TT Systems and Ze and Zs readings | on ElectriciansForums

Discuss TT Systems and Ze and Zs readings in the Electrical Wiring, Theories and Regulations area at ElectriciansForums.net

R

Rambhai

Could some one help me?

What readings should you get when installing new circuits for TT systems?
I am aware that you have to get a reading for the earth rod but what should you have for the following Ze and Zs.?
 
Ze for TT system should be under 200 ohms. as your Zs reading will be far higher than max. allowed for disconnection times to be met, fit RCD/RCBO to all circuits.
 
:eek:Thanks for that.

So if the readings Ze was 15 ohms at the earth rod and the installation has a 100mA main RCB protecting the whole installation, what would you suggest I should tell the client.
 
he should have, apart from the 100mA RCD, 30mA RCDs or RCBOs on all circuits. end of story.
 
best way to configure the board is to use the 100mA RCD as main switch and fit 2 additional 30mA RCDs, split board. if this is not practicable, due to space, then RCBO each circuit. expensive but the ideal way as tripping of 1 cct. will not affect any other ccts.
 

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