12-volt lighting indoors on central transformer(s)

[UBG]

Greetings all. I'm trying to clean up an existing lighting installation in the home of a new customer.

There are a total of 14 mono-point-type fixtures, which have had their integral transformers removed and are all powered from a group of three 120Vx12V magnetic transformers (one 0.5 kVA, and two 0.25 kVA). The 0.25 kVA xfmrs. supply 3 fixtures each, and the 0.5 kVA xfmr. supplies the other 8 fixtures.

The problems are many. One certain problem is the 12V wiring: it was done entirely with 12/2 landscape cable (in the attic, and exposed on the open beams of the ceiling). Also, the splices, while sometimes in the wiring compartment of the fixtures, are sometimes in the open.

At least the original installers knew enough to not overload the cables. The six fixtures supplied by the two 0.25 kVA xfmrs. are each fed by a separate 12/2 cable from the wiring compartments of one of those xfmr's. The eight fixtures supplied by the large xfmr. are a bit sketchy: three 12/2 cables run from the xfmr. wiring compartment; two of those cables supply 3 fixtures apiece, and the remaining cable supplies 2 fixtures. The 12/2 cables splice to 16/2 cables to feed the individual fixtures.

All three transformers are supplied by one 1000W dimmer, which of course is NOT LV-rated. The dimmer is easily changed to a magnetic LV type, but there do not appear to be any markings on any of the xfmr's either prohibiting or allowing them to be dimmed.

The transformers are installed in the attic, and have no OCP on the primary (other than the branch CB) and no OCP on the secondary. This brings me to the main questions I have:

1. are these xfmrs. OK to be installed in the attic?
2. do they need OCP on the primary and/or secondary?
3. If yes to OCP, how to size it, and what best/easiest to use?
4. Given the lack of specific info re: dimming, is it safe to dim them with an appropriate dimmer?

I know that the 12/2 cable is not rated for this use, and that the wiring should method should be a Chap.3 technique (e.g. NMC). Ripping it all out and starting from scratch, however, would be pretty tough. If the existing open splices were all put into boxes, and the transformers got OCP as required, what is the potential harm in leaving the 12/2 LV cable as is (other the the fact that it will be non-compliant)?

Lastly, whether the wiring method was corrected or not, would these fixtures be required to be grounded?

Thanks in advance for reading and responding.

 

[iwire]

In my opinion to be truly code compliant it is a 'rip it all out and start again' type of deal.

The lighting fixtures have to be listed, no doubt modifying them by taking out the transformers has put the listing into question.

The wire used has to come out and the transformers have to be listed for use as LV lighting supplies.

 

[UBG]

Thanks iwire for your response.

In my opinion to be truly code compliant it is a 'rip it all out and start again' type of deal.

Was afraid that would be the dominant opinion.

The lighting fixtures have to be listed, no doubt modifying them by taking out the transformers has put the listing into question.

A possible saving grace here is that the mfctr. (WAC Lighting) does offer a transformer-less version of these fixtures.

The wire used has to come out and the transformers have to be listed for use as LV lighting supplies.

I understand the simple code issue about the wire. But what are the "practical" concerns underlying that? Physical damage, temperature rating, max volt rating of the insulation, or ?

Is the attic crawlspace an acceptable location for the listed LV lighting supplies?

 

[acrwc10]

I would also question if the transformer was a "land scape" lighting transformer. The ones that are made for outside installation (like Malibu Xfmrs) are not listed to be installed inside. Check with the manufacturers installation instructions.

 

[PetrosA]

Any of the magnetic 12-24V lighting transformers from WAC, Seagull or Tech I've installed had load side OCP, or something akin to it. Electronic transformers have circuitry that plays that role. Line side is whatever the branch circuit is supplied by.

I doubt that feeding those fixtures with a 12V circuit violates the listing, since the individual transformers are not integral to the fixture, but are rather installed in the JB that the fixture is attached to.

I would certainly eliminate the landscape wire and replace with 12/2 or 10/2 as needed for load and install boxes if none are present. Landscape wire is probably rated for much lower ambient temperatures as it's designed to be buried below grade. If there are no boxes present, I would recommend checking the diameter of the canopies - plastic 4" remodel boxes will stick out past many low volt monopoint canopies and you'll need to get 3.5" remodel boxes instead. This is an issue that I really wish the fixture manufacturers would address, since you can't get the 50W transformers into the 3.5" boxes. They need bigger canopies.

 

[iwire]

I doubt that feeding those fixtures with a 12V circuit violates the listing, since the individual transformers are not integral to the fixture, but are rather installed in the JB that the fixture is attached to.

