BS7671 test and internal electric heating

[davesparks]

Would doing a Ze test with all the EARTHS in give you a real Dam Low 0.04Ohms value, apose to the 0.23 Ohms the last time

That would be a Zs test, if done at a DB it's commonly called Zdb

 

[YoungScud]

Would doing a Ze test with all the EARTHS in give you a real Dam Low 0.04Ohms value, apose to the 0.23 Ohms the last time

As YoungScud (so wanted to type in YoungStud then) said IR is a DEAD test, so No power Great, Zs a Live Test other wise its the R1+R2+Ze=Zs with no Power would be yes.

Leaving the parallel paths in circuit might or might not significantly affect the reading (the more parallel paths, the more likely the difference will be large). It's the whole reason that Ze measurements should be done with the customer's bonding conductors disconnected, and consequently the installation switched off.

By the way, YoundStud is Ok with me. That gives me an idea...

 

[DuaneMHunt1976]

It was more of me suggesting that they really do a Zs/Zdb reading and why the 0.04ohms for Ze

With more points to Earth the resistance will drop (ie parallel Resisters)

 

[Soup]

Right then gents, got another response in this continuing saga.

Regarding his inability to read the Zs on the heating circuit and the off-peak immersion, I asked the following question:

"regarding the Zs reading, it seems you can "calculate" the Zs using the R1+R2 and Ze readings as an alternative in certain circumstances (eg if the power is off, like in our case). Maybe that's how the previous electrician calculated the Zs for both the off-peak immersion circuit and the heating circuit on the 2008 report? (although I note the 2008 figures don't quite match using this calculation, they are very close)."

His response :

"Yes, indeed it can be done this way, but then you have to measure the values of r1 and r2 which as I mentioned before, this continuity testing was not done in this case as you have to actually have continuity without switches or timers in the way. I can’t comment on how the 2008 test was done."

My 2nd question was:

"Just out of interest, having now had sight of the 2008 periodic inspection report, is there anything you noticed from the comparative figures that you think I should be aware of? ie are there any notable differences in the figures between the two tests that points towards degradation of any sort, potential problems now or in the future etc- eg Ze figure of 0.04Ω in 2015 vs 0.23Ω in 2008; also, cooker Zs jumped from 0.23 in 2008 to 1.2 in 2015, the latter figure being above the maximum permitted Zs figure of 0.85 noted on the 2008 report."

His reply was :

"This is getting a bit vague as it was a while ago now, but this value was probably obtained from the socket on the side of the cooker switch rather than the cooker circuit on its own, hence the higher value reading."

So... any thoughts on his comments on either of these? Does the point about switches/timers affecting continuity make sense?

He hasn't really answered the Ze point on my 2nd question, nor has he commented whether the Zs value on the cooker is overly high/outside of the maximum permitted figure of 0.85 per the 2008 report either (NB the cooker is "hard-wired" rather than having a 3-pin plug).

 

[Leesparkykent]

Are you withholding payment on this poor bloke or something?

 

[Richard Burns]

Overall you have had an EICR done on the property, you have been supplied with the appropriate paperwork.
The electrician has failed to cover one aspect of the inspection, which you had specifically asked about, and his response about this was that it was outside his expertise to do this.
You are then querying further aspects of his work (which are somewhat odd but likely he was pushed for time and could not cover all the additional slow testing) and have now produced a report that could have saved him a significant amount of time and you some money and are now querying the comparisons which he had no opportunity to make.

I do not think you are going to be successful in getting any further work from this electrician as it will seem as if there is nothing he can say that will bring this to a close.

 

[Soup]

Overall you have had an EICR done on the property, you have been supplied with the appropriate paperwork.
The electrician has failed to cover one aspect of the inspection, which you had specifically asked about, and his response about this was that it was outside his expertise to do this.
You are then querying further aspects of his work (which are somewhat odd but likely he was pushed for time and could not cover all the additional slow testing) and have now produced a report that could have saved him a significant amount of time and you some money and are now querying the comparisons which he had no opportunity to make.

