RCD Type for UV Pond Filter

BarrySingh · 4 May 2026

My pond has a UV filter that is protected by ballast. The current outdoor socked does not have an inbuilt RCD. This is my second UV filter, the first developed a fault but instead of tripping the breaker on the distribution board it tripped the RCD on the board and took out half the house. I was reading it probably wasn't an earth fault.

If I were to upgrade the outdoor socket would I need one with a standard or type A RCD? The latter seem harder to come by.

chivers67 · 4 May 2026

https://www.tlc-direct.co.uk/Main_I...tected_Range/RCD_Protected_Range_5/index.html

What do the manufacturing instructions say for the UV Filter? What type of plug does it have?

BarrySingh · 4 May 2026

Ta for the links - B&Q supply similar Type A through a third party - but they are a rare bird - nothing on Amazon.

Sorry - any instructions that came with the filter are long gone. But similar products simply say "Ensure:" "A residential current device (RCD) is used for additional safety". Amongst other things.

pete01 · 4 May 2026

By fitting an rcd socket that won't stop the one in the house tripping it will be pot luck which one trips or maybe both.

Harry Bloomfield · 4 May 2026

It needs to have its own circuit, not on the main house RCD, but on either an RCD, or RCBO, located at the source of the supply. That would avoid the entire house supply being tripped. Useful, would be to also have it supply something none essential, though more obvious - when it did trip, so you would be made aware of it.

The more up-to-date way, is for all circuits to have their own RCBO, rather than an RCD covering multiple ciruits - a combined MCB, and RCD, in one unit.

ericmark · 4 May 2026

There are 10 mA RCD sockets, but these are often a silly price. I have three outdoor sockets, two on their own RCBO, and one on a shared RCBO with half of the house sockets, and yes, that was the one which went faulty.

The use of an active RCD socket may help, this means with a power failure, it will auto trip, so if the main RCD fails, and you try resetting it, the outside socket will remain dead.

But then how would you know when it has failed?

BarrySingh · 4 May 2026

ericmark said:
There are 10 mA RCD sockets, but these are often a silly price. I have three outdoor sockets, two on their own RCBO, and one on a shared RCBO with half of the house sockets, and yes, that was the one which went faulty.

The use of an active RCD socket may help, this means with a power failure, it will auto trip, so if the main RCD fails, and you try resetting it, the outside socket will remain dead.

But then how would you know when it has failed?

The pond pump runs off it too.

ebee · 4 May 2026

Ideally I would have each circuit on its ow RCBO,
Dual RCDs are a bit old hat.
My Consumer unit is older hatter than that though.
One RCD for the whole installation.
(Well actually two - one for off peak and one for normal supply).

hoh - no SPD in sight (except on a few devices including BT point too)

Murdochcat · 4 May 2026

BarrySingh said:
My pond has a UV filter that is protected by ballast. The current outdoor socked does not have an inbuilt RCD. This is my second UV filter, the first developed a fault but instead of tripping the breaker on the distribution board it tripped the RCD on the board and took out half the house. I was reading it probably wasn't an earth fault.

The last sentence is almost certainly wrong. It probably was an earth fault.

With single or dual RCD boards it’s often cumulative leakage that takes out the RCD

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RCD Type for UV Pond Filter

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