main bond

[Engineer54]

I'm sure to a greater extent your quite right, but i'm also sure that certain area's in the UK, the water is heavily mineralised (hard water) with lets say, the wrong kind of minerals. Most water that i've seen tested for conductivity, would not come anywhere close to being suitable for MV/HV insulator jet washing...

 

[malcolmsanford]

Listen mate anyone wanting to spray water at HV is welcome to it lol ....................Your quite right though not being HV do they still do the practice of sparying

 

[alanl]

I went to a pub recently to investigate a faulty immersion heater "we can hear it bubbling, but the water only gets luke warm".

It was clearly a faulty element, so I took it out, and amazingly, the outer insulation was completely rotted away, leaving a broken element in the water, a gap of an inch or 2 between L + N.
Yet it hadnt tripped the RCD (or MCB for that matter).
I was a little surprised about this, and asked a lecturer I knew. He said it was common, if you put a live flex, with L and N around 2 inches apart, into a bucket of water, then all it would do is heat up the water between the L and N, and so long as you are wearing shoes, and not soaking wet yourself, you could put your hand in and not get a shock, as the shortest path would always be between the L+N terminals.
He also said there were some industrial water heaters that worked on this principle.

Alan.

 

[Engineer54]

Yes!! it's the only real economical way of keeping insulators free of foreign body build-up!! Generally undertaken every five to 7 years.... They Use a lorry similar to a fire engine with a high pressure pumps. The lorry is continuously fed with water, from registered water tankers.

Your missing out then, ...spraying/jetwashing pylon isolators is great fun, if it's getting a little dark, you can sometimes see the corona of the spay ionising!! haha!!

 

[Engineer54]

I went to a pub recently to investigate a faulty immersion heater "we can hear it bubbling, but the water only gets luke warm".

It was clearly a faulty element, so I took it out, and amazingly, the outer insulation was completely rotted away, leaving a broken element in the water, a gap of an inch or 2 between L + N.
Yet it hadnt tripped the RCD (or MCB for that matter).
I was a little surprised about this, and asked a lecturer I knew. He said it was common, if you put a live flex, with L and N around 2 inches apart, into a bucket of water, then all it would do is heat up the water between the L and N, and so long as you are wearing shoes, and not soaking wet yourself, you could put your hand in and not get a shock, as the shortest path would always be between the L+N terminals.
He also said there were some industrial water heaters that worked on this principle.

Alan.

That's the basic requirments of a water baseed ''Load Bank''!! Depending on what sort of load they want to actually go upto ,they will sometimes add salt to the load bank. But generally is the amount of plate that's exposed to the water, as to what load you can draw...

 

[malcolmsanford]

Yes!! it's the only real economical way of keeping insulators free of foreign body build-up!! Generally undertaken every five to 7 years.... They Use a lorry similar to a fire engine with a high pressure pumps. The lorry is continuously fed with water, from registered water tankers.

Your missing out then, ...spraying/jetwashing pylon isolators is great fun, if it's getting a little dark, you can sometimes see the corona of the spay ionising!! haha!!

You just confirmed what I always thought mate ...............mad as a hatter lol

 

[SPARTYKUS]

Original poster- your answer has been posted. If you want to be sure whether to bond or not bond, doesn't matter what is said in any guideline or regulatory publication the only way is to test it and provide proof! Its a five minute job.

Never easy this job....let us know what value you get...?

 

[davemack]

Been back toproperty today and tested between met and pipework under sink got a reading of 320 K ohms so guess no need to bond!

 

[NMc]

Guess again

 

[pushrod]

Guess again

Care to explain why?

 

[SimpleSimon]

Maybe I've missed the post, but when you went to the main stop cock to check for the bonding clamp, was it plastic or copper than on entry?

 

[NMc]

Let me recap

You are doing a PIR. all you can see if copper pipes and a tank and you can't find any plastic. You get a reading of 320K between MET and water pipe

Sound to me like you have extranuous metalwork which under the regs needs to be bonded. You have 320K reading which suggests to me there may be some kind of conection but not good enough

The property is 3 years old so likely to have a TN-C-S supply which under the ESQCR need the water pipes to be bonded yet you cant find it, so has the original been installed incorrectly?

The 320K between MET and water pipe would suggest no main bonding or a bad termination

You can prove the continuity of the pipework through tests at all the different water outlets with a long lead if you get low readings the pipework is continuious. This will let you know if one bond connection at point of enty will be sufficient. You may need to consider some supplementry bonding

The bottom line is you are carrying out the PIR as a competant person and you will sign the cert as so. Anything wrong could bite you

 

[pushrod]

If you have a resistance between a metal part and the MET of 320kΩ then the metal part would not be considered to be an extraneous-conductive-part as it would limit any current to 0.7mA (not even detectable with your skin) and as such, as far as i know and have read, would not need supplementary protective bonding. The usual resistance at which a part is considered not to be an extraneous-conductive-part is 23KΩ (see GN8) so there is a lot of leeway from the OP's reading.

As the person doing a PIR i would not want to recommend unnecessary work.

 

[DurhamSparky]

DONT BOND! above limit and thus you bonding will introduce a path!

 

[davemack]

Not going to bond as reading is above 25Kohms , must be 1000 houses on this estate and i have now been into 3 all have no main bond although gas pipes are main bonded, spoke to main contactor
and he's told me there is no need to bond!

Still seem's alien to me as so used to bonding water mains for the last 30 years although i can see it could indeed introduce a path, thinking i sould have tested with the tap running just out of intrest.