EPO switch power

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cppoly

Senior Member
Location
New York
Can line side power to an EPO switch come from a branch circuit in a panel that will shunt itself (main circuit breaker shunt trip) and another two circuits on another panel?

Or does this power need to come from a separate source?
 

cppoly

Senior Member
Location
New York
Ok, so it shouldn't be a problem to get the power from a branch circuit to shunt trip the main in that panel as well as other branch circuit shunt trip breakers in other panels?
 

cppoly

Senior Member
Location
New York
I'm realizing this situation wouldn't work the way I described it.

If I power an EPO switch from a breaker in panel contained in a panel with a main shunt trip breaker, this breaker would be shut off after the main shunt trip breaker is turned off. If I were to use this breaker as the source to trigger two shunt trip breakers for HVAC units located in another panel, it wouldn't work since the coils wouldn't energize as the breaker would have no power.

I would have to power EPO from another panel that does not contain the main shunt trip breaker. This way this breaker would be on and able to shunt the HVAC breakers as well.
 

jap

Senior Member
Occupation
Electrician
I'm realizing this situation wouldn't work the way I described it.

If I power an EPO switch from a breaker in panel contained in a panel with a main shunt trip breaker, this breaker would be shut off after the main shunt trip breaker is turned off. If I were to use this breaker as the source to trigger two shunt trip breakers for HVAC units located in another panel, it wouldn't work since the coils wouldn't energize as the breaker would have no power.

I would have to power EPO from another panel that does not contain the main shunt trip breaker. This way this breaker would be on and able to shunt the HVAC breakers as well.

I- WIRE is correct.

Also, its a good idea to keep the EPO control circuit coming out of the panel that's being shunted.
Around here we are required to do so.
If the power came from a different panel, and someone shut that panel down for some reason, you'd loose your shunt control circuit.

If you've got multiple shunt trip breakers coming out of different panel, you might want to consider a control circuit that doesn't leave all your eggs in one basket.

JAP>
 

cppoly

Senior Member
Location
New York
I- WIRE is correct.

Also, its a good idea to keep the EPO control circuit coming out of the panel that's being shunted.
Around here we are required to do so.
If the power came from a different panel, and someone shut that panel down for some reason, you'd loose your shunt control circuit.

If you've got multiple shunt trip breakers coming out of different panel, you might want to consider a control circuit that doesn't leave all your eggs in one basket.

JAP>


That makes sense about someone potentially shutting off EPO control power without realizing it. Is this a code violation to power the EPO this way though?

I'm worried though that the distance for the main shunt trip breaker to be tripped is less than 5' while to trip the other HVAC breakers in an other panel is about 200' away. I know electricity is fast but is there STILL a possibility of the main shunt trip breaker tripping out first....??? Even if it's a small possibility.
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
That makes sense about someone potentially shutting off EPO control power without realizing it. Is this a code violation to power the EPO this way though?

I'm worried though that the distance for the main shunt trip breaker to be tripped is less than 5' while to trip the other HVAC breakers in an other panel is about 200' away. I know electricity is fast but is there STILL a possibility of the main shunt trip breaker tripping out first....??? Even if it's a small possibility.

The general answer is no, but only because there is a time lag during which the moving parts are moving to open the main contacts.
A similar question would be about breaker coordination among branch feeder and main breakers. The answer there, particularly if different brands are involved, is that without looking hard at the trip curves and deliberately coordinating all that you can say is that one or more of the breakers will open. Beyond that it is unpredictable without specific analysis.

For good reason, it is common to take the shunt trip supply voltage from the load side of the breaker which MUST be tripped.
Even that does not let you shut trip a breaker which does not have any power applied at the time you push the button. (When the main or feeder is closed, the EPO's equipment on a controlled branch breaker may start up again.)
 

iwire

Moderator
Staff member
Location
Massachusetts
That makes sense about someone potentially shutting off EPO control power without realizing it. Is this a code violation to power the EPO this way though?

No

I'm worried though that the distance for the main shunt trip breaker to be tripped is less than 5' while to trip the other HVAC breakers in an other panel is about 200' away. I know electricity is fast but is there STILL a possibility of the main shunt trip breaker tripping out first....??? Even if it's a small possibility.

Not even a possibility.

Electricity is not just fast, it is instant.

Picture a pipe 200' long, the pipe diameter allows a single row of balls to be placed in it all nicely touching each other from one end to the other.

