Would you accept a Ze of 199Ω on a TT Installation which also has an RCD.

[Jonspark]

Yeah went past there other week on way to Patrington caravan park

 

[DPG]

Nice area around there. Nice bit of military history at Kilnsea and Spurn point. Daz

 

[baldsparkies]

Don't start giving these ISIS Jihad types any ideas for fooks sake!!!

Remember when working at a nuclear power station just after 911.
Security was tighter than the proverbial ducks bottom.
We needed to change a supply source during a re furb.
UPS system for comms was signed off as being healthy, and we were give permission to shut down, lock off and transfer.
We were there as a contractor, and the in house maintenance sparks were also present.
All good to go says the in house sparky's with a thumbs up.
No problem bud, says I.
As soon as you throw the switch we will start the transfer.
Oh !! right ok he says.
Ker clunk,
Should of had a full half hour, system went down in less than five minutes.
Now back then if comms go down, all hell breaks loose.
The UPS service engineers were for the high jump, and when they asked who had isolated the supply I was able to say "I know nothing senor"
Moral of the story.
Don't be the scape goat for somebody else's responsibility.:ack2:

 

[Jonspark]

Quite like spurn point but it's a bloody long walk now.

 

[DPG]

Have they not rebuilt the road yet from last year?

 

[Jonspark]

do you can only drive as far as the twitchers hut, then its a long walk to the end

 

[DPG]

Cheers. Do you think I would get down on my Armstrong? (off-road bike, road legal though)

 

[Jonspark]

Cheers. Do you think I would get down on my Armstrong? (off-road bike, road legal though)

should do, although it can be quite sandy in places

 

[Jonspark]

on the other hand i think all motor vehicles might be prohibited

 

[DPG]

Been down before on the bike - it's OK, it does sand ! I guess they might be stopping all vehicles. I'll check before I go next. Cheers, Daz

 

[Deleted member 9648]

Re: Would you accept a Ze of 200Ω on a TT Installation which also has an RCD.

That's what happens when the old bugger doesn't put his glasses on.
Many thanks for correcting me kind sir.
Just wish they could come up with some decisive information or even come to a reliable conclusion as to what makes a max value stable and then at what point its not.
I have corrected TT system readings above 400 ohms.
And yet the 30ma rcd's protecting those circuits have, under test, operated within 40ms/200ms no problems.
If un-stability is a science it needs practical clarification so that we have a definitive cut off value that all adhere to with no grey areas.
In the mean time I will continue to go with 100 ohms purely because logic dictates its a safer bet than 200 ohms.
No other reason, and if someone proved conclusively that below 200 is still a safe option then so be it.

Thats got to be one of the most illogical statements I've ever seen on this forum. You might as well go with 1000 because it's safer than 1667!

 

[D Skelton]

Re: Would you accept a Ze of 200Ω on a TT Installation which also has an RCD.

Thats got to be one of the most illogical statements I've ever seen on this forum. You might as well go with 1000 because it's safer than 1667!

Like saying "I'll only drive at 190mph on the autobahn because it's safer than 200mph" lol!

And.. 'three'.. 'two'.. 'one'... Eng is back in the room!

 

[7029 dave]

Why do people get so twitchy with TT? first you have to understand the system it an earth to earth system, with an good rod or earth matt, the biggest earth conductor(yes 16mm) I have achieved 2 figures.

 

[richy3333]

Re: Would you accept a Ze of 200Ω on a TT Installation which also has an RCD.

Does everything need to be a poll?

We'll be having designs put to a poll soon!

We should have a poll to find out the answer

 

[baldsparkies]

Re: Would you accept a Ze of 200Ω on a TT Installation which also has an RCD.

Thats got to be one of the most illogical statements I've ever seen on this forum. You might as well go with 1000 because it's safer than 1667!

"In the mean time I will continue to go with 100 ohms purely because logic dictates its a safer bet than 200 ohms".

In context with the rest of the quote it seems logical to me !!
Where a TT system is used I will always attempt to get sub 100 ohm readings as opposed to 200 ohms because its a safer bet.
Is not the whole point to reduce the resistance of the earth return path to a point where stability issues are minimised.
Technically we can often go much higher than that, but I prefer not to always rely on what's technically correct.
Otherwise we can bring into play your own analogy of 1667 or even 1000 which I agree would lack logic, but on paper !!
BS 7671 are looking at values below 200 ohms.
NICEIC have quoted below 100 ohms, as does BS 7430.

Actually BS 7430 is a very interesting read so here's a link,

http://jack.nazwa.pl/doc/UK.17th/BS/BS 7430 Earthing.pdf

With reference to Skelts 200 mph vs 190 mph,
If its a Ferrari, with decent brakes, on a traffic free autobahn !!

GO FOR IT unk: