Should a giant steel framed human aquarium be earth bonded?

I have a large, portable steel framed tank. approx 6m x 2m x 2m. It is used for actors/models to perform in for a variety of productions.

For many years now, I have had conflicting advice about whether or not it should be earth bonded. The initial response is "it's a giant steel structure, bond it!!". But then invariably someone else comes along and points out that, should the tank itself become energised, the people in the water within the tank would become part of the return to earth - the current would flow through the tank and them. If it was not bonded, as it is by design insulated, they would be ok. At least until they tried to leave the tank.

To date our solution has been to be super cautious of anything that could even present the possibility of bringing current to the tank itself. But how do we make a once and for all decision on whether it should be bonded without any professional consensus of opinion?
 
Sorry, couldn't resist this..
electrician-fish-tank.jpg
 
Hi - just a couple of thoughts :)
- Has the installation been done in accord with BS7671 section 7 and BS7909 ?
- RA and full test prior to each use?

Hi,

The only part of section 7 which in spirit is tough to enforce is others placing/moving lamps closer to the tank than the regs would permit. I say "in spirit" as that requirement is specific to certain locations such as bathrooms, with specific rules for each defined special location.

Was there a particular requirement you were thinking of?

Regards BS7909, yes. That's the one that all event/studio sparks are well read up on. We don't have full control ourselves over what goes where in the layout of the temporary installations, such as the running of power cables and lighting in the area, but we do flag anything that is obviously a concern or may not have been given full consideration.

The sparks on site always ensure the following key areas:

- Every new electrical feed/cable is tested prior to being made available for connection, incl RCD

- All must be 30ma unless special equipment required a different solution.

- All third party electrical equipment is checked for testing within past 12 months and in general scrutinised for suitability of safety precautions.

- in potential wet areas (ie filming in a carpark where it could rain and water could pool) all portable distribution boxes are raised from the ground.

In general everything is considered, checked/tested ahead of each use, most of which last only a few days before being used for something else and being tested again. You could compare it to fully testing and reviewing the electrical installation in your bathroom everytime you take a bath.

The question of whether or not to earth the tank itself does remain a sticking point, but I can say sparks in charge of power on site do everything reasonable to make the surrounding electrical installation as safe as possible. They're 'on it'.
 
In terms of bs7671
Bonding - only if it can introduce a potential. The only way i can think is if it was sitting directly on the earth. In that situation the earth would be the extraneous conductive part.
Earthing - only if it is a part of the electrical installation designed to protect people from electricity eg class I appliance or fitting.

So it sounds like the answer is connection it to the main earthing terminal is like bonding a spoon.

If it's a temporarily installation other rules apply other than bs7671. In terms of common sender, to me, any conductive surfaces have a risk, and bonding them all just changes the risk to a different one.
 
Could you post ( I have only looked quickly over the previous posts so you may have done already) - a sketch of the set up including where the items of electrical equipment and their wiring are in relation(including distances) to the aquarium? Also, what voltage is the equipment and what is the electrical supply ie: generator, mains, TT/TNCS/TNS. Where is the water supply which fills it and include the pipework and whether metal or plastic?
 
I can see why you've not reached a conclusion on this question. I can imagine setups where it may add safety, perhaps as performers enter and exit the tank and stepping onto GME while touching the tank etc. If you've a repeated system of installation (tank placement, access and egress, steps etc) that could be assessed perhaps and a conclusion reached. Personally, I want to TT the installation and connect all conductive parts, but it's not a cattle shed so I'm probably wrong :)
 
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I can see why you've not reached a conclusion on this question. I can imagine setups where it may add safety, perhaps as performers enter and exit the tank and stepping onto GME while touching the tank etc. If you've a repeated system of installation (tank placement, access and egress, steps etc) that could be assessed perhaps and a conclusion reached. Personally, I want to TT the installation and connect all conductive parts, but it's not a cattle shed so I'm probably wrong :)



I have similar thoughts to you on this but still need to see a sketch - my early thoughts before seeing sketch are to make it a 55V-0-55V TT installation centre -tap earthed and the 110V passed through a 10mA double-pole RCD. 110V provided by a safety isolation transformer supplied by mains through a 30mA double pole RCD. Then bond all metalwork together and to terra-firma. OP - this is not a definitive answer.
 
