[BC] to fluorescents

[Mike McCarthy]

A design EE friend told me the origins of using 277 for lighting came about 
when fluorescent space lighting became wide spread in LARGE office 
buildings using 480V as the primary building service. Gone were location 
specific task lighting fixtures.  Obviously, they wanted as many new 
fixtures on a single circuit and switch or contactor as practically 
possible without going to oversized conductors....which one would need to 
do with as few as 25 fixtures at 120V. With 277, I seem to recall up to 60 
two "U-tube" fixtures can be on a single 20A circuit.

That and why transform down (wasted heat and added costs) something which 
doesn't {{need}} to operate at 120/208.

In Chicago, 277 and 120 can not share anything.  They need to be in 
separate boxes and conduits.

AFAIK, 277 is classed as a 600V service because of the phase to phase 
voltage between the conductors.

MM

At 06:58 AM 10/31/2007 -0600, Gary Glaenzer wrote
>yes, but with 277 V, the requirement for barriers between adjacent switches
>(as an example) does not come into play
>
>I have no idea what other 'high voltage requirements' might be bypassed by
>using 277 V, however
>
>
>----- Original Message -----
>From: "Mike McCarthy" <Towers at mre.com>
>To: "Broadcasters' Mailing List" <broadcast at radiolists.net>
>Sent: Tuesday, October 30, 2007 10:41 PM
>Subject: Re: [BC] to fluorescents
>
>
> > I would disagree with that 300V conclusion Peter.  Most 277 installations
> > carry more than one phase in a conduit and come from a 600V class load
> > center or panel. Therefore the all equipment and cabling used on that
> > circuit would be subject to the 600V requirement. I know here the second
> > 277/480 enters the picture nothing below 600V class equipment is allowed
> > until a derived service of 240 or 208/120 is realized down stream.  At
> > which point, 240V rated equipment is permitted on for those downstream
> > circuits.
> >
> > That and you can't mix 120/208 and 277/480 circuits in the same conduit
> > since they do not share a common overload/control point.
> >
> > Been there done it many times....
> >
> > MM.
> >
> > At 07:06 PM 10/30/2007 -0700, PeterH5322 wrote
> >
> > > >> I'll bet it was 277/480 fluorescents and not 120/240.
> > > >>
> > > >please elaborate
> > >
> > >Many older installations had 120 for lighting, regardless of the service,
> > >even if it required a customer-owned "dry type" transformer.
> > >
> > >Most new installations are 277/480 Y, and the fluorescent lighting is
> > >277, which is still "300 volt class", as is 120 volts, so the same wiring
> > >methods and materials may be employed, yet there is no need for a
> > >customer-owned transformer.
> > >
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