TT to PME conversion

[mtraczykowski]

Can someone confirm the procedure to convert a domestic system fron TT to a PME system?

 

[topquark]

First step is to check with the supplier to see if it's available in the area (it may not be).

Edit: I guess whilst you're doing that you could be gathering R1+R2 for all the circuits to see if they'll be ok when combined with a worst case TNCS Ze (0.35).

 

[WayneL]

I guess the first step would be to ring the DNO and ask them when they can do it

 

[topquark]

Kinda thought that went without saying, but I guess not

 

[mechelec]

First step is to check with the supplier to see if it's available in the area (it may not be).

Edit: I guess whilst you're doing that you could be gathering R1+R2 for all the circuits to see if they'll be ok when combined with a worst case TNCS Ze (0.35).

0.35 is by no means the worst case for PME it depends on the cutout fuse size. Ask your DNO

 

[topquark]

Ah, OK, ta! I was always told that 0.35 ohms was worst case you should allow for TNCS and 0.8 ohms for TNS (up to 200 ohms for TT) and if it was outside that then to contact the DNO.

 

[mechelec]

Just found the latest figures from my local DNO for PME

main fuse size 100A max Ze 0.38 ohm
main fuse size 80A max Ze 0.52 ohm
main fuse size 60A max Ze 0.73 ohm
main fuse size 45A max Ze 1 ohm

This info was given to me a couple of months ago

 

[Deleted member 9648]

Bonding will need to be a minimum of 10.0mm......lots of TT'S are in 6.0mm......sorry if that is stating the bleeding obvious but it is part of the procedure