How many Camlok Connections - NEC 520.54(H)

rphilip

Active Member
Was discussing the limit on the number of mated connector pairs in a power cable with Cam lock cables in mind and decided to go look up the actual code requirement for this which is in NEC 520.54(H) as of 2017.

NEC 2017 520.54(H) Number of Supply Interconnections. said:
Where connectors are used in a supply conductor, there shall be a maximum number of three interconnections (mated connector pairs) where the total length from the supply to switchboard does not exceed 30 m (100 ft). In cases where the total length from supply to switchboard exceeds 30 m (100 ft), one additional interconnection shall be permitted for each additional 30 m (100 ft) of supply conductor.

A couple questions:
- How to count connector pairs. If I'm plugging into a company switch with installed Cam locks on one end and a dimmer rack on the other with no intermediate connector pairs is this 0, 1 or 2 connections? What if it's short tails tied into a fused disconnect with a set of cam to cam cables that then connect to the dimmer rack: 1, 2 or 3 connector pairs?
- Does this apply to only Camlock and other similar cables or would it also apply to Soca, & PBG/Edison/Stagepin cables?

Thanks

Philip
 
Was discussing the limit on the number of mated connector pairs in a power cable with Cam lock cables in mind and decided to go look up the actual code requirement for this which is in NEC 520.54(H) as of 2017.



A couple questions:
- How to count connector pairs. If I'm plugging into a company switch with installed Cam locks on one end and a dimmer rack on the other with no intermediate connector pairs is this 0, 1 or 2 connections? What if it's short tails tied into a fused disconnect with a set of cam to cam cables that then connect to the dimmer rack: 1, 2 or 3 connector pairs?
- Does this apply to only Camlock and other similar cables or would it also apply to Soca, & PBG/Edison/Stagepin cables?

Thanks

Philip

1. "Connectors in a supply conductor" includes those that may be panel mounted on a company switch or utilization equipment. So, if both were present, that would count as two mated connector pairs. Short tie-in tails on a company switch or flying leads on a dimmer rack or PD are the functional equivalent of a panel-mount connector for the purposes of counting mated pairs.
2. This section covers only supply (feeder) conductors to a portable switchboard. The other connectors you mentioned are rarely, if ever, used in that application.

The whole purpose of this section is to prevent stringing together short lengths of single-conductor feeder, resulting in too many mated pairs in unsupervised locations.

ST
 
1. "Connectors in a supply conductor" includes those that may be panel mounted on a company switch or utilization equipment. So, if both were present, that would count as two mated connector pairs. Short tie-in tails on a company switch or flying leads on a dimmer rack or PD are the functional equivalent of a panel-mount connector for the purposes of counting mated pairs.
2. This section covers only supply (feeder) conductors to a portable switchboard. The other connectors you mentioned are rarely, if ever, used in that application.

The whole purpose of this section is to prevent stringing together short lengths of single-conductor feeder, resulting in too many mated pairs in unsupervised locations.

ST
Thanks, glad to see the answer from THE expert

Philip
 
How do camlock tees fit into this equation?

Let's take a hypothetical installation of two dimmer racks and a power distro, none of which have pass-throughs. The disconnect (tie-in) has permanently mounted tails. So, Disconnect --> cam tee -- cam tee -- cam tee, with each of those tees also having a length of feeder to either a dimmer rack or power distro.

Do I count all of the connectors downstream of the disconnect, or just from the disconnect to each particular device?

Since we are talking about "mated connector pairs" that assume cable in between, I think it is reasonable to call a tee or stacked tees one connector, no matter how many females result.

Just my 2 cents.

ST
 
So, If I'm reading this right, If I use two(2) 50' lengths of feeder cable together. Plug them into the company switch at one end and my Distro at the other, I have reached my 3 pairs of connectors? So adding one more 50' allows one additional connection because it's over 100'. If this is correct, basically the NEC 4/0 feeder runs are limited to 150'. Mostly because 4/0 almost is never available to rent in longer than 50' runs.

Interesting. Somewhat moot point, since most contracts, I do specify 50' maximum power source from stage, and we plan 100' to be sure. Interestingly, There are lots of well known and professional power companies that probably violate this standard. Often they are using a 1 or 2 meg dual synchronized generator and distributing transformers and camlock disconnects around a festival site or movie set, etc, often meeting the 3 connector max BEFORE another vendor connects to the disconnect. Maybe there is another part of the NEC that grants an exception for this type of thing; don't know.
 
What about if you have several racks being looped? Or do you only count from supply to the first rack and consider the other racks to be part of the switchboard?
 
