Zs on tt

[Lyngarth]

hi,

Sorry for the silly queston but was just checking what the max zs is on a 32amp breaker. Just checking a ring before adding 2 more scokets, but all my books are in back on van, which my mate has and not back for 2 hrs.

Cheers

System is TT plus also max on 6amp lighting if you would be so kind.

 

[Zeespark]

BS 60898 MCB bud? if so its 1.16ohms (32amp) & 6.18ohms (6amp)

AndyGuinness

 

[Lyngarth]

BS 60898 MCB bud? if so its 1.16ohms (32amp) & 6.18ohms (6amp)AndyGuinness

Hi, yes thats the one, cheers for that.

Sadly just tested the ring and got 14.89 ohms.

So not going to be a quick 10 minute job by the looks of it.

Thanks for your reply.

 

[kme]

But......it`s a TT.

You`ll hardly ever comply with max Zs for disconnection times on a TT - the Ra is too high. This is the reason for using a 30mA RCD - the disconnection time in the event of a fault is provided by the RCD, NOT the CPD.

HTH

KME

 

[Lyngarth]

hi,

so seeing as the board has a rcd, is it ok to fit the new 2 sockets ??

Not sure myself, and this is my first tt system in 2 yrs!!

 

[Zeespark]

Its fine bud.

AndyGuinness

 

[Lyngarth]

many thanks, will now put down the coffee and get to work.

Cheers to all for taking time to reply.

Lyngarth

 

[sparkytim]

Zs of 1666.66 ohms will comply with 50 Volt max touch voltage requirement fot TT.

 

[Zeespark]

Is that all sizes of RCD time or just 30mA ones?

AndyGuinness

 

[Andy™]

Is that all sizes of RCD time or just 30mA ones?AndyGuinness

just 30mA

50/ 0.003 = 1667 ohms

500mA

50/.5 = 100 ohmd

 

[kme]

Just 30mA mate (R=V/I)

Lyn - ensure it IS a 30mA - some of the older TT installs had a 100mA "front end" instead!

Don`t forget, you also need to test the RCD for correct operation within time limits at 15mA, 30mA and 150mA; on both pos & neg halves of the waveform

KME

Pushy ruddy shovey headbang

:^O :^O:ApplaudGuinness

 

[steptoe]

Just 30mA mate (R=V/I) Lyn - ensure it IS a 30mA - some of the older TT installs had a 100mA "front end" instead!

Don`t forget, you also need to test the RCD for correct operation within time limits at 15mA, 30mA and 150mA; on both pos & neg halves of the waveform

KME

Pushy ruddy shovey headbang

:^O :^O:ApplaudGuinness

or even a voltage trip,

 

[Lyngarth]

Hi

Job now done, I checked the RCD and it was a 30ma, and tested fine.

Have also made sure from now on my books stay with me.

Cheers all

Lyngarth