Flexwatt electrifying foil... how so?

[Herpocrite]

Hey... So I'm setting up my baby with her own mansion. I got a sweet deal on a 7'x2'x2.5' aquarium and decided to go ahead and get it. But that's not the problem... the problem is this:

I am heating the enclosure with flexwatt heat tape on about 2/5 of the bottom of the tank. I hooked the wires with the plugs to the 11" flexwatt using the clip set with the insulating covers. Then I covered both open ends of the coper strip that runs down the flaxwatt with electrical tape. Finally I attached the whole thing to the bottom of my aquarium with Nashua 324a foil tape as I read somewhere that this helps to reflect more of the heat upwards and spread the heat out well. The problem... the whole foil thing attached to the bottom of my aquarium becomes electrified when I plug in the flexwatt.... which could be useful if my aquarium were being attacked by a giant squid... but otherwise anoying and dangerous. What's worse is that I can't figure out where the current is escaping from the heat tape and coming in contact with the foil tape. After reading around I realize that I should have used aluminum foil tape to attach the heat tape to the aquarium because it doesn't conduct electricity, but I still would like to know how the electrical current is coming in contact with the flexwatt. Any ideas? Am I being extrordinarily obtuse? Lemme know.

Herpocrite.

[Stockwell]

I think I know whats wrong... here's a couple things to check.
To start with how are you ascertaining that the tape is live?? Are you feeling a zap when you touch it.. explain.. what was the path of the zap, from hand to where? What was on your feet?
I personally don't like seeing conductive metal tape on flexwatt and while its common, I never recommend it.
If there is an abraison or pin hole in the thin plastic it might be making contact with the tape. This would be the worst scenario and would represent a real conductive path from the live conductors to the foil tape.

But there is something else that I have seen.
I suspect you are feeling capacitively coupled current flow through the tape.
What can happen is that the mylar coating on the heat tape acts like the dielectric of a capacitor when metal is placed over it. A small charge is actually stored in the plastic coating that becomes sandwiched between two conductive surfaces. This is not a direct connection to a live wire, but yes you'll feel a discharge.
A few years ago I had a similar weird experience with an old tank that had a chrome rim rather than the usual black plastic ones.
I simply had placed the metal rim of the aquarium on the heat tape and while in socks on the bare basement floor felt a bit of a shock when my arm brushed the rim of the aquarium.
I quickly pulled out my meter and started conducting some tests. I discovered that there was no direct connection and there was no current potential but there was in fact a voltage present on the rim of the aquarium, which at that point presumably represented one plate of a capacitor.
Slightly elevating the metal rim off the heat tape by using some plexiglass shims, eliminated the problem.
I suggest you remove the metal tape and use a new piece making sure it only contacts the outside plastic edge and doesn't extend over the internal bus runners... OR
Two other fixes, are using non conductive tape(cloth type) or putting a non dielectric spacer between the metal tape and the flexwatt. A piece of plexiglass should work, and even covering the heat tape with electrical tape before applying the metal tape will likely work. You need to increase the distance between the metal tape and the flexwatt

[Herpocrite]

The shock I feel when I touch the metal tape is the constant tingling feel of a continuous current, not the sharp shock of a built up electrical discharge. The cage rests on some alluminum rods about an inch off the concrete floor of my basement apartment. Does this mean there is a pin-hole somewhere in my flexwatt and that the current is escaping in that manner? Would alluminum metal tape work better? Should I just go ahead and use some regular, grey duct tape to attach the stuff? Or maybe a layer of standard alluminum foil and then the duct tape? What do you folks think?

Thanks,
Herpocrite.

[Stockwell]

Put the tank on a piece of wood and avoid having the heat tape contact anything electrically conductive and that includes aluminum rods and all foil tapes even aluminum. Aluminum tape is just as conductive as steel. If you want to use foil tape as a reflector, stick it to a piece of plexiglass first and have it on the back side, not directly touching the flexwatt.
It's a good idea to have a space between the flexwatt and the bottom of the tank to prevent overheating of the tape and the bottom of the aquarium. Use some spacers of plexiglass, glass, or wood between the tank and the heat tape.
You should be especially careful with electrical applications in a room with a concrete floor, as concrete will conduct directly through the slab to ground especially if slightly damp making it quite dangerous especially in socks or other uninsulated foot wear. For safety you might consider carpeting the floor in that area which will also keep your herp room warmer.