Shower Isolation

[Weedrip]

Good morning.
A couple of questions if I may of the qualified electricians.
I attended a call to a customer who was having a problem with water running from an electric shower.
10.5kw job, the problem is a defective solenoid valve on the unit. No problems there except the unit is a wet room for a disabled gent who is wheel chair bound and the shower is only means of washing. Discuss the option, wait for part or replace unit. Customer wishes to replace unit.
Now the question.
MCB on the CU with cable direct to shower unit. The MCB 50amp is the only circuit isolation [for live conductor?] Main CU isolator is the only real means to isolate shower. This shuts down whole house.
I am a Plumber by trade not an electrician, so I would like to ask is a double pole switch in the supply to the shower the very least one would expect to find.
Is an RCD in the supply to the shower a requirement or is it non-regulatory best practice.
Work was completed 2.5 years ago. The original work was undertaken by an electrician who has issued a number of certificates.
I ask for my own benefit as the situation caused me some thought about what I ‘think’ I know the answer should be.
Hope you can help
Regards

 

[bernardgreen]

Ability to isolate the shower local to ( preferable in ) the shower room is necessary.

In view of the person being dis-abled extra consideration should be given as to the location of the isolator.. A ceiling pull cord isolator is often adequate provided the person can reach it in an emergency.

Does the disabled person use the shower on their own or is there always a carer assisting them. If they do use it alone and prefer to lock the door then a second isolator outside the room may be necessary.

RCD protection is almost always required, it should be specific to the shower and tripping of the RCD by the shower should NOT turn off lighting in the room.

 

[Weedrip]

Hi Bernard, thanks.

The wet room is open to the sleeping quarters [there is no door between]

The space was converted to sleeping and toilet / wash facilities. the CU is in the sleeping area in the original position when the property was first built.

Distance wise its about a 1.5mtr from the entrance area to the wet room the height of the existing consumer unit would not allow the gent to reach up and reset the whole house trip.

An able body spouse is normally around so I guess that would be consideration.

regards

 

[linkyplumb]

Also check cable size. 10.5 kw should be 10.0mm cable

 

[Cremeegg]

Assume 10.5kW at 230volts = 45.6Amps - according to Table 4D5 in BS7671 6mm2 cable will take 47 amps when clipped direct so 6mm2 may be OK subject to other factors being OK.

Check manufacturers instructions - they nearly always require RCD protection and separate double pole isolator.

 

[sparkwright]

Have you checked any nearby cupboards for a switch?

 

[Weedrip]

Hi all thanks for the info to date.

Have recovered installation instructions of the net. They only note

The shower unit must be permanently
connected to the electricity supply, direct
The cable size required is determined by
the kW rating of the shower and the
distance between the shower and the
consumer unit. The table below will help
you choose the correct cable for your
installation, but it will depend upon the
precise circumstances of the installation. If
you are in any doubt consult an electrician.
from the consumer unit via a double pole
linked switch with a minimum contact gap
of 3mm. The switch must be readily
accessible and clearly identifiable and out
of reach of a person using a fixed bath or
shower tray, unless the switch is cord
operated. The wiring must be connected
to the switch without the use of a plug or
socket outlet.

I have looked all around the shower and in the sleeping area. Isolation is as stated above in my first post. I Have at this time not excluded the possibility of it being under a first floor bedroom, after nearly 40 years I am never surprised at the possibilities!

Am not uncomfortable with the cable size as being within 7m run from the CU what I see is what I expect to see. But thanks for the info.

As for RCD and / or D/pole isolation, The situation got me wondering as per my question. is it a actually a regulatory Requirement or simply Best practice setting aside the obvious common sense need to isolate a unit without taking the whole house power supply down.

regards

 

[EFLImpudence]

It is a regulatory matter because one of them says the manufacturer's instructions must be followed and (now) they will stipulate a DP switch and RCD.

All new circuits in special locations must be RCD protected.

However, the regulations aren't retrospective nor, indeed, statutory but ...

 

[JohnW2]

All new circuits in special locations must be RCD protected. ... However, the regulations aren't retrospective nor, indeed, statutory but ...

Indeed and, perhaps more to the point, having an electric shower which is not RCD protected is (IMO) just plain daft. Although we may sometimes debate the extent to which RCDs 'save lives', the argument for having them must surely be at it greatest when wet naked people are in close proximity to electricity ... whatver regulations may say.

Kind Regards, John

 

[Spark123]

Assume 10.5kW at 230volts = 45.6Amps - according to Table 4D5 in BS7671 6mm2 cable will take 47 amps when clipped direct so 6mm2 may be OK subject to other factors being OK.

Check manufacturers instructions - they nearly always require RCD protection and separate double pole isolator.

Don't assume, you need to read the instructions! Most of the showers I come across give their rated outputs at 240v, sounds better in the sales blurb.

For example Triton say their 10.5kW showers are 10.5kW at 240v, 9.6kW at 230v.

 

[JohnW2]

Most of the showers I come across give their rated outputs at 240v, sounds better in the sales blurb.

True - but as well as sounding better in the sales blurb, it's probably also closer to the voltage that most people have than is 230V, hence the 'headline power' is probably closer to the power they are likely to actually get from their shower.

Kind Regards, John