Too Many Conductors in a Raceway

[Ravenvalor]

So the multiple circuits are the output circuits of the dimmer pack! In that case what does the code say is the effective protection of the output circuits? Does the 10A breaker count for that or does each output circuit require 40A wiring?!? Or do you have to install separate UL approved (non-supplemental) breakers for each output?

Good questions. I will call ETC Monday morning and let you know what I find. I believe that they will refer me to my local inspector and he will let me use the 10-amp circuit breakers as the effective protection of the output circuits.

Thanks,

 

[n1ist]

As I understand it, if the dimmer rack outputs are hard-wired to the rack, the internal breakers are sufficient. If the outputs of the rack have receptacles and the house wiring plug into them, then the house wiring needs its own breakers. I have only seen the additional breakers when you have a patch panel or touring rack.

/mike

 

[Little Bill]

Good questions. I will call ETC Monday morning and let you know what I find. I believe that they will refer me to my local inspector and he will let me use the 10-amp circuit breakers as the effective protection of the output circuits.

Thanks,

If you have a lighting panel/rack, all you have to do per the NEC is supply the cabinet with the proper sized conductors and OCPD. The rack/cabinet should be a listed assembly with the total voltage and amps on the nameplate or in the cut sheet. The internal breakers in the lighting rack provide protection to each pack.

I work on one occasionally (Lutron) that is fed with a 3 ph- 208V breaker. It has, internally, 60A breakers for a group or zone, and 10A breakers for each smaller sub group. Depending on the light and it's current draw, some will be the only light on a 10A breaker, while there may be 3-5 lights on some of the 10A circuits.

I think you are fine with what you have.

 

[iwire]

My answer is in post #11. I'll assume no further.

Same here.

Good point, especially if he rearranges the existing circuits.
Not counting the grounded conductors would require that the circuits actually be wired as MWBCs. In the OP's case they are not currently so wired, but unless he is forced to always count the neutral because of non-linear load from the dimmer packs he can rewire his 8 existing circuits as MWBCs and save 8 CCCs, getting a total of 8 CCC plus 4 unused former grounded conductors (which are the wrong color to use for most other purposes) and 16 spares.

It would be extremely unusual to have MWBCs on the load side of dimmer packs.

 

[George Stolz]

You'd still have to change the breakers to 15A. The 10A CB's in the dimmer packs are supplementary OCPD and are not a substitute for branch circuit OCPD [240.10].

Why can't he have 10A branch circuits? :?

 

[Smart $]

Why can't he have 10A branch circuits? :?

He can. I just said 15A because its the maximum permitted standard ocp rating and he said they were on 20A breakers in OP.

 

[SceneryDriver]

PVC conduit notwithstanding, remember that there is great diversity-of-load with theatrical lighting. Many times, circuits are on for short times, driven at less than 100%, or off completely. It's a rare thing to have need to drive every dimmer circuit in a theater at 100% while carrying anywhere near full load. Is there record of any engineering studies from when the equipment was originally installed? Electronic Theater Controls (ETC) often does, or helps with, the lighting system design and engineering. I wonder if they keep records going back that far?

I would be very surprised if the individual 10A breakers in the dimmer packs are not rated for branch circuit protection. No dimmer rack I've ever seen or heard of has supplemental protection downstream of the rack. The rack is typically fed with a 400A - 800A service, and then each dimmer tray (that controls two circuits) feeds each LX circuit in the theater.


SceneryDriver

 

[Ravenvalor]

You might also take a look at 518.4(C). There are locations where RNC can be used in Places of Assembly.

I just looked at the code and see a glimmer of hope for this existing installation meeting code.

Thanks,

 

[Ravenvalor]

You might also take a look at 518.4(C). There are locations where RNC can be used in Places of Assembly.

Hello augie,

I took a look at 518.4(C) and It looks like I can use RNC if it is installed in a suspended ceiling with a minimum 15-minute finish rating.
This takes care of the portion of the conduit that is above the suspended ceiling.

However, in this storage room where the electrical panel and dimmerpack are located the RNC is surface run from the dimmer pack to the suspended ceiling and also from the panel to the dimmerpack (the panel is only about 6" from the dimmerpack). I believe this is a code violation because the RNC is not concealed within a wall per 518.4(B).

