Lachlan James

In a recent post about Rios, it was mentioned that someone was looking at making a ground probe out of bike spokes. Can any one tell me how to do this, or how to make a probe any other way. Thanks for any info.

Dallas Warren

Lock, drop into a good bike store, such as Cecil Walkers in the city and pick up a single titanium bike spoke. Sometimes they are a bit difficult to get on their own, you have to get enough for an entire wheel from some stores ;-). All you then have to do is fix a wire to one end, then make sure that solder is well sealed and no copper is exposed. Use some epoxy paint or coating to do this and then place it such that the joint doesn't come into contact with your system water. Then attach the other end of the wire to a plug and the earth pin on it. Stick that into a power point, the probe in your sump or tank and vola. Nothing to it.

Kerry Fell

And now for the dummies???? Am I correct in thinking that some stray voltage in the tank will go up the bike spoke, into the wire into the powerpoint (This is turned off of course, isn't it?) and then what? How does this work? You know us girls don't like electric shock stuff!!!!

Lachlan James

Dallas Warren

The grounding probe provides a place for stray electricity to go, to earth. So lets say you stick a wire from the active terminal of a power point into your aquarium. Without a grounding probe your tank is at a potential of 240VAC and if you stuck your hand in you would be lucky to get away with your life. On the other hand if there was a ground probe then the electricity would go directly to earth, and it would not both passing through you if you stuck your hand in. If this last example really happened, then something else in the circuit would burn out, likely the active wire, but I am just trying to illustrate the point clearly.

You have grounding probes for exactly the same reason you have ground wires on electrical appliances. So that if there is a short in the appliance when you touch it you don't get killed, but rather it is drained to earth.

In conjunction with this you should have a safety switch, that will detect any discrepancy between the amount of current flowing through the active versus the neutral wires. If there is a difference then that indicates there is some leakage somewhere, to earth or something like that. When it reachs a threshold value it will then cut power off, and this cut off is low enough such that it wont cause you any harm. It will also happen so quickly that you wont feel anything either, just hear the click of the switch as it trips.

It is best to have two separate safety switch circuits running an aquarium, and split up your pumps etc between them. That way if something shorts out then there will be some pumps to keep it going when you get back.

Tony Fendt

Wire the probe to the ground pole of a three prong plug and just plug it in - your son won't know the difference :o)

Caevan Sachinwalla

If you are grounding your tank, because you are worried about electrocution from say a faulty pump. I would not bother. Firstly all pumps heaters carry both an active and a neutral. Any fault in the wiring would cause an imediate short and blow a fuse or trip a circuit breaker. All houses in Australia SHOULD be wired to the AS3000 standard that stipulates that the neutal and earth are connected in your fuse/ meter box. In other words the neutral present in your wiring is a defacto earth.

I am more worried about people not knowing what they are doing electrecuting themselves, whilst making a grounding probe. If you are worried about elcectrocution have an electrician wire in an Earth Leakage Cicuit Breaker (Safety Switch). If you really want a grounding probe, buy one ready made or have someone who knows what they are doing wire it to a 3 pin plug for you, so it can be safely plugged in to a power socket.

Andrew

I disagree. I have measured > 35VAC coming from my Rio pumps. If what you say is true, I shouldn't feel the tingling by putting my hand in the tank - but I do. With the load I have on that circuit, the circuit breaker should have blown - but it hasn't.

While my electrician was doing some other work the other day, we proved that a ground probe would make a difference.

I do agree, however, that if you don't understand electricity you should not do any DIY electrical projects.

Dallas Warren

On several occassions I have felt a tinging sensation in a tank due to faulty electrical equipment. So something in the reasoning is breaking down, most likely the amount of current involved is not enough to short things out.

Simply earthing the tank, reflectors etc will remove this danger. And installing a safety switch either on the switch board or on the power point will add another vital layer of security.

Caevan Sachinwalla

Firstly 35vAC is an order of magnitude out, if you consider pool lighting is 24v AC, it is a fairly safe voltage, it is not going to do you any damage. Your circuit breaker trips on current, not voltage. If your Rio pump is faulty would it not be smarter to replace it rather than, masking the problem with a grounding probe. Also depending where you put the probe you will have a nice voltage drop in you tank between your pump and your grounding probe. Where as before the leaking voltage had no path to ground (baring your hand). I do not know what effect this would have on you fish.

