Led Transformers Question

[James S.]

I have run into these a couple of times and I am confused. I was taught that you don't mix 120v with low voltage in the same box but I am seeing these transformers with the leads for both the 12v and the 120v in the same side of the box. It seems to me that it is designed to connect both in the same space but since I am not that smart I am asking for input from you guys. Is there something I am missing? Was I taught wrong? Did something change?

 

[broadgage]

My understanding is that line voltage and low voltage must be seperated when the low voltage is REQUIRED to be low voltage for safety reasons.
A good example would be a bell ringing transformer, the bell is probably wired in lightly insulated wire and neither the bell itself nor the bell push are constructed to the standards required for line voltage equipment.

If however the designer CHOOSES low voltage for reasons of economy, expediance, or better performance, then the low voltage conductors are not intended to be exposed to touch, and may be mixed with line voltage.
A good example would be an industrial control panel in which 24 volt relay coils are used because they are cheaper and more reliable, not becuase line voltage would be unsafe.

As regards lighting, if low voltage is a REQUIREMENT, then I do not believe that the transformer illustrated would be acceptable.
If however low voltage is a DESIGN CHOICE because low voltage filament lamps or LED replacements give a better light, then it should be fine.

 

[mwm1752]

Looks like a class 2 transformer

300.3 Conductors (C) Conductors of Different Systems.
(1) 600 Volts, Nominal, or Less. Conductors of ac and dc circuits, rated 600 volts, nominal, or less, shall be permitted to occupy the same equipment wiring enclosure, cable, or raceway. All conductors shall have an insulation rating equal to at least the maximum circuit voltage applied to any conductor within the enclosure, cable, or raceway.
Informational Note No. 1: See 725.136(A) for Class 2 and Class 3 circuit conductors.
Informational Note No. 2: See 690.4(B) for photovoltaic source and output circuits.

 

[dereckbc]

So long as the low voltage conductor insulation is equal to or greater than the higher voltage insulation, and can be distinguished by use of colors can occupy the same space. Basically use 600 volt cable insulation for both low and high voltage circuits, and use something like Red and Blue insulation for the low voltage circuits. Doing that will comply with 300.3. Hope that helps

 

[James S.]

Very helpful. Thanks guys, that makes sense. I figured it had to be something relatively simple...I just didn't know what it was. :thumbsup: