R1 + R2 readings

[Traineeboy]

Do you have to measure R1 + R2 readings or is it acceptable to take live ZS reading and deduct the ZE reading ? 

 

[Murdoch]

What are you testing?

 

[boltonsparky]

One theoretical example: Old house, central heating pump has a FCU, You test Zs at that point, reading within spec for the protective device. Deduct Ze from Zs, fill out your R1+R2 on the cert. A week later along comes the plumber and puts a load of plastic pipe in. you're unlikely to go back again for another 5 years but say you did go back after the plumber, do your Zs again open circuit because the cpc has been open circuit all along but you were getting a reading through the earthed metallic pipework which the plumber has kindly now removed..

You haven't proved continuity of conductors doing it the way you mention. You could be getting a Zs reading from a parallel path that could later be removed. Most of all it's just lazy, do your R1+R2 or R2 properly.

 

[Traineeboy]

One theoretical example: Old house, central heating pump has a FCU, You test Zs at that point, reading within spec for the protective device. Deduct Ze from Zs, fill out your R1+R2 on the cert. A week later along comes the plumber and puts a load of plastic pipe in. you're unlikely to go back again for another 5 years but say you did go back after the plumber, do your Zs again open circuit because the cpc has been open circuit all along but you were getting a reading through the earthed metallic pipework which the plumber has kindly now removed..

You haven't proved continuity of conductors doing it the way you mention. You could be getting a Zs reading from a parallel path that could later be removed. Most of all it's just lazy, do your R1+R2 or R2 properly.

I thought that was the case. I always do but a new spark that started working with my boss said to save time deduct the Ze. I said you shouldn’t but he said I was just a Squeaky clean newbie, so wanted your thoughts. Thanks all makes sense. Cheers chaps 

 

[Sidewinder]

Your boss is an idiot obviously.

 

[Sharpend]

Leave said company and find a proper one. 

 

[Andy™]

you can calculate Zs from Ze + R1R2 but you cannot calculate R1R2 from Zs-Ze

also, for a new circuit going in, all dead tests must be done before its switched on and live testing done

 

[Geoff1946]

Leave said company and find a proper one. 

Easier said than done I would think.

If you get an opportunity then grab it, but otherwise I would say maintain your questioning approach and keep your standards high whatever others do.

 

[Traineeboy]

Easier said than done I would think.

If you get an opportunity then grab it, but otherwise I would say maintain your questioning approach and keep your standards high whatever others do.

Yes Geoff your right . Got a placement so I’m sticking with it but questioning everything I’m learning so much by doing so. 

 

[kerching]

t questioning everything :-)

The only stupid question is the one you don't ask!

keep asking

you'll get a lot of help on here as you appear to have the right Attitude! Unlike a lot who just want their homework doing

keep asking and we will keep answering

 

[Sharpend]

Yes Geoff your right . Got a placement so I’m sticking with it but questioning everything I’m learning so much by doing so. 

respect for perseverance, one day you’ll be able to look back with pride that you learned to ignore all the bad habits you’ve been shown. 

 

[Traineeboy]

Thanks chaps. Another thing I just wanted clarity on please. 
 

Do you have to issue a minor works certificate ? I know about notifications and when to and also EIC’s. But if say change a light fitting or add a socket do you have to issue a Minor works ? My colleague seem to think you don’t have to issue them. Is this lazy or the done thing ? 
 

 

[Murdoch]

Do you have to issue a minor works certificate ?

I know about notifications and when to and also EIC’s. But if say change a light fitting or add a socket do you have to issue a Minor works ? My colleague seem to think you don’t have to issue them. Is this lazy or the done thing ? 
 

If the work is like for like then there is no need, except where you might need to CYA and / or the customer asks for it

tin hat on

 

[Sharpend]

Adding an extra socket then MW cert is required. 

 

[Sidney]

you can calculate Zs from Ze + R1R2 but you cannot calculate R1R2 from Zs-Ze

Unless you use a Megger and there's the option for the MFT to do it for you...

 

[Murdoch]

Unless you use a Megger and there's the option for the MFT to do it for you...

How does the Megger rule out parallel paths? 

Just curious

 

[SPECIAL LOCATION]

Thanks chaps. Another thing I just wanted clarity on please. 
 

Do you have to issue a minor works certificate ? I know about notifications and when to and also EIC’s. But if say change a light fitting or add a socket do you have to issue a Minor works ? My colleague seem to think you don’t have to issue them. Is this lazy or the done thing ? 
 

Basic rule of thumb is have you changed any circuit parameters?

i.e. If you have added some additional wiring to a circuit then you should be testing & issuing a MWC..

Whereas like-for-like replacement or accessory upgrade..  e.g. swap dimmer switch for LED compatible item,

or change double socket to USB double socket..

Then the original wiring is no different to before you did your work..

and can be argued that a MWC is unnecessary... 

But swapping a single pendant for 6 recessed spot lamps has changed the circuit characteristics. 

However it can also be argued that swapping a pendant & rose, like for like,

could have disturbed the earth continuity or polarity to fittings further down the circuit if looped at light..

So if you don't test and/or document your tests, how do you prove it is all still working safely after you have left?

Guinness

 

[Traineeboy]

Great thanks again chaps appreciate the input. 

 

[Sidney]

How does the Megger rule out parallel paths? 

Just curious

An excellent question I would like to answer...

 

[Murdoch]

An excellent question I would like to answer...

which remains unanswered so as you posted the original comment is there an answer?