Max Zs readings where circuits are protected by 30ma RCD's

[baldsparkies]

But we have to assume competency on the part of the installer or the entire content of BS7671:2008 is pointless.

The 200 Ohm figure for earth electrode Ra is a figure that allows for degradation of soil resistivity from freezing/drying etc. but as i've said many times, I'd take an Ra of 500 Ohms on a deeply driven rod rather than 200 Ohms on a 1.5 Metre rod because on the first good drought or frost, my deeply driven rod will be almost immune.

I accept that there are installers that are not competent, I read their PIR's every day but we can't alter the regulations to suit the lowest common denominator.

Been talking to a couple of old friends on the subject,
Respected and very competant electrical engineers I might add.
Enjoyed our pint, and one said.
If you were driving down a road where the speed limit was 60 mph. You wouldnt just keep to that speed because it says so.
You would use your own judgement as a competant driver to negotiate bends in the roads ect at much lower speeds than stated, and for reasons of safety.
When put like that, who am I to argue.

 

[IQ Electrical]

Been talking to a couple of old friends on the subject,
Respected and very competant electrical engineers I might add.
Enjoyed our pint, and one said.
If you were driving down a road where the speed limit was 60 mph. You wouldnt just keep to that speed because it says so.
You would use your own judgement as a competant driver to negotiate bends in the roads ect at much lower speeds than stated, and for reasons of safety.
When put like that, who am I to argue.

If I'd have been more 'skilled with the pen' I'd have used that analogy, perfect!

 

[telectrix]

wish my van could do 60.

 

[giio]

if I were to be pedantic, as a lot of people on here are, by saying they put 1667 because that is what it says ,then they are wrong the actual figure is 1666.67 so they should be filling in 1666 if they are rounding it off ( round down not up, it's the pessimistic nature of all regulations especially IEE ones)

50 (volts) / 30 (milliamps) = 1666.67

 

[IQ Electrical]

While I can't dispute your maths, the 1667 Ohm value is taken from Table 41.5 in BS7671:2008

 

[telectrix]

no mate. roundeedd off it's 1667 to the nearest whole number. if i remember correctly the last significant figure of 1666 was the great fire of london. now that was a disaster, but at least it killed off the plague. let's hope this figure related to our work don't kill off anyone.

 

[giio]

no mate. roundeedd off it's 1667 to the nearest whole number. if i remember correctly the last significant figure of 1666 was the great fire of london. now that was a disaster, but at least it killed off the plague. let's hope this figure related to our work don't kill off anyone.

a few ohms were lost in that one

 

[IQ Electrical]

a few ohms were lost in that one

13200 Ohms were lost, apparently telectrix picked up a fair old few rewires from it.

 

[baldsparkies]

13200 Ohms were lost, apparently telectrix picked up a fair old few rewires from it.

Yep, But Telectrix was just a young apprentice in those days. lol

 

[Des 56]

Yep, But Telectrix was just a young apprentice in those days. lol

I will have you know,he was well qualified and had "countless" years of experience behind him by then

 

[IQ Electrical]

I only started this because of his Arsenal trophy joke this morning!

 

[Guest123]

Some say that he wrote the 1st edition on the back of his JPS packet.......and that if it wasnt for him the RCD would be a myth.......all we know is he's called.......what ever we feel like at the time!!!!

 

[IQ Electrical]

Some say that he wrote the 1st edition on the back of his JPS packet.......and that if it wasnt for him the RCD would be a myth.......all we know is he's called.......what ever we feel like at the time!!!!

And he's the oldest spark (ten second Clarkson pause) in the world.

 

[Des 56]

And he's the oldest spark (ten second Clarkson pause) in the world.

and
His rewiring times are legendary

 

[baldsparkies]

and
His rewiring times are legendary

With 13200 homes/Ohms to cover, they need to be. lol