A few questions regarding domestic swimming pool..

HappyHippyDad · Jul 22, 2019

I have been asked to price for a supply to an outdoor swimming pool (domestic).

The electric supply will be for a air source heat pump and the pool pump. (see pics)

The pool is above the ground rather than buried in it (so figure 702.2 applies with regards zones). It has metal sides and metal bars going into the ground to support the sides (see pic). It also has a metal rim going around the top of the sides.

The property is TT. Ze = 37ohms

My questions are:

1. Do the metal bars supporting the pool frame need bonding? I haven't tested them yet but lets assume they test as extraneous as they are sunk into the ground. They would not be simultaneously accessible with any exposed conductive parts, however I think 702.415.2 says they need to be connected to the CPC of exposed conductive parts in any of the zones.

2. Would the metal sides and rim need bonding? They would not test as extraneous so i cant see why they would.

3. Would I need any rotary switches for isolation? There will be a IPx5 consumer unit in zone 2 for the heat pump and pool pump. This will have 30mA RCD so there will be local DP isolation already but not for each item. I would think a separate rotary switch for both the heat pump and pool pump would be a good idea.

4. Do the heat pump and pool pump need to be outside of zone 1? Also, does the switch gear (i.e CU) need to be outside of zone 1. The switchgear will all be IPx4 or IPx5. 702.53 says no to switchgear in zone 1 but 702.512.2 says electrical equipment (i.e the pumps) have to be IPx4 inside zone 1. I'm guessing the pumps can be zone 1 and the CU needs to be outside.

pool

pool pump

heat pump

inside heat pump

pirate · Jul 22, 2019

Thanks for posing this question HHD. I am about to start some work on pool maintenance and would be very interested to hear what people have to say on this.
On an above-ground pool like the picture, surely the only connections to the pool will be water inlet/outlet/drain and all be plastic pipe insulated from any electrical supply?
Built-in submerged lighting is different, of course, but the couple I have examined recently are dismountable items with waterproof screw-on connectors to sealed units, at 24V so not likely to cause too much hassle...

Deleted member 9648 · Jul 22, 2019

It would be utterly pointless to bond anything there, the whole idea is to create a zone of equal potential which is impossible for a structure completely surrounded by the general mass of earth.
All the other questions are answered in section 7.

HappyHippyDad · Jul 23, 2019

Thanks to Wirepuller for his suggestions on the bonding aspect.

I do struggle a little making sense of section 702 although I know some will say 'Why'?!

Any takers for the positioning of the electrical equipment (i.e heat pump /pool pump and switchgear)? The heat pump is IP23. It will be located in a small wooden structure (lets call it a small shed) so I feel that could be classed as inside and therefore be ok for zone 2 as per 702.512.2? The pool pump may be in zone 1 and will be IPx4 at least, is that ok?

The consumer unit will be in the same shed in zone 2 this is fine, but I'd be interested to know if others would use rotary switches as well as the RCD and MCB's?

Lastly coming back to the bonding (much to Wirepullers annoyance

), 702.415.2 does say that any extraneous in any of the zones needs supplementary bonding. However, it also says in accordance with 415.2 which states that it is only extraneous that is simultaneously accessible to the exposed CP that needs bonding, so Wirepuller is right, it doesn't need bonding.

Deleted member 9648 · Jul 23, 2019

IMO bonding the metal struts on the pool would increase the shock risk, a person in contact with a strut for the duration of a fault is likely to be stood barefoot on damp ground which is likely to be at zero volts. Any rise in voltage due to the strut being connected to the earthing system whilst a fault is in progress will pose a substantial shock risk.