Please Help L3 Design Project Selv

[Mark Wright]

Hi, i'm currently doing my Level 3 design project and it's going to be tricky with the coronavirus and lack of contact with Tutor and other students.

Its the Hotel Swimming pool one

and I have to select luminaries for the cafe pool.

I haven't chosen my luminaries but I'm thinking to do it all with SELV 12V now how do I do cable calculations and Max Demand for a Selv circuit? Also what cable should I use, I was thinking FP200 as it's a public area is this ok for Selv?

You may laugh at my suggestion but any help would be great.

 

[SparkyChick]

We have a trainee only area... you should contact @Dan or @Lou to get access to it. Things like this are covered in there much more than in the public area.

 

[Mark Wright]

We have a trainee only area... you should contact @Dan or @Lou to get access to it. Things like this are covered in there much more than in the public area.

Ok thanks, ill give it a go.

 

[SparkyChick]

In the meantime however... what's the basis for your choice of SELV?

 

[Lister1987]

In the meantime however... what's the basis for your choice of SELV?

Logically it would make sense, why run 240v when 12v will be inherently safer and do the same job, you can get presentation converters to change ES type bulb holders to take 12v bulbs

 

[davesparks]

Maximum demand and cable calculations are the same for SELV as they are for LV, however voltage drop plays a much bigger role, and is far more noticeable if you get it wrong.

I don't understand your statement that you think it should be FP200 because it is a public area.
FP200 is a fire performance cable designed to be used for circuits which need to continue to operate when exposed to fire, different grades being available for different fire performance requirements (FP200 gold, FP200 enhanced). FP200 is usually not an ideal choice for general wiring applications as it doesn't have the same mechanical strength as the other options plus it is more expensive than the alternatives.

Being in a public area, or public building suggest you should be using a cable with LSF insulation(and sheath if sheathed).
When chossing the type of cable you need to consider things like the potential for mechanical damage, installation method, ease of future alteration, environmental factors, price, fitting in with the design/aesthetic of the building.
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Logically it would make sense, why run 240v when 12v will be inherently safer and do the same job, you can get presentation converters to change ES type bulb holders to take 12v bulbs

As the voltage is lowered the cable size goes up dramatically, this is why we don't run everything at a safer, lower voltage.

Why would you need to convert ES lampholders to another type on a 12V system?

 

[Mark Wright]

Thanks for the reply's the questions are
here HELP PLEASE!!! 2365/615 electrical system designs - https://www.electriciansforums.net/threads/help-please-2365-615-electrical-system-designs.169479/#lg=attachment45404&slide=0

Basically I would like to get started and do some calcs etc but I can't even find suitable lights

Ideally if I was doing this for real I would like to use Selv max of 50v and LSF cable - I think FB200 is LSF

but I can't find any kind of Selv light that would be suitable for this setup also can't find any info for calcs on voltage drop of a Selv cable.

I suppose I can just use some normal high IP lights as there on the ceiling.

but any advice would be great

 

[westward10]

Are these lights actually submerged in the pool if not do they fall within any of the zones.

 

[Mark Wright]

Are these lights actually submerged in the pool if not do they fall within any of the zones.

No there on the Ceiling but in terms of maintenance and in general SELV seems like a good idea although I guess not essential here.

So maybe something like this ?Weatherproof Batten Light Fittings | Medlock Electrical - https://www.medlocks.co.uk/lighting-lamps/commercial-lighting/weatherproof-batten-light-fittings

 

[westward10]

SELV should be avoided unless absolutely necessary. Do they fall within one of the zones. Is it actually in the vicinity of the pool or a separate room.

 

[JAWS]

You need to read the assignment properly Mark & not make it complicated becuase your tutor will just hand it back to you & ask why. You dont need Selv for the pool area or nothing like LSF cable.
Make it simple

 

[Mark Wright]

SELV should be avoided unless absolutely necessary. Do they fall within one of the zones. Is it actually in the vicinity of the pool or a separate room.

The drawings are here in PDF

2365 drawings - Google Search

The ceiling directly above the pool what Zone would that be? 2 I think its ok.

 

[JAWS]

Doesnt matter Mark what Zone it is above the Pool as you're not going to put lights there. You just need wall lights & non-maintained emergency lights on the walls.

 

[Mark Wright]

Wall lights would be Zone 2 and wouldn't be very good.

 

[JAWS]

Wall lights would be Zone 2 and wouldn't be very good.

This is where you would use your assumptions regarding height of walls where to fit etc

 

[Mark Wright]

After further looking Zone 2 only needs Selv if it is not protected by a RCD can anyone confirm this?

 

[davesparks]

Thanks for the reply's the questions are
here HELP PLEASE!!! 2365/615 electrical system designs - https://www.electriciansforums.net/threads/help-please-2365-615-electrical-system-designs.169479/#lg=attachment45404&slide=0

Basically I would like to get started and do some calcs etc but I can't even find suitable lights

Ideally if I was doing this for real I would like to use Selv max of 50v and LSF cable - I think FB200 is LSF

but I can't find any kind of Selv light that would be suitable for this setup also can't find any info for calcs on voltage drop of a Selv cable.

I suppose I can just use some normal high IP lights as there on the ceiling.

but any advice would be great

The voltage drop calculation is the same at any voltage.

Yes FP200 is LSF, but so are a lot of other cable types which are more suitable for the application.
You can get LSF singles, T&E, SWA, flex and flexshield type cable

 

[Mark Wright]

I probably can get away with not using Selv to me its not doing it properly, but if I did use Selv you mentioned Voltage drop problems could you just expand on that.

 

[SparkyChick]

Voltage drop is dependent on the length of the cable and the current flowing through it.

So, longer = higher drop... higher current = higher drop.

Lower voltage = higher current for the same power. Work out the current for a 50w 240v lamp and a 50w 12v lamp and that will make it clear.

As for the 'not doing it properly'. There are very specific cases where SELV is mandated, for most other cases an LV supply is totally acceptable and is preferred for the reasons that should become obvious when you run the numbers above.

 

[Mark Wright]

Voltage drop is dependent on the length of the cable and the current flowing through it.

So, longer = higher drop... higher current = higher drop.

Lower voltage = higher current for the same power. Work out the current for a 50w 240v lamp and a 50w 12v lamp and that will make it clear.

As for the 'not doing it properly'. There are very specific cases where SELV is mandated, for most other cases an LV supply is totally acceptable and is preferred for the reasons that should become obvious when you run the numbers above.

Thanks for your replies, when I say properly I mean adhere to the Regs, it seems I can only just get away with it being in Zone 2 and not needing SELV, one other member also asked about this on the forum, one of the later questions asks you to draw a SELV transformer makes you wonder.......