Help with diversity

[Markymark981]

[COLOR=rgba(0, 0, 0, 0.701961)]Hi wonder if u could help me [/COLOR][COLOR=rgba(0, 0, 0, 0.701961)]
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[COLOR=rgba(0, 0, 0, 0.701961)]Just rewiring a 3 storey house that's going to be student lets, communal kitchen lounge bathrooms etc[/COLOR]
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[COLOR=rgba(0, 0, 0, 0.701961)]I have worked out the following diversity and demand [/COLOR]
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[COLOR=rgba(0, 0, 0, 0.701961)]Emergency lights 6a x 0.66 = 2.64a[/COLOR]
[COLOR=rgba(0, 0, 0, 0.701961)]Smoke alarm 6a x0.66 = 2.64a[/COLOR]
[COLOR=rgba(0, 0, 0, 0.701961)]4 light circuits 4 x 6a x 0.66 = 10.56a[/COLOR]
[COLOR=rgba(0, 0, 0, 0.701961)]4 ring mains 32a + (3 x 32 x40% = 38.4a) = 70.4a[/COLOR]
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[COLOR=rgba(0, 0, 0, 0.701961)]That all totals 86.24a [/COLOR]
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[COLOR=rgba(0, 0, 0, 0.701961)]Dilemma I have is adding electric cookers and electric radiators [/COLOR]
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[COLOR=rgba(0, 0, 0, 0.701961)]Customer ideally wants 2 stand alone electric cookers but I've worked out each cooker assuming 40a would equal 29.16a if he had 2 it would be 58.32a [/COLOR]
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[COLOR=rgba(0, 0, 0, 0.701961)]Then he wants 500w convector heaters either 7 or 15 of them spilt over 3 floors in total 15 would bring 7kw and need to be on a 32a fuse and if he went for 7 it would be 3.5kw and need a 16a fuse, apply diversity and that would add 21a or 13a[/COLOR]
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[COLOR=rgba(0, 0, 0, 0.701961)]Questions I have are[/COLOR]
[COLOR=rgba(0, 0, 0, 0.701961)]1. if he had the electric rads could I put 3 radial circuits into one 32a fuse [/COLOR]
[COLOR=rgba(0, 0, 0, 0.701961)]2. As it stands without cookers or rads it's would be[/COLOR]
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[COLOR=rgba(0, 0, 0, 0.701961)]86.24a[/COLOR]
[COLOR=rgba(0, 0, 0, 0.701961)]115a with one cooker[/COLOR]
[COLOR=rgba(0, 0, 0, 0.701961)]144a with 2 cookers[/COLOR]
[COLOR=rgba(0, 0, 0, 0.701961)]157a with 2 cookers and 7 rads[/COLOR]
[COLOR=rgba(0, 0, 0, 0.701961)]165a with 2 cookers and 15 rads[/COLOR]
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[COLOR=rgba(0, 0, 0, 0.701961)]Which would be acceptable, my old old lecturer stated if it exceeds 100a it'll just blow main fuse so don't worry

Also found someone using the add up all themcb values and times by .40 anyone else used this or know if it's ok?

cheers

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[Markymark981]

Hall stairs and landing are on their own as I've been asked to fit the pneumatic switches so when one is pushed all the lights on all the hallways come on the way that they had to be wired are a direct N feed from the CU into the fitting and line and switch line into switches

 

[malcolmsanford]

Hall stairs and landing are on their own as I've been asked to fit the pneumatic switches so when one is pushed all the lights on all the hallways come on the way that they had to be wired are a direct N feed from the CU into the fitting and line and switch line into switches

I'm assuming here you mean intermediate switching

 

[davesparks]

Hi dave this is the first time I have been asked for emergency lighting I've checked onsite guides and it didn't mention anything about them been on either a separate circuit or the lighting circuit, I just did it on a separate circuit for identification on the cu

would I be ok to connect the emergency lighting into the same mcb as the downstairs lights if they don't pull much power?

sorry to ask so many questions but these two topics (emergency light and demand) I've not had issues with in the past

cheers mark

Are you sure you are competant to design an emergency lighting installation then?
They need to be connected to the lighting circuit serving the area they are in, otherwise how do you expect them to come on when the normal lighting fails?

 

[davesparks]

i understand but each floors as its own circuit and the hall and landings have their own circuit so could I join the hallways and emergency lighting feeds into the same mcb save me having to go back and re wire?

No, the emergency lights need to be connected to the lighting circuit serving the area the are fitted in. Otherwise they will not operate when the lighting circuits fail!

 

[davesparks]

I'm assuming here you mean intermediate switching

I wouldn't have thought so if he's using pneumatic switches, they'll just be 1way switches wired in parallel

 

[malcolmsanford]

I wouldn't have thought so if he's using pneumatic switches, they'll just be 1way switches wired in parallel

I know I did my training a few years ago but I always thought staircase lighting was wired as an intermediate circuit, but things do change and if there is a newer better way to do them them then fair dos

When the OP said Pneumatic switches I sort of thought he meant something like these

https://www.sparksdirect.co.uk/ellipse-adjustable-time-delay-push-button-switch#.VW_xANKqqko

Which are intermediate switches

 

[davesparks]

2way and intermediate switching is normal for houses etc but communal staircases have used time lag switches in parallel for far longer than I've been in the job.

That's not an intermediate switch, it's a 1 way switch, look at the connection diagram. An intermediate switch would have 4 terminals rather than the 2 which that one has.

 

[malcolmsanford]

Dave I'm not going to fall out over this. It is a domestic installation it is 3 story house as in the OP.

pneumatic switches are time lag switches.

The link to the switch I put up indicate that it can be used for intermediate circuits on the web page and the PDF

• This kind of Time lag switches can be used in two way and intermediate switching arrangements without any extra wiring
• Conventional Wiring Wire the units as in diagram 1. When using multiple switch positions
  see diagram 2.
  For two way and intermediate switching follow the diagrams overleaf.
  Note that as long as each switch position has a Live feed
  and a Live Out connection to the load then the switch will be
  properly wired.

They can and are used on an intermediate circuit. If you look on the 2nd page under the heading intermediate switching you will see a diagram showing a switch with the 4 terminals and then how to wire these switches

 

[davesparks]

Actually look at the diagrams you are referring to, the time lag switches are wired in parallel in the 3way switch example with a diagram above showing a 2way and intermediate circuit. Each time lag switch only has live and sw live connections.
If they were intermediate switches then you'd have all sorts of problems with lights going off when I second switch is pressed during the time period, then defaulting to lights on instead of off etc