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  #81  
Old 01-30-2009, 11:58 AM
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INTEGRA Bespoke Lighting INTEGRA Bespoke Lighting is offline
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Well I have posted over 2000 times on this forum, and I have to say that this thread is probably the worst yet. Even "Pete's" participation was better then this drivel.

Jimmy, you do what you need to do, and the rest of us will do what we know is right.

Now, can we end this?
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  #82  
Old 01-30-2009, 09:26 PM
jimmy1111 jimmy1111 is offline
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Quote:
Originally Posted by INTEGRA Works Lighting View Post
Well I have posted over 2000 times on this forum, and I have to say that this thread is probably the worst yet. Even "Pete's" participation was better then this drivel.

Jimmy, you do what you need to do, and the rest of us will do what we know is right.

Now, can we end this?
James...go your rocket science LED made-up already !!!...we are all expecting free 20 LED supplies ...or you need to chip some your canadian stack to this site by now after 2000 posts for your LED...let's admit it you owe it to this site
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  #83  
Old 01-30-2009, 09:47 PM
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INTEGRA Bespoke Lighting INTEGRA Bespoke Lighting is offline
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Pardon me? Perhaps you could re-state that in english?
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  #84  
Old 01-31-2009, 12:08 AM
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TXNSLighting TXNSLighting is offline
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Quote:
Originally Posted by INTEGRA Works Lighting View Post
Pardon me? Perhaps you could re-state that in english?
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  #85  
Old 01-31-2009, 10:22 AM
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Chris J Chris J is offline
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Bartender, I'll have another.
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  #86  
Old 01-31-2009, 10:30 AM
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Make that a double.
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  #87  
Old 01-31-2009, 01:18 PM
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Venturewest Venturewest is offline
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Quote:
Originally Posted by jimmy1111 View Post
Geesh guys......just asking a simple question on how you calculate VD's when you loop your runs...
Okay Jimmy, I am going to be nice and answer this question once and for all and hopefully end this thread. I apologize in advance if this has been answered somewhere in the previous 9 pages!!!!

A widely accepted formula for calculating voltage drop is:

Vd= Length x Watts/ Cable Constant

There is a chart that lists the cable constants for low voltage cable: I will list the relevant few:

#12 CC is 7500
#10 CC is 11920
#8 CC is 18960

If you use the loop method and come back to the transformer you are effectively using 2 runs of 12 gauge wire. This is a common meathod, not a big deal.

You end up with a wire constant of 15,000

So, 2 x 12 gauge has less drop than 10 gauge but a little more than 8 gauge.

If you do one of your examples:
250 Watts at 100' and run a 12 gauge loop then formula as follows.

100' x 250/ 15000 = 1.67 volts as your drop
That is basically what you came up with.

As you can see the loop isn't magic and it also isn't intrinsically evil. It doubles your wire.

One thing to keep in mind is that you still can't exceed the amps for your wire but you seem to know that.

Also, you could just have 2 separate runs of 12 gauge, say one runs to 3 lights and the other runs to 3 lights instead of a loop that runs to all 6.

One other thing to note also. This is a parallel circuit as is every other method of wiring in low voltage AC. Same as in a home.

The only way to effectively combat VD is with antibiotics. But Vd can be dealt with using effective wiring methods.
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  #88  
Old 01-31-2009, 01:29 PM
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Venturewest Venturewest is offline
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One more note. 12 gauge wire is only rated at 20 Amps. That is 240 Watts at 12 volts of course.

I guess NEC requires any electrical device operating 3 hours or more to be derated to 80% capacity. (I got this out of Unique's lighting manual)
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  #89  
Old 02-01-2009, 07:40 AM
jimmy1111 jimmy1111 is offline
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Quote:
Originally Posted by Venturewest View Post
Okay Jimmy, I am going to be nice and answer this question once and for all and hopefully end this thread. I apologize in advance if this has been answered somewhere in the previous 9 pages!!!!

A widely accepted formula for calculating voltage drop is:

Vd= Length x Watts/ Cable Constant...I thought all along the VD formula was/is: VD = 2 X Length X Watts/Cable Constant....that's also reflected in Joey D's formula and few other sources and manuals I saw. The factor of 2 is missing from your formula...now i'm puzzled...also from the fxl wire gauge tables the factor of 2 seems to have been included.

There is a chart that lists the cable constants for low voltage cable: I will list the relevant few:

#12 CC is 7500
#10 CC is 11920
#8 CC is 18960

If you use the loop method and come back to the transformer you are effectively using 2 runs of 12 gauge wire. This is a common meathod, not a big deal....Thank you...almost everyone made it sound like out of space.

You end up with a wire constant of 15,000

So, 2 x 12 gauge has less drop than 10 gauge but a little more than 8 gauge.

If you do one of your examples:
250 Watts at 100' and run a 12 gauge loop then formula as follows.

100' x 250/ 15000 = 1.67 volts as your drop
That is basically what you came up with.

As you can see the loop isn't magic and it also isn't intrinsically evil. It doubles your wire.

One thing to keep in mind is that you still can't exceed the amps for your wire but you seem to know that.

Also, you could just have 2 separate runs of 12 gauge, say one runs to 3 lights and the other runs to 3 lights instead of a loop that runs to all 6.

One other thing to note also. This is a parallel circuit as is every other method of wiring in low voltage AC. Same as in a home.

The only way to effectively combat VD is with antibiotics. ...where do i pt that darn pill? on top of the fixture ???...just kidding. But Vd can be dealt with using effective wiring methods.

Thanks for the details....but the VD seems to be conflicting with other sources.
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  #90  
Old 02-03-2009, 10:26 AM
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JoeyD JoeyD is offline
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Quote:
Originally Posted by Venturewest View Post
Okay Jimmy, I am going to be nice and answer this question once and for all and hopefully end this thread. I apologize in advance if this has been answered somewhere in the previous 9 pages!!!!

A widely accepted formula for calculating voltage drop is:

Vd= Length x Watts/ Cable Constant

There is a chart that lists the cable constants for low voltage cable: I will list the relevant few:

#12 CC is 7500
#10 CC is 11920
#8 CC is 18960

If you use the loop method and come back to the transformer you are effectively using 2 runs of 12 gauge wire. This is a common meathod, not a big deal.

You end up with a wire constant of 15,000

So, 2 x 12 gauge has less drop than 10 gauge but a little more than 8 gauge.

If you do one of your examples:
250 Watts at 100' and run a 12 gauge loop then formula as follows.

100' x 250/ 15000 = 1.67 volts as your drop
That is basically what you came up with.

As you can see the loop isn't magic and it also isn't intrinsically evil. It doubles your wire.

One thing to keep in mind is that you still can't exceed the amps for your wire but you seem to know that.

Also, you could just have 2 separate runs of 12 gauge, say one runs to 3 lights and the other runs to 3 lights instead of a loop that runs to all 6.

One other thing to note also. This is a parallel circuit as is every other method of wiring in low voltage AC. Same as in a home.

The only way to effectively combat VD is with antibiotics. But Vd can be dealt with using effective wiring methods.
you need to multiply by 2.........
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