Main bondage

[ultinator]

Does main bonding in every circumstance always need to be under 0.05. main bonding in a house where the main water was moved has 10mm cable but resistance of 0.25 ohms!!>>

 

[VoltzElectrical]

I am perfectly willing to accept thanks for the information given in Voltz's posts if you think it is valuable, after all I missed much of the Wales Vs France game to explain it to him in detail!

sorry bud, I did not take credit for your valuable input, but perhaps i should have given you more direct credit for your enlightenment. I remembered something along the lines of which you were trying to explain to me a while go and this brang it all home to me while i was perusing the forum and keeping half an eye on a stalemate game at the time.

Thanks for the chat and at least the boys done good after we finished talking!

xx

 

[VoltzElectrical]

First time i've read this thread but the most amusing point of it for me is the fact post #14 explained the 0.05 value and it seems to have taken a day for many others to catch up....

Really! I fail to see how post no.14 sheds any light on the understanding of this issue.

 

[GLENNSPARK]

it is an existing bonding cable, was gonna change the board for an assessment but now i'll need this to be sorted. p.s. the cowboy who installed this bodged quite alot so dunno what is going on

well then always keep an open mind. as soon as you see turd at an install....

 

[VoltzElectrical]

well then always keep an open mind. as soon as you see turd at an install....

come on Glenn, don't be a slow starter, you are well up on the regs, let's have your input on this issue.

Only READ ALL THE POSTS FIRST AND HOLD OFF THE FULL STOPS!!!

xx

 

[capitolltd]

The 0.05 relates to the bonding connection, not the conductor length. This is to conform the clamp is connected to the conductive part with a low resistance joint. (i.e. paint removed from pipe). This relates over to the 0.1 + R of lead used in the COP for portable appliance testing, as there are 2 points of connection (0.05+0.05=0.1)
The purpose of the main protective bonding conductor is to equalise the potential, so we only see the volt drop (touch voltage) of the R2 conductor, between conductive parts under fault conditions. If no bonding is present, we will see the volt drop of the R2 conductor, plus the volt drop of the external earth. Obviously this will be greater in TT installations, due to the higher resistance in the earth electrodes.

 

[netblindpaul]

The 0.05 relates to the bonding connection, not the conductor length. This is to conform the clamp is connected to the conductive part with a low resistance joint. (i.e. paint removed from pipe). This relates over to the 0.1 + R of lead used in the COP for portable appliance testing, as there are 2 points of connection (0.05+0.05=0.1)
The purpose of the main protective bonding conductor is to equalise the potential, so we only see the volt drop (touch voltage) of the R2 conductor, between conductive parts under fault conditions. If no bonding is present, we will see the volt drop of the R2 conductor, plus the volt drop of the external earth. Obviously this will be greater in TT installations, due to the higher resistance in the earth electrodes.

Quite, think about the clamp and the pipe, simultaneously accessible conductive parts...

 

[ezzzekiel]

Seems to me a few varied explanations yet not one definitive answer, 0.05 appears to be a standard value used with no understanding of the reason.

Be nice to know the correct theory

 

[Guest55]

this value of 0.05 ohms is irrelevent regardless of how its measured , you size the bonds as per the requirements of section 544 bs7671.
no mention of maximum resistance or length is even mentioned in the regs.
when push comes to shove , the numbers suggested in the guidance notes dont mean jack , theyre just suggestions for the many different ways of compliance.

 

[Guitarist]

As a few of us have already stated, the fact that it's over 0.05 on a relatively short run is indicating that it's not continuous and needs investigating.

 

[KAS1]

"Does main bonding in every circumstance always need to be under 0.05. main bonding in a house where the main water was moved has 10mm cable but resistance of 0.25 ohms"

a few of us have already stated, the fact that it's over 0.05 on a relatively short run is indicating that it's not continuous and needs investigating.

- - - Updated - - -

Noooooooooooooooooooooooooooooooooooo it does not have to be so

 

[KAS1]

he may well have a fault be he's asking does it have to be 0.05ohms or under the answer is NO

 

[VoltzElectrical]

is it just me? i thought we cleared all this ages ago?

 

[Gavin A]

he may well have a fault be he's asking does it have to be 0.05ohms or under the answer is NO

The only way it can be over 0.05ohms is if there is a fault / most likely a high resistance joint, therefore if it's over that figure (or at least over it significantly) then it can not just be left, it should be investigated and rectified.

OK so you don't need to test the cable if you can see it for its full length, but in this case it was tested to verify its integrity because part of the length was hidden, and the test shows a probable high resistance joint in the circuit, which therefore needs to be rectified one way or another as it's the equivalent of having run the bonding in something like 1.5mm2 cable, although it's worse than that as it's likely that the high resistance joint will degrade further if it's just left.

This thread is pretty worrying tbh, as I said earlier this should be basic bread and butter stuff to any spark.

 

[Guitarist]

he may well have a fault be he's asking does it have to be 0.05ohms or under the answer is NO

Haha, agree with you mate. However..... it would not be prudent simply to say "0.25 is pretty low so that'll do"

 

[Gavin A]

Can I ask a question of those who're saying that the 0.05ohms figure should be the maximum resistance reading between 2 different extraneous conductive parts, but not the maximum figure for the bonding cable itself?

How would you see this figure being guaranteed between for example a water pipe and a gas pipe if the figure for the main bonding cables was itself higher than 0.05ohms?

Surely if the figure for the bonding cable is higher than 0.05ohms, then the bonding isn't going to be able to cause the reading between any other ET parts in the house to be lower than 0.05ohms unless this figure was already being achieved prior to the bonding being carried out in the first place.

OK so you could also argue that assuming very high resistance between ET parts in the first place, then both bonding cables being at 0.05ohms themselves wouldn't guarantee that the reading between the ET parts would then be lower than 0.05 ohms, but you can guarantee that in this situation if the reading on the bonding cable is higher than 0.05ohms then the reading for the resistance between the ET parts must also be higher than 0.05 ohms.

So regardless of the precise wording of the regs, you'd need to have a reading of 0.05 ohms or lower on the bonding cable itself in order to stand any chance of this bonding then causing the reading between any 2 ET parts to also be lower than 0.05ohms.

or have I missed something?