What transformer will I need for this to work?

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  #1  
Old 04-19-12, 06:30 AM
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Question What transformer will I need for this to work?

Hi all,

I have a set of track lights with the following setup:

- 5 lights 20 watts each
- A transformer (model DA-105-12T by TDC) with the following specs:
--- Input: 120VAC 60Hz 120VA
--- Output: 12VAC 8.75A 105VA

My question is the following: if I want to increase to 10 lights (same 12V/20W bulbs), what transformer will I need?

Thanks
 
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  #2  
Old 04-19-12, 06:49 AM
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That would be 200 watts, ~17amps, 200VA. I'd suggest at least a 20 amp, 240VA transformer to allow for line losses. Keep in mind voltage drop can be critical on low voltage circuits so wire gage may need to be increased or transformer placed mid circuit.
 
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Old 04-19-12, 06:56 AM
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Hi ray2047,

Thanks for your answer. What wire gauge would you recommend for this application, assuming I get a 20 amp / 240 VA / 12V transformer? Also, is this a fairly normal size / price transformer for a household application?

Thanks.
 
  #4  
Old 04-19-12, 12:49 PM
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Found two transformers after some digging.

- Electronic Low Voltage Transformer, 210-Watt, 12-Volt, AC, PTA-210S

- LET 201 AC (12V/200W) Halogen Lighting Transformer

My question is, why does it say that they are not for use in suspended cable systems? What is the difference between those and let's say a rail system?

Thanks.
 
  #5  
Old 04-20-12, 04:08 AM
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It is prudent to allow for 10% to 20% of headroom when calculating the requirements for a transformer. Some of the energy in a transformer is dissipated as heat, and when it is fully loaded the transformer can run very hot.

10 lamps at 20 watts = 200 watts. I would look for a minimum 220 watt transformer.
 
  #6  
Old 04-20-12, 05:36 AM
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Hi Rick,

Thanks for the reply. Other than that though, is there anything else preventing me from using this one: Electronic Low Voltage Transformer, 210-Watt, 12-Volt, AC, PTA-210S I called their cs line and they couldn't tell me why they don't recommend it for systems with hanging cables but rails only... My total cable length is about 13 feet btw
 
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