Shower Pump Under Bath with an UK 3Pin Plug with FCU

John2016 · 21 May 2018

Hi,

We are getting my parents bathroom fitted and as we are having a shower installed, I would like to also install a shower pump. The only area which the pump can be located is under the bath, in the front.

Next to the bathroom we have an airing cupboard, which has an immersion FCU. I'm planning on breaking into the FCU and spur'ing of a cable to another FCU and then running this cable toward the underneath of the bath for the shower pump.

The cable itself will be run, under the floor boards, therefore can someone advise which cable (rated) I need?

Also the shower pump comes with a UK 3Pin Plug, I would going to remove the plug and the cable and re-cable the wire from the FCU into the pump directly, thus avoiding any sort of connectors underneath the bath - is this OK to do?

Would appreciated any advise.

Many thanks,
John.

John D v2.0 · 21 May 2018

does the pump need an earth connection?
pretty much any mains rated flex would do if you make sure the fuse in the fcu is 3a. depending on whether you need an earth would determine if it needs to be 2 or 3 core.

John2016 · 21 May 2018

John D v2.0 said:
does the pump need an earth connection?
pretty much any mains rated flex would do if you make sure the fuse in the fcu is 3a. depending on whether you need an earth would determine if it needs to be 2 or 3 core.

I would probably install a three core flex cable to future proof the design. Does it affect any regs if I use flex core under the floor boards, in-between joist?

Also what cable (rate amps) would you recommend between the FCU and the shower pump, bear in mind this will go under the floor boards.

I was thinking of using this for when joining the shower pump cable and the cable from the FCU,
https://www.screwfix.com/p/teetube-ip68-3-pole-in-line-cable-joint/92911 - is this OK to use?

Thank you.

ban-all-sheds · 21 May 2018

John2016 said:
I would probably install a three core flex cable to future proof the design. Does it affect any regs if I use flex core under the floor boards, in-between joist?

No.

Also what cable (rate amps) would you recommend between the FCU and the shower pump, bear in mind this will go under the floor boards.

I was thinking of using this for when joining the shower pump cable and the cable from the FCU,
https://www.screwfix.com/p/teetube-ip68-3-pole-in-line-cable-joint/92911 - is this OK to use?

You don't (we all hope, especially you

) need it to be IP68 rated. Plus it will, by the sounds of it, be fairly inaccessible. Use this instead:

https://www.tlc-direct.co.uk/Products/ASJ803.html

Or better still, if the cable into the pump is replaceable, replace it with a single length with no junction boxes.

winston1 · 22 May 2018

The fuse is to protect the cable not the pump. So use 1.5mm cable and you won't need another FCU. Just wire it into the output of the immersion FCU.

DaveHerns · 22 May 2018

winston1 said:
Just wire it into the output of the immersion FCU.

Input, surely? Then it will work without the immersion being on.

winston1 · 22 May 2018

DaveHerns said:
Input, surely? Then it will work without the immersion being on.

Ah, yes, silly me.
But we don't know where the immersion feed is coming from. If it is a spur from a ring final you cannot spur again off the input.

JohnW2 · 22 May 2018

winston1 said:
Ah, yes, silly me. But we don't know where the immersion feed is coming from. If it is a spur from a ring final you cannot spur again off the input.

Indeed - and even if it is a dedicated radial, or a branch of a radial, one could not extend it with 1.5mm² cable (as you suggested) if the OPD is rayted above 16A.

Kind Regards, John

Simon35 · 22 May 2018

winston1 said:
The fuse is to protect the cable not the pump. So use 1.5mm cable and you won't need another FCU. Just wire it into the output of the immersion FCU.

Is there not a requirement to comply with 552.1.2 in the yellow book, or does the motor have built-in overload protection?

Just asking, I don't know for sure, although I would assume there is a requirement to comply.

JohnW2 · 22 May 2018

Simon35 said:
Is there not a requirement to comply with 552.1.2 in the yellow book, or does the motor have built-in overload protection? Just asking, I don't know for sure, although I would assume there is a requirement to comply.

That's one I wasn't even aware of!

However, I imagine that a shower pump would be likely to qualify as "an item of current-using equipment complying as a whole with an appropriate British or Harmonised Standard", in which case the requirements of that regulation would not apply.

Kind Regards, John

EFLImpudence · 22 May 2018

Is it likely a shower pump will be more than 370W (½hp) or cause an overload greater than the CCC of the cable?

JohnW2 · 22 May 2018

EFLImpudence said:
Is it likely a shower pump will be more than 370W (½hp) or cause an overload greater than the CCC of the cable?

I doubt the former, and probably also the latter, but I don't really know how high a current can be drawn by a stalled/jammed motor of the sort of size we're probably talking about. However, as I said, I suspect that the pump will be compliant with some 'appropriate Standard', in which case the question becomes moor - at least, regs-wise.

Kind Regards, John

EFLImpudence · 22 May 2018

Oh, just had a look - some are quite a bit more than 370W.

JohnW2 · 22 May 2018

EFLImpudence said:
Oh, just had a look - some are quite a bit more than 370W.

We've been duplicating effort! I've also been having a quick look, and was about to post a similar finding

Mind you, a lot are around 200W - and most of those I saw which mentioned fuses called for a 3A one.

Kind Regards, John

winston1 · 23 May 2018

But we all know the fuse is to protect the cable, not the pump. We also know that in most other countries it would be wired direct to a 16 amp MCB. So once again we have manufacturers who don't know what they are talking about.

So sufficient to say wire the pump in 1.5 mm cable on it's own circuit on say a 6 amp MCB, or via a FCU off the ring, but not immersion circuit, with a 5 amp fuse.

diynot

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Shower Pump Under Bath with an UK 3Pin Plug with FCU

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