I see you wish to run two lamps, but what wattage/size of T5HO are they? This is important to know so that you use the correct number of red wires per lamp and whether the WH5 can do the job. Here are a couple of links (hope they still work) to more information on WH ballasts and compatibility with various sizes of lamps.
http://www.naturallighting.com/pdf_f...e_diagrams.pdf
http://www.1000bulbs.com/pdf/Fulham-...t-brochure.pdf
I'm currently overdriving two 54 watt (48 inch) lamps with WH8 ballast and have fans mounted at each end of each lamp for active cooling. The thing with these ballasts is that each end cap needs a jumper wire (both red and yellow side) between the contacts as well as the feed from the appropriate number of red wires and yellow wire at the other end. Here are a couple of photos of my endcaps, HTH.
I used black jumpers and feed wire from terminal at the yellow end.
This is the red end. Two red wires were joined at a terminal board with a single red from the terminal board to the endcap... and the jumper wire of course
If you don't want to solder, use wire nuts to connect the wires together before terminating them in the end cap, or do as I have and use terminal boards.
Pics of the DC fans I'm using to cool the lamp ends. Don't recall when I last changed lamps and they're still shining bright with absolutely no sign of blackening at the ends despite being overdriven. Active cooling at the ends makes a world of difference
