3 phase supply to classroom, unsure to TT?

[mpoy222]

Why do you think the armour is insufficient. Is it required to support main protective bonding.

Hi there is no CPC being taken fron the main building so i was wondering if the SWA would be sufficient to use as the main CPC. It just has 4 core 16mm SWA

 

[mpoy222]

Maybe a silly question but why 3 phase?
Would single phase not do for what you are intending to install?

Good point I did think that but as the 3 phase supply is there i thought i should ustilise it and i dont know what they are planning on doing heating wise yet. They dont have the budget for heaters at the moment but i can imagine the second its all installed they will want 10x 3kw heaters installing!

 

[mpoy222]

as previous. wtf do you want 3 phase over there ?

4 core cables already in place from previous building and there is a chance of them adding lots of heaters

 

[mpoy222]

But 3 phase for the above seems OTT. What would you do? Put 1 phase for the sockets, 1 phase for the lights and 1 phase for the small water heater?
Or is the OP leaving spare phases for the 'heating, which isn't decided yet'?
I would be interested to know.

Hi , yeah thats the idea to try and balance the loads, i know with things like this in the past they always say they just want a couple of sockets and lights then plans change and if there isnt the option to expand then i will probably get be to blame!

 

[mpoy222]

Do the adebiatic equation to see if the armour is sufficient for cpc, i would also consider using single phase only so you have the spare conductors to export the main earth at the main school.

How do i work out the CSA of the SWA though? There is also a join in the cable with an earth strap in place to keep the continuation of the SWA but i'm assuming thats all its good for.

 

[mpoy222]

I tested a small what they call a mobile class week before last, consisted of two class areas, WCs and entrance lobby. Twenty two circuits.

Only 22!
You should see the boards in the main part of this school its only a small village school and they have really gone to town on the amount of circuits its mind boggling. Its frustrating because a lot of them arent clearly marked either and there is no paper work from the last periodic.

 

[mickfred]

There is a table in the earthing guidance note book . Am sure Pete will have it .

 

[westward10]

Is it required for main protective bonding.

 

[Wilko]

I tested a small what they call a mobile class week before last, consisted of two class areas, WCs and entrance lobby. Twenty two circuits.

Must be a Special Location - dimensioning rules 1 circuit per student ...

 

[Toneyz]

What is the mobile classroom made of?

 

[westward10]

Probably one of these new eco buildings they have.

 

[Toneyz]

Probably one of these new eco buildings they have.

Not seen one of those (probably not with NCC not having any money) the only ones I've seen is the wooden type in sections.

 

[mpoy222]

What is the mobile classroom made of?

Its all timber, its actually more like a log cabin!

 

[mpoy222]

What is the mobile classroom made of?

Its all timber, its actually more like a log cabin!

 

[westward10]

Nothing eco about them aside from fancy wood fascias which will need replacing in a few years and some led lighting.

 

[davesparks]

Hi there is no CPC being taken fron the main building so i was wondering if the SWA would be sufficient to use as the main CPC. It just has 4 core 16mm SWA

Your use of terminology is confusing, you say there is no CPC and say it is SWA? This is somewhat contradictory!

 

[davesparks]

How do i work out the CSA of the SWA though? There is also a join in the cable with an earth strap in place to keep the continuation of the SWA but i'm assuming thats all its good for.

If you don’t know how to do this are sure you should be doing it without supervision?

What type of joint is it? What do you mean by an earth strap?

 

[Cadgey123]

If you don’t know how to do this are sure you should be doing it without supervision?

What type of joint is it? What do you mean by an earth strap?

I think he means the flexible braid which is connected between the armours with the steel spring bands. God knows what type of joint?

 

[mpoy222]

Your use of terminology is confusing, you say there is no CPC and say it is SWA? This is somewhat contradictory!

There is no seperate CPC. The SWA is earthed but i wasnt confident in using this as a main earth for the installtion of the building because of the join.

 

[mpoy222]

I think he means the flexible braid which is connected between the armours with the steel spring bands. God knows what type of joint?

Thats the one mate. The earth strap in these kits cant have the same CSA as the armour so i didnt want to use it as a main earth. Its a resin joint.