Acceptable Ze value for a TT System

[smyler86]

Hi All

Hope you are having a good day.

What is an acceptable Ze value for a TT system??

I know TNCS = 0.35 and TNS = 0.8.

Cheers

Dan

 

[DONKEY]

Hi Dan. The On Site guide says that Ze for a TT system should not exceed 200 ohms. Elsewhere it says it should be as low as possible

 

[smyler86]

Thanks donkey

I had a feeling I had read that somewere but couldnt find it!

Cheers again

Dan

 

[scotsparky]

if you get below 100ohms your fine normally normally easy done as well.

 

[Mr Mark Sparks]

regs <200 ohms
nic<100 ohms

 

[byrneboy]

i thought it was a max of 21 ohms for a TT system ??

 

[Spudnik]

i thought it was a max of 21 ohms for a TT system ??

Thats the DNO electrode at the transformer

 

[smyler86]

Ive just checked my own and its 364 ohm With a PFC of 0.63!

I think I may be installing another Earth Electrode!



Dan

 

[baldsparkies]

With 364 ohms thats a good idea, reading is pretty high and its surprising how much a second rod can improve things. If you can get down to 100 ohms you will have a much more stable system.

 

[Mr Mark Sparks]

the extra rod should be 1 rod length away from existing
or change it for the ones that thread together

 

[smyler86]

Thanks

I didnt know that!

On a similar note, I was at a mates house (TT system) and they had the main earth electrode, but were they had bonded the gas supply, they installed a new earth electrode on its own (not connected to the MET)

I cant decide if this is ok, I am thinking no.

What do you guys think?

 

[baldsparkies]

If you can see the Sydney Opera House youv'e gone to deep.

Thanks

I didnt know that!

On a similar note, I was at a mates house (TT system) and they had the main earth electrode, but were they had bonded the gas supply, they installed a new earth electrode on its own (not connected to the MET)

I cant decide if this is ok, I am thinking no.

What do you guys think?

Sorry Smyler my jest came at the same time as your post, to answer your question I would say the two earth rods need to be cross connected to avoid a potential differance between the two

 

[smyler86]

Thanks BaldSparky

That was along the lines of what I was thinking!