Question for BAS or anyone with knowledge !

[burntwire]

I may need to apologise in advance for this when someone with better knowledge than me reads this !!!!

I am looking at a job fitting a new board in a hotel ( small B+B) They currently have 2 boards running from 40 metres of 16mm twin and earth, split in a henley between both , We are slowly modernising the hotel and ive advised them that one new board fed with a SWA would be alot more suitable and safer than this altough the load pulled at any one time is not great,

Trouble is I need a 20 or more way board, owners would like RCD protection but I cant find anything suitable, which would allow me to split up the circuits as I would for a 17th edition board,

So ive been thinking what about using a three phase board with sinlge phase kit fitted but remove the main switch and replace with 3no RCBO's and no switch for the neutral but there would be a main switch back at the incoming supply for the whole board,

Any ideas anyone ?

 

[Spark123]

Think about how you are going to connect the neutrals through the RCBOs

 

[Lectrician]

You cannot do that.

Why does the customer want RCD's? It is not a "I would like" sort of choice.

A hotel does not actually require RCD protection for conceiled cables, and I would always avoid RCD's where ever possible in this sort of environment.

Obviously use them where they are required, but dont bung them in for the sake of it.

 

[RF Lighting]

Why not do like it has been done for years in commercial installations.

Nice big DB. Probably a 3 phase board fitted with a single phasing kit.

Then RCBOs protecting the outgoing ways which are deemed to require RCD protection.

Simple really.

Do the submains really need to be SWA?
Split concentric may be a better choice for this sort of installation.

 

[ban-all-sheds]

A hotel does not actually require RCD protection for conceiled cables.

Why not?

 

[burntwire]

Ok well its only a thought I was having the other was dual boards which I know square d make,(but maybe not 17th availiable yet)

Yep I know that RCD's not needed but, after discussion with owners they liked the idea of total protection - also staff live in this building all year round.

Think about how you are going to connect the neutrals through the RCBOs

Well I thought i could go straight to b-bar and use main switch in Plant room (incomer) as isolation

You cannot do that

Thats why I posted for some info - im still young with alot to learn !!

Do the submains really need to be SWA?

I thought it the best option has to run up 2 stories through 2 loft spaces and down 2 stories SWA is always my first choice for this kind of installation, what would you use ?

Thanks

 

[GaryMo]

A hotel does not actually require RCD protection for conceiled cables.

Why not?

Installation under the control of a skilled or instructed person?
You may want a covering letter from the hotel showing an understanding and accepting responsibility though.

 

[burntwire]

I was under the impression that with a supervisor on site that RCD protection was not always required - Im sure thats the way they told me at my 17th upgrade course - along with ' basically treat everyone like idiots - because most people are when it comes to electric ' - am I wrong ?

 

[ban-all-sheds]

Installation under the control of a skilled or instructed person?

But it's not though, is it?

They may be skilled and instructed at running a hotel, but it's a small B&B - they won't have an electrician on the payroll.

 

[GaryMo]

Installation under the control of a skilled or instructed person?

But it's not though, is it?

They may be skilled and instructed at running a hotel, but it's a small B&B - they won't have an electrician on the payroll.

It was an attempt at Lectricians line of thinking.

In any case, having an electrician on the payroll wouldn't stop somebody from putting up a calendar with a 30mm nail.
Unless the company has accepted responsibility on paper (which would be attached to the relevant certificate) I would fit additional RCD protection for concealed cables in accordance with 522.6.6(v) and sockets outlets not exceeding 20A.

 

[burntwire]

It has 20 rooms if that helps, what is the definition of an ' instructed person' my regs book is outside and im in my pj's ? I thought instructed by an electrician - again im probably wromg !![/u]

 

[burntwire]

Garymo, is a disclaimer/ responsibility acceptance acceptable ? or would a court deem that the electrician shouldnt leave something, that relies on a bit of paper to get him out of trouble - if you see what i mean -

 

[GaryMo]

Skilled person

A person with technical knowledge or sufficient experience to enable him/her to avoid dangers that electricity may create.

Instructed person

A person adequately advised or supervised by skilled persons to enable him/her to avoid dangers which electricity may create.

Here's a link to a Factsheet written by the ECA

 

[NoSparks]

An Instructed Person: (abridged) A person adequately advised by a skilled person to avoid danger.

A Skilled person: (Plagiarised) A person who knows better (think about that for a while)

 

[NoSparks]

I can see nothing wrong with the two board approach using a single RCD in each (or more if you fancy)

My thoughts are more on the overall design. With 20 rooms, even tiny 3x4 rooms the overall area would be 240 sq m so there will be a minimum of 3 rings, leaving 17 other circuits each with a minimum of 6 amps. That gives me a Demand Load of 140 amps.

We don't know the length of run for the sub-main but 2 stories up and down and 2 lofts sounds like a minimum of 30m.

So the sub-main cable would have to be 35mm at least. (assuming a voltage drop of 5.67v were acceptable at the CUs).

So my question is how would you terminate the sub-main? In a phase block with 25mm tails to the CUs (should that be 35mm tails) or would you need a 2 way Dist board before the CUs with 2x80A Fuses?