I have a 24 volt monorail track lighting system. It consists of a 120v single pole switch(that will eventually be changed to a dimmer)that turns on a 1000va 120/24V transformer. On the secondary side I ran #10 MC cable about 10 feet to a J-Box. At the J-Box I connected to the track power feed. Before I enegized the track i tested the output voltage and it read 27v.The track power feed cable drops down about 10 feet to the track.The track is about 14 feet long with 200 watts of load connected. When i turn on the transformer the secondary wire insulation starts to melt off(takes about 30 seconds). When i turned on the transformer the lights didn't come on either. Any idea of what is wrong?
24 volt lighting wires melting
- Thread starter gregorsc
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LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Short circuit.gregorsc said:
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
I agree it's a short. Check the field made connections-- also take off all the tracks and see if the same scenario exist. It could be in one of the tracks. What brand monorail are you using???
- Location
- New Jersey
- Occupation
- Journeyman Electrician
Ditto the short circuit. Check the track first without anything attached to it, then check each light to see where the short is.
RUWIREDRITE
Senior Member
- Location
- PA, Business' in NJ/PA
Transformer
Transformer
Perhaps a short yes, but how did you tie in the transformer? perhaps and overlooked connection?
Transformer
Perhaps a short yes, but how did you tie in the transformer? perhaps and overlooked connection?
jack horner
Banned
- Location
- America
Yes perhaps a short, perhaps.RUWIREDRITE said:
Pierre C Belarge
Senior Member
- Location
- Westchester County, New York
What about secondary protection of the 1000va transformer?
Pierre C Belarge
Senior Member
- Location
- Westchester County, New York
Bump!
Bump!
I am curious as to the secondary protection for these type transformers.
Anyone Biting???
Bump!
I am curious as to the secondary protection for these type transformers.
Anyone Biting???
Pierre C Belarge
Senior Member
- Location
- Westchester County, New York
Gregorsc
Was that a toroidal type transformer? Or was it a transformer supplied with the lighting? Or did you purchase the tranformer separately?
Do you know the model/make of the transformer?
Am I making it hard to see that I am very interested in this thread
Was that a toroidal type transformer? Or was it a transformer supplied with the lighting? Or did you purchase the tranformer separately?
Do you know the model/make of the transformer?
Am I making it hard to see that I am very interested in this thread
- Location
- Bremerton, Washington
Is this an Art 411 type system that you have assembled from various parts?
Sorry I was gone so long. To answer some of the questions I purchased this transformer separatley.It's an ACME brand 120/24v 1 phase transformer.I tied the transformer into the circit with MC cable 12-2 coming in and 10-2 going out to a j-box. At the j-box the mc splices to the power feed cable that came with the fixtures and track. The power feed is like a heavy duty lamp cord rated for 25 ampsat the track connection end is a "shiny crome looking clamp " that clamps around the monorail track. The fuxtures connect in a similar fashion. I did notice that the track cable was very warm and the outer jacket was melting but the metal shiny clamp was not warm at all. Since my lights didn't come on I figure the short could be in the cord itself.The insulation on the mc cable wires had melted off in some spots. Before I connected the track power cable i tested the output voltage and didn't notice any insulation damage then. So i t sounds like the track power cable could be the problem.
- Location
- Bremerton, Washington
If this is an Art 411 application it has to be a listed system. If you assemble with parts you purchase then its not a listed system.
Since your system exceeds the power and voltage limits of a Art 725 Class II system, it needs to be installed with a chapter 3 wiring method on the secondary and transformer protection per 445.
Just because its low voltage does not mean its safe from fire or shock.
Since your system exceeds the power and voltage limits of a Art 725 Class II system, it needs to be installed with a chapter 3 wiring method on the secondary and transformer protection per 445.
Just because its low voltage does not mean its safe from fire or shock.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Sounds to me like either the #10-to-track connection or the track itself is shorted. Remove all wires and fixtures and check for continuity between track rails; it should measure as an open circuit (no continuity). If that checks okay, reconnect the #10 and check for the same at the transformer end.gregorsc said:
dbuckley
Senior Member
- Location
- Canterbury, New Zealand
Because... the fact the transformer output is working into a short doesn't mean the input is shorted, just that the input is drawing sufficient line current to equal the output power of the transformer. With these sorts of transformer, the design is such that the output power capability is deliberately limited.gregorsc said:
So your transformer is 1KW at 24V, so the output current at full load is something like 42A. So just full load current will be a handful for a #10. (I note that the estimated load will be 200W, rather than 1K, so under those circumstances the #10 is adequate, as long as the volt drop not excessive. Perhaps the transformer is too big for the job at hand, though I appreciate that economics has a part to play here)
Now lets short the thing out. Let's say under short conditions, given the resistance of the #10 from the tranny to the fault, the tranny can deliver 100A, the power drawn from line is then about 2KW, so about 20A at 120V. Your 20A breaker will stay closed all day, meanwhile the #10 with 100A through it drips away...
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- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
gregorsc said:
It will burn out the transformer on the low voltage side before it will trip the high voltage breaker. If you fuse the secondary I bet it will pop immediately.
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