[reefburnaby]

Hi,

Okay...I went digging around. And here's what I found and I tried to answer them.

There are a couple ways where a ground probe can fail to protect you when a GFCI is present.

1) The short within the tank is so great that it creates a voltage drop between the tank water and the actual ground. In this situation, there is a couple of amps flowing through the probe. Due to the resistance of the probe, the water will actually have a non-ground voltage. This is bad...and you can get electricuted.

To fix...use a better ground probe. The current breed of ground probes have very thin and long wires -- hence high resistance or high backpressure (in plumbing terms). A little bit of current through the probe, and a big voltage drop occurs. Of course, this situation can definitely happen if there is no GFCI [img]images/smiles/icon_smile.gif[/img]

What if there is a GFCI ? Well...now it really depends which device is shorting out. If it is the usual powerheads, heaters...no this can't happen - GFCI will go off.

Now...if it was the electronic ballast driven lamps shorting to the water...then GFCI will not go off. The electronic ballast are actually isolated power supplies that are not protected by GFCI and they (supppose) to share the same ground.

If you are using power conditioners or power backup (APS), then you need to be very careful. You'll need a GFCI on both sides of the APS...on the power company side and on the output of the APS. Otherwise, you'll be in the same situation as the electronic ballast.

2. There is another scenario where there is no short within the tank, but the ground probe is attached to a faulty ground wire. In other words, the ground on the AC outlet is not really ground. This can be cause by faulty devices within the house or around your tank (like a little giant pump). Usually, it is the pumps...so some find that plugging the probe directly to the AC outlet fixes this problem.

We are more sensitive to electricity when our hands are in salt water (especially, hands with a fresh wound) than when they are dry or in fresh water. Keep in mind that small electrical problems around salt water can give you a bigger electrical shock than normal.

One of the puzzling things is the statement that ground probes can cause problems. And it is true, but it depends on the situation. Some reefers have been shocked (slightly) when a ground probe is used. Usually it is one of the problems stated above. So, how does removing the probe prevent you from getting a shock ?

In the first case, the probe created the voltage. So, when it is removed, the water will be at the same voltage as the short (which is usually AC). If you touch the water, your whole body will be at the same voltage as AC. This works as long as your toes, feet, hands are not touch a ground. If you do...toast. Otherwise...you'll be fine.

In the second case, the bad ground caused the problem. If the water is not grounded to the bad ground, then you won't get shocked when you touch the water.

I still think that a proper probe and a GFCI is best. I also think reefs should wear shoes/slippers or stand on a plastic mat/chair when you work in you tank. Even better...turn off your electrical equipment when you work in your tank. Electricity is a dangerous thing to play with. I am sure electricians, like Gord, can share some great horror stories.

Hope that helps.

- Victor.

[ 03 February 2002: Message edited by: reefburnaby ]

[ 03 February 2002: Message edited by: reefburnaby ]</p>