Back to the suspended ceiling. After the RNC enters the suspended ceiling it makes a 90-degree left hand turn and exits the building. Then it makes another 90-degree turn and goes up the outside wall of the place of assembly room to the attic. Once it reaches the attic it makes a 90-degree turn inside the attic and runs along the ceiling for about 15' until it terminates into a junction box. I believe this is also a code violation because the RNC is not concealed within a wall in the attic per 518.4(B).

I hope that I have made this easy for you to picture. If possible, your input would be appreciated.

Thank you,

 

[Ravenvalor]

You might also take a look at 518.4(C). There are locations where RNC can be used in Places of Assembly.

Hello augie,

I took a look at 518.4(C) and It looks like I can use RNC if it is installed in a suspended ceiling with a minimum 15-minute finish rating.
This takes care of the portion of the conduit that is above the suspended ceiling.

However, in this storage room where the electrical panel and dimmerpack are located the RNC is surface run from the dimmer pack to the suspended ceiling and also from the panel to the dimmerpack (the panel is only about 6" from the dimmerpack). I believe this is a code violation because the RNC is not concealed within a wall per 518.4(B).

Back to the suspended ceiling. After the RNC enters the suspended ceiling it makes a 90-degree left hand turn and exits the building. Then it makes another 90-degree turn and goes up the outside wall of the place of assembly room to the attic. Once it reaches the attic it makes a 90-degree turn inside the attic and runs along the ceiling for about 15' until it terminates into a junction box. I believe this is also a code violation because the RNC is not concealed within a wall in the attic per 518.4(B).

I hope that I have made this easy for you to picture. If possible, your input would be appreciated.

Thank you,

 

[Smart $]

Hello augie,

I took a look at 518.4(C) and It looks like I can use RNC if it is installed in a suspended ceiling with a minimum 15-minute finish rating.
This takes care of the portion of the conduit that is above the suspended ceiling.

However, in this storage room where the electrical panel and dimmerpack are located the RNC is surface run from the dimmer pack to the suspended ceiling and also from the panel to the dimmerpack (the panel is only about 6" from the dimmerpack). I believe this is a code violation because the RNC is not concealed within a wall per 518.4(B).

Back to the suspended ceiling. After the RNC enters the suspended ceiling it makes a 90-degree left hand turn and exits the building. Then it makes another 90-degree turn and goes up the outside wall of the place of assembly room to the attic. Once it reaches the attic it makes a 90-degree turn inside the attic and runs along the ceiling for about 15' until it terminates into a junction box. I believe this is also a code violation because the RNC is not concealed within a wall in the attic per 518.4(B).

I hope that I have made this easy for you to picture. If possible, your input would be appreciated.

Thank you,

It seems to me the storage room where the panel and dimmer packs are located and the attic are both not "portions of buildings or structures designed or intended for the gathering together of 100 or more persons"... correct?

 

[Ravenvalor]

It seems to me the storage room where the panel and dimmer packs are located and the attic are both not "portions of buildings or structures designed or intended for the gathering together of 100 or more persons"... correct?

The storage room is about 20' x 20'. On one end of it is a doorway into the great room (meeting room). On the other end is a doorway leading into a corridor which has offices. The conduit eventually runs into the attic above the meeting room. From there it branches out to lights with EMT.

Thank you,

 

[Smart $]

The storage room is about 20' x 20'. On one end of it is a doorway into the great room (meeting room). On the other end is a doorway leading into a corridor which has offices. The conduit eventually runs into the attic above the meeting room. From there it branches out to lights with EMT.

Thank you,

As long as it is not in exposed in any 100+ occupants "room", should be good IMO.

 

[jumper]

As long as it is not in exposed in any 100+ occupants "room", should be good IMO.

Ditto.

 

[Ravenvalor]

Same here.

It would be extremely unusual to have MWBCs on the load side of dimmer packs.

I did call ETC and they dittoed your thoughts and do not recommend MWBC's on the load side of their dimmer packs.

 

[kwired]

As long as it is not in exposed in any 100+ occupants "room", should be good IMO.

Beat me to it, that is my interpretation also.

In, OP's situation the church sanctuary, assembly hall, or whatever you want to call it is definitely a place of assembly. There may also be a social hall of some kind that is likely a place of assembly. Most other areas of the facility are probably not places of assembly. Some AHJ's will want at least a 1 hour finish between areas that are not to be considered place of assembly before they will allow it to be deemed a separate space, but otherwise a room that can't have 100+ occupants is not a part of the place of assembly.