(R1+R2) +\- tolerances

[marc_v33]

Guys looking for some opinions here.
for talking sake we have a rfc r1=0.62 rn=0.62 and r2 =1.03

ok excellent we have correctly configured rfc.

onto (R1+R2) if going by the equation (r1+r2)/4 we end up with 0.41ohms
obviously as we are testing we will be aware of the higher reading at Spurs, but if you were getting higher than expected readings at socket outlets what +/- tolerance would you use before issuing a code and what code would you issue on an EICR?

I understand some would say why not investigate further and rectify but our client just wants a condition report returned as is, without any repairs carried out unless exposed live parts etc( I know it's daft but that's what they want )

TIA

 

[Octopus]

Variances of readings can simply put down to "unused" or "worn" sockets.

I would be more concerned if you had much higher readings and the Zs readings were higher than the OCPD will recommend.

As for the client only wanting a "satisfactory" report - I hope you didn't submit a fixed price!

 

[Pete999]

If your client doesn't want any repairs done after, or during an EICR then he's a Muppet, as far as your responsibility goes do the test, code it as required,give it to your client, get your money and await his response.

 

[Risteard]

If your client doesn't want any repairs done after, or during an EICR then he's a Muppet

I suppose in fairness to the client he may wish to get a number of quotes for remedial work.

Or of course it could be that he has no intention of doing it. Who knows?

 

[Pete999]

I suppose in fairness to the client he may wish to get a number of quotes for remedial work.

Or of course it could be that he has no intention of doing it. Who knows?

The problem for the "client" is if marc has found something unsafe during the testing, and noted it on the EICR then the "client" has been made aware of any short comings with the installation, and someone is injured or something happens, he will be up poo creek without a paddle, ergo he was aware of the problem but chose to ignore it.

 

[marc_v33]

Sorry should have said anything which would warrant a c1 would be sorted there and then,c2s they would price for and c3 are pretty much ignored. what I was more getting at is would you code a higher than expected R1+R2 or leave it as is should the Zs of the circuit be acceptable as Murdoch mentioned?

 

[Andy78]

Depends, are any of the high readings pointing to possible unfused spurs with more than one outlet on them ?
If I suspected that I would probably whip off a few suspect sockets and spend 15 mins investigating that, but then that all depends on the limitations of your report.

 

[Risteard]

The problem for the "client" is if marc has found something unsafe during the testing, and noted it on the EICR then the "client" has been made aware of any short comings with the installation, and someone is injured or something happens, he will be up poo creek without a paddle, ergo he was aware of the problem but chose to ignore it.

Perhaps, but I believe the OP said that he was asked to correct anything which was immediately dangerous.

 

[Risteard]

Sorry, hadn't read through the new replies before posting. It appears that marc has confirmed that my suggested sequence of events is in fact the accurate one with regards to what the client wishes to do.

 

[westward10]

Not uncommon for clients to want no repairs, I have returned to sites five years on and often nothing is done and often it is worse. Some see it as a task to be done and just file the Report.
As for the ring final circuit the readings should be in the same ball park, allowing for spurs as you say. As Andy says if you get odd readings and not just higher readings, a lower than expected reading can mean it is interconnected then further investigate, this way you can put accurate observations in your Report.

 

[Risteard]

Not uncommon for clients to want no repairs, I have returned to sites five years on and often nothing is done and often it is worse. Some see it as a task to be done and just file the Report.

Certainly not uncommon. I wouldn't make a habit of rectifying observations anyway as if you have been engaged to compile a report then that is what you should do. Remedial work is a separate job which can be quoted for then (and indeed others may quote for it). I couldn't possibly know what price correcting the installation will be before I have thoroughly examined it!

It's certainly not part of periodic inspection and testing to fix the installation! It is ultimately the Client's decision what to do when they receive the Report.

 

[Gnasher]

The R1 R2 readings do not have a tolerance as such if you refur to the table in the onsite guide it will give you resistances values for different size cables these figures can be used to calculate the resistance of the circuit if you know the length or length of conductors if you know the resistance. All circuits will different depending on cable size and length. These values are also used to calculate the Zs of a circuit if you know the Ze at the design stage.
Zs=R1+R2+Ze this is the real test to confirm values.
The R1+R2 test is normally used to prove continuity of the cpc. If the resistance seems a little high work out what it should be using the OSG tables.
One test to confirm this on a ring with smaller size cpc would be to connect phase and neutral together at one end measure the resistance and decide by 2 this will give you the resistance of 1 conductor. Now multiply this value by 0.62 this should be the resistance or the cpc. To prove this connect phase and cpc at 1 end and measure the resistance, subtract the value found in the first test this should give you the calculated cpc resistance.

Sorry a bit long winded but hope it helps.

 

[HandySparks]

Provided that the measured Zs is lower than the required value for the OCPD at all the points that I measure, I generally allow ring continuity and R1, R2 values to vary a bit before I think it's worth coding or investigating further. For example, on ring continuity of 2.5/1.5mm² T&E, if r1 and rn were both 0.6 ohms, so expecting r2 to be around 1 ohm, I'd certainly allow it to go up by 20% to 1.2 ohms.

I find that it's quite hard to keep test leads 'reliable'. I bought some new ones (actually Megger) for my Fluke MFT a few months ago. When new they zeroed at about 0.1 ohm. Recently they've crept up to about 0.5 ohm. I then discovered that taking them apart, removing the fuses (which are not disturbed when changing tips) and re-assembling, brought the zero back down to just under 0.1 ohm again. Unfused leads don't deteriorate so badly.

 

[Pete999]

Perhaps, but I believe the OP said that he was asked to correct anything which was immediately dangerous.

If it is far too dangerous to leave and a bit costly to repair in the eyes of the "client" switch the circuit OFF lock it OFF take the key away, inform the "client" what you have done and why you have done it, tell the "client" what is required to rectify the problem, and the predicted costs, if the "client" refuses to pay walk away with the keys in your pocket, better still the OCPD.

Might seen drastic but the "clients" of this world need to be educated with regards to the dangers of dangerous installations.

I doubt if a judge would convict anyone for stealing the OCPD as the outcome could possibly be lethal.

 

[Gnasher]

The OP was asking about tolerances for R1+R2 values there are no tolerances. However understanding what these values are, what can effect them along with how to calculate what they should be will help the tester determine if they are in the range expected.
With this knowledge the tester can make an informed decision if any further action is required.