Garden pond wiring

[Smooshy]

Hi all

Long time reader, first time poster...

I'm about to purchase a pond pump and filter which have a 3 and 5amp fuse rating respectively. I planned to wire these into a fused IP66 switch box next to the pond which will then run to the house. At the moment I have an RCD double socket on the outside wall which I assume has been spurred from the living room circuit but I don't know for certain (it was previously a regular socket but I swapped it with an RCD after buying the house). I use the socket for various tools and bits so the Mrs doesn't kill me in my sleep.

My question is this; should I stick a 30Ma RCD socket before the spurred socket and wire the pond switches into this, or should I put the RCD after the plug socket?

The outside socket is only used occasionally so there isn't an appliance coming off it regularly but obviously I don't know what the position will be when I'm not around.

I know multiple RCD and fuses is somewhat redundant with minimal benefit but it's outside and I'd rather have multiple redundancies in the event of a problem.

(This seems like an obvious one but I think I'm having a bit of a moment).

Thanks for any help in advance!

 

[PrenticeBoyofDerry]

If the circuit being spurred off of, is a ring final, then you are not allowed to take multiple spurs.

I would suggest fitting an RCD fused connection unit prior to the first spurred socket off, the ring. This would make all sockets after that RCD protected and multiple socket there after can be connected, as can any switch/isolation arrangement for pond pump.

I assume this feed socket circuit is not RCD protected at the main fuse board?

 

[Smooshy]

Thanks, that's what i thought.

I honestly don't know if it is spurred or not, the chap who owned the house was an electrician and rewired the entire house but he cut corners that have had to be fixed. So I have just assumed it is as a precaution.

The fuse box is RCD protected but I like the extra redundancies as it's outside and water.

If I plug something in that uses a rating above 13amps I assume it would trip the fuse once the pond is wired in and switched on?

 

[PrenticeBoyofDerry]

Thanks, that's what i thought.

I honestly don't know if it is spurred or not, the chap who owned the house was an electrician and rewired the entire house but he cut corners that have had to be fixed. So I have just assumed it is as a precaution.

There is very little benefit to having a secondary RCD on a circuit.

The fuse box is RCD protected but I like the extra redundancies as it's outside and water.

The primary RCD at the fuse board will take care of that, the problem is there is no guarantee that the RCD on the external socket will trip before the main fuse board RCD.

If I plug something in that uses a rating above 13amps I assume it would trip the fuse once the pond is wired in and switched on?

That would depend on the size and time period of the overload.

 

[Smooshy]

Thanks again for the help.

So I'm good to go with a RCD FCU (even if an extra RCD is a bit unnecessary) connected to the double socket and switch box?

I use the outside sockets for the hedge trimmer, saws and drills every now and again - basically what I'm getting at is whether using the sockets while the pond pump and filter is on is a) dangerous (which I assume it isn't thanks to the RCD FCU) and b) just going to trip straight away so I'll have to turn pond off first?

 

[PrenticeBoyofDerry]

a) The only danger is that an overload could cause the fuse to trip/blow(as it should) and if you are using something that is a danger when stops suddenly.
RCD trips are different to overload trips.
b) The pond pump demand, would depend on the volume of water you are pumping to what the desired current is required, but generally they are very low power rated and 1A would do for a wattage of less than 230. It is possible that power tools and garden tools could require 13A, so it is borderline that a overload would exist for a long enough period to cause a fuse to trip.

 

[Smooshy]

Brilliant, thank you very much, it's much appreciated.

 

[ban-all-sheds]

I honestly don't know if it is spurred or not

When you changed it, how many cables did you find?

If I plug something in that uses a rating above 13amps I assume it would trip the fuse once the pond is wired in and switched on?

That would depend on the size and time period of the overload.

Time-current characteristics for 3A and 13A BS1362 fuses:

 

[Smooshy]

I don't recall, it was years ago. If I had to guess I'd say it was just the one cable protruding from the wall to the outside socket.

 

[aptsys]

So I'm good to go with a RCD FCU (even if an extra RCD is a bit unnecessary) connected to the double socket and switch box?

I wouldn't install an extra RCD. Every time you come to test the RCD you'll probably trip the other RCD and never actually be able to test it.

 

[Smooshy]

Hadn't thought of that.

So just a regular old fashioned fuse to start the spur? If i overload the circuit though I'll just be replacing the fuse everytime i use the socket though, won't I?

 

[bernardgreen]

The supply to a water feature is best via a two pole ( Live and Neutral ) isolator so that in the event of a fault the supply to the water feature can be fully isolated. Switching OFF just the Live and leaving the Neutral still connected to an faulty appliance can still cause the RCD to trip.

 

[ban-all-sheds]

I don't recall, it was years ago. If I had to guess I'd say it was just the one cable protruding from the wall to the outside socket.

This it's a spur, and you must do what you first suggested if you want to connect more outlets - put an FCU before it.

 

[Smooshy]

Thanks.

I planned to have a fused switch with ratings no more than 3 and 5amp by the pond for the equipment. So that will probably be enough should there be a fault with the actual pump and filter with the FCU at the start of the spur?

 

[ban-all-sheds]

If there is a fault there would be zero guarantee that a 3A or 5A fuse would operate before the 13A one in the FCU at the origin of the spur. Either or both might blow.

By all means have switches to allow the individual pond items to be isolated, but you don't need FCUs.