3phase tt supply setup
- Thread starter Lee321
- Start date
Help Support Talk Electrician Forum:
OK, so it may be a new install, my Q's still really apply.
After a fashion.
What are you going to use as an earth electrode?
Where are you going to site it?
What is the install for?
Domestic, commercial, industrial?...
After a fashion.
What are you going to use as an earth electrode?
Where are you going to site it?
What is the install for?
Domestic, commercial, industrial?...
Site for Rod.
How will you know its suitable?
Would you be happy replying on a single rod for a 3ph commercial install?
What are the sorts of loads?
Will TT be suitable?
Why TT, why not TN?
How will you know its suitable?
Would you be happy replying on a single rod for a 3ph commercial install?
What are the sorts of loads?
Will TT be suitable?
Why TT, why not TN?
Why is TN unavailable?
Is there a transformer near?
Could you get PNB?
---------- Post Auto-Merged at 20:10 ---------- Previous post was made at 20:09 ----------
What test will you use to select the site for the rod before you install it?
Is there a transformer near?
Could you get PNB?
---------- Post Auto-Merged at 20:10 ---------- Previous post was made at 20:09 ----------
What test will you use to select the site for the rod before you install it?
structural steelwork?
Im not meaning to get up on one here,
but are you sure you are competent to do this Lee?
there are a lot of fairly basic questions coming .
Im not meaning to get up on one here,
but are you sure you are competent to do this Lee?
there are a lot of fairly basic questions coming .
not steel steps/m107.
thats why i'm asking steps design is something i've been away from for along time however i do have the competence to install once i have gathered enough design criteria.
thats why i'm asking steps design is something i've been away from for along time however i do have the competence to install once i have gathered enough design criteria.
Last edited by a moderator:
Manator
©Honorary Essex Boy™
What Kind of supply have the DNO left you with, or will you be requesting a new supply? You need to think carefully about the siting and size of the rod/s, on a small supply similar to the one you describe I had to "ring" the building with rods, one being placed 1m off direct corners. Larger installs could have more, even smaller ones if certain earthing requirements are needed.
The design is pretty easy, providing you have tested soil quality and demand, and of course earthing suitability.
The design is pretty easy, providing you have tested soil quality and demand, and of course earthing suitability.
Just because it is overhead does NOT preclude TN.
However, even IF you have any kind of TN on overheads, i would recommend a rod at the origin, just in case.
However, even IF you have any kind of TN on overheads, i would recommend a rod at the origin, just in case.
hmmm lots to consider. i have no idea as to why you had rods at "corners" and mention "distance"?
as long as rod earthing is low enough? 1 point could be sufficient. multiple rods for where you cannot obtain acceptable earthing yes but. ??
there is a existing tt overhead.
as long as rod earthing is low enough? 1 point could be sufficient. multiple rods for where you cannot obtain acceptable earthing yes but. ??
there is a existing tt overhead.
Manator
©Honorary Essex Boy™
Corners for ease of access, distance due to subsoil and building foundations,multiple due to the specified earthing maximum imposed, are just a couple of basic reasons.
OK so TT supply is existing thus not a new install.
Is it definitely TT, or is it an overhead TN?
Is it definitely TT, or is it an overhead TN?
[quote name='Lee
Manator
©Honorary Essex Boy™
Thanks Andy.
Yes sometimes the specification and requirements can be imposed on you, normally with TT this will be in the form of max Ra allowed, but sometimes they will insist on a max Zs for one or more circuits.
Yes sometimes the specification and requirements can be imposed on you, normally with TT this will be in the form of max Ra allowed, but sometimes they will insist on a max Zs for one or more circuits.
