TT system

[Buzz-light-bulb]

Hi all again

Just upgraded a domestic property today new consumer unit e.t.c now I've installed new earth spike with 16mm earth. Provided 30ma rcd protection for all final circuits, Ze readings are 25.2 ohms which is well below 200 ohms, Zs reAdings on final circuits are very high in the region of 30 ohms is all sounds well to me anyone else got any info to help me get better readings or should I just leave it as rcd protects up to 1667 ohms

 

[Silly Sausage]

I'd be looking into why you're gaining the extra 5 Ohms on your circuits from.
R1+R2 of 5 seems rather high to me!

 

[Doctorsparks]

These readings are perfectly expectable. I personally would leave it as is.

 

[Buzz-light-bulb]

I'd be looking into why you're gaining the extra 5 Ohms on your circuits from.
R1+R2 of 5 seems rather high to me!

Fair point I will investigate tomorrow as I've not done full test as yet, as it's a void property

 

[telectrix]

measure your Zs at the CU ( L busbar to E.). the 5 (ish) ohms could come from MCBs.

 

[GLENNSPARK]

These readings are perfectly expectable. I personally would leave it as is.

no it isn`t acceptable...

come on..think about it...as it wont just be the Ze...there will/should be parrallel paths to consider as well...

no...5 ohms increase is way too high..

to the OP....whats (R1 R2) like?

 

[GLENNSPARK]

Fair point I will investigate tomorrow as I've not done full test as yet, as it's a void property

so...if you had done the tests properly (in sequence)...then you may/will have found high values of (R1 R2)..

how come all Zs values are in the region of 30 ohms?..

get end to ends on rings for a start...then do the calc for expected (R1 R2).....

 

[Buzz-light-bulb]

I've just re tested Ze and pfc values I got

L-e 25.2 ka 10
L-n 0.11 ka 2.2

I'm pretty sure this system may already be converted to pme but the property hasn't ever been upgraded and just requires earth conductor to connect into incoming neutral obviously I can't do that

 

[telectrix]

L-E 25.2. PEFC = 9Amps. not kA.

 

[Buzz-light-bulb]

Yes your right tel thanks for correcting me

 

[Buzz-light-bulb]

What do you think tel based on readings

 

[telectrix]

your Zs readings should not be 5 ohms higher as the bonding will bring them down 9 parallel earth paths). as i said earlier, check at L busbar to E. internal resistance of RCDs, MCBs and main switch can affect the readings.

 

[GLENNSPARK]

your Zs readings should not be 5 ohms higher as the bonding will bring them down 9 parallel earth paths). as i said earlier, check at L busbar to E. internal resistance of RCDs, MCBs and main switch can affect the readings.

my point at #6