I do not think you are going to be successful in getting any further work from this electrician as it will seem as if there is nothing he can say that will bring this to a close.

Thanks for taking the time to reply, but I think you're missing the point here a little.

The previous report - which I was only reminded of after the recent test because I was querying why he hadn't completed testing on certain circuits - was only sent to him to ask him how the previous electrician may have managed to get readings where he couldn't (I know I have since asked him to compare the figures on the report but my reasoning for this is set out below).

At the end of the day, as a landlord I need to be able to say that the internal electrics of the property are safe. The previous report had more detail generally, as well as completed readings for the tests he was unable to complete - and this coupled with the fact that there is further doubt about the reliability of some of his readings/methods (even you say that some aspects of his work are "odd" in your post), makes we wonder whether his report as a whole can actually be relied upon. Hence my questions to the good people of this board, and further questions to the electrician, to try and understand it all a bit more and ascertain whether this is the case - which I'm well within my rights to do.

Put simply, I don't see why I should pay for a job if it has not been done properly (if indeed this is the case here). And to be honest, I'm still unsure what the true situation is! :rolleyes4: And even if I do ultimately get a resolution I'm unsure if I would use this electrician again anyway, given the protracted nature of the post-report discussions I've had with him.

And finally, just an FYI - I am being charged a flat fee for the work, so no extra costs for time spent as far as I am aware.

 

[Richard Burns]

I think you have raised an interesting point with us, you are unhappy to pay for a report that is unreliable, however you have not raised this point with the electrician, you have only kept asking him further questions of a specific nature.
I would suggest that if you are unhappy with the report that you inform the electrician, as you have just done here, of your reasoning and see what comes of that.
We are unable from a distance to be able to specifically state if something is definitively wrong; there are some "odd" items but these may be due to various circumstances that we are unaware of as we only have the information you have given us..

 

[Soup]

I think you have raised an interesting point with us, you are unhappy to pay for a report that is unreliable, however you have not raised this point with the electrician, you have only kept asking him further questions of a specific nature.
I would suggest that if you are unhappy with the report that you inform the electrician, as you have just done here, of your reasoning and see what comes of that.
We are unable from a distance to be able to specifically state if something is definitively wrong; there are some "odd" items but these may be due to various circumstances that we are unaware of as we only have the information you have given us..

I have already told the electrician I was unhappy he didn't/was unable to test certain circuits that I had specifically asked him to ensure were looked at, prior to starting the report.

However, like I said in my previous post, I'm still unsure if the report is unreliable, or if he has actually done anything wrong which warrants me complaining further. There are a lot of "question marks" here, but at the end of the day it wouldn't be right for me to make baseless or ill-informed accusations at him if he's done his job properly. Hence my continued questions on here trying to get to the bottom of it all!

I do understand your point about being unable to specifically state if something is definitively wrong "from a distance", as you put it. I was aware this was unlikely to be a straightforward black and white problem and the responses to date have indicated that. However, IF there was something in the information I had provided that you guys highlighted which was clearly incorrect/wrong then I could query him on it - and this is what I was trying to ascertain in my last set of queries.

Hope that clears it up!

 

[DuaneMHunt1976]

The Ze, I think 0.04 is dam low, you living next door to a sub station.
As for the value can be got by measure or just asking, don't think the board will give a value that meets.thenbs7671 standards for your setup

R1+R2, could I guess link at db (turning off power to this) and doing a.R1+R2 To the accom7 and then link at the accom7 then to the heater
Zs = Ze + (R1 + R2 [Db to accom7]) + (R1 + R2[accom7 to heater])

This may get edit because saying some thing shouldn't do, but R1 is about the same value as Rn and the circuit works, so I know R1 is good
So would doing Zs = Ze + Rn + R2 be about the same as Zs = Ze + R1 + R2
It will prove continuity for R2 and Rn, and we know R1 works as the heater works
Insulation Resistance test too