no water bond, code query

[graham123]

Doing a periodic at a primary school and am unable to locate where the mains water is isolated from, the earth bar doesnt account for a bond to the water as ive found where all the other go. Ive been told in the past no bond is a 1, but in this case i cant find where it is isolated so a 2 or 3? opinions welcomed

 

[i=p/u]

could be in plastic pipe so you need to find it or put in limitations

 

[Richard Burns]

If you can't find the connection for the water bonding then do a continuity test from MET to the furthest part of the water system to see if there is bonding in place. If there is apparently bonding in place then it is 3 requires further investigation (though really this should be found at the time). If there is no indication of bonding in place then this would I think be a 2 as there is the potential for danger in the case of a fault.

 

[telectrix]

agree ^^^^

 

[Deleted member 9648]

If you can't find the connection for the water bonding then do a continuity test from MET to the furthest part of the water system to see if there is bonding in place. If there is apparently bonding in place then it is 3 requires further investigation (though really this should be found at the time). If there is no indication of bonding in place then this would I think be a 2 as there is the potential for danger in the case of a fault.

'Fraid I dont entirely agree with the test method. It is not the furthest point of the water system that requires bonding,it is the nearest. Parallel paths through conductive parts in contact with the water system will give false results. And it is because the system may be at the potential of the general mass of earth that it needs bonding at the point of entry....if it is at earth potential...you are liable to get a misleading continuity reading to the MET whether it is bonded or not.
The point of entry needs to be found,from there you can establish whether or not the water is an extraneous conductive part. If it cant be located you should assume it is not bonded and apply a code 2,as Richard states...perhaps with an explanation such as. "Unable to locate incoming water supply and associated main bonding,requires improvement"

 

[Richard Burns]

'Fraid I dont entirely agree with the test method. It is not the furthest point of the water system that requires bonding,it is the nearest. Parallel paths through conductive parts in contact with the water system will give false results. And it is because the system may be at the potential of the general mass of earth that it needs bonding at the point of entry....if it is at earth potential...you are liable to get a misleading continuity reading to the MET whether it is bonded or not.
The point of entry needs to be found,from there you can establish whether or not the water is an extraneous conductive part. If it cant be located you should assume it is not bonded and apply a code 2,as Richard states...perhaps with an explanation such as. "Unable to locate incoming water supply and associated main bonding,requires improvement"

Yes, this is a better description, I was probably being a little simplistic.
If the point of entry cannot be found then it is not possible to determine correctly if the water is bonded so a code is required of some sort.

I was working on the principle that if you have a continuity check of say 0.01 ohm at a distant part of the water pipework then the consideration may be that the water pipework is in effect bonded (though possibly not correctly bonded, as evidenced by the lack of the conductor at the MET) and would be unlikely to cause a danger in case of a fault so a code 3 may be appropriate.
If you get say 4 ohm then this is not effectively bonded and would need a code 2.

However this "method" is not an approved or regulated means of determining correct bonding and as you say could well be a misleading reading.
Explanations on the form are always good (wish I had thought to put that!)

 

[dingledong]

i have to agrre with you richard i have been unable to find the water bonding i then test here and there and if i get a good reading i'd code it as a 3

 

[Deleted member 26818]

I would not put this as a code 3.
If you cannot find the connection, but believe there is one, then it must be inaccessible, which could be either code 2 or 4 depending upon how dangerous you believe having an inaccessible connection is. It would warrent being recorded as a LIM in any event, as there should be no other reason for you to be unable to find the connection.

 

[IQ Electrical]

On any report with my name signed, if I can't be sure of a bonding connection including sight of an appropriate clamp etc. then it's a code 2.

Why would you allow any discrepancy or ambiguity in your report?

There is no advantage to you as the inspector in recording this as a code 3 or 4.

 

[i=p/u]

if all circuits was rcd protected , would there be a need for main bonding...

 

[IQ Electrical]

if all circuits was rcd protected , would there be a need for main bonding...

Absolutely, there is no 'get out' for bonding an extraneous-conductive part.

 

[i=p/u]

how are you iQ..??

plastic pipe?

we doing kitchen rewire at moment, and i aint seen any bonding in this house at all.. they do have 300mA power breaker installed before old 3036 board...

im working myaelf up there in morning, im going to have search...

 

[i=p/u]

Zs is determined as compliant if the nominal voltage over the current causing disconnection in the required time is greater than the measured/ calculated value of Zs. i.e. Zs * Ia <= Uo

so 1.24 x 100A= 124v so my 230v to earth is more so will comply..???

 

[i=p/u]

cant see how that workds

 

[IQ Electrical]

how are you iQ..??

plastic pipe?

we doing kitchen rewire at moment, and i aint seen any bonding in this house at all.. they do have 300mA power breaker installed before old 3036 board...

im working myaelf up there in morning, im going to have search...

I'm fine thanks lol, how are you? Lol!
You mention plastic pipes but they aren't extraneous-conductive parts.

The adequacy of existing bonding should be checked before any additions or alterations to the installation.

 

[IQ Electrical]

Zs is determined as compliant if the nominal voltage over the current causing disconnection in the required time is greater than the measured/ calculated value of Zs. i.e. Zs * Ia <= Uo

so 1.24 x 100A= 124v so my 230v to earth is more so will comply..???

You need the current multipliers of the protective devices for the equation eg:

Type B = X5
Type C = X10
Type D = X20

So max Zs for a B 32 = 230/32X5 = 1.44 Ohms

 

[goldie]

if all circuits was rcd protected , would there be a need for main bonding...

Ofcourse there is! why wouldnt there be?

 

[i=p/u]

i understand that part but how do you know a circuit will comply with a similar summ.. maybe ive picked up wrong what other guy was telling me.. tea?

You need the current multipliers of the protective devices for the equation eg:

Type B = X5
Type C = X10
Type D = X20

So max Zs for a B 32 = 230/32X5 = 1.44 Ohms

 

[IQ Electrical]

i understand that part but how do you know a circuit will comply with a similar summ.. maybe ive picked up wrong what other guy was telling me.. tea?

Because you compare the result of the sum (maximum Zs for the device) with the measured or calculated value of Zs for the circuit.

We use a factor of 0.8 on the maximum Zs figure from the sum to allow for increased conductor operating temperatures under load.

So in the example that I did, you'd take your Zs measurement or calculated value for the circuit and compare it with the value from the sum X 0.8.

As long as your measured/calculated value for the circuit is equal or less than that figure then the circuit is deemed to comply for ADS purposes.

 

[i=p/u]

comprende!! any other tricks up you sleave.. what about this one hope we havent been here before and you getting sore head.. adding of 1.24 for temperature for volt drop and what other cases..??