Sanity check on my RCD please?

[Blair]

Hi all,

I'm about to install a whirlpool bath; clearly something that uses electricity to swish water about (whilst you're sitting in the water) is considered somewhat more risky than usual

Before I bought the bath I knew an RCD was going to be needed; the bath has arrived, and the instructions state:

"The applicance should be supplied through a residual current device (RCD) having a rated residual operating current not exceeding 30mA. The supply line should be fed via a suitable rated doube-pole isolater having a minimum gap separation of 3mm in all poles. The isolator and RCD must be fitted outside the bathroom area (this may be sited in the consumer unit or separately). This appliance must be permanently connected to fixed wiring."


OK, not rocket science. But I've never bought an RCD before, so I wanted to check I've chosen a suitable one; it's here:
http://www.screwfix.com/app/sfd/cat/pro.jsp?id=69659#

It seems ideal - I'm not missing anything am I? Clearly I'll be getting it inspected post-installation, as per the new regs, but I'd rather know it's suitable before I fork out for it


Just to complete the picture, I have 10mm cable running to the RCD site, in the airing cupboard next to the bathroom (I had a 9.5kw shower that died, replaced it with a venturi shower so the cabling's free for the whirlpool bath).

Thanks in advance

 

[breezer]

the unit is fine, but the mcb is probably a bit too big for the application, what is the pump rating?

 

[Adam_151]

I'm assuming you intend to put that on the end of the shower cable and make it like a submain, right?

As Breezer says you'll need to swap out the MCB in there for a smaller one, and Volex is a bit rubbish. You might be better off with an MK garage CU like this: http://www.screwfix.com/app/sfd/cat/pro.jsp?cId=A331829&ts=69253&id=33248 , if you intended to connect flex to it, then use an appropiate suffing gland (actually I'd come out of the breaker in 2.5 t+cpc to a FCU with switch, flex outlet and 3A BS1362 fuse)

Or you could use an FCU FCU off the upstairs ring: http://www.screwfix.com/app/sfd/cat/pro.jsp?cId=A231858&ts=69453&id=14770


I'm assuming you have something like a 300w pump and your consumer unit doesn't already have an RCD on the circuits in question?

 

[JohnD]

I'd go with the RCD FCU. Smaller, neater, cheaper, incorporates the RCD and an appropriate fuse cartridge (3A or 5A, I imagine). Put it just outside the bathroom door.

No harder than a shower pump.

As this is in a bathroom it is notifiable under building regulations.

Remember to supplementary-bond in the bathroom.

 

[securespark]

What's wrong with this?

http://www.screwfix.com/app/sfd/cat...d/cat/pro.jsp?id=14770&slotName=null&homeRef=

 

[securespark]

YOU B*TCH!!

[Securespark dragged kicking and screaming off forum by Mods....]


[Calms down....]

Why oh why oh why do you and I always do this????? I reckon you sit by your PC, waiting for "securespark" to appear in registered users on-line...

It's a conspiracy, I tell you!

 

[JohnD]

Hee hee!

 

[Blair]

Thanks for the speedy response chaps

the unit is fine, but the mcb is probably a bit too big for the application, what is the pump rating?

Unfortunately neither the documentation or the pump give the rating (I expected it to be found somewhere on the pump, perhaps it's on the surface bolted to the underside of the bath).

I'm assuming you intend to put that on the end of the shower cable and make it like a submain, right?

Basically the pump (which comes with a 4m cable which will comfortably reach the airing cupboard) will be wired (according to the intstructions that came with the bath) first into the double-pole isolator, which is then wired into the RCD, which will sit on the end of the 10mm ex-shower cable.

As Breezer says you'll need to swap out the MCB in there for a smaller one, and Volex is a bit rubbish. You might be better off with an MK garage CU like this: http://www.screwfix.com/app/sfd/cat/pro.jsp?cId=A331829&ts=69253&id=33248 , if you intended to connect flex to it, then use an appropiate suffing gland (actually I'd come out of the breaker in 2.5 t+cpc to a FCU with switch, flex outlet and 3A BS1362 fuse)

Thanks for the recommendation, I shall go for that one instead then

Or you could use an FCU FCU off the upstairs ring: http://www.screwfix.com/app/sfd/cat/pro.jsp?cId=A231858&ts=69453&id=14770[/QUOTE]
Is that equally suitable for attaching as I described, that is, straight onto the 10mm cable that runs to the fusebox? The reason I ask is the 10mm ex-shower cable just happens to be physically located in just the right place, whereas the upstairs ring isn't

I'm assuming you have something like a 300w pump and your consumer unit doesn't already have an RCD on the circuits in question?

I don't know the pump rating, but yes, there is no RCD on that circuit (apart from the main RCD between meter and CU, and I don't want to rely solely on that - apart from anything else, if it trips I'll find myself lying in the bath in the dark )


Many, many thanks for the replies already chaps - much appreciated!

 

[Blair]

Thanks to all of you for posting!

Sounds like the RCD FCU is a popular choice - which just leaves the main question, is it OK to be cabled into the 10mm run straight to the CU?

Thanks all!

 

[breezer]

if it will fit yes.

also the cu end should be on its own mcb

note. you can always use a bigger cable required for a job, never a smaller one. only problem is making it fit

 

[JohnD]

Better brands will accept 3x4mm or 2x6mm cables. You want to put in 1x10mm which should fit OK. But use a deep box as you will find it difficult to bend the cable round.

Fuse down the radial to no more than 20Amps as the FCU will not be rated to carry more. You could use a 16A MCB; I wouldn't go lower.

You can put additional outlets on this radial if you want to.

(edited: not quite quick enough

 

[Blair]

Thanks chaps.

 

[Adam_151]

What rateing is the RCD between the meter and the CU? unless its a 100ma or 300ma time delayed one then its unlikely it'd descriminate with the 30ma anyway, and if it is itself a 30ma part then there is no chance of descrimination.

(though thinking about it more.... better hope it is an RCD rather than an old voltage opperated ELCB!)

And as far as I know, the pump needs the rateing on it to comply with the appropiate british standards?