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#64520 04/09/06 01:54 PM
Joined: Jan 2003
Posts: 4,391
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Moderator
PDH for a guy who is not 'a code expert, nor an electrician', you do pretty good. [Linked Image]

I have actually in the past suggested (and was shot down) your idea of driving the circuit high. In my case we where asked to supply 24 volt camera power from a central point. The customer was quickly convinced to go to local power supplies.

However I think overdriving a circuit would be a violation.

Quote
110.4 Voltages.
Throughout this Code, the voltage considered shall be that at which the circuit operates. The voltage rating of electrical equipment shall not be less than the nominal voltage of a circuit to which it is connected.

It is also a questionable design as the load is not fixed, as lamps burn out the voltage will rise.

Call me conservative but site lighting has a long history and in my opinion re-inventing the wheel is not the best way to go.

I deal with site lights all the time.

The most common ways to deal with voltage drop are to use the highest voltage available and increase conductor size.

Many commercial buildings use 120 volt bollards around the perimeter, it is not uncommon for these circuits to be very long.

We don't place transformers at each one we just use larger conductors with 3 phase multiwire circuits and try to feed the middle.

Costs, complexity and reliability are key factors in the design.

IMO site lighting should be kept as simple and basic as possible.

JMO, Bob


Bob Badger
Construction & Maintenance Electrician
Massachusetts
#64521 04/09/06 02:11 PM
Joined: Mar 2005
Posts: 1,803
Member
Light emission from an incandescent bulb drops about 12% @ 3% v.drop, about 20% with @ 5% v.drop, and about 50% a@ 15% v.drop. Running a lamp below its design volts also changes the color of the light emitted toward yellow, and whatever the wattage bulbs chosen, variation will still be painfully obvious. The customer will notice.

Alan


Wood work but can't!
#64522 04/09/06 02:50 PM
Joined: May 2003
Posts: 2,876
E
e57 Offline
Member
Silly question: Is the service coming up this same 1200' driveway? If so, MM /w dist at the begining of the drive, with the recept, and 1/2 the lights controled via a contactor, the other 1/2 from the house.


Mark Heller
"Well - I oughta....." -Jackie Gleason
#64523 04/09/06 04:45 PM
Joined: Jan 2005
Posts: 155
D
Member
Ahhhh, Let's put this thing to bed. Hopefully this may be something you may have forgot about or say "why didn't I think of that." But, never the less I completely overlooked this approach.
Read on.........
One forgets about the problem that has been overcome with the lengthy runs or airport runway lighting. Have you ever thought about how they do that?
They use a ring type system but with transformers located at each light.
Think of 10 transformers, in this case, with their primaries wired in series, Line to H1 and H2-H1, H2-H1, etc and the last transformer H2- back to the source.
The source voltage must be sufficient to provide the correct voltage across the pri. of each transformer. The secondary of each transformer supplies power for the light.
Now your questions will be how high will the voltage have to be to supply this circuit?
How about using (10) 120-24v 150va transformers and use the to step up from 24-120v. Wire the (10) 24v secondaries in series, apply 240v to the series (ring) circuit which will provide 24v to each 24v winding to supply each 120v light. Every light will get exactly the same voltage. The only variable will be a load change if a light burns out the others would get a bit brighter.
This is all done with a simply 240v L-L supply using a 2p breaker. (10)common 150va 120-24v transformers are used and common 2w-w/G UF cable is used. All lights will have exactly the same voltage. Because the supply voltage is 240v the amperage will be 1/2 that of 120v and the wire sized for voltage drop accordingly.
Simple.

#64524 04/09/06 05:32 PM
Joined: Jan 2003
Posts: 4,391
I
Moderator
Dave airports have full time qualified personal to service the constant current systems.

I am hoping the other section was joking around as it seems exceedingly complicated and trouble prone just to run a few post lights that could simply be supplied like the millions installed already. [Linked Image] [Linked Image]

Bob


Bob Badger
Construction & Maintenance Electrician
Massachusetts
#64525 04/09/06 07:48 PM
Joined: Feb 2005
Posts: 693
L
Member
I'll say it again, but differently. Use the 3-wire setup, alternating phases for each post.

I'd run (as an example, not having done the math) #8 for the first third of the circuit, #10 for the second third, and #12 for the last third.


Larry Fine
Fine Electric Co.
fineelectricco.com
#64526 04/10/06 12:22 AM
Joined: Feb 2003
Posts: 687
A
Member
Did anyone have the idea yet of running the 10 120v bulbs in series on a 1200v circuit? It could be more fun then Christmas lights. Or how about a service for each lamp?

Just joking.
Multi wire it and start digging.

#64527 04/10/06 02:50 AM
Joined: Mar 2005
Posts: 1,803
Member
Having sorted out the circuit, how about using PIRs / delay timers to switch the lamps automatically- it would be neat if they preceded your progress up and down the drive, with maybe just 1st and last permanently on after dusk and a small LED at each position demarking the drive.


Alan


Wood work but can't!
#64528 04/10/06 05:44 AM
Joined: Jan 2003
Posts: 4,391
I
Moderator
Just lay 'rope lights' along the edges of the driveway and tell the landscapers not to hit them with mowers or plows. [Linked Image]


Bob Badger
Construction & Maintenance Electrician
Massachusetts
#64529 04/10/06 09:01 AM
Joined: Feb 2005
Posts: 693
L
Member
Alan, that's it! Motion sensors on each post, timed to turn back off seconds later. That way, only one light is on at a time. Voltage drop problem solved! (Well, reduced)


Larry Fine
Fine Electric Co.
fineelectricco.com
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