Multiple Shunt Trip breakers & EPO buttons

[soundman1]

We have a job with the following that needs to be tripped by 2 epo buttons

GE Main Breaker - 2 black wires
Siemens 50A 2 pole breaker- Breaker has 3 pole with 1 white wire and one terminal.
2 HVAC units with 24vdc trip contacts

2 epo buttons with N/O / N/C contacts


what is the best way to get this all wired up?

 

[LarryFine]

Soundman, welcome to the forum!

We have a job with the following that needs to be tripped by 2 epo buttons

GE Main Breaker - 2 black wires
Siemens 50A 2 pole breaker- Breaker has 3 pole with 1 white wire and one terminal.
2 HVAC units with 24vdc trip contacts

2 epo buttons with N/O / N/C contacts


what is the best way to get this all wired up?

If either button must trip, they simply get paralleled. Supply 120v from a 1p "shunt-trip" breaker (unless you already have an appropriate control circuit) to 'line' side of the pair of buttons.

The 'load' side of the buttons connects to either black wire of the GE breaker and the terminal of the Siemens 2p. (Are both breakers in the same panel? If so the Siemens would be redundant.)

The other GE black wire and the Siemens white wire connect to the neutral bus of the same panel the new 1p breaker is in. Ideally, this 1p breaker is in a panel protected by one of the shunt-trips.

(A shunt-trip breaker has a solenoid that trips the mechanism by remote control. Some shunt-trip breaker's can't withstand having their coils continuously energized.)

If the low-voltage DC tripping units are powered, and just need a dry-contact closure to trip, a 1- or 2-pole breaker with a 120v coil wired in parallel with the shunt-trip breaker coils should work.

 

[soundman1]

Thanks Larry,

they are not in the same panel one is a 225 amp panel with "clean" power for the server room the 50A double pole is power for a portable back-up A/C they wanted off a separate panel.

there is a control circuit off of the same panel as the 50A which is not shunt protected.

the buttons specified are locking buttons requiring a key to reset

so we should move the control circuit to the server panel that is protected by the shunt trip main

then wire the buttons in parralel. would we use N/O or N/C? essentially are shunt trip breakers activated when 120v power is applied, or when 120v power is removed? and must then be manually reset? So if you reset the server panel without resetting the switch it would instantly turn off again. however if you turned on the single 50A breaker and not the server panel then the breaker would stay on even though the epo switch was still activated.

how can i find out if the shunt breaker will get damaged if voltage is constantly supplied?

 

[soundman1]

damn, i typed a reply but not sure where it went

okay so to summarize the last one i typed

how do we find out if the breaker will be damaged from constant power? reason i ask is the 50a is in a separate panel from the main server room panel that has the main shun trip. epo buttons are locking on and require a key to reset. so if you hit the button it would trip the main and the 50a. if control power was from the server panel and you reset the server panel with the button locked, the panel would turn off again. but if you turned the 50a on by itself it would turn on, since the epo circuit has no power, since it is supplied by the server room panel.

also i assume the shunt trip functions when power is applied to the breaker from the circuit.

 

[LarryFine]

so we should move the control circuit to the server panel that is protected by the shunt trip main

Usually. The breaker documentation includes a warning if this is necessary.

then wire the buttons in parralel. would we use N/O or N/C?

N/O. When you want to make a circuit with more than one control, you use N/O in parallel; when you want to open a circuit from more than one control, you use N/C in series.

essentially are shunt trip breakers activated when 120v power is applied, or when 120v power is removed?

Applied. You can get breakers that open upon power loss, but not standard shunts.

and must then be manually reset? So if you reset the server panel without resetting the switch it would instantly turn off again.

Absolutely.

however if you turned on the single 50A breaker and not the server panel then the breaker would stay on even though the epo switch was still activated.

The breaker will allow you to reset it if the coil is de-energized.

how can i find out if the shunt breaker will get damaged if voltage is constantly supplied?

See top answer in this post.

 

[hillbilly1]

If you have concerns about losing the control power, replace the N/O & N/C contact block with two N/C N/C blocks, you will be able to provide a dry set of contacts for each shunt trip mechanism this way. Might get a little crowded in the enclosure though.