Cameron

A few things to remember here, safety switches (there are a couple of different types) typically measure the difference in current flow between active and neutral and trip the circuit when there is a variance. This variance can only occur when the "stray current" is dissipating to an alternate source, typically earth. If there is no grounding device fitted to the tank there is nowhere for the stray current to go, therefore no trip. The next time you happen to stick your hand into the tank you will provide the alternate source for the stray current to dissipate to and the safety switch will trip, that is of course if you have one fitted, if not you will get a nasty zap. Therefore it is a good idea to ground your tank (the water as well as any conductible material that is not alternatively earthed) so you isolate problems as soon as possible. I personally would not run a tank without one.

Also if you do have any stray voltages in you tank I am certain that this is not something that your inhabitants experience in the wild. Rather like living directly under a dirty great big set of high-tension power lines I would imagine.

Lastly always fit a safety switch to the circuit running you tank, even better as Dallas has suggested run your tank off two separate circuits (both safety switch protected) and this will give you some redundancy if you do happen to have a problem. And please if you have any doubts as to what wire needs to go where contact an electrician, it is not worth saving a few dollars and attempting to do it yourself and possibly putting yourself, your family and your tanks inhabitants at risk.

Andrew

Yes, 35VAC is not 240VAC, but it means there is current flowing - at least when I put my hand in the tank. Maybe it's a few hundred milliamps, but when added together with the current being drawn by the heaters, lights, etc...

I don't believe the Rio pump itself is faulty - it is their design as every one of my 6 Rio pumps does the same thing. Yes, I'll replace them when I can find an equivalent pump.

The value of the ground probe will be if the pump does in fact fail and put 240VAC into the tank, the saftey switch will trip then rather than waiting for me - or my wife - to put their hand in the tank.

As for circuit breakers tripping - yes, I know it is current that trips them. Rememeber, however, that the circuit breaker is rated for a higher current than the plugs and sockets. e.g. a circuit breaker might be rated at 16A or greater and yet a socket/plug is rated at 10A.

A few years ago I had a situation where a tank overflowed and dripped water on a plug in a socket. The water conducted just enough current (just over 10A) such that the plug melted down (yes, even the copper) but did not blow the 16A fuse.

If you want to try this, put >10A load on one wall socket.

Caevan Sachinwalla

The phenomenon you described with your plug very likely had nothing to do with high current. But what is called a hot joint where a you have a bad contact and sufficient heat is generated to vapourize the copper. Just as your circuit breaker is rated at greater than 10 amps so is your copper cable. In fact you could put twice that much current through your cable and it would not melt but your circuit breaker would go. The current rating for cable has to be far higher than that of the protection device. If you say there is nothing wrong with the pump. Then the only way you could get exposure to 240 volt is if the cable was damaged at this point both active and neutral would come in contact with the water and you would blow your fuse. If you do not believe me you can always cut the cable and put it in the water and see what happens, in fact cut the cable with the power turned on and see how fast your circuit breaker trips. In case your wondering I have done the equivalent and yes it tripped instantly.

I would also hope that in event of any pump failure, it would be designed in such a way that you would not be exposed to dangerous voltages unless the cable had been damaged in some way. Anyway if it gives you peace of mind by all means ground your tank. Just make sure you know what you are doing. More people have died from incorrectly wiring extension leads than, tank electrocution.

Oh yeah I do know of any power lines that run above a reef in the open ocean. And in the unlikely event that they did I do no think it could be called a natural environment. Heck I wouldnt live under them. I also think you are confusing voltage with electromagnetic induction.

Cameron

I think the point of a fuse/circuit breaker is being missed here, it is not there to protect you against electrocution it’s purpose is to protect the cable against overheating, therefore potential fire risks. That is why most fuses/breakers have a thermal element as well as a current element to their trip curves. There is a very real risk of exposure to 240V from any piece of equipment from within a tank (be it a heater, powerhead etc.) especially from the cable being damaged. All portable equipment must have double insulated cable, ie. the active and neutral cores are individually insulated, and another layer of insulation wrapped around both of these. In the case of the cable being damaged (which is quite easy considering that tanks and lids are made from glass) it is just as likely that only one conductor will become exposed as it is that both will. And be it either the active or the neutral core that is damaged you have leakage potential. Now if you tank is earthed you instantly have a fault to ground and pop goes your fuse. If not your tank water becomes live until next time you stick you hand into it.

