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Science Forum Index » Engineering - Lighting Forum » voltage drop and dimmable fluorescent ballasts...
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| hrlight... |
 Posted: Wed Jun 25, 2008 4:06 am |
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I designed a small light industrial shop recently where I needed to be
talking with the electrician of the job and not an electrical
engineer. I specified dimmable ballasts in a fluorescent system of 6
8' T8 single row fixtures. The electrician told me he was unable to
wire it in sequence (daisy chained) because the distances between
fixtures were too great; and that he worried about voltage drop. I
have never heard this before. Was he mistaken and confused low
voltage with the electronic ballasts used for fluorescents? Or, is
there something I should understand/ I have looked this up in my
books and the web and have not found anything about this. Am I
ignorant? Thanks for your help. |
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| NeilCarmichael... |
| Posted: Wed Jun 25, 2008 6:37 am |
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On Jun 25, 3:06 pm, hrlight <hrli... at (no spam) gmail.com> wrote:
Quote: I designed a small light industrial shop recently where I needed to be
talking with the electrician of the job and not an electrical
engineer. I specified dimmable ballasts in a fluorescent system of 6
8' T8 single row fixtures. The electrician told me he was unable to
wire it in sequence (daisy chained) because the distances between
fixtures were too great; and that he worried about voltage drop. I
have never heard this before. Was he mistaken and confused low
voltage with the electronic ballasts used for fluorescents? Or, is
there something I should understand/ I have looked this up in my
books and the web and have not found anything about this. Am I
ignorant? Thanks for your help.
I think your electrician friend may be a little confused, make sure he
understands to use a six-core mains cable (for simplicity and
flexibility) and it should be fine.
I recently did an install where there were 15 1-10v dimmable fixtures
over a stage and 30 DSI fixtures over a sports hall no problem at all,
it is quite normal to have a long run for the control cable in a scene
set system as the location of the controller is often away in a switch
room.
The reason to recommend six core cable is you cover all bases by
provided a constant line for the emergencys as well as a data pair all
in a single flex which is easier for the electrician to handle and by
using a pair of mains cables for data you side step volt-drop issues
you.
The only dimmable florescent protocol that is highly sensitive to volt-
drop is DALI which is why cables with a cross-sectional area of 1.5mm
and above is often recommended by manufacturers |
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| RickR... |
| Posted: Wed Jun 25, 2008 1:40 pm |
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On Jun 25, 7:06 am, hrlight <hrli... at (no spam) gmail.com> wrote:
Quote: I designed a small light industrial shop recently where I needed to be
talking with the electrician of the job and not an electrical
engineer. I specified dimmable ballasts in a fluorescent system of 6
8' T8 single row fixtures. The electrician told me he was unable to
wire it in sequence (daisy chained) because the distances between
fixtures were too great; and that he worried about voltage drop. I
have never heard this before. Was he mistaken and confused low
voltage with the electronic ballasts used for fluorescents? Or, is
there something I should understand/ I have looked this up in my
books and the web and have not found anything about this. Am I
ignorant? Thanks for your help.
Voltage drop is very real, but shouldn't effect this situation unless
there is something weird going on. If you look up landscape lighting
they will talk about it. Basically it's just the internal resistance
of the wire lowering the amperage you can put through it, at least
without melting something. The solution for voltage drop is to use
larger wire.
Perhaps he is confusing the low voltage dimming signal with the power
to run the lights. If he is confusing "daisy chaining" fixtures with
series wiring you need a new electrician.
Just how small is this shop, and what wattages & voltages are we
talking about?
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RickR |
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| hrlight... |
| Posted: Sun Jun 29, 2008 1:09 pm |
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On Jun 25, 7:40 pm, RickR <r... at (no spam) silhouettelights.com> wrote:
Quote: On Jun 25, 7:06 am, hrlight <hrli... at (no spam) gmail.com> wrote:
Perhaps he is confusing the low voltage dimming signal with the power
to run the lights. If he is confusing "daisy chaining" fixtures with
series wiring you need a new electrician.
Just how small is this shop, and what wattages & voltages are we
talking about?
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RickR
Yes, it was an odd conversation. The shop room is nom 20' x 20';
wired 120 V. The lamps are (12 ) T8 30W (32W equiv) and I requested
to connect the two linear runs installed on opposing walls (20'
apart). Because of the added expense of ballasts and work time the
owner opted not to use the ballasts and dimmers. We decided to set
the fixture runs on individual switches. My feeling is that the
electrician did not want to run the cable.
I thank you both for the information. |
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