Disconnecting Panelboards HELP

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KP089

Member
Location
Edison, NJ
I need a way to disconnect the panel boards in a line side tap if the building main breaker were to trip (requirement from the fire marshal).

I was thinking:
*shunt trip at the 2 panel boards with shunt trip and auxiliary contacts connected to a mini power zone
*mini power zone being powered from the building switchboard before the building main disconnect

So, when the building's disconnect switch is pulled, it disconnects power to the mini power zone which trips the auxiliary contacts in the panel boards: disconnecting the panel boards.


Is this a viable plan or is there a better option, if this is a decent course what are some potential downfalls I can encounter.(using NEC 2011)

I'm fairly inexperienced in the solar world, so any help would be greatly appreciated.
 

Strathead

Senior Member
Location
Ocala, Florida, USA
Occupation
Electrician/Estimator/Project Manager/Superintendent
I need a way to disconnect the panel boards in a line side tap if the building main breaker were to trip (requirement from the fire marshal).

I was thinking:
*shunt trip at the 2 panel boards with shunt trip and auxiliary contacts connected to a mini power zone
*mini power zone being powered from the building switchboard before the building main disconnect

So, when the building's disconnect switch is pulled, it disconnects power to the mini power zone which trips the auxiliary contacts in the panel boards: disconnecting the panel boards.


Is this a viable plan or is there a better option, if this is a decent course what are some potential downfalls I can encounter.(using NEC 2011)

I'm fairly inexperienced in the solar world, so any help would be greatly appreciated.

I am having a hard time envisioning what you mean. Others may get it, but it would help if you posted a sketch of the riser. My instinct says that a requirement that the panels disconnect would negate the use of shunt trip because if there was no power the shunt trip wouldn't work. Then you bring solar in to it without prior explanation. Why is the Fire marshal requiring the panels be opened?
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
If there is no issue with disconnecting the solar input when the power goes out then I would say just install a 20 amp circuit to a contactor and have the solar panel fed thru the contactor. Power goes out and the contactor opens and the solar panel is disconnected. Would this work?
 

hbiss

EC, Westchester, New York NEC: 2014
Location
Hawthorne, New York NEC: 2014
Occupation
EC
I am having a hard time envisioning what you mean.

I think what he is saying is that the solar feed is connected directly to the utility after the meter. So if the service main breaker is opened those conductors and equipment will still be hot.

Problem in my mind is that even if you were to disconnect the solar feed at the utility end the conductors will still be hot unless you shut down the solar itself.

-Hal
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
I think what he is saying is that the solar feed is connected directly to the utility after the meter. So if the service main breaker is opened those conductors and equipment will still be hot.

Problem in my mind is that even if you were to disconnect the solar feed at the utility end the conductors will still be hot unless you shut down the solar itself.

-Hal
A grid interactive inverter (grid tie inverter) will not produce any output once the grid connection is interrupted.
Most AHJs will consider such a line side PV connection just another disconnect under the six handle rule (or as an allowed seventh) which will be manually opened along with the existing service disconnect.
Requiring an automatic PV disconnect when the main CB opens under a fault is a local aberration not mandated by the NEC.
 

pv_n00b

Senior Member
Location
CA, USA
I would try working with the fire marshal first to find out what their reasoning is. This is a very unusual requirement and it probably comes from a misunderstanding about how PV systems work. Most likely if a building had multiple service disconnects the fire marshall would not require them all to trip off if one tripped off, so why require it with the PV supply side interconnection?

If you just can't convince them then an undervoltage trip breaker should do the job. Connect the voltage sense to the main panel, if it trips off the UV breaker will trip.
 
I would try working with the fire marshal first to find out what their reasoning is. This is a very unusual requirement and it probably comes from a misunderstanding about how PV systems work.

Probably

Most likely if a building had multiple service disconnects the fire marshall would not require them all to trip off if one tripped off, so why require it with the PV supply side interconnection?

I wonder if it is because (if this is the case with the OP) the disconnects (PV and "normal") are not grouped? Not that there is a NEC requirement to shunt trip non grouped disconnects, but at least that would have a slight bit of logic to it....
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
Probably



I wonder if it is because (if this is the case with the OP) the disconnects (PV and "normal") are not grouped? Not that there is a NEC requirement to shunt trip non grouped disconnects, but at least that would have a slight bit of logic to it....
There is no NEC requirement to shunt trip non grouped disconnects because they are not allowed in the first place AFAIK.
 
There is no NEC requirement to shunt trip non grouped disconnects because they are not allowed in the first place AFAIK.

Never say never, Mr. GoldDigger (I almost get two bond references there)....I was referring to the few situations such as PV, fire pumps, two services, where the disconnects are not grouped. But yes, in general the disconnects must be grouped.
 
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