Low voltage transformer

[hhsting]

I have 120V to 12V transformer to feed low voltage light on a structure outside.

Would the transformer be considered separately derived or non separately derived?

 

[winnie]

The diagram you posted does not provide the necessary information with absolute certainty.

The key question: is the transformer primary electrically isolated from the secondary. Transformers can he built isolated or not isolated, and if not isolated then the secondary is not considered 'separately derived'.

The diagram doesn't specify isolated or not.

It is very likely that this transformer has an isolated secondary and creates a separately derived system. But if you need to know with certainty then you need more data.

Jon

 

[don_resqcapt19]

It doesn't matter at that voltage.

 

[tom baker]

If the transformer is UL listed for the application that is all that is required. LV wiring is per NEC Art 511.

 

[hhsting]

The diagram you posted does not provide the necessary information with absolute certainty.

The key question: is the transformer primary electrically isolated from the secondary. Transformers can he built isolated or not isolated, and if not isolated then the secondary is not considered 'separately derived'.

The diagram doesn't specify isolated or not.

It is very likely that this transformer has an isolated secondary and creates a separately derived system. But if you need to know with certainty then you need more data.

Jon

Would this be considered isolating type transformer or not NEC 2017 Article 411.6(B)??

 

[hhsting]

If the transformer is UL listed for the application that is all that is required. LV wiring is per NEC Art 511.

511 for commercial garage. 411 perhaps?

 

[don_resqcapt19]

Would this be considered isolating type transformer or not NEC 2017 Article 411.6(B)??

In general, all transformers, other than an auto-transformer, are isolating. There are special isolating transformers that have a grounded shield between the primary and the secondary, but the rule does not require that for this application. This is a listed product intended for this use...nothing more to look at.

 

[hhsting]

In general, all transformers, other than an auto-transformer, are isolating. There are special isolating transformers that have a grounded shield between the primary and the secondary, but the rule does not require that for this application. This is a listed product intended for this use...nothing more to look at.

The transformer is used for outside art structure low voltage 13V light purpose. Its primary 120V to 13V secondary.

I dont see how NEC 2017 Article 411 doesn’t apply?

 

[augie47]

Art 411 requires a listed power supply. Supposedly you have that so you are set to go,.
Most of the systems I see are "listed assemblies".. power supply, cord & lumaires...just hook it up & drive off.

 

[don_resqcapt19]

The transformer is used for outside art structure low voltage 13V light purpose. Its primary 120V to 13V secondary.

I dont see how NEC 2017 Article 411 doesn’t apply?

I didn't say the rule does not apply, I said the power supply is listed for the purpose and there is no need to even think about it, let alone look a it.

 

[hhsting]

Art 411 requires a listed power supply. Supposedly you have that so you are set to go,.
Most of the systems I see are "listed assemblies".. power supply, cord & lumaires...just hook it up & drive off.

I dont see in 411 requiring listed supply?

Also data-sheet in OP where it says listed for low voltage?

 

[hhsting]

I didn't say the rule does not apply, I said the power supply is listed for the purpose and there is no need to even think about it, let alone look a it.

I dont see in OP datasheet it says listed for low voltage or isolation transformer? Where do you see this?

 

[tom baker]

511 for commercial garage. 411 perhaps?

Yes, sorry

 

[hhsting]

Ok its not in OP datasheet but its on their website that transformer is UL listed for 1838. See link below and snapshot

https://bklighting.com/collaterals/specs/specs-667.pdf

Does UL listed for 1838 mean transformer is in compliance with NEC 2017 Article 411 including isolating type?

 

[tortuga]

Yes its fine, UL 1838 = complies with article 411.
Article 411 was added to the 1999 NEC and the whole listing requirement just adds confusion to a simple install IMO they should allow class1 or class2 to cover it.
Here are the key things to know about landscape lighting xfromers:

* Isolating power supply required 750 VA or less;
* Not over 30V (or not over the peak voltage equivalent of 30V RMS ac, 42.4V);
* 25A maximum size for all circuits on the secondary side;
* The secondary circuits must be ungrounded and insulated from the primary supply by an isolating transformer. Exposed bare conductors are permitted under certain conditions. Bare conductors are permitted at least 7 ft above the finished floor unless specifically listed for a lower height.
* The systems must be supplied from a 20A (max.) branch circuit (any voltage).