The transformer must be UL listed as a landscape transformer and not just a general purpose transformer to insure that it has the proper protections built in. The more you spend on a landscape transformer the better it is designed. The highest quality use the best stainless steel enclosure, are pool/spa rated, are multitap voltage selectable, have plug in accessories, toroidal transformers, choke coils, can order with multiple circuit breakers as you need, may have more than one transformer in the box, etc. etc. As you go down in price you give up features. Once you drop below landscape UL listed you may not have the required fusing or circuit breaker or the transformer winding shielding.

You cannot pass the typical UL listed landscape cable through any part of your structure, not even through the vent per the UL listing and the NEC. Only QTrans, as far as I know, makes a landscape cable UL listed to go anywhere, inside or outside of a building.

Thank you for the reply! Which UL listing code denotes landscape transformer (class 1, class 2, etc)?

Also, for this application I am not concerned with features; I just want to run a few low-voltage spot lights on my plants and toggle them on and off with a wall switch but I do not want to invite a fire-risk. The transformer that I was looking at is here:

http://www.allelectronics.com/make-a-store/item/HTX-150/150W-TRANSFORMER-FOR-HALOGEN-LAMP-UL/1.html

With the transformers that I see at Lowes and Depot stamped with "OUTDOOR USE ONLY" is that due to fire risk? Will it still be safe to mount outdoors and under my deck so it is out of sight?

Thanks for the help!

DK

UL and NEC are all about safety from shock and fire.

At the link you can look at the installation guides and find the relevant listings and NEC info that can apply to low voltage lighting transformers.

Here is a link that might be useful: Q-Tran

dim4fun -- the UL/NEC issue is the cable rating, right? Indoors is 90C and outdoors is (typically) 60C. The NEC is primarily aimed at cable placed inside a wall, whereas presumably the landscape wiring comes in a hole in the basement and connects to a nearby transformer as entirely exposed. True, a technical code violation.

But surely there are ways around this. Why can't one use traditional romex from the transformer, and run it to a box immediately outside the house where it connects to landscape low-voltage cable? No need for special cable all around, and the OP can locate his transformers inside.

NEC chapter 3 wiring methods can be used where the wiring runs through the structure. If romex is OK in your area then that should work.