Pre site inspection 2391-52 scenario

[gazdkw82]

Been on thr 2391-52 course this week. I'm really enjoying it and keeping up with the material.

However the tutor was painting a scenario and it got us all in a heated debate.

The scenario was something along the lines off "next door neighbor has asked for you to install a new shower circuit etc, what should you consider" it wasn't an actual question we were all just chatting over coffee break.

It got Abit heated when I said I always do a Ze before Install any new circuit. Everyone else disagreed and even the tutor seemed to question me, however he did say he wasn't saying I was wrong.

It got me thinking, let's think if this scenario... You are asked to install a shower for your neighbour and go ahead with the work. The shower is a small shower (say 8kw) and you decide to install a 10mm t+e because that's what you have in the van/shed etc. You do the install and all tests come back good (including Zs) you walk away, everyone's happy.

However isn't there a potential the Ze is actually too high (higher than allowed for whatever earthing system is installed) but it passes because the R1+R2 value is so low. Would such a scenario exists?

Isn't it always a good idea to test Ze as part of a pre site survey??

Could see it the other way too.. you do the install and then perform Zs and find no Ze at all? Now your responsible for making it safe? Or at least communicating with the DNO and sorting it?

Sorry for the long post :-/

 

[ruston]

Bearing in mind that you have to confirm that the installation is suitable for the new addition , how would 'they' have verified that.

 

[gazdkw82]

Bearing in mind that you have to confirm that the installation is suitable for the new addition , how would 'they' have verified that.

Yes exactly. I always do Ze as a minimum. If it's a board change then I'd do Ze, PFC, IRT and nominal voltage. How else would you know what your installing your circuit into?

 

[ruston]

What was their argument or controversy ?

 

[gazdkw82]

What was their argument or controversy ?

Tbh I think they we're sayin they either just install it or install it and confirm a compliant Zs

 

[ruston]

Well in that case I would have given you the job
Was no mention made of the assessment of the general characteristics?

 

[gazdkw82]

Well in that case I would have given you the job
Was no mention made of the assessment of the general characteristics?

No, which is strange because it's been discussed and everyone agreed.

 

[ruston]

What was the tutors view?
What did everyone agree on , Just to do it ?

 

[westward10]

He sounds like a good tutor making off the cuff scenarios to get you all worked up.

 

[gazdkw82]

What was the tutors view?
What did everyone agree on , Just to do it ?

Tutor seemed confused that I would do a Ze (but also admitted he was not saying I was wrong)

There was no conclusion. The tutor moved the conversation on because I was adamant I would do it and others were basically calling me a lier.

I have no idea why others would make such a comment but there is a few odd ones in the group.

 

[gazdkw82]

He sounds like a good tutor making off the cuff scenarios to get you all worked up.

Actually he is a brilliant tutor (best I've had). It was just a passing conversation (can't quite remember why we was talking about it) but it eventually got onto what we test prior to installing a new circuit.

 

[westward10]

If you are going to carry out alterations or additions you need to check out the suitability of the existing installation this includes earthing so in my eyes you are going about it the correct way.

 

[gazdkw82]

If you are going to carry out alterations or additions you need to check out the suitability of the existing installation this includes earthing so in my eyes you are going about it the correct way.

Agreed. Thanks westward10.

 

[ruston]

Inspection precedes testing , so if you keep the correct order you are correct,
Assessment of the general characteristics came in a lot in the old 2391.
They are sticklers for terminology . or they were.

 

[Andy78]

Tutor seemed confused that I would do a Ze (but also admitted he was not saying I was wrong)

There was no conclusion. The tutor moved the conversation on because I was adamant I would do it and others were basically calling me a lier.

I have no idea why others would make such a comment but there is a few odd ones in the group.

The best tutors are like this. I had one in recent times that was perfect with his fluid maths and knowledge of theory, really knowledgeable guy. He wouldn't pretend to know anything or get stuck in his ways though. If he didn't know an answer he would say " I don't know, but I'll look it up and get back to you next session" Next session would come and he would say " Right, I've done some research, I've also chatted with my mates at the IET and NICEIC and the answer seems to be....."
Every day's a school day, even for the teachers.

Your checking of Ze where others would not is you interpreting and understanding the requirements of 132.16 better than your peers I would say.