There is no doubt in my mind it does as the labeling on the fixture would say 120 volt.


I don't see a safety issue, just a paperwork one.

 

[PetrosA]

There is no doubt in my mind it does as the labeling on the fixture would say 120 volt.


I don't see a safety issue, just a paperwork one.

These aren't fixtures in the traditional sense. It's a 12V monopoint luminaire (like Tech lighting makes) matched to a 12V canopy. The canopies can be purchased with or without a transformer included, but it's the same 12V rated canopy. Technically, you may be right about the paperwork issue for the canopy, but that's all that would be affected, not the luminaire. I'm sure once you install them without the canopy mounted transformers, you need to use a WAC transformer to maintain listing for a low voltage lighting system which probably makes the removal of the individual transformers a moot point.

 

[hurk27]

The transformer the OP describes sounds more like a buck boost transformer, I have seen people use them for LV lighting before hence why they is no OCPD's, also a .5 kva transformer will produce 41.66 amps on its secondaries, a little high for a 12/2 conductor?

 

[UBG]

Thanks to all the recent replies; I've been a littel swamped in the field the last few days but will post a more detailed reply later today or tomorrow.

 

[UBG]

I would also question if the transformer was a "land scape" lighting transformer. The ones that are made for outside installation (like Malibu Xfmrs) are not listed to be installed inside. Check with the manufacturers installation instructions.

Neither of the existing XFMR's are landscape type. One is a buck-boost, the other two are listed as lighting transformers. I am now certain that I will replace at least the buck/boost, or possilbly all.

Any of the magnetic 12-24V lighting transformers from WAC, Seagull or Tech I've installed had load side OCP, or something akin to it. Electronic transformers have circuitry that plays that role. Line side is whatever the branch circuit is supplied by.

I discovered that WAC makes a Class 2 lighting transformer. They are available with one to five Class 2 outputs in a single enclosure, and if I fed each fixture from it's own Class 2 output, it seems to me I could use Class 2 cable to do that.

Here are my questions:

1. all of the 16/2, 14/2, and 12/2 Class 2 cable that I see for sale is labeled as "audio cable". (Here is a sample for reference). It IS labeled and listed as Class 2, so does anybody see a violation in using Class 2 "audio cable" for powering these light fixtures? (it will be concealed in the attic crawlspace).
2. The mfr. makes the following claims on it's web page (linked above) for their class 2 xfmr: (a) Secondary wiring for Class 2 transformers does not require conduit sheathed cable or clamp wiring techniques, and (b) Non-metallic sheathed cable may be used for secondary wiring in walls and ceilings. I cant find anything that says the listing for that equipment REQUIRES NMC, or FORBIDS Class 2 cable. And, FWIW, what does anybody think they mean by "clamp wiring techniques"? What I get from that phrase is "Use NMC but you don't have to use clamps where it enters the enclosures and boxes". Well, yeah, no clamps needed for Class 2, but why is there no reference to Class 2 cable? Maybe it's due to my question #1 above re: the "audio" cable?

Thanks again to all readers and responders.

 

[GoldDigger]

They are available with one to five Class 2 outputs in a single enclosure, and if I fed each fixture from it's own Class 2 output, it seems to me I could use Class 2 cable to do that.
...
[*]all of the 16/2, 14/2, and 12/2 Class 2 cable that I see for sale is labeled as "audio cable". (Here is a sample for reference). It IS labeled and listed as Class 2, so does anybody see a violation in using Class 2 "audio cable" for powering these light fixtures? (it will be concealed in the attic crawlspace).

The cable at the link you mentioned is labelled as audio cable, but in the absence of any manufacturer's documents restricting it to that use, the fact that is it rated CL2 (and also dual rated as CM for Communications Cable with similar power limitations but in section 800) allows it to be used for Class 2 circuits including lighting. (since that lighting application is power limited in compliance with a Class 2 power supply. )

Table 800.154(a) gives a detailed list of the places and orientations where CM may be used. The description of allowed locations for CL2 are not as clearly spelled out.

 

[darekelec]

can you change light bulbs to leds to lower wattage and then install class 2 transformers? then it would be legal.

 

[PetrosA]

can you change light bulbs to leds to lower wattage and then install class 2 transformers? then it would be legal.

If the fixtures are rated for 50MR16s, you can't just leave them all on the common feed and throw in LEDs to make the install Class 2 compliant. Someone could come along later and put the 50 watt MR16s back in there, making it non-compliant again. A Class 2 circuit is current limited, so the OPs idea of running separate feeds to each light would make it a compliant Class 2 install.