Low voltage cable lighting

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Jesse7623

Senior Member
Location
eastern Mass
I am on a job where the lighting designer is specifying a 2 inch diameter opening on a box that serves a 12 volt track/cable lighting strip.The load is about 300 watts and the xformer is about 40 feet away.In this case the xformer/lighting manufacturer recomend either 1 AWG or 1/0 copper.How in the world can I make up a 1/0 conn. in a 2 inch dia. mud-ring?
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
Sometimes there is no way to install something that has been poorly designed. In your case the transformer needs to be very close to the hole so that you can use smaller conductors or the designer needs to come up with a better plan. For what it's worth we run into this problem quite often when dealing with LV lighting and designers who just don't understand the problems associated with running 12v long distances.
 

iwire

Moderator
Staff member
Location
Massachusetts
Sometimes there is no way to install something that has been poorly designed. In your case the transformer needs to be very close to the hole so that you can use smaller conductors or the designer needs to come up with a better plan. For what it's worth we run into this problem quite often when dealing with LV lighting and designers who just don't understand the problems associated with running 12v long distances.
Well put.

I agree, you want to place the transformer as close as possible to the fixture.
 

Jesse7623

Senior Member
Location
eastern Mass
Alright thanks guys, the only issue now for me is that the designer just now got me the specs.and the insulators start this afternoon....well oops.:cool:hmm
 

Sierrasparky

Senior Member
Location
USA
Occupation
Electrician ,contractor
I don't see how a 300 watt load at 12 volt would require 1/0 wire.
Hey your 12 starter on you car is cabled with #4 or #2 . starters consume more than 300 watts.
Is this a solid state transformer?
 

Jesse7623

Senior Member
Location
eastern Mass
well the first thing is that the length of wire is in the 31 to 40 foot category. And the starter does not run continuosly.The transformer is magnetic.
 

Sierrasparky

Senior Member
Location
USA
Occupation
Electrician ,contractor
did anyone try that low voltage calculator.
Well I did
# 8 or 10 should work .
as I felt earlier # 1 for 300 watts.
I'm gonna buy a copper mine!:smile:
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
did anyone try that low voltage calculator.
Well I did
# 8 or 10 should work .
as I felt earlier # 1 for 300 watts.
I'm gonna buy a copper mine!:smile:
I tried it and it wouldn't work presumably because the wire size ended up being too large:

You choose: 12 Voltage, 80 Feet, and 300 Wattage, with a 1.5 drop multiplier.

Minimum Cable Constant = 30000


This is not a recommended circuit.
Try recalculating using either an increased voltage, decreased distance, or decrease wattage.


 

hardworkingstiff

Senior Member
Location
Wilmington, NC
I checked the VD on the spreadsheet I use and to get the VD under 10% you will need #6 wire. #4 gets you very very close to 5%.


With low voltage lighting, I don't believe VD is as critical as it is in AC with motors. The lights just burn dimmer, but they will last longer.

If you have a better transformer, you might have mulitple secondary voltages to use and maybe you could use a slightly higher voltage and a #10 wire?
 

benaround

Senior Member
Location
Arizona
Jesse7623,

As for how to connect the 12v supply to the fixture, after reading 411.3 (A)&(B), IMO it

would be on the manafacture to supply the 'listed' part. I'm not 100% sure of that.
 

charlietuna

Senior Member
When you have a problem like this it's time to consider locating the transformer next to the junction box. Thats why they make fire rated access doors for drywall. We had a millionaire customer who had an eye desease that he required more and more light to be able to see--eventually he would be blind. But he contacted a fixture rep(A CROOK) that specified "Lucifer Lighting" which are low voltage lighting tracks, and this was the method to control general lighting throughout a double penthouse apartment where they could be controlled thru dimmers, and we had no other choice but to remote the transformers. The lamp life is terrible and they are very ,very expensive --the millionaire was upset about it--something like 700 hours.
 
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