Installing new shower

[Big D]

Right I have only limited electrical knowledge but I need to find out the best way to go for the installation of a new shower.

The Shower is a 10.8kW

Firstly 10mm or 16mm cable? Walls are cardboard lattice type insulated.

Secondly my 100A CU is a crabtree unit. The MCB should be 45A - the only option for my existing unit is 40A or 50A - is it safe to go to 50A?

The MCB will be fitted into a spare slot along side 32A ring socket circuits on the RCD protected circuit (63A 30mA) - is this okay?

I don't think the existing Type 1 MCBs are still available (house about 15yrs old) - will an up to date type B crabtree MCB still fit? I do not want to go separate block for shower to keep cost down.

Any info would be appreciated.

 

[Adam_151]

1) Have you heard of part P?
2) I can't think of why 50A breaker would pose a problem, as long as the cable calcs for the chosen cable show its ok, I guess if the shower failed, it would fail in a way that makes 5A on a breaker neither here nor there, as long as the chosen breaker meets the 0.4 sec disconnect time, I mean its not like its going to fail by suddently starting to draw 10A more than it should...likely to just go to direct short

3) Maybe upgrade the RCD for one with greater switching capacity

Just the first points that popped into my head

 

[andy]

10mm should be adequate, aswell as a 50A MCB. what else is RCD protected? 63A with a 50A shower doesnt leave you much room. you may be best changing this for an 80A RCD

also, are you aware of part p?

 

[andy]

1) Have you heard of part P?
2) I can't think of why 50A breaker would pose a problem, as long as the cable calcs for the chosen cable show its ok, I guess if the shower failed, it would fail in a way that makes 5A on a breaker neither here nor there, as long as the chosen breaker meets the 0.4 sec disconnect time, I mean its not like its going to fail by suddently starting to draw 10A more than it should...likely to just go to direct short

3) Maybe upgrade the RCD for one with greater switching capacity

Just the first points that popped into my head

beat me to it

 

[Big D]

Thx for the help guys. To summarise 10mm and a 50 A MCB is ok.

Now for the other confusing bits - No I have never heard of a part P - what is it - do I need one and how do I fit it?

Also concerned that I would need to upgrade the RCD. There is two ring mains on it. One 32A for kitchen sockets and one 32A for the rest of the house sockets. Doing simple maths I suppose 32+32+45/50 = 109A (I suppose the system is never going to be on full load though) - I really need to upgrade or go stand alone dont I?

Go slow on me - I am slowly learning!!

 

[oddy]

No I have never heard of a part P - what is it - do I need one and how do I fit it?

Try doing a search for part P

 

[Adam_151]

Upgrade rcd to at least 80A, or use RCBO on none RCD side

50A should be fine, but you really should calculate the disconnect time to make sure...(volt drop et all while you are at it)

Part P, is the latest bit of the building regs covering electrical work, phone up building control, inform them of what you intend to do, they will tell you what you have to do to comply with their system (varies from council to council), it could be that they have someone from building control inspect, or they sub contract an electricain to check it, or want a test certificate from someone who is competant (and has the right test equipment) to write one, oh and they will want some money off you as well.

Type B is what you should use

You haven't mentioned earth bonding, is it place?, you need to join the shower circuit to it, if not in place, you need to fit it, join all metal pipework and earths of electrical circuits together with 4mm earth cable where they enter the bathroom

You haven't mentioned a dp shower isolater, you are aware that one should be fitted?

 

[ban-all-sheds]

Now for the other confusing bits - No I have never heard of a part P - what is it - do I need one and how do I fit it?[/quoute]
Ho ho.
The search on Screwfix works a lot better than here, so try this:

http://www.screwfix.com/talk/search...userID=&numResults=30&submit.x=47&submit.y=11

But in a nutshell installing a shower is notifiable in terms of Part P of the Building Regulations and therefore you are required to either have it done by a qualified electrician who is also registered with a Competent Person's scheme and can self-certify compliance with the Building Regulations, or if you DIY or have it done by a non-registered electrician, you are required to notify your council's Building Control dept in advance.

Go slow on me - I am slowly learning!!

IMHO installing a shower is not suitable job on which to learn....

 

[ban-all-sheds]

50A should be fine, but you really should calculate the disconnect time to make sure...(volt drop et all while you are at it)

And then when done test the circuit for insulation resistance and measure R1+R2....