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I have similar thoughts to you on this but still need to see a sketch - my early thoughts before seeing sketch are to make it a 55V-0-55V TT installation centre -tap earthed and the 110V passed through a 10mA double-pole RCD. 110V provided by a safety isolation transformer supplied by mains through a 30mA double pole RCD. Then bond all metalwork together and to terra-firma. OP - this is not a definitive answer.
That was one of my initial thoughts but if you read further up there's reference to third party equipment such as lighting, with BS7909 being referenced that tells me this is a very temporary structure that could be used in numerous locations fed from varying supplies.

I would say at each location the installation should be assessed by the set sparky. You can take all the precautions you want but all it takes is a gust of wind to blow over a high level set light to completely balls things up.
 
Could you post ( I have only looked quickly over the previous posts so you may have done already) - a sketch of the set up including where the items of electrical equipment and their wiring are in relation(including distances) to the aquarium? Also, what voltage is the equipment and what is the electrical supply ie: generator, mains, TT/TNCS/TNS. Where is the water supply which fills it and include the pipework and whether metal or plastic?

The usage scenario and layout, equipment is different at each use, and generally we arrive just ahead of use, and would start to fill the tank as soon as it's loaded into position (baring any obvious safety concerns that would prevent us doing so). Of course this is a very different way of working compared to what most sparks on here would consider reasonable - but that's TV/events. You hit the ground running.

The need for speed is the reason all studios and event teams have on site dedicated sparks to monitor/test/re-arrange in real time. And the sparks will live that life full time.

The water supply isn't really an issue as the tank is filled once, then disconnected from supply. In any case, the supply would be rubber/pvc hose of some form. The permanent pipework between the tank and it's filter system is PVC. The filter system itself is bunded to protect against internal leaks, with all electrical on the outside of the bund. And of course, RCD on board for each circuit, even though it would only ever be fed by a site feed that is also protected and tested prior to each use.

I think mostly in the UK at least exhibition/event venue power to each stand is TNS/TNCS. In studios normally TNS, and when we're in the middle of nowhere relying on generators, TT. Not much help huh?..

I have similar thoughts to you on this but still need to see a sketch - my early thoughts before seeing sketch are to make it a 55V-0-55V TT installation centre -tap earthed and the 110V passed through a 10mA RCD. 110V provided by a safety isolation transformer supplied by mains through a 30mA RCD. Then bond all metalwork together and to terra-firma. OP - this is not a definitive answer.

The industry is firmly on 240v, and this will not change. The specialist equipment needed doesn't exist in 110. In many ways 110v would probably make a great deal of sense as in reality, studios and exhibition venues represent about the most intensive construction environments you can imagine.

Everything else steel in these places will be connected to earth by default. That's certainly standard practice, it's just the tank which makes the sparks stop and reconsider sometimes. Hence my asking on here.

Whilst so much varies the constants are:

There will always be temporary 240v 30ma protected power routed all over the place around the space the tank is in, supplying hundreds of items of equipment for A/V, lighting, cameras, the list would be endless.

There will always be people entering/exiting the tank at times that the surrounding power supplies are needed to remain on.

People will always be in the tank at some point to perform in some way.
 
That was one of my initial thoughts but if you read further up there's reference to third party equipment such as lighting, with BS7909 being referenced that tells me this is a very temporary structure that could be used in numerous locations fed from varying supplies.

I would say at each location the installation should be assessed by the set sparky. You can take all the precautions you want but all it takes is a gust of wind to blow over a high level set light to completely balls things up.

Indeed. anything can happen and not only is there limited time to plan ahead, the nature of the industry is that things can quickly evolve on site during testing/rehearsal.

The in house sparks or production sparks do indeed assess in advance as much as possible, and in real time throughout each production.

As for the set light falling into the tank scenario - yup, that's the obvious one. Albeit a whole team of very conscientious people make damn sure it won't happen. But it has to be assumed that one way or another there is a remote possibility something could cause the tank to become live, hence the ultimate question: are those in the tank at the time best protected by the tank being isolated or earthed?
 
Hi - next question(s) how do the performers get in and out? And how is the water heated and or filtered?

Varies of course :)

I've gone into deals of the filter system further up, but it's essentially a swimming pool filter system, with swimming pool heaters in a bunded enclosure with all electrical on the outside of the enclosure.

Access is normally via platforms built by set construction. If there is any exposed steel it's typically connected to earth - although that's really the responsibility of the sparks and whoever has designed/built the structure. We just supply the tank and the filter system.
 

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