Connecting aqua lisa processor via light circuit

[simsum]

Hi, can anyone please advise me if i can run a cable from my lighting circuit to a 3Amp switch fuse for an aqua lisa shower processor, which is less than 0.5 Amp.
The wires in my loft are the old red ones and i would be using 20 Amp junction box.
Would i need to sleeve the old wires with the new colours if i connect them to power off for the shower.
Just to mention all circuits in the house are rcd protected.

 

[ColJack]

generally, no..

there's nothing to stop some idiot in the future putting a larger fuse in and the lighting breaker is only rated at 6A usually..

fused spurs are best put into the power circuits, not the lighting circuits... not least of all because the next poor bugger in your house won't be expecting his shower run off the lights..

 

[electronicsuk]

Still, there is nothing stopping you from doing it other than generally poor workmanship, it's not something that should be done where possible. Even if it means a bit more effort on your part, it would be far better to feed via FCU from a ring final.

There must be some sockets nearby, and after spending whatever you have done on the Aqualisa digital (I have one of their digital showers and a digital bath filler, and I know they aren't cheap) you might as well do the job properly.

 

[simsum]

Thanks to both ColJack and Electronicsuk for the advice.
I'll try and run off a socket nearby.
The only problem is that all the walls upstairs are dry lining in the house and I would need to mechanically protect the cable and run it up from a cupboard across the loft and down into the boiler cupboard adjacent to the ch/hw control.
But it was worth asking anyway.
Many thanks again.

 

[RF Lighting]

Where will this unit be located?

 

[ColJack]

surely there's a boiler feed in the boiler cupboard?

can't you put the spur off this?

 

[simsum]

The aqua lisa processor unit is already in the boiler cupboard (upstairs) waiting to be connected to the pipes, it is about 6 ft x 3 ft ventilated for the boiler.
I have a feed to the ch/hw but that is a fused switch and i thought i could not feed of a fused switch to another fused switch.
The feed directly to the boiler is in white flex cable.

 

[electronicsuk]

Firstly, stud walls are ideal for running cables and generally very easy to work with. If the cables are RCD protected then you can run them unprotected in the stud wall as long as you keep within the safe zones for concealed cables.

Secondly, it's fine to run an FCU from the LOAD side of another FCU, although you would need to be sure that power is always present at the boiler, some older installations switch the entire supply with the programmer/stat.

The boiler FCU may even be fed off the ring final, in which case you could easily break into the ring or spur off to another FCU.

 

[simsum]

I guess I can spur off the cable before the fused switch then for this aqua lisa processor.
I'm attaching a picture of the fused switch. Could you please confirm if you mean the white flex that is connected to the boiler if not the grey cable to the fused switch.

Untitled

• simsum
• 10 Mar 2009
• 1

for the ch/hw and the black cable above it is the processor cable.

Untitled

• simsum
• 10 Mar 2009
• 1

 

[electronicsuk]

From your pictures it would seem that the FCU (or 'Fused switch' as you put it) is fed by a single length of 2.5 grey twin & earth. If this grey cable is a spur off the existing ring final then you cannot feed another FCU off the supply side of the existing FCU that currently feeds the boiler.

However, if the boiler feed is a dedicated radial circuit protected by it's own MCB at the consumer unit, it should be find to come off the supply side with another piece of 2.5 to a new, seperate FCU. You would need to confirm that the supply is indeed a radial circuit.

Your other option, assuming the supply is a spur from a ring final circuit, is to take a feed from the load terminals on the existing FCU. Said terminals will be where the white flex in your picture disappears to.

 

[simsum]

Thanks for the advice it has been much appreciated.
Could you just tell me what does fcu mean ?

 

[electronicsuk]

FCU = fused connection unit, sometimes incorrectly called a fused spur or fused switch, it's the unit shown in your picture next to the CH programmer.

Spur = feed taken via a single length of cable from a point on a ring final circuit to feed an electrical accessory, without forming a part of the continuous ring itself.

 

[ColJack]

Fused Connection Unit. - a general term that includes switched and unswitched versions..

what you need to do is take the grey cable from the existing switched fused spur and put it into a third FCU with a 13A fuse in it, then from the LOAD side of this one, to the FEED side of th existing FCU and a second FCU to feed the aqualiser..

 

[simsum]

Many thanks for all your help.