Limits on Plug-in Multi-Outlet Assemblies

[DataCenterGuy]

Is there an NEC limitation on attaching Cord and Plug-connected Multi-outlet Assemblies to other Cord and Plug-connected devices? I can't find one, but am being told (without reference) that there is.

Specifically, this question arose with regard to the connection of asecured, in-rack multi-outlet strip to a rack-mounted UPS which has chassis-mounted receptacles and is, in turn, plugged into a legal twist-lock receptacle. The UPS may or may not contain an isolation transformer, so may not be a separately derived source.

This happens to be an AV application, but does not seem to be prohibited, or specifically permitted, anywhere, including Article 640. But it could also be as simple as unsecured multi-outlet strips strung across a table top for something like temporary classroom PC instruction.

 

[raider1]

This would be covered under 110.3(B).

A "multi outlet strip" is called a relocatable power tap according to UL.

A relocatable power tap is not listed to be plugged into another relocatable power tap (daisy chained).

Here is what the UL white book says about relocatable power taps;

RELOCATABLE POWER TAPS (XBYS)
Relocatable Power TapsXBYSUSE AND INSTALLATION
This category covers relocatable power taps rated 250 V ac or less, 20 A or less. They are intended for indoor use as relocatable multiple outlet extensions of a single branch circuit to supply laboratory equipment, home workshops, home movie lighting controls, musical instrumentation, and to provide outlet receptacles for computers, audio and video equipment, and other equipment.
Relocatable power taps consist of:
a) One attachment plug and a single length of flexible cord terminated in a single enclosure in which one or more receptacles may be mounted, or
b) One attachment plug and a single length of flexible cord terminated in a single enclosure in which one or more receptacles may be mounted. Up to six lengths of flexible cord, not exceeding 1-1/2 ft in length, may exit the enclosure with each length terminating in a separate, single cord connector, or
c) One attachment plug and a single length of flexible cord terminated in an enclosure in which one or more receptacles may be mounted. A second enclosure in which one or more receptacles may be mounted that is interconnected to the first enclosure with flexible cord, maximum 1-1/2 ft long, may be employed. An interconnected switch housing may also be employed to remotely control the relocatable power tap, provided that the length of the flexible cord between the enclosure and switch housing is not greater than 6 ft.
They may, in addition, be provided with fuses or other supplementary overcurrent protection, switches, suppression components and/or indicator lights in any combination, or connections for cable, communications, telephone and/or antenna.
Relocatable power taps are intended to be directly connected to a permanently installed branch circuit receptacle. Relocatable power taps are not intended to be series connected (daisy chained) to other relocatable power taps or to extension cords.
Relocatable power taps are not intended for use at construction sites and similar locations.
Relocatable power taps are not intended to be permanently secured to building structures, tables, work benches or similar structures, nor are they intended to be used as a substitute for fixed wiring. The cords of relocatable power taps are not intended to be routed through walls, windows, ceilings, floors or similar openings.
The length of the power-supply cord, as measured from the outside surface of the enclosure of the relocatable power tap to the plane of the face of the attachment plug, should not exceed 25 ft (7.62 m) nor be less than 1.5 ft (0.46 m).
Relocatable power taps have not been investigated and are not intended for use with general patient care areas or critical patient care areas of health care facilities as defined in Article 517 of ANSI/NFPA 70, "National Electrical Code."

Chris

 

[DataCenterGuy]

Certainly answers stringing these things together, which had to be prohibited somewhere, but now know why it couldn't be found specifically in NEC. Thanks.

But does this really also apply to a fuse or breaker-protected high-end strip plugged into a fuse or breaker protected rack-mount UPS that is plugged into a breaker-protected permanent receptacle, all with proper ratings and cordage?

 

[wireguru]

Certainly answers stringing these things together, which had to be prohibited somewhere, but now know why it couldn't be found specifically in NEC. Thanks.

But does this really also apply to a fuse or breaker-protected high-end strip plugged into a fuse or breaker protected rack-mount UPS that is plugged into a breaker-protected permanent receptacle, all with proper ratings and cordage?

To expand on that, I wonder if manufacturers such as APC have their UPS and power distribution listed as a 'system' so the rackmount power switches and remote reboot devices can be plugged into eachother and into a UPS.

 

[DataCenterGuy]

Not sure, but after this enlightenment on the topic, I'm going to find out. Stand by.

 

[nhfire77]

Certainly answers stringing these things together, which had to be prohibited somewhere, but now know why it couldn't be found specifically in NEC.

OSHA has something to say about it too. I've seen it pointed out on an OSHA visit. Read this bulletin:

http://www.compliance.gov/forms-pubs/eresources/fastfacts_daisychains.pdf: