Auxiliary Gutter to Switchboard

[oceanobob]

As a long time reader of this forum: respectfully requesting some suggestions/ideas.

Have a new 1200 480vac freestanding switchboard to be mounted on a new concrete pad adjacent to an existing typical metal building (warehouse). Reason: present switchboard is a brand that is no longer manufactured: installed around 1970/1980, would like to change the voltage and also obtain more power for future loads.

Utility feed to new switchboard is underground.

Wish to bring power into the building using a vertical auxiliary gutter from the side (or end) of the new switchboard which has been furnished with a 26" extra space on the end next to the circuit breaker section [yes the busworks are shielded with a baffle]. Unit is 3R and don't wish to enter the top, thus the request for the side. The auxiliary gutter will be approximately 30" wide in elevation view and about 12" deep. Conductors will enter the lower portion of the side where it is quite adjacent to the switchboard and will exit via the back upper section where the raceway EMT conduits are in the peak of the building roof on a unistrut trapeze. Vertical length of auxiliary gutter is to be about 20 feet, maybe 22 feet.

Prior experience with this installation of panelboard to aux gutter has involved the use of Myers Hubs with a short close nipple. The auxiliary gutter method when compared to individual raceway conduits provides a clean/orderly installation, helps with wire pulling, etc. Other than the somewhat arbitrary 30 conductor rule with little alternative to the 31st circuit conductor (not control or signal) wire subjecting it all to derating :rant:, the auxiliary gutter accomplishes the task at hand and that extra space on the new switchboard will do so as well.

Here is the question: this switchboard has been labelled with the new [to me] Seismic (yes this project is in California) and it seems the use of about four or six of these 4" hub assemblies to connect the aux gutter to the switchboard will so to speak "lock" the switchboard to the auxiliary gutter. This may interfere with the seismic...some say it will improve it, some say install the aux gutter as low on the side as possible to minimize effect of the sway. The guideline manuals published on this topic are helpful to an extent but unfortunately don't show any conduit raceways attached to freestanding enclosures. Installing the hubs as low as possible isn't a good idea because once we fill this gutter to 30 conductors we will have to add another auxiliary gutter next to this one, thus we will want to save some "end of cabinet" and "lower end of auxiliary gutter" for later, thus the first to be used group of hubs must to be high enough in the auxiliary gutter to allow future space below so we can astutely avoid 30 conductors in any cross section; this will allow the next aux gutter a place to connect near the very bottom end of this first auxiliary gutter. These future conductors will pass through the bottom of the aux gutter and avoid the other 30...cant use nipples to go from panelboard to the second auxiliary gutter as the new gutter is at least 30" wide and that will break the rule of 24" for the short conduit raceway.

Attached is a picture of a similar switchboard (without the extra empty space) and an auxiliary gutter for some additional circuits installed to the circuit breaker section to help with my explanation. Thanks in advance.

 

[brantmacga]

Auxiliary Gutter to Switchboard

Weatherproof expansion couplings?

No field experience with seismic requirements but that's the first thing that came to mind.

This will require though your gutter to be installed a few inches off to the side of the switchboard. Actually more like 18" or so off to the side.

Cooper makes them up to 4" diameter, and no external bonding jumpers required.

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[Smart $]

Have you considered covered cable tray?

 

[oceanobob]

Not yet investigated about the covered cable tray and how it would address the differential movement of the switchboard and the building?

Have looked into using a few items of sealtight with a steel core although would want to keep the contrivances less than 24": said item in 4" size is a four foot diameter circle as the tightest bend, upon subtracting the collars on the fittings lucky to have 20" of flex to (try) form as an offset to allow some axial displacement as well as differential planar.
Another idea is something called a wireway nipple and a similar one with a round flange is called an auxiliary gutter swivel nipple, although these won't do much for axial displacement.

In elevation, the closer the connections are to the housekeeping slab, the less the deflection and am keeping this point in mind.

 

[oceanobob]

Fexible wireway

Fexible wireway

Continuing to search for and resolve information for my submittal(s).

Came across a Flexible Wireway fitting in the Cooper b line as well as likely a similar contrivance in the Hoffman catalog. B line has footnote indicating no UL nor CSA approval....however the item is described as Nema 12. Any experience with such? Am thinking about two or three of these to connect the switchboard to the aux gutter.

Other suggestions/ideas included the less than 24" oa length flexible metallic conduit (Sealtight name as lingo). Material seems unlikely to accomplish much of a shallow offset bend in this short of distance [offset being suggested in order to allow some axial displacement].