Lighting, Light Fixtures, Ceiling and Exhaust Fans - Dimmer installation - blown fuse...

When I installed a dimmer in my bedroom i realized that the light ficture box didn't (seem to) have a ground wire. I capped the ground wire from the dimmer with with a strip insulation cap. I only had two caps so I used one for the single ground wire and the other for capping one of the black wires with one of the light fixture box wires. The last two wires I twisted and 'capped' with insulation tape (inexperienced?).
When I turned the breaker back on the main fuse blew. After getting electricity back on I de-installed the dimmer and put the original switch back in.
What did I do wrong? Missing ground wire or insulation tape - Or both?
Any help appreciated! :confused:

Twisting wires together and taping them is not an acceptable means of splicing. You should use the wire nut that you used on the ground wire for splicing the 2 black wires and put the tape on the ground wire. If you connected the dimmer to the same 2 wires that were connected to the old switch then I would say your tape job wasn't any good. Try connecting the wires again with the wire nuts and see what happens. You say the main fuse blew? It should have tripped the breaker that feeds the switch. Is the light you're trying to dim a flourescent? You can't use a dimmer on an ordinary flourescent.

There are many reasons why you might have tripped the breaker. The most likely in my opinion is simply bad workmanship that produced an accidental short.

As mgb said, tape is not an acceptable way to make any electrical connection (even on the grounding wires). But this mistake is more likely to cause a fire than to trip the breaker.