to bond or not to bond

[leep82]

I know its been done to death but in going to ask for your thoughts opinions anyway.

Just turned up on a job that ive been on for a while where i have had no communication with the plumber. Everything has been through the customer. The plumber has fitted a new central heating system with a boiler that is oil fed. The bund for the oil sits on a concrete pad and has been in for weeks. I was told by the customer that the pipe to feed the boiler would be surface fixed and of plastic, hence, no need for any bonding. Standing looking at it now and the pipe has been buried for 2/3 mtrs and although it has a thick plastic coating is quite clearly a copper pipe. Is the plastic coating enough to suggest that bonding may not be necessary?

 

[davesparks]

basically BS7671 allows that a 10mA current through the body is safe (22k ohms. but niceic accepts 30mA. ( 6.7k ohms ). any niceic officials want to test their theory? "get hold of these while i switch on". i know where i'd sooner be if coming into contact with a live cable, considering the state of my furred up arteries.

I have been on the receiving end of a shock in which my life was saved by a 30mA RCD. It knocked me out cold for about half an hour, and it hurt like hell, the last thing I remembered when I came round was hearing the click as the RCD operated.

What was I doing to get such a shock? I was tacking a BT cable round an architrave with a metal stapler, I discovered that the switch cable had been tucked in behind the architrave when I fired a staple into it. Because my hand was clenched to fire the staple and I was pushing on the stapler at the time I didn't stand a chance of getting away from it.

 

[yellowvanman]

With a test meter which has a suitable measurement range

Thats a helpful response!

Are you aware of a specific instrument that has the necessary resolution, when using a 500V insulation tester? If so, I would be interested in what it is.

 

[davesparks]

Thats a helpful response!

Are you aware of a specific instrument that has the necessary resolution, when using a 500V insulation tester? If so, I would be interested in what it is.

I made no mention of tester resolution, only measurement range plus How would using a 500V insulation tester affect another test instruments resolution?

I think what you are trying to ask is whether or not I know of a test instrument which tests at 500V and has a suitable measurement range? In which case no I do not, but I'm not entirely sure why you would want one?
This is not a measurement of insulation resistance, it is a measurement of resistance and as such any meter capable of accurately measuring resistance will do the job.

Insulation resistance testers are generally used as they are the most convenient instrument for most electricians and generally have a suitable range when considering a 10mA current. But as far as I know they are not required.

Personally I use a megger AVO410 multimeter.

 

[LeeH]

I think this is a perfect example of a time where it's harder to prove it isn't extraneous then it is to bond it.

Just my 10 pence...

 

[davesparks]

I think this is a perfect example of a time where it's harder to prove it isn't extraneous then it is to bond it.

Just my 10 pence...

I completely agree

 

[madmaz]

I've just had to complete strange bonding thanks to a plumber !!! Main water supply to a detached outbuilding enters property in alcathene then drops to copper after stop tap, this copper drops under the concrete into speed fit which runs in the concrete supplying hand basins, each set of pipes to each basin are copper connected to a speed fit tee under the concrete the bottom 1" of each copper pipe is buried in concrete when I tested each pipe the resistance to met was below the 23000 ohms but different to each other, readings of 2.9k - 14.5k I've had to bond all pipes together thanks to this,

 

[yellowvanman]

I made no mention of tester resolution, only measurement range plus How would using a 500V insulation tester affect another test instruments resolution?

I think what you are trying to ask is whether or not I know of a test instrument which tests at 500V and has a suitable measurement range? In which case no I do not, but I'm not entirely sure why you would want one?
This is not a measurement of insulation resistance, it is a measurement of resistance and as such any meter capable of accurately measuring resistance will do the job.

Insulation resistance testers are generally used as they are the most convenient instrument for most electricians and generally have a suitable range when considering a 10mA current. But as far as I know they are not required.

Personally I use a megger AVO410 multimeter.

Not aware of how GN8 defines how the measurement is made, but from an ECA publication it states:

'Using a 500 volt DC insulation tester,
measure the insulation resistance between
the item and the main earthing terminal.
If the resistance value is 23 000 ohms or
greater, and inspection confirms that the
resistance is unlikely to deteriorate, then the
item can reasonably be considered not to be
an extraneous-conductive-part.'