Loop test

[1stfix2ndfix]

136.4 ohms at lights whilst doing the loop test before we change the board. Guessing they've been lucky ? Plus side is I get to put an earth stake in were see how much I remeber from the one I did 2 years ago

 

[Farmelectrics]

have you investigated why you have a high reading

 

[Pete999]

136.4 ohms at lights whilst doing the loop test before we change the board. Guessing they've been lucky ? Plus side is I get to put an earth stake in were see how much I remeber from the one I did 2 years ago

What was the loop test at the other circuits? what was the ZE?

 

[telectrix]

as above ^^^^. if you have TN earthing, bloody well use it. get it fixed if it's outside parameters. howewver, if it's TT, then you'll probably be installing jointed rods to get an acceptable ( an d i don't mean < 200) Ra/Ze.

 

[1stfix2ndfix]

Not sure what the ze is yet as my mate is in that area but I think it's so high as the 16mm earth cable went from the board to no where basically. It was just cut of and poked through the hole in the wall which made it look like all was ok. Some people are very dodgy.

 

[1stfix2ndfix]

So far I've bashed in one copper earth rod which was about a meter and a bit long. I don't think I'll be making it longer as we've only got the one and even if I had two tere no where to joing the next one on. I'll report back how we get on and hat I learnt about it

 

[Octopus]

Why the f are you doing this? Surely your gaffer is taking control and making the decision. If he exists

 

[Silly Sausage]

Why the f are you doing this? Surely your gaffer is taking control and making the decision. If he exists

Nothing surprises me with this poor lad's boss!!!

 

[Simonslimline]

Quite amusing, but also not good at the same time :6:

 

[Pete999]

Just had a look at the OPs profile, trainee with little or no quals or experience (not his fault and in no way getting at him) but what's the Gaffer thinking leaving the poor guy to do work like this unsupervised?

 

[Engineer54]

Sounds like his boss is a electrical trainee to boot!! ...lol!!

 

[Pete999]

Sounds like his boss is a electrical trainee to boot!! ...lol!!

So in effect the whole outfit is a 10ww

 

[Engineer54]

So in effect the whole outfit is a 10ww

I dunno, because this lads profile say's he has C&G 2330 and 17th!!!! Also say's above, he installed a stake 2 years ago, Yet seems to know little to nothing about the reasoning behind installing a rod. Couple that with the rod he has installed here, sounds very much like a one of those short thin twigs, that are just about totally useless to man nor beast, and certainly not extendable....

 

[Fox]

The problem with the 'rod' you have used is that it is not extendable so it's not going to remain stable between different seasons and weather spells. I would not rely on it for a safe and reliable means of earth.

I'd never tend to use a single 5/8'' or 3/4'' rod for the same reason.

 

[HappyHippyDad]

I'd be interested to know what putting in another 1m rod is going to do? Unless it is in particularly suitable soil that has a very low resistivity I doubt it will bring the Ra down to a suitable resistance to aid in disconnection.

I have added a rod once to an existing TT which had an Ra of over 200Ω simply to bring it below the level required by the regulations. I realise this wouldn't really achieve anything else though.

Infact, I am unsure if it is realistic in a domestic situation to aim for an Ra value that could be used without RCD to accomplish reliable disconnection. I realise Trev has achieved a very low result but is this realistic in the majority of households?

If a copper rod 5cm in diameter and 10m in length (HUGE compared to the usual rods of 3/8" or 5/8" diameter) is buried in clay soil with a resisitivity of 10Ωm it will achieve an Ra = 1.02Ω which could perhaps be classed as getting close to a suitable Ra. Even then the Zs of a ring probably wouldn't be within the limits set by BS7671.

Also the soil resistivity of clay is very low, more realistically there will be some chalk/sand/rock mixed in with it which will increase the soil resistivity. Plus... if there is a dry spell one summer this figure will increase even more so it could be argued even if you got it down to 1Ω it wouldn't be stable.

I'd be genuinely interested if E54 or indeed any of the experienced chaps think it is 'realistic' to achieve a suitable Ra in a domestic situation which could be used without RCD to achieve safe disconnection times?