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.