Fused Switches and RCD!

14 Mar 2006
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West Glamorgan
United Kingdom
I need to install a pump in my airing cuboard for my new mixer shower. The instructions says that it needs to be wired to a 3 amp fused switch, my question is there is already a fused 3 amp switch in the aring cuboard that is for the central heating control box (or what ever it is called), can I just wire the new pump into this existing switch or does each piece of equipment need its own fused switch????

The other question is the instructions for the pump also says that an RCD with a trip rating of no more than 30mA should be included in the circuit. I was thinking of using the RCD that is on the electric shower that will soon be replaced. But I cannot see on it anywhere what the trip rating is, there is a value of 40A and some greek letter then 0,03A 240V made by Hager.
It says it has a Inter Differential x U740 uI 20066.

What should I be looking for to know if it is suitable????

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That 0,03A is 30mA rated RCD
You have one item supplied by a 3A fused switch and you ask if you can add another item that needs a 3A fused switch.
If the manufacturer say an item needs 3Amps adding another for the same amount could cause the fuse to blow.
I would doubt your boiler is on the RCD anyway, so best to down rated the shower circuit and add a FCU to the end.
Thanks for that!

By "down rating" do you mean I should reduce the size of cabling from 1.5mm to 1.0mm or something like that?

I have taken out the old electric shower now, so the RCD is redundant at the moment! If I use it for the shower pump for my new mixer shower that I have just plumbed in, extend the cable (I think it is a 1.5mm, its a pretty large cable!) to the airing cuboard to a junction box, then taking to branches from it, one for the existing FCU that is supplying the Central Heating Timer and motorized valve etc, and the other to a new FCU for the new shower pump, does this sound safe?

Hope this makes sense!
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Ignore the last post I was completly wrong! I have just checked the existing wiring, its not 1.5mm at all, was getting it mixed up with the wiring supplied with the new shower pump.

The existing wiring from the 0,03A RCD is 6mm (big grey cable). I plan to fit a junction box at the end of this cable, then from this, run a 1.5mm cable to the existing 3 AMP FCU (which controls my Drayton Push Fit Central Heating Contoller and mechanized valve), and to the new 3 AMP FCU (for the the new shower pump).

With a 6mm cable going in and a 1.5mm cable going out of the junction box, what AMP junction box do I need???

Does this sound safe?? Oh and none of this is anywhere near the bathroom!!!

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