The only complete way to protect yourself from electrocution is with a safety switch and your tank being earth along with this. It is quite easy under the correct conditions to get an electric shock that does not draw sufficient current through the fuse to blow it, but has enough potential to give an extremely nasty shock.

Andrew

As Cam says, the CB will only trip if the current reaches it's rated level. If dropping both cables in the water draws enough current fine, if not I don't want to be putting my hand in.

A permanent earth to the tank plus a safety switch will ensure a quick and safe cut of the power without me or my wife having to be the earth to trip the Safety Switch.

Caevan Sachinwalla

I think you both miss the point, I am fully aware of the function of a Circuit breaker, or fuse. But if you look back to the beginning of this thread people were asking about how to make a grounding probe. It would be irresponsible to make people believe that it is a necesary requirement for a tank and therefore go build one. I would say a person is far more at risk of electrocution from making a grounding probe and not knowing much about electricity, than someone who does not have one on there tank. I do not want people reading this feel they have to rush out and make one. Most of the things you are worried about can be taken care of by periodic checks of the wiring and cables and anything else electrical you put in your tank. While your at it you might as well check your Earth Leakage CB. The sign on it says test regularly, when was the last time you tested yours ?

Cameron

Agree with you completely, as I said before it is not worth the risk if you are not 100% sure of what you are doing. The other thing to remember is that you don't have necessarily run you earth to the power point (and therefore run the risk of connecting it up incorrectly), usually I find the most convenient earth point is one of the tanks light fittings. They are typically made of steel, they are right at the tank so no long messy wires and they should be earthed through their 3-pin lead. The earth probe on my last freshwater tank was a bike spoke. All I did was to simply drill a hole at one end of the fluoro light fitting (clearance size for the spoke). And using the thread at the end of the spoke, with a nut on each side and a couple of star washers to bite into the steel to make a good connection, attached it to the fitting. The other end simply hangs in the tank. Doesn’t get any easier than that.

Andrew

When did I last test ours? May, 2000, when possums knawed threw a mains cable in the ceiling. Actually, they had knawed threw it previously and were actually sleeping on the cable. While I was OS, the Safety Switch kept tripping every 30 minutes as the possums rolled over.

I agree, that if people don't know what they are doing they shouldn't do any electrical work themselves.

A properly connected gound probe (especially if the circuit has a safety switch) is almost a necessity. While you can regularly check all your wiring, etc (and I do) it is impossible to tell when a heater will blow up, or one of your lights might drop into the water.

Caevan Sachinwalla

Okay if you feel in necesary to have a grounding probe and want to do it correctly. Clipsal make a nice little plug where you can attach your earth wire to a single screw at the end of the plug. So all you need to do is connect your earth probe to one end of the cable and this plug to the other. The plug alows you too plug other plugs into it to you do not lose a socket. The part if you are interested is a Clipsal Antistatic Plug Adapter Catalogue Number 463AS. You should be able to get it from any electrical wholesaler , in NSW look up John R Turks, TLE, or Laurence and Hanson. I do not know the equivalent in Victoria.

Do not connect your earth to a metal tank fitting, because unless you are have any knowledge of electrical wiriing you have no way of knowing if the the fitting is itself grounded. I am still unconvinced that it is a mandatory requirement, and do not be fooled it to thinking you need one. Just remember any device designed to be immersed in you tank has to be manufactured in such a way to eliminate any chance of electrocution in case of failure. If this were not the case most would be broke by now from law suits. Just think how many people use these products for years and do not ground there tank and have not been electrocuted. If you are that worried you might as well not go out on the road. In ATJs case of his RIO pumps that seem to create a voltage. Grounding the tank may render the pumps useless if that is there normal operation and the keep tripping the RCD.

Cameron

I like to think of earth probes and safety switches like a cars seat belt and airbag. When you drive around they don't do much, but if you do have an accident, the combination of these two devices may just make all the difference. Anyhow I think I might go and do a water change (with complete and utter confidence that is).