Now stand in at one end and push another ball into the pipe How much delay before a ball pops out the other end?

Take that in combination with the fact it takes time for the shunt to pull in and more time for the contacts to open, they will all open.
 

jap

Senior Member
Occupation
Electrician
I've also seen instances where they took a 1p breaker in the panel that was being shunted and ran it to the coil on a N/O contactor above the 2nd panel then ran the branch curcuits from the 2nd panel thru the contactor to the HVAC units.

When the 1st panel was shunted it caused the contactor to fall out, thus opening the circuits from the 2nd panel to the units.

Not sure if it's a decent design or not. I've just never been a big fan of knowing a contactor has to be pulled in 24/7 for a scenario like this to work.

JAP>
 

gadfly56

Senior Member
Location
New Jersey
Occupation
Professional Engineer, Fire & Life Safety
I've also seen instances where they took a 1p breaker in the panel that was being shunted and ran it to the coil on a N/O contactor above the 2nd panel then ran the branch curcuits from the 2nd panel thru the contactor to the HVAC units.

When the 1st panel was shunted it caused the contactor to fall out, thus opening the circuits from the 2nd panel to the units.

Not sure if it's a decent design or not. I've just never been a big fan of knowing a contactor has to be pulled in 24/7 for a scenario like this to work.

JAP>

How much less of a fan would you be if a shunt trip failed to operate because there was no power to the coil? Maybe not a big deal for the first panel that powers the EPO since if the panel is off for some reason then your equipment is already de-energized. The problem would be for other shunts paralleled off the EPO for other panels. If panel "A" is down, or a there's a broken wire, "B" and "C" aren't going to cycle off. These things are typically unmonitored. It's why I prefer contactors that have to be powered on. Constant duty contactors are not hard to find.
 

iwire

Moderator
Staff member
Location
Massachusetts
Basically shunt trips are used as they are the cheapest way to get it done.

Personally I think they are unreliable due to the reasons already mentioned.

Like gadfly I think normally open contactors are a much better way to go. They self supervise themselves and the control circuit.
 

jap

Senior Member
Occupation
Electrician
How much less of a fan would you be if a shunt trip failed to operate because there was no power to the coil? Maybe not a big deal for the first panel that powers the EPO since if the panel is off for some reason then your equipment is already de-energized. The problem would be for other shunts paralleled off the EPO for other panels. If panel "A" is down, or a there's a broken wire, "B" and "C" aren't going to cycle off. These things are typically unmonitored. It's why I prefer contactors that have to be powered on. Constant duty contactors are not hard to find.

Use what you want.
I'd could care less.
Just my opinion.

Jap.
 

jap

Senior Member
Occupation
Electrician
For every bad shunt trip you could show me I could probably match it with a burnt out coil.

Jap^
 

iwire

Moderator
Staff member
Location
Massachusetts
For every bad shunt trip you could show me I could probably match it with a burnt out coil.

Jap^

As gadfly points out, normally open contactors will fail safe and if the control circuit is compromised they will open as well.

With a shunt you have no idea if the control circuit is ok.
 

jap

Senior Member
Occupation
Electrician
As gadfly points out, normally open contactors will fail safe and if the control circuit is compromised they will open as well.

With a shunt you have no idea if the control circuit is ok.

You have no idea that the contacts aren't welded closed on a contactor either.

Nothing electrical is completely fail safe.

JAP>
 

jap

Senior Member
Occupation
Electrician
You can argue it both ways.
Whether you use shunt trip breakers or N/O Contactors, if they're both operating properly, use whatever suits you.
I don't see the advantage of one over the other.
If shunt trips are so undependable, it seems no ones aware of it since I see a whole lot of them spec'd on a whole lot of projects.

jAP>
 

iwire

Moderator
Staff member
Location
Massachusetts
No you can't even begin to claim the shut is as reliable as NO contators.

Both have contacts and mechanical parts that can hang up so they are equal there.

In ALL other repects the contractor set up is more reliable and fail safe.
 

jap

Senior Member
Occupation
Electrician
No you can't even begin to claim the shut is as reliable as NO contators.

Both have contacts and mechanical parts that can hang up so they are equal there.

In ALL other repects the contractor set up is more reliable and fail safe.

I'd have to see the statistics your basing that on.
If they are unreliable, people need to be notified so they can be taken out of the specs for Kitchens, Elevators, and the like.

JAP>
 
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