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Clarification on cam-lock usage for private residential applications

3454 Views 3 Replies 3 Participants Last post by  Keyrick
"Single-Pole Separable Connectors" (a.k.a. cam-lock) seem to be only referred to in NEC CHAPTER 5 SPECIAL OCCUPANCIES (e.g. live concert, carnivals, circuses, etc.).

The scope of this Chapter and the below referenced articles seems not to apply to private residential usage, are cam-locks restricted to SPECIAL OCCUPANCIES usage and does Chapter 5 solely govern them?

ARTICLE 520 Theaters, Audience Areas of Motion Picture and Television Studios, Performance Areas, and Similar Locations
520.53 --> (P)
"Qualified Personnel. The routing of portable supply conductors, the making and breaking of supply connectors and other supply connections, and the energization and deenergization of supply services shall be performed by qualified personnel, and portable switchboards shall be so marked, indicating this requirement in a permanent and conspicuous manner.
Exception: A portable switchboard shall be permitted to be connected to a permanently installed supply receptacle by other than qualified personnel, provided that the supply receptacle is protected for its rated ampacity by an overcurrent device of not greater than 150 amperes, and where the receptacle, interconnection, and switchboard comply with all of the following:
(a) Employ listed multipole connectors suitable for the purpose for every supply interconnection
(b) Prevent access to all supply connections by the general public
(c) Employ listed extra-hard usage multiconductor cords or cables with an ampacity suitable for the type of load and not less than the ampere rating of the connectors."
and similarly
530.22 Single-Pole Separable Connectors

I was hope that I could get some help with NEC interpretation of standards & compliance in wiring methods and materials as it pertains to residential use of cam-loc with Manual Transfer Equipment (a.k.a. MTS ) and Nonseparately Derived System (a.k.a. non-SDS) 702.5 (B)(1) 702.10(B).

In simple terms, I want to assess the feasibility of using cam-lock connections from trailer mount genset to a MTS that is fixed to a private residential home.

This video gives an overview of connecting a trailer mounted genset via cam lock to a MTS - I am trying to determine if this kind of private residential home cam-lock application is valid (the guy in video mounted thecam-locks directly on the MTS, I am pretty certain that this is not street legal and I was not suggesting/considering this but rather a separate enclosure for the cam locks. I actually contacted a few transfer switch manufacturers, such as Ronk, they believed that this type of field modification would invalidate their switch’s UL 98 &1008 listing).

Here would be the hypothetical scenario application:
1. Existing. Utility meter 200 amp service à 1 - service conductor/wire à 1 - 200A main breaker panel/load center.

2. Install. Service entrance (i.e. service disconnect) rated single-phase, 60 HZ, 120/240V 2-pole 200A MTS (non-switched neutral) between meter & load center.

3. Mount Cooper Crouse-Hinds E1016 Cam Lok with CAM-LOK NEMA 3R receptacle covers on to a NEMA 3R trough (e.g. WIEGMANN, Hoffman, etc.) sized ~ 6x6x18. A permanently wired conductor would run between this cam-lock receptacle box/enclosure and the MTS.

It would look similar to this (or one of the other many pre-fabricated cam-lock tap box solutions on the market):

4. 36KW trailer mount diesel generator. Single-phase, 60 HZ, 120/240V, 3 wires with the 3rd wire being a solid neutral (i.e. 2H+N+G).
ii. The nameplate current rating 150A @ 240V. The generator's circuit breaker/OCP consistent with NEC 445.13.
iii. The genset would be connected to a MTS thus this application falls under Art. 702 (Optional Standby System) - not 590 (“"temporary installation") and would be grounded in accordance with this article. The genset would located in 10 feet proximity from meter & MTS in a backyard gated area of a residential single-family home - not visible to the public or neighbor(s) and more than 500 yards away from a public road.
iv. The neutral & ground NOT bonded (i.e. floating neutral/ungrounded neutral) thus it would be a nonseparately derived system (a.k.a. non-SDS).

5. The portable power cable would be in accordance with Table 400.4 lists "Portable Power Cable", 1-6 conductors, Type W as suitable for portable extra hard usage. Using a CABLE per Table 400.4 is an approved wiring method thus Art. 300.3(A) Single Conductors per Table 310.13 should not have to come into play via 300.1 (A) “All Wiring Installations. This article covers wiring methods for all wiring installations unless modified by other articles”. Simply put, the portable power cables are not conductors but under Art.300.1 (A) these cables are allowed as a wiring method. The portable power cables would be 2000V, 100A-400A rated to NEC table 400.5 (B).

I know that trailer mounted diesel gensets with cam-lock that are connects to residential homes is a real-world occurrence but I am not interested in what others are doing but rather what is in compliance w/ NEC standards?

50A-60A plugs/receptacle/cables are the norm & amp limit for portable gas generators but their amp limits would the throttle the capacity of a 36KW trailer mount diesel genset. Sure there are other high amp connectors solutions other than "Single-Pole Separable Connectors" such as pin and sleeve receptacles (e.g. Meltric) but due to cost considerations I want to determine the viability of cam-lock use for residential application.

I have requested an interpretation from AHJ but got nothing thus I was hoping I could get some feedback from the pros on this topic.

I appreciate any help,
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This is not official feedback but I do notice that a setup using Cam Lok or similar connectors leaves open the possibility that the neutral of a 120/240 volt circuit might be disconnected first leaving both hots connected and energized. This immediately produces the problem of an open neutral.

The same rationale leads to the requirement of approved transfer facilities for generator connections, so that "it must not be possible for both the generator and utility power to be connected to the same system at the same time."

So I can see the reason why Cam Lok connectors may be restricted to situations where only experienced professionals work with them.
Yep, these cam-lock quick-connect/break feeder splicing and terminating devices definitely have a greater safety risk associated than plugs-receptacles hence only “qualified person”/”experienced hands” argument and not for weekend warriors (whom may have too much beers). With 4 cam-lock connectors (L1, L2, N, G) there are many more moving parts (and safety risk) than a single plug-receptacle pair, such as dropping a hot in a water puddle while energized, dangerous sequencing of connect/break as you suggested, etc. There are some cam-lock related safety devices that have built-in safeguards that can minimized the risks, such as posi-loc (forced order sequencing of connect/break) or MTS that will not allow to connect/break connections until cables are deenergized ( BUT... much of the dangers could be avoid by taking the simple safety precaution of the deenergizing the cable prior to connect/break. That said, I can’t finds anything that says residential are probated ; I think I will connect a few companies that manufacture these cable-cam-lock the assembles – I am sure they will know code since it has legal implications for sellers of these goods.

These cam-lock locked contacts will withstand a pulling force of 1,000 lbs. I always found it odd that most portable gas generators =>12KW (e.g. Generac) utilize NEMA 14-50R 50a receptacles (paired with NEMA 14-50P straight blade plugs) versus using Hubble CS6364 twist-lock receptacles (like Honda gas portable and trailer mounted generators use), the twist-lock surely reduces the potential for plug-receptacle separation or the cable being kicked-out of the receptacle.
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