Shower/Fan Ceiling Switch

[alanellicott]

EFLImpudence said
"If a rewirable fuse is used the cable's current carrying capacity should have been derated by 0.725 which would result in it not being suitable.
It will be alright with the mcb."

Yes I mean one of them. Thanks again for sensible help.

 

[EFLImpudence]

Disregard my previous post about derating the cable as a single load (the shower) cannot overload the circuit so it does not apply.

 

[Scoby_Beasley]

I'm just wondering if there is any RCD protection for this circuit?

 

[PrenticeBoyofDerry]

I can pretty much guarantee that the 9.5kW rating is at 240V, not 230.

The shower will demand 41A, so ideally 45A or 50A MCB.

Naughty PBoD.

The 9.5kW will be quoted by the manufacturer at 240V and so is 39.6A

At 230V it will be 8.74kW and so 38A.

Really http://www.tritonshowers.co.uk/media/11251/inscriptions_electric_shower.pdf

The MI states 230V-240V, selection of devices 40A/45A.

 

[EFLImpudence]

The MI states 230V-240V, selection of devices 40A/45A.

I haven't read it all but I think the figures to which you refer are stated in two different places but either way 40A is stated.

Page 5.

230-240 is the voltage for which the shower is designed and ...

table 4

states for 9.5kW, mcb 40/45A

but there will be stated somewhere on the pack or shower 9.5kW @ 240V.
It may also state (Gainsborough do) 8.7kW @ 230V.


Furthermore table 4 does show inconsistencies between the ratings of mcb and cartridge fuse.

 

[PrenticeBoyofDerry]

Is a 40A BS1361 a standard rating?

 

[EFLImpudence]

Is a 40A BS1361 a standard rating?

Yes.

 

[alanellicott]

Well everything is fine now and the shower is working absolutely OK.
I have decided to leave the fan out of the equation and wire it separately and I am thinking of doing the following.
We need the function of the timer on the fan but I do not wish to wire it into the lighting curcuit (difficult access). I therefore intend to take a feed off a ring main junction box in the loft and place a 13 amp socket on a joist above the bathroom ceiling. I will then feed a ceiling pull switch from the socket via a plug with a 3 amp fuse.
Bearing in mind the fan has three wires ( two red and one black), can I use a single pole pull switch with one of the reds on the load side of the switch and the other red on the supply side and then take the neutral back to the plug.
Will I do any damage to the fan if I get the reds the wrong way round as I don't know which is which?

 

[alanellicott]

....place a 13 amp socket on a joist above the bathroom ceiling. I will then feed a ceiling pull switch from the socket via a plug with a 3 amp fuse.

I do realise I could use an in line fuse.

 

[PrenticeBoyofDerry]

....place a 13 amp socket on a joist above the bathroom ceiling. I will then feed a ceiling pull switch from the socket via a plug with a 3 amp fuse.

I do realise I could use an in line fuse.

So why don't you?

 

[EFLImpudence]

Bearing in mind the fan has three wires ( two red and one black), can I use a single pole pull switch with one of the reds on the load side of the switch and the other red on the supply side and then take the neutral back to the plug.

That's fine.

Will I do any damage to the fan if I get the reds the wrong way round as I don't know which is which?

No, you just won't have the 'run on'.

The plug will be a means of isolation otherwise you will need a double pole switch.