Told I need to have Ze checked, an R1+R2 test, and possibly downrate a 40A fuse to 32A - any way to save money here?

[Murdochcat]

I'm not incompetent!

Did I name anybody

 

[Murdochcat]

I guess I'll just have to get an electrician in - I'm just nervous about what @ericmark said about DNO's required checks:


So I fear I might pay someone £120 p/h, not agreeing to a fixed price/time, and then them telling me either they can't do the tests required (as @ericmark says), or that they do do the tests and it's a high Ze but still under 0.8Ω (as @JohnW2 said). And then I've spent hundreds and still no closer to just replacing a hob. :sigh:

If they say they can’t do the tests, then don’t let them in your home OR pay them

This is extremely basic stuff

 

[333rocky333]

(this is Zone 4 London).

What area are you?

 

[justanotherguy]

What area are you?

Finchley Central

 

[justanotherguy]

If they say they can’t do the tests, then don’t let them in your home OR pay them

This is extremely basic stuff

One poster was suggesting it was about the right to access a sealed fuse rather than about competence. I’m just a layman trying to figure out who’s right, hoping that will help me establish which electrician to part my cash with.

 

[Murdochcat]

One poster was suggesting it was about the right to access a sealed fuse rather than about competence. I’m just a layman trying to figure out who’s right, hoping that will help me establish which electrician to part my cash with.

Access to the sealed fuse is completely irrelevant and I’m not even sure why it’s mentioned

 

[EFLImpudence]

Access to the sealed fuse is completely irrelevant and I’m not even sure why it’s mentioned

Because UKPN said it was one of things Marcos had to tell them before they would attend.

Keep up.

 

[Murdochcat]

Because UKPN said it was one of things Marcos had to tell them before they would attend.

Keep up.

It’s rather odd that the DNO is asking for this, especially as it is largely irrelevant, and if it’s sealed then the DNO should do it

What a stupid situation to be in and just nonsense

The OP needs confirmation from the DNO that they are happy for a spark to break the seal

 

[Risteard]

That connection to the PILC incoming cable looks like it's via an earth clamp, which is a no-no.

Best replaced with a constant force spring which is a coiled strap which is wrapped around the lead sheath of the incoming cable. Only the DNO can work on the incoming supply.

The maximum allowable Ze for TN-S is 0.8 ohms, but hopefully the DNO will get a much lower Ze, allowing you to get a Zs comfortably within spec at the end of the hob circuit. Thought a 40A breaker max Zs was 0.92 ohms? Maybe my rusty brain misremembers?

That is for a type B. If it's a C the maximum Zs will be lower still.

It's inaccurate to state that it's the maximum permissible - generally a declared maximum might be more accurate.

 

[securespark]

Whenever I have reported a Ze above 0.8 for TN-S and 0.35 for TN-C-S, the DNOs have attended to get it below those readings.

 

[JohnW2]

I have to say, in the strongest possible terms, that I strongly disagree with you. I have been called to countless TN-S and TN-C-S supplies where the Ze has been outside the spec, often wildly.

Eh? - what are you 'strongly disagreeing' with'?

I merely said (as you quoted) that if Zs of the circuit was only 1.19Ω, then the Ze could not possibly be very 'high' (relative to what most people regard as the 'maximum' {'spec'} for TN-S). Even if the final circuit were of zero length (i.e. R1+R2 = 0), it would only be 0.39Ω above that 'maximum'/'spec'- and with any real-world final circuit would be much closer to 'spec' than even that, maybe even 'in spec'.

Are you 'strongly disagreeing' with that?

 

[securespark]

I am strongly disagreeing with your ridiculous assertion that

It seems fairly unlikely that the DNO-supplied earth is significantly 'high resistance'.

I would have thought it was obvious that this was what I was disagreeing with this, judging by my comments:

I have to say, in the strongest possible terms, that I strongly disagree with you. I have been called to countless TN-S and TN-C-S supplies where the Ze has been outside the spec, often wildly.

Two of the most memorable were a TN-C-S supply where the reading (if I got one) was 1000+ ohms. There was a bad connection in the cutout.

The other was a TN-S supply where the lead sheath had broken down under the ground and the DNO had to lay a new cable and connect to a sound piece of PILC cable under the pavement.

In this case it looks like a TN-S supply with what looks like an earthing clamp providing the connection to the incoