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Science Forum Index » Engineering - Lighting Forum » Substituting Two 24" lamps for One 48"
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| Zink |
 Posted: Fri Mar 02, 2007 11:32 pm |
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Does anyone have any comments on using 2 24" lamps, in series, in
place of a single 48" lamp of the same type (T8, T12)? And this is
with an electronic ballast. How is it different than using a single
lamp?
I am actually asking this because some people, one claiming to be an
electrician, say this is really unsafe. I happen to be sure it is
perfectly safe, if properly wired, and have done this many times.
Haven't some of you former lighting engineers done variations on this?
By the way, I actually know this is perfectly safe with an electronic
ballast, but what about a magnetic ballast? I myself would not choose
to use a magnetic ballast for that, but if done, would that absolutely
require the lengths to add up to be safe (2-24" = 48")?
Ron Seadler |
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| Andrew Gabriel |
| Posted: Sat Mar 03, 2007 6:32 am |
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In article <1172892754.240661.245110@n33g2000cwc.googlegroups.com>,
"Zink" <rons@louintlairport.com> writes:
Quote: Does anyone have any comments on using 2 24" lamps, in series, in
place of a single 48" lamp of the same type (T8, T12)? And this is
with an electronic ballast. How is it different than using a single
lamp?
I am actually asking this because some people, one claiming to be an
electrician, say this is really unsafe. I happen to be sure it is
perfectly safe, if properly wired, and have done this many times.
Haven't some of you former lighting engineers done variations on this?
By the way, I actually know this is perfectly safe with an electronic
ballast, but what about a magnetic ballast? I myself would not choose
to use a magnetic ballast for that, but if done, would that absolutely
require the lengths to add up to be safe (2-24" = 48")?
It's standardly done with two 24" tubes in 240V countries on a 48"
series ballast, using a glow starter per tube. There's not enough
voltage headroom on 120V for this simple control gear, so I can't
comment on what would happen with your more complex 120V control
gear.
--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup] |
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| Clive Mitchell |
| Posted: Sat Mar 03, 2007 1:50 pm |
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In message <1172892754.240661.245110@n33g2000cwc.googlegroups.com>, Zink
<rons@louintlairport.com> writes
Quote: Does anyone have any comments on using 2 24" lamps, in series, in place
of a single 48" lamp of the same type (T8, T12)? And this is with an
electronic ballast. How is it different than using a single lamp?
I am actually asking this because some people, one claiming to be an
electrician, say this is really unsafe. I happen to be sure it is
perfectly safe, if properly wired, and have done this many times.
Haven't some of you former lighting engineers done variations on this?
By the way, I actually know this is perfectly safe with an electronic
ballast, but what about a magnetic ballast? I myself would not choose
to use a magnetic ballast for that, but if done, would that absolutely
require the lengths to add up to be safe (2-24" = 48")?
It's not as simple as just slapping two tubes in series and adding the
inches. Each set of electrodes introduces a significant cathode voltage
meaning that depending on how the ballast drove the tube it may result
in the output of the electronic ballast running at a voltage it was not
designed for.
The technique for running two 24" tubes on one ballast is used in the UK
with suitable 110V glow starters and a ballast rated for the job. It's
a cheap and nasty economy move that results in excessive flickering and
flashing when one tube fails.
How were you panning on wiring the two tubes to the electronic ballast?
--
Clive Mitchell
http://www.bigclive.com |
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| Victor Roberts |
| Posted: Sun Mar 04, 2007 12:17 am |
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Guest
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On 2 Mar 2007 19:32:34 -0800, "Zink"
<rons@louintlairport.com> wrote:
Quote: Does anyone have any comments on using 2 24" lamps, in series, in
place of a single 48" lamp of the same type (T8, T12)? And this is
with an electronic ballast. How is it different than using a single
lamp?
I am actually asking this because some people, one claiming to be an
electrician, say this is really unsafe. I happen to be sure it is
perfectly safe, if properly wired, and have done this many times.
Haven't some of you former lighting engineers done variations on this?
By the way, I actually know this is perfectly safe with an electronic
ballast, but what about a magnetic ballast? I myself would not choose
to use a magnetic ballast for that, but if done, would that absolutely
require the lengths to add up to be safe (2-24" = 48")?
Ron Seadler
I'm not sure why it would be unsafe, but in many cases the
lamps might not start.
If you had an instant start system then the lamps should
start, though as others have stated the operating voltage of
a 2-foot lamp is more than half the operating voltage of a
4-foot lamp due to the electrode voltage drops and the
combination might not run properly under low line voltage
conditions.
If you had a European switch start type system and each lamp
had its own starter, then it would also work.
However, if you had a US-style rapid start system the lamps
would most likely not start, or at least not start properly,
since one electrode on each lamp would not have any external
heating power.
--
Vic Roberts
http://www.RobertsResearchInc.com
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