Control Transformer Class

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J

Jacob S

Senior Member
Hello all!
I am hoping you guys can help me with a quick question I have. I need to build a very small control cabinet consisting of a few ice cube relays and some remotely mounted illuminated buttons. I would like to treat the wiring between the cabinet and the buttons as a class 2 circuit. In the past when building something similar, I would always find a transformer that is listed and labeled as being class 2. In this case, I was wondering if I could use a "control transformer", such as the one I have linked, and by using appropriately sized primary and secondary fuses, treat the secondary as class 2. My hunch says (based on the poorly written section 725 of the NEC) anything connected to this transformer would need to be class 1 and use standard chapter 3 wiring methods, but I thought I would check anyway. Thanks!
Jacob
http://www.automationdirect.com/adc/Shopping/Catalog/Power_Products_%28Electrical%29/Power_Transformers/Compact_Control_Transformers/240x120_VAC_to_24x12_VAC/PH50PG
 
Buck Parrish

Buck Parrish

Senior Member
Location
NC & IN
The picture in the link you posted looks like a relay. It's not an ice cube relay that I am use to seeing. It has exposed parts. However I did notice that it comes with a clear cove like an ice cube relay.

Just curious what are you building this for?

Would your situation allow for you putting it in a 12x12 box?
 
J

Jacob S

Senior Member
Thanks Buck,
The picture is the transformer I would like to use to feed the relays and indicators. I have not drawn the ladder diagram yet, but it will be a simple cabinet with that will allow users to remotely turn on and shutdown a contactor with a time delay. I do plan on mounting the components in a 12x12 nema 1 enclosure, but the buttons would be remotely mounted. Thanks,
Jacob
 
C

Cold Fusion

Senior Member
Location
way north
Jacob -
A couple of questions:

Are you a UL508A shop (or equivalent)?

Are you building this panel per NEC Article 409?

Are you planning on getting this panel field NRTL evaluation?

I'm absolutely fine with you not being a UL shop, and not getting the panel field NRTL evaluated and instead building the panel to NEC 409.

There are others here that believe that a panel built to NEC 409 must be field NRTL evaluated, because it (paraphrased) is not in accordance with the NEC and certainly will not be allowed to be installed in the State of XX.

cf
 
V

Volta

Senior Member
Location
Columbus, Ohio
You couldn't use it directly to feed a Class 2 circuit if not listed that way. You could comply if you inserted a current-limiting impedence or thermocouple in the circuit.
See exception 2 to 725.121(A)(3).
 
J

Jacob S

Senior Member
Thanks guys,
This panel is being built to NEC 409 and will be approved by the AHJ. Now the fun begins looking at ch9 table 11(A). After glancing at it briefly, i think i will go for an already listed class 2 transformer. It looks like the table is intended for manufacturers and panel shops, and not for my use anyway. Out of time at the moment, so i might be back later for more questions. Thanks again,
Jacob
 
J

Jacob S

Senior Member
Frank,
The only components that I will be installing in the enclosure are all 24VAC relays and such. I have decided to feed these components with a RIB listed class 2 power supply instead of the control transformer I posted in my original post. The contactor is remotely mounted and is a factory assembled contactor/cabinet. Using this design, I did not think I needed to be concerned about SCCR. Is this correct? Thanks!
 
B

benaround

Senior Member
Location
Arizona
Jacob S said:
Frank,
The only components that I will be installing in the enclosure are all 24VAC relays and such. I have decided to feed these components with a RIB listed class 2 power supply instead of the control transformer I posted in my original post. The contactor is remotely mounted and is a factory assembled contactor/cabinet. Using this design, I did not think I needed to be concerned about SCCR. Is this correct? Thanks!
Click to expand...

You are correct, I read it as contactors would be in this new cabinet, sorry for my mix-up.
 
J

Jacob S

Senior Member
Thanks, I just wanted to make sure I was not missing something. It is awesome having such a skilled group of people to answer these types of questions!
Jacob
 
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