little confused on the wiring. I may be overthinking it. Is it like wiring a switch? Line to one terminal and load to the other and the E-Stop when pressed sends the 120volts telling the Shunt to Trip the 480volt breaker?

Thanks in advance for the advise.
Tommy
Click to expand...

If you want to think of the e-stop as a switch (which it is) then think of the shunt device as a light fixture.

I think there are special labeling requirements for the 480V panel indicating multiple sources since you have a foreign branch circuit in the enclosure.

Would it not be safer to use a contactor and the NC from the estop. Seems to me that if your 120V trips or otherwise fails, you no longer have the ability to use the e-stop.
 
Tommy Blackmon said:
I am getting ready it install a 480volt Siemens BQD Breaker with a Field Installed 120v Shunt Trip for a Boiler. The Shunt Trip is going to an E-Stop Button near the exit of the building. I have run a black(hot), red(return), white and green to the E-Stop from a 15amp 120v Breaker and into my 480volt panel.
I have not installed a Shunt Trip in years and am a little confused on the wiring. I may be overthinking it. Is it like wiring a switch? Line to one terminal and load to the other and the E-Stop when pressed sends the 120volts telling the Shunt to Trip the 480volt breaker?

Thanks in advance for the advise.
Tommy
Click to expand...
Piece of cakeTommy.
You need a reliable120vac source which in properly protected. Is that source Bering feed by the breaker that you want to open?
You need the E stop, it could be as simple as a toggle switch but more likely a conspicuous mushroom head push button switch that in conspicuous and easy to see/find located in a convenient spot. Since a breaker shunt trip consists of a solenoid that can be fried if !eft energized for any length of time there in a "cut-off switch" as part of the coil aßembled that opens instantasneou see ly when the breakers is tripped by the shunt trip on the cut off switch opens deenergizing the shunt trip coil. As such the switch (push button) that you choose to use can we either be maintained or momentary.
If you choose a maintained switch you will not be able to close the breaker as it will start to close and immediately trip again.unless you release the external switch to the open position. Keep in mind that this could be an extremely important feature in that case the emergency switch/push button often is remote. The question is do you want someone to reset and close the breaker it you want it to remain open? A maintained contact switch that if left close Weill prevent the breaker from being closed unintentionally of without authorization.
Please note that if you do choose a maintained contact and it is kept closed, yes the breaker will be prevented from being closed but if you have an unqualified person attempt to close the breaker it will trip immediately in the process of being closed. If done numerous time the breakers trip mech is often damaged. A unauthorized person closing the breaker may not be an issue but never the less should not be ignored.
You could even go so far as to add an indicator light to indicate if 120v power is available of the supply side of the circuit and/or an indicator light showing that the shunt trip is being energized. Indicator lights do make it easier to establish the status of the shunt trip circuit depending upon how critical the shunt trip feature is.
One other this. If you do bring power into the enclosure from a separate source you should either have a cut off switch of the door handle to disconnect the external power when opening the door or it is easier to attatch a yellow label to the outside of the door which states that there is an external power source present even though the breaker is open.
 
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If this is a safety device then I would go for a maintained DC supply for the shunt trip. I certainly wouldn’t go for a separate external AC supply, far too unreliable.

Maintained DC protection is standard practice for MV switchgear.
 
Tony S said:
If this is a safety device then I would go for a maintained DC supply for the shunt trip. I certainly wouldn’t go for a separate external AC supply, far too unreliable.

Maintained DC protection is standard practice for MV switchgear.
Click to expand...
In not knowing what the actual application is your point with the DC supply as used in MV grear is a very good point.
 
ADub said:
No not like a switch. The two leads coming off the breaker are for the coil. Once you put 120 volts across the leads your breaker will open. So feed one lead with the control circuit neutral and the other with the hot conductor fed from the load side of the push button.


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Click to expand...

That makes sense. It has been awhile in installing one. I wanted to make sure. And the paperwork on the Shunt has so many directions it becomes confusing.
 
luckylerado said:
If you want to think of the e-stop as a switch (which it is) then think of the shunt device as a light fixture.

I think there are special labeling requirements for the 480V panel indicating multiple sources since you have a foreign branch circuit in the enclosure.

Would it not be safer to use a contactor and the NC from the estop. Seems to me that if your 120V trips or otherwise fails, you no longer have the ability to use the e-stop.
Click to expand...

Thanks for the advice. The 120volt panel is not more than five feet from the other so labeling will not be an issue. I will have to remember about the contactor if I ever install another one. Thanks again.
 
Tony S said:
If this is a safety device then I would go for a maintained DC supply for the shunt trip. I certainly wouldn’t go for a separate external AC supply, far too unreliable.

Maintained DC protection is standard practice for MV switchgear.
Click to expand...

This is temporary as in about 2months I am changing out the 120volt panel that is feeding the Shunt. The panel is within 5ft of the 480panel and can be switched out at that time.

Thank you again, for the info.
 
Tony S said:
In which case I would use a 110V under voltage trip instead of the shunt. If you loose the 110V then the system fails safe.
Your E-Stop(s) would then need to be normally open contacts.
Click to expand...

That's another option as a UVR needs to be continually energized and will trtip the breaker when deenergized. To trip the breaker manually then yu our E-stop needs to have a N/C contact that when the EStop is pisher the contact operns removing power from the UVR mech which trip the breaker.
Keep in mind that the UVR mech must be energized in order to reset and close the breaker. Failure to do so will cause the breaker to immediately trip when there is an attempt try to close the breaker. By repeatedly doing this the breaker trip mech is likely to be damaged. As such it is imperative that the UVR mech be energized before attempting to reset and CV lose the breaker.
 
templdl said:
That's another option as a UVR needs to be continually energized and will trtip the breaker when deenergized. To trip the breaker manually then yu our E-stop needs to have a N/C contact that when the EStop is pisher the contact operns removing power from the UVR mech which trip the breaker.
Keep in mind that the UVR mech must be energized in order to reset and close the breaker. Failure to do so will cause the breaker to immediately trip when there is an attempt try to close the breaker. By repeatedly doing this the breaker trip mech is likely to be damaged. As such it is imperative that the UVR mech be energized before attempting to reset and CV lose the breaker.
Click to expand...


I’ve been down that route with “we want” the breakers to do this, well you “can’t have!” I did do it eventually but there was enough warning labels to cover a wall. I had to do something I hate doing. 110V AC in the 30V DC OCB protection panel and 30V DC in the MCC ACB protection cubical.

Once I’d designed the system our group engineering department phoned asking if I’d considered the system getting in to a loop. After a few choice words I put the phone down.
I’d an audience when it came to testing the setup, all waiting for me to fall flat on my face. I really was ever so sorry to disappoint them ;-)
 
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