Re: 277 volt vs 120 volt lighting

[Frank White]

If the building has a 480V/277V service and you have a lot of lights
to install, then the contractor can use smaller wire with 277V
lighting but will have to use more expensive lighting panels.
Also you will not be putting the extra current load on your existing
step down transformers if you use 277V.

I would talk to the contractor and the owner and ask them each to
present thier case. As far as the lighting goes, there really isnt
much difference. 120V installations tend to be cheaper and safer
if you have enough power at that voltage.

I have a new small commercial building being designed and the building
owner wants 277 volt lighting and the electrical contractor would like
120 volt lighting. What are the advantages and disadvantages of both
systems? Help! Thank you.

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[Bob Ferapples]

If the building has a 480V/277V service and you have a lot of lights
to install, then the contractor can use smaller wire with 277V
lighting but will have to use more expensive lighting panels.
Also you will not be putting the extra current load on your existing
step down transformers if you use 277V.

I would talk to the contractor and the owner and ask them each to
present thier case. As far as the lighting goes, there really isnt
much difference. 120V installations tend to be cheaper and safer
if you have enough power at that voltage.




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And conversely, if you don't already have a 480/277V service, 277V
lighting make no sense at all. It is mainly a convenience for
facilities that have 3 phase 480V 4 wire service because phase to
neutral is 277V, so no transformer is needed. If your facility has 1
phase service, or 208V 3 phase service, then 120V lighting is what you
want. The electrician probably already knows this. The owner probably
has no clue.

 

[Ryan Evans]

Is the 480V a wye (3 phase + neutral)? If so, you don't need a transformer
for the 277.

RE

 

[SQLit]

The building does have 3 phase 480 volt...so a transformer is needed
but whether 277V or 120V lights a transformer would be required.
Correct?
Is there a cost savings on initial cost of 277V lights vs 120V lights?
Is there life cycle cost savings? Thank you.

Your missing the point. if the service is 480 3 phase then you need a
transformer for the 120 loads. depending on the load on the transformer the
lighting might push it up one size.

other than losses through the transformer to step down the voltage to 120 I
am not aware of any real difference.

With out a intimate knowledge of the installation and rate structure and a
couple of hundred other things I know of no good way to make a
recommendation.

Fixtures will cost the same no matter what voltage you buy.

 

[Beachcomber]

Your missing the point. if the service is 480 3 phase then you need a
transformer for the 120 loads. depending on the load on the transformer the
lighting might push it up one size.

other than losses through the transformer to step down the voltage to 120 I
am not aware of any real difference.

With out a intimate knowledge of the installation and rate structure and a
couple of hundred other things I know of no good way to make a
recommendation.

Fixtures will cost the same no matter what voltage you buy.

The main advantage of 277V. lighting circuits (assuming 277V is
readily available) is that you have less voltage drop, the means to do
longer runs (from panelboard to fixture), and more fixtures can be
attached per circuit breaker (vs. 120V lighting circuits). In the
long run, if done properly, this leads to economies of scale and
allows for a cheaper, more economical, and efficient installation.

The 277V. circuits use less current (for equal amounts of light on
the equivalent 120V circuits) and you may be able to get away with
installing a smaller lighting panelboard than otherwise might be
necessary.

Beachcomber

 

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| The main advantage of 277V. lighting circuits (assuming 277V is
| readily available) is that you have less voltage drop, the means to do
| longer runs (from panelboard to fixture), and more fixtures can be
| attached per circuit breaker (vs. 120V lighting circuits). In the
| long run, if done properly, this leads to economies of scale and
| allows for a cheaper, more economical, and efficient installation.
|
| The 277V. circuits use less current (for equal amounts of light on
| the equivalent 120V circuits) and you may be able to get away with
| installing a smaller lighting panelboard than otherwise might be
| necessary.

To clarify, you could have more lights on the same circuit, reducing the
number of circuits and thus the number of slots in the panel. The higher
voltage panels are slightly larger for the same number of circuits when
compared to the 3/4 inch Square-D QO/NQOD and Cutler-Hammer CH series if
you went with 208/120 for everything. For 480/277 you would use panels
like Square-D NF or Cutler-Hammer PRL2.