So, If I'm reading this right, If I use two(2) 50' lengths of feeder cable together. Plug them into the company switch at one end and my Distro at the other, I have reached my 3 pairs of connectors? So adding one more 50' allows one additional connection because it's over 100'. If this is correct, basically the NEC 4/0 feeder runs are limited to 150'. Mostly because 4/0 almost is never available to rent in longer than 50' runs.

It's not 150' max, it's one connection per 100' over the initial 100'. At that point you're likely running 100' cables anyways, so it shouldn't be that bad.
 
It's not 150' max, it's one connection per 100' over the initial 100'. At that point you're likely running 100' cables anyways, so it shouldn't be that bad.
@danTt I believe the OP already mentioned 4/0 feeders longer than fifty feet are scarce as unobtainium in his neck of the woods.
Toodleoo!
Ron Hebbard
 
Most places only have 50' lengths of 4/0 and 100' #2 (hots banded, and N+G banded) There are IBEW contracts on weight lifting limits.At least that's the reason I have been told.

Sunbelt, United, Cat Power, etc
You must be in a different part of the world than me. I've never encountered an issue sourcing 100' feeder from any shop I've worked with, and I know for sure that Cat power (in the northeast) uses 100' feeder on a regular basis. Both banded and single runs--though for 4/0 I'll take single runs any day.
 
What about if you have several racks being looped? Or do you only count from supply to the first rack and consider the other racks to be part of the switchboard?

This^

Also, Switchboard seems like a poor term. "Hey, Sparky? It's Radar. I need to reach San Fransisco, can you patch me through to Honolulu?"

I might use 3-4 racks on a single 400a. I also use Lex Cam PDs that have a 400a in and 4- 100a outputs. I wonder does having a breaker in line make a different part of the NEC apply? Is that PD considered a new service and the 3 connection applies again from there on? The same thing, Does a Transformer and disconnect reset the connection limit?

I don't know if it is correct but it is certainly common in the industry.
 
You must be in a different part of the world than me. I've never encountered an issue sourcing 100' feeder from any shop I've worked with, and I know for sure that Cat power (in the northeast) uses 100' feeder on a regular basis. Both banded and single runs--though for 4/0 I'll take single runs any day.

It might be local IBEW contracts that have dictated availability, but throughout the US I have received 50' 4/0 runs 90% of the time. Banded is usually 100'

I seldom need more than 150' though.
 
This^

Also, Switchboard seems like a poor term. "Hey, Sparky? It's Radar. I need to reach San Fransisco, can you patch me through to Honolulu?"

I might use 3-4 racks on a single 400a. I also use Lex Cam PDs that have a 400a in and 4- 100a outputs. I wonder does having a breaker in line make a different part of the NEC apply? Is that PD considered a new service and the 3 connection applies again from there on? The same thing, Does a Transformer and disconnect reset the connection limit?

I don't know if it is correct but it is certainly common in the industry.
I would say a panel mounted output on a transformer, PD or dimmer rack resets the limit of mated connector pairs.

And, from NEC article 520:

520.2 Definitions

Stage Switchboard. A permanently installed switchboard,
panelboard, or rack containing dimmers or relays with associated
overcurrent protective devices, or overcurrent protective
devices alone, used primarily to feed stage equipment.

Stage Switchboard, Portable. A portable rack or pack containing
dimmers or relays with associated overcurrent protective
devices, or overcurrent protective devices alone that are used to
feed stage equipment.

Portable Power Distribution Unit. A power distribution box
containing receptacles and overcurrent devices.

And:

520.53(D) Supply Feed-Through. Where a portable stage switchboard
contains a feed-through outlet of the same rating as its
supply inlet, the feed-through outlet shall not require overcurrent
protection in the switchboard.

ST
 
I would say a panel mounted output on a transformer, PD or dimmer rack resets the limit of mated connector pairs.

And, from NEC article 520:

520.2 Definitions

Stage Switchboard. A permanently installed switchboard,
panelboard, or rack containing dimmers or relays with associated
overcurrent protective devices, or overcurrent protective
devices alone, used primarily to feed stage equipment.

Stage Switchboard, Portable. A portable rack or pack containing
dimmers or relays with associated overcurrent protective
devices, or overcurrent protective devices alone that are used to
feed stage equipment.

Portable Power Distribution Unit. A power distribution box
containing receptacles and overcurrent devices.

And:

520.53(D) Supply Feed-Through. Where a portable stage switchboard
contains a feed-through outlet of the same rating as its
supply inlet, the feed-through outlet shall not require overcurrent
protection in the switchboard.

ST

Thanks for doing the research on this, Steve. All of that makes complete sense in regards to how power distribution is done on large sites.
 

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