Wiring in FCU's via Junction Box

[old wrinkly]

An electrician friend of mine has said that it's OK for me to make all the connections to a couple of new FCUs I need, PROVIDED, he makes the final connection to a new MCB at the consumer box. See my earlier post Bathroom re-vamp

With that in mind I want to lay in all the cables ( I have some Wickes twin and earth 2.5mm ring main cable rated max 23 amps) and switches for an electric towel rail element and under tile heating, both to be fed through a neon switch sited in my airing cupboard for isolation purposes. I will leave a tail of cable for connection to the new MCB.

In the past I would have broken the live, (leaving the neutral and earth intact) passed this through the neon switch, back to a spare terminal in a junction box and then off to the appliance to be controlled.

This was quite straight forward when using a 4 or 5 terminal box. I've been looking but so far I have only been able to find 3 terminal 30amp and 4 terminal 20amp junction boxes, which I already have. Could I use the 4 terminal 20amp for this purpose or must it be 30amp?

I've read somewhere that junction boxes aren't so common in use nowdays but can't find that now.

If I can't use the 20amp junction box I was wondering if anyone could tell me the best way to make the connections to the FCUs so that I can isolate using the neon switches or if there is a better way to tackle this?

Thanks

 

[Gaz the Sparky]

An FCU breaks the live and neutral conductors aswell as fusing. you Have a live and neutral in terminal sometimes marked L1 N1 or L in N in then you have two terminals for connecting the load these are marked either L2 N2 or L load N load

 

[RF Lighting]

Run the 2.5mm² t&e feed from your consumer unit directly to the first FCU. Then fit another piece of 2.5mm² t&e from the first FCU to the second FCU.

Then connect the the towen rail to the first FCU and the UFH to the second FCU.

No crappy joints, and everything double pole isolated.

Also your equipotential bonding in the bathroom will need extending to include the new circuit you are installing.

 

[old wrinkly]

Thanks for the replies.

I was sitting having my dinner and I suddenly thought "Why on earth did I ask that question".

For some reason I kept thinking of a light switch whereas the neon switch has L & N Feed and L & N Load so can be connected straight from the MCB and then directly to the FCU.

Although the FCU will break the circuit with the fuse removed I need to control both the towel rail heater and UFH with a neon switch so that I can turn them off when not needed. I also want a visible indicator when they are on so that I don't waste electricity. I'm not planning to use a timer thermostat with the UFH as it won't be my main source of heating.

I don't expect to use the FCU unless either the towel rail heating element needs replacing or the UFH thermostat or mat fails. If the mat itself fails I would isolate the circuit completely as I won't want to lift the floor tiles.

As for bonding. At the moment the hot/cold pipes to the basin are bonded as is the main water feed in. I can't see any bonding on the 22mm hot/cold pipes to the bath taps but these could be bonded in the loft.

I'm going to have extra hot/cold pipes for a separate shower and was going to bond these. Is there any other bonding I need to be aware of?

rf lighting. You say No rubbishy joints, and everything double pole isolated. The first is obvious, I always make sure my connections are tight and the cables properly fitted. I understand DPSt & DPDT switches but I'm just a bit vague on what double pole isolated actually is. I want to make sure I do the job properly and safely so when my friend comes there aren't any issues so would grateful if you could explain exactly what you mean.,

Thanks

 

[Gaz the Sparky]

doube pole switching /DP switch means that the switch disconects boths poles at the same time eg Phase and Neutral

Single pole switches SP only disconects one pole eg the phase conductor and these sould always be fitted in the phase conductor

hope this clears everything up

 

[old wrinkly]

Thanks, I more or less knew as much but still worth being reminded.

The FCU I believe would be classed as DP but not to sure about the neon switch but as it's also fused I'm assuming this would be classed as the same thing so I should have double protection for isolating the circuit.