Tt and tns sytem together

[tester11]

Hi folks, I have issues with a job I was on today with an outside metal enclosure being bonded from a tns system and right next to it I have another metal enclosure which is bonded thought an earth pit and tt system as there are supplies to caravans protected by the tt system. My issue is the fact 2 different earthing systems are simultaneously touchable and could have different potentials, what's everyone's take on this ? Thanks

 

[Darkwood]

Are the origin of supply the same but just differing earthing arrangements at these 2 points.

 

[davesparks]

I would question why the caravan supplies aren't on the TNS supply?

You're right that this is not a good situation as you have two separate earth potentials in close proximity

 

[Martyc]

I would guess that work was carried out, earthing was previously via armour of swa back to intake origin, which has since deteriorated and giving an unacceptably high efli, so they've gone TT to bypass the existing tns.

Well at least that's what I've seen contractors do before on these places when I worked on them

 

[Darkwood]

If the supply origin is common then Rod the TNS as well as leaving its earthing as is, if they come off different origins then this increases the risk of a PD between the 2 earthing set-ups.

 

[davesparks]

I would guess that work was carried out, earthing was previously via armour of swa back to intake origin, which has since deteriorated and giving an unacceptably high efli, so they've gone TT to bypass the existing tns.

Well at least that's what I've seen contractors do before on these places when I worked on them

Which is not compliant, if the SWA has deteriorated then it is unfit for continued service and should be replaced.

 

[tester11]

Not exactly sure why they haven't used the tns Earth, but yeah it is swa into enclosure 1 with the tns protection then a supply from enclosure 1 to the 2nd enclosure where the caravan supplies are fed from with the Earth pit adjacent.

any thoughts of a code on a condition report for this am Thinking code 2 ?