Electric Shower to pumped shower.

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Hi.

I'm changing my shower from an electric to a pumped shower.I also wish to utilise the electric supply that is already there.The switch in the bathroom is a 45 amp pull cord switch with a dedicated feed from the consumer unit on a 45 amp fuse with 45 amp cabling.

What I want to do is utilise this cable and switch to power the new pump and the electric capabilities of the steam shower I have bought.Both the pump and the shower have standard fused 3 pin plugs on,the shower has a circuit breaker built in too.

What I want to do is take the feed from the switch (that is currently going into the electric shower) into a junction box and take 2 feeds from the junction box to 2 seperate sockets,one for the pump that will be close to the hot water tank and the other to a socket that will be located behind the shower unit.

The reason I wanted to do this is so that the shower and the pump only have an electric supply when I pull the switch in the bathroom as I think there is no need to have electric supply to these whilst the shower is not in use.

Otherwise,I could take the supply to the pump and shower before the switch so that the sockets are live continuously.

Is there a problem with either method or is one preferable over the other or am I going about this all the wrong way.It's just that whilst I've got the cable installed and it's dedicated then it's better to use it.

Also,I wouldn't mind fitting an electric towel rail (thermostatic 600 watt) and ditching my radiator from the bathroom.Would I be able to do this from the same circuit.

Much obliged for any help.
 
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The problem you have is that because the fuse is 45A, then all the cables downstream need to be 10mm², so in your plan you'd need 10mm² going to the JB, 2 x 10mm² going from it to the sockets (or 3 x 10mm² if you have the towel rail as well).

It will be a total PITA to wire, even if you can get 10mm² cable into socket terminals, which I doubt.

You need to go from the switch (if you want to keep it) to an FCU, and then from there you can use smaller cables to the sockets etc. (which can now be daisy-chained).

If you can't get 10mm² into an FCU, you could use 6mm², if it's a short run and unlikely to get damaged, but if you do then ideally you should fit a smaller fuse in the CU.

What is the total load of all 2 or 3 appliances? Will a single 13A supply be adequate? Another option might be a small CU fed by the 10mm², with circuit(s) from there for the appliances.

Are you aware of the wiring regulations concerning bathrooms (e.g. no sockets allowed, the requirements for supplementary equipotential bonding etc)?

Are you aware of the legal requirements of the Building Regulations, which state that this work is notifiable?
 
ban-all-sheds said:
The problem you have is that because the fuse is 45A, then all the cables downstream need to be 10mm²

Not exactly, only if the 45A fuse is providing overload protection, if you have overload protection downstream then the 45A only needs to provide short circuit protection to the cable which means that the cable could probably be quite a bit thinner but you'd have to calculate it, got a rough fiqure for the I²t of a BS1361 60A of about 40,000 which if you plug it into the adibatic equation gives you a minimum conductor of 1.73mm²

when using breakers the situation is complicated by the fact that the I²t isn't constant and depends on the fault current (if you get the technical info from the maker, you'll find a graph similar to this one: http://imagehost.darkernet.co.uk/i/1143198941_mksentrytypebisquaredtgraph.JPG )

Its exactly the same prininciple that allows spurs off a ring final circuit

I've probably confused the OP totally now...

*picks up chalk, turns to blackboard*

I will remember that this is not the IEE forum
I will remember that this is not the IEE forum
I will remember that this is not the IEE forum
... :LOL: :LOL:
 
Thanks Guys.

First of all,I've now ditched the idea of the electric towel rad,I'll just be plumbing one in instead of the standard rad.

Understand the probs with sockets in the bathroom so what I'll do is remove plug from shower unit and hard wire into an FCU behind the shower unit instead of a socket.

The shower pump is rated at 3.2 amps and the only thing I can see on the shower control box are 2 fuses,one rated at 2 amps AC and the other is rated 5 amps DC.The instructions are in pidgeon english and not very imformative on the electric side.There is a steam generator built into the shower as well.The circuit breaker wired into the shower supply lead is 16 amp with a 13 amp fused plug on as well.

The only reason I want to keep the switch is so that the pump and shower don't have the power when not being used.

All wiring apart from down the wall cavities will be in the loft, so,could I go from the switch using 6mm cable to an FCU say a couple of feet away and then from the FCU to a juction box that will split the feed to the FCU in the bathroom for the shower and one to the socket for the pump.It's just that the shower and pump are on either side of the switch and it will be easier than daisy chaining.

Would I need to down rate the ampage of the MCB even though I'll have a FCU for the shower,fused plug on the pump and the initial FCU from the switch.

Really appreciate the response so far

Thanks Keith.
 
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Keithcunliffe said:
Would I need to down rate the ampage of the MCB even though I'll have a FCU for the shower,fused plug on the pump and the initial FCU from the switch.
you don't HAVE to but i wouldn't consider it good practice to have the rating of a protective device far higher than it needs to be.
 
plugwash said:
Keithcunliffe said:
Would I need to down rate the ampage of the MCB even though I'll have a FCU for the shower,fused plug on the pump and the initial FCU from the switch.
you don't HAVE to but i wouldn't consider it good practice to have the rating of a protective device far higher than it needs to be.

So a 16 amp or 20 amp would be advisable.
 
Adam_151 said:
Not exactly, only if the 45A fuse is providing overload protection, if you have overload protection downstream then the 45A only needs to provide short circuit protection to the cable which means that the cable could probably be quite a bit thinner but you'd have to calculate it, got a rough fiqure for the I²t of a BS1361 60A of about 40,000 which if you plug it into the adibatic equation gives you a minimum conductor of 1.73mm².
Well that's easy for you flash gits with your flash copies of Amtech (or whatever it is) to say... ;)

Us poor ROT folks have to suck air through our teeth whilst sticking a wet finger in the air and decide that anything less than 6mm² is not to be recommended....
 
Could someone please confirm whether this is acceptable or not.

All wiring apart from down the wall cavities will be in the loft, so,could I go from the switch using 6mm cable to an FCU (13 amp ?) say a couple of feet away and then from the FCU to a juction box that will split the feed to the FCU in the bathroom for the shower and one to the socket for the pump.It's just that the shower and pump are on either side of the switch and it will be easier than daisy chaining.
 
ban-all-sheds said:
Well that's easy for you flash gits with your flash copies of Amtech (or whatever it is) to say... ;)

Meh, nothing but windows calculator, I almost feel compelled to write a short guide on it (though I'm sure it won't be quite as usfull as kevin boone's guide to cable selection*)

*that set me on the road to recovery from being a typical ignorant DIYer who thought it was as simple as 2.5mm rings and 1mm lights, and had no clue about earthing arrangements, Ze, VE, derating factors, etc, ad nausem :oops: (feel incrediably embarassed about that), the mroe you learn, the more you realise that there is more to learn
 
Changing the subject almost entirely, the pull-cord isolator sounds like a great idea to me but...

you should not rely on a neon indicator to tell you if a circuit is isolated (e.g. the neon might have failed). See if there is a red plastic indicator as well. If not (since a pull-cord doesn't have an on/off position like a toggle cord does), I wonder if there is another clever way?
 

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