If anyone is interested in running two of these units in series to create 24volt just the same as bobby has done you will need to "Float" the DC ground of one of the Units
Basically what this means is that you need to isolate the 12volt negative side from the earthing of the main case.
This will also allow you to mount both PSU together without any insulation between them.
Its really easy with these power supplies to isolate the DC ground. Its much easier than on the HP PSU that i used for my charger setup.
So here goes.
Open up the case and seperate all of the internal circuits from outer case. This is pretty easy to do just be careful of the LED at the back of the case near the fan.
Make sure you dont damage the black insulation covers as you need to put those back in.
The main circuit boards are mounted to the case at three locations. This is where the circuits are connected to the case completing the ground.
This is where we need to isolate the circuit boards from the case
The circuit boards use metal screws to hold them in place and it is these that help create the contact with ground, so the fist thing to do is to replace these with nylon screws.
I didnt have any in my box that were the correct size so i drilled out the mounting posts and tapped them for M4 thread as that was the size of the nylon bolts i had on hand.
This was made super easy as i have a set of metric drill tap/combo that does this in one easy step.
Replacing the metal screws for nylon screws will not completely isolate the circuit from ground as there are also some metal pads on the bottom and top of the circuit boards around the mounting holes that also make contact with the case, so we need to isolate these as well.
To do this I made some small nylon caps that snugly fit over the top of the mounting post to electrically isolate the circuit boards.
I made these from old servo horns as the inner hole diameter was a nice snug fit. This take only a couple of minutes with a Dremel and a steady hands.
These Nylon caps just fit snugly over the top of the metal mounting posts to completely isolate the circuit boards from the metal case.
All that's left to do is to re-install the circuits into the case using the nylon bolts, making sure that the nylon caps stay in place.
once you have finished reassembling the PSU you need to double check that the 12 volt Negative out put is completely isolated from the case by using a multi meter in continuity mode.
There should be no longer be any connection between the negative output and the case.
The only other mod you need to do to get these PSU to power on is to solder a resistor across a couple of the other smaller terminals
More details and more pictures on how to do all of the above in a slightly different way can be found on the RCHN website Here
They also show the value and exactly what to do with the resistor and where to put it.
The resistor is easily available from your local Radio Shack
It was very easy and quick to do so dont be afraid to have a go.
These are great little units and i can recommend them to anyone in the market.
Hope this helps.