Help! Any Sparks out there!

[iamjemima]

Hi all
I wonder if someone can help me. I've bought a metal halide lighting unit for my seawater aquarium. The unit looks like an 8ft long canopy that's suspended from the ceiling above the tank.

The unit contains four metal halide lamps, has a pair of mechanical timers at one end and is connected to the mains via a manufacturer fitted spring-coiled cable and a fitted 13 amp plug. I don't know a lot more about it other than there's a sticker on the hood that says danger high voltage and says that there's a few thousand volts inside the unit when it's running.

My problem is that when I plug the unit in, it trips all the electric in the house seconds later. Has anyone any idea what could be wrong with the unit?

Thanks.