Poor splice.
It appears there is no protection on the splice and it is not tight.
Wire nuts or crimp splices would be a good idea here.
While the voltage is low, the currents get large very quickly.
Tight connections are needed to prevent localized heating.
Some protection from moisture would not hurt either.

Do I need to get special OUTDOOR low voltage type wire nuts ?
I saw some at Home depot the other day.
They were not OPEN ENDED where the wires insert to twist together. It looked like flexible plastic that might act as a moisture deterrent ?

thanks for the advice though !!!
and yes.. this "hub" is a plastic utility box, I just took off the lid to take the pic ;)

First of all, you say it is a 600w transformer but from your diagram you only have 1 piece of 12/2 supplying all of the lights, is that correct? A 600 w transformer has 2 separate 300w circuits. Each are completely independent and cannot be wired together. So you would have to have 2 separate 12/2 wires. 1 (2 conductors from the first circuit) running to 5 lights(if the total is less than 300w) and 1 running to the other. Besides that, the splice really doesn't look like it's in good shape. Just b/c it is low voltage it is still high amperage. (300w @ 12volts is over 20 amps) That kind of current definately requires a good solid connection of all the conductors or you could get arcing, and/or the wires could get very hot and even start to melt the insulation. Hope this helps, good luck.

Plain wire nuts are actually fine.
I always leave them pointing upwards so any condensation can drain out.
The ones with a seal are not hermetic so moisture can still get in.
The connection between the wires is gas tight when the nuts are installed correctly.
Twisted together wires come loose from thermal cycling (both heat from carrying current and from day-night variation).
Once the connection is loose heating becomes even worse.

You guys are awesome ! Thanks so much for the prompt and informative advice ! I truly appreciate your info and time to help a "landscape light newbie" out. ;)

****** Nope... not one single 12/2..... but as in the drawing , there are 2 legs that run to 10 lights,...5 a piece.

I will surely pursue better connections and reduce the amount of lights.

many thanks !

I hate those things , you have it corrected for now you will probably be at it again inthe spring if they last that long ..... GO Green Solar lights do the trick with a lot less aggravation and some area utilities give partial money back and the only ongoing cost is replacing the batteries clean the lens....................

Martin,

No offense, comments are good, but I'm just wondering why you've dredged up some long dead threads in the forum. This one is 6 weeks old, for example.

The point in this forum is to help people with their electrical problems. But with these old threads, there's nobody to help. In most cases the original poster has long since solved the problem.

We do have some regulars, but the typical pattern with Internet forums is that someone will join and post with a question, get the answer, and then never return unless he has another question. Once a thread is about a week old, the original poster is usually long gone and will not see what you write.

Basically, any thread that isn't on the first page in the forum is pretty much dead.

It's up to you, I just hate to see you waste your time.