rcd main switch

[SuperSwift]

hi everyone im asking for advise in the rating in miliamps on a main switch to be used. The main power is provided via a 25 kva 3 phase generator for powering up a log cabin classroom. ive looked through big red book but section on building not list or may be ive missed it, fairgrounds amusment parks is the only section that say 300ma, i would of fitted a 30ma rcd few years ago but with the latest regs say you must provide discrimination from normal circuits. thanks look forward to everyone views.ps i tried nics technical helpline still waiting it may be weeks

 

[Zeespark]

What means of earthing is it?

AndyGuiness Drink

 

[Zeespark]

Nice Avatar by the way, wish I could get my ex into wearing that stuff around the house

AndyGuiness Drink

 

[SuperSwift]

TT system earth rod or rods

 

[Andy™]

TT system earth rod or rods

if you dont understand the basics of generator earthing, i suggest you leave it well alone.

any genny that size will have neutral-earth linked*, and have a TNS output. it should also have an earth rod (or more) installed, but this is not to make it a TT

anyway, back to original question on RCD, id suggest this is not a 'special location' (but without knowing all details its hard to give a definate answer). i would think it should be treated as a normal installation, but fed from private supply rather than DNO - the building wiring will be the same

Which RCD are you wanting to know rating of? there may be some protection at genny side, feeding into a DB inside. any RCD's (if req'd) in there will most likely be 30mA

 

[SuperSwift]

im only asking at this stage for quoting purpose at distrubution board generating company sets the geny up so if you need more info then i will get more info for myself elsewhere thanks anyway

 

[SuperSwift]

read the question from 1st post bs7671 regs not yours

 

[green-hornet]

Be carefull here, you have to allow for discrimination.

If I was setting this up I would require more information but would be extremely cautious as soon as children are concerned.

You would have to class this as a temp installation and like you say the nearest regs that would apply are the ones you mentioned.

If the classroom is used for normal everyday activities, and does not involve any laboratory work, then I would go for a main rcd at 3oomA and circuit protection at 30mA.

Or you could go for a S type main which would give you some delay, so the 30mA type b trips first.

If any science projects or experiments are involved then I would protect the classroom with a 10mA rcd, for the sockets.

 

[SuperSwift]

thanks green hornet for your answer in a the correct manner, not been lectured,i have only found the same reg the installation is at a horse riding school and farm im going to just price for 300ma plus a bit to cover my costs many thanks again

 

[Andy™]

thanks green hornet for your answer in a the correct manner, not been lectured,i have only found the same reg the installation is at a horse riding school and farm im going to just price for 300ma plus a bit to cover my costs many thanks again

stop moaning. i was pointing out something you may have overlooked which does make a major difference, and if you did bother to finish reading my post i did suggest what RCD to use.

you will also find that both points i mention would be under 7671. ESQCR doesnt apply to a private supply