 

[gazdkw82]

The best tutors are like this. I had one in recent times that was perfect with his fluid maths and knowledge of theory, really knowledgeable guy. He wouldn't pretend to know anything or get stuck in his ways though. If he didn't know an answer he would say " I don't know, but I'll look it up and get back to you next session" Next session would come and he would say " Right, I've done some research, I've also chatted with my mates at the IET and NICEIC and the answer seems to be....."
Every day's a school day, even for the teachers.

Your checking of Ze where others would not is you interpreting and understanding the requirements of 132.16 better than your peers I would say.

Yes that is what he is like too. He admits if he doesn't know anything and I think he enjoys hearing from those who are on the tools as he hasn't for the last 20 years (although I'd say he is only mid 40's)

I think he was generally just intrigued that I was saying I'd test Ze and the others said they wouldn't. Although I'm pretty sure he said he wouldn't (which I guess is concerning)

 

[westward10]

Don't assume what he is thinking this may just be a way of testing your resolve. Having an opinion different to the others does not necessarily make it incorrect and he may just be sitting on the fence.

 

[Andy78]

Yes that is what he is like too. He admits if he doesn't know anything and I think he enjoys hearing from those who are on the tools as he hasn't for the last 20 years (although I'd say he is only mid 40's)

I think he was generally just intrigued that I was saying I'd test Ze and the others said they wouldn't. Although I'm pretty sure he said he wouldn't (which I guess is concerning)

As a retort to support your position I would read through the wording of 132.16.
To me "ascertain" in that reg would involve both inspection and testing of relevant equipment to ensure compliance.

 

[ruston]

It is also a credit to you that you stuck to your guns, especially in the face of the tutor . You will do well?

 

[gazdkw82]

It is also a credit to you that you stuck to your guns, especially in the face of the tutor . You will do well?

Thanks Ruston.

I'm putting the effort in and it seems to be working so far. And more to the point (as cheesy as it is) I actually enjoy learning and improving my knowledge and skillset

 

[ruston]

I would say that all the members on here love their job and the challenges it brings. Once the understanding is there everything falls into place , the more understanding you get the easier it gets and the more you want to know......

 

[PEG]

I think you were correct. Ignoring the regs and requirements,for a minute,the tests to check the supply characteristics,are not onerous or particularly time consuming.

They can,on occasion,flag up issues,and lead us in other directions,sometimes directly concerned with safety,which is a primary reason for most of our governance.

I would hazard a guess,that the others on your course,giving you a hard time,were probably older,maybe considering themselves to have so much more experience,these tasks were unnecessary. They are wrong.

We can all shoe,a dead horse. It is probably easier.
But sooner or later,when we stick our hand out for payment,someone is going to ask if we checked...

 

[richy3333]

Had almost this situation in real life. Went to do an addition. Checked EFLI before starting and they’d lost their earth due to corrosion of conductors on the pole outside. DNO came straight out and fixed it.

 

[gazdkw82]

Passed the theory exam today. Very hard

 

[westward10]

Top job well done.

 

[westward10]

Earth fault loop impedance revision of ENA Engineering Recommendation P23 - https://electrical.----------/wiring-matters/issues/72/earth-fault-loop-impedance-revision-of-ena-engineering-recommendation-p23/ This is an interesting read for max Ze values probably one of the few places you will find it recorded, Engineers Recommendation P23/2:2018.

 

[H]

Passed the theory exam today. Very hard

Well done firstly

How and in what way was it difficult?

 

[ruston]

Well done mate , I just knew by your questions you had it in the bag

 

[gazdkw82]

Well done firstly

How and in what way was it difficult?

Understanding what the question is truly asking if the biggest challenge. Once you break the questions down it's usually simple but the questions are really tricky.

For example I had one that said something along the lines of "a 30ma RCD was tested at 150ma and found to trip at 500ma. What would this indicate"

Possible answers were,

A. The rcd provides efficient fault current protection

B. The rcd will be subject to noisance tripping

C. The rcd test button has been regularly checked

D. (Something along the lines of) the rcd is working perfectly.

It had me guessing because it's not obvious.

Some of the questions were difficult to find or work out. For example, if a earth electrode has a resistance of 27ohms, what would be the maximum rated rcd allowable on the installation....

Just a few examples. I can remember quitr a few but I'd be here all night.