Question regarding immersion heater dedicated circuit

[Bonce]

I have an external socket which is run back to a 16A MCB under RCD protection in my consumer unit.

I currently do not have any wiring connecting my immersion heater at my hot water cylinder. It looks like it used to have wiring but at some point (presumably when electrics were done) they decided not to bother with the immersion.

If possible I would like to be able to connect this up. I have read other posts about immersion heaters and the fact that usually these are on dedicated 16A circuits to the consumer unit due to the power they consume, but I have also seen posts where people have advised that it may be possible to run off another circuit if that circuit does not get used heavily.

I do have a spare way in my CU but don't have a 16MCB (only a 6A - presumably what the CU came with - this isn't in the CU by the way there is a blanking plate) I know I could buy a 16A MCB but am worried about overloading the RCD (even if all circuits are not being used at the same time.

Therefore as the outside socket is only used occasionally when I cut the grass would it be possible to use this for the immersion circuit as well?

By the way I have no intention of doing this myself but would like to have an understanding of whether this is possible before contacting a local electrician.

Thanks for any help.

 

[holmslaw]

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[Bonce]

Thanks Holmslaw. If thats a bodge then I'll keep well clear. It is a split board CU and its and 80A 30mA RCD that I was talking about.

At work at the moment, but off the top of my head think it has down power circuit 32A, 16A outside circuit (mentioned), kitchen 32A (though don't have any high power devices i.e. cooker is gas), down lights 6A, and I think something else maybe smoke alarms 6A?.

Theres one spare way as mentioned but if I filled this with a 16A MCB wouldn't that (even with diversity) be too much for the RCD?.

 

[Taylortwocities]

No it wouldnt be too much for the RCD.
The MCB will be 16A but the fuse in the plug for the mower will be much less (13A, maybe 5A).

The new MCB must be on the RCD side of the board and, you are right, you'll need a competent person to do this. Find a nice clean shiny one at www.competentperson.co.uk.

PS Heaters for water vessels over 15litres should be on their own supply - Building Regs, I think...

 

[holmslaw]

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[Bonce]

Thanks Holmslaw and Taylortwocities, advice is much appreciated. I have a couple more questions if you can spare the time

Regarding the MCB's under the RCD protection; I had just assumed that the RCD should not have more MCB's than add up to the 80A under it i.e. I currently have (2*32) + (2*6) + 16 = 92, presumably then this is not the case (is there a 'rule of thumb' for this - just interested)? and it doesn't matter if I add another 16A MCB 'under' this RCD? taking the total to 108?

I guess I was concerned that I could have down lights on and be using down power and kitchen power as well as outside socket and immersion at same time and was therefore concerned that this could affect the RCD.

In the future I may want to run some pond equipment off the external power supply (I imagine this would all be low voltage stuff) would this make any difference to this?

I can appreciate that it may be difficult to comment on this without knowing exactly what I may want to install but I can say that the distance form house to pond which would need armoured is less than 10m (probably around 5m) adn it would probably only be a very small pond pump.

 

[holmslaw]

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[Bonce]

Ok thanks Holmslaw for satisfying my interest , very much appreciated and luckily I' not a cannabis grower!

Thanks again.