The dual output transformer is two separate transformers in one housing with two separate outputs. There is the caution that you need to balance the loads on each transformer; that is, each transformer is only rated for 1/2 of the max. wattage and can't be exceeded. The multi-tap transformers have multiple voltage outputs (24/26/28/30 for a 24V transformer) to let you compensate for voltage drop in the output wiring. Low voltage lighting typically runs at high current (thus the heavy wire used) which can lead to large voltage drop in long runs of wire. The multi-tap transformer allows one to increase the voltage at the transformer output to compensate for this voltage loss in the wiring. There is a caution from Seagull that at the first bulb in the lighting circuit the voltage should not be greater than 25V or bulb life will suffer. The difference between bulb voltage (for the same wattage bulb) is in the current draw of the bulb. Watts = Volts x Amps, so for the same wattage bulb, using a 24 volt instead of a 12 volt bulb will cut the current (amps) drawn in half. This will also lower the voltage drop in the wiring to the bulb and may allow the use of smaller wire. Re: "At this point I'm thinking 24V 500W and using two runs of 12/2" - With your total load of about 300W, split roughly equally into two runs, I don't see the need for a multi-tap transformer (150W at 24V is about 6 Amps which would have minimal voltage drop using 12/2) and I really don't see the need for a dual output transformner. I'd go with the 24V, 500W, single output transformer.

One other thing that comes to mind and this is also keeping in mind that the "rules" for who can legally install low voltage equipment vary from state to state, many like here in WI have no licensing required at the state level, some have a separate low voltage license that can be obtained often with a bit of training, but don't require you to be a licensed master electrician to do so, which I think either way makes sense since few electricians seem to be getting into the growing low voltage landscape lighting biz, or in your case a doorbell and I think it was NJ I heard that recently bumped it down to 10 volts for needing a licensed electrician. (bet the IBEW had a hand in that one!) Yet, like in my municipality, they do add just a bit in the local codes that specify the system, be it a doorbell, low voltage landscape lighting, etc MUST be tied into the AC power source via a cord and plug going to a legal receptacle and that part would need to be done by a real electrician and if outdoors would need GFCI protection, etc so assuming you're not a licensed electrician, once you choose to hard wire it, you may be crossing over into the "danger zone" and I always mention that for me or anyone I'd think, "getting busted" by the local inspector and paying some fine or double permit fees or something is peanuts compared to IF at some point like after you'd sell the place due to a new job out of town, there's a fire and large $$$ of property damage or God forbid, someone is badly hurt or killed, now YOU have a good chance of being on the WRONG end of a HUGE $$$ lawsuit and even when people say, "oh come on how many doorbells or low volt path lights burn homes down, what if the goofy buyers decide to rewire some stuff and they're idiots! If you've ever seen how ins co's investigate fires with big $$ claims, its very intense and just proving that your probably illegal, hard wired transformer was NOT the cause will likely come at a great expense and hassle to you, assuming you're able to clear your part of it!

Depends on how you want to control them. If all you are doing is turn them on and off, it shouldn't be much of a problem. If you want to dim them, that's where issues start to crop up. Not to be too reductionist or too simplistic here, but most LEDs are solid state electronics, not really technically electrical, and require low voltage DC power, so not only is there a transformer (whether you see it or not), but usually some sort of AC/DC rectifier. Not all electronics behave well to being dimmed with typical rheostat wall switch dimmers. That's also why some LED lights have a slight delay turning on, the electronics. Even if they say they handle 120v and can be dimmed, it doesn't always work as advertised. Depending on why people on these forums recommend the Inspire LEDs (I'm not familiar with them) I would still stick with something either I know or people I respect know. If I want to dim LEDs today, I would buy a whole system that includes the lighting controller—like a Philips HUE system for traditional style light bulbs. LEDs have not been perfected to the point that anything you buy will behave properly. But if none of that matters, just get whatever you want that behaves like you want it (if you don't want the delay in turing on, for instance) Joe

I just commented on you're other post about the bulbs and sockets. Anyway, it looks like you're looking to retrofit the cans to accommodate LEDs. It might just be an easier (and possibly cheaper) option to go buy four new LED remodel cans and replace the four you have, than rip out all the guts (transformers and sockets) and replace them with new LED drivers (if you can find ones that will fit in the can housing) and sockets. Just sayin'. Sounds like you'd have to pull out the existing cans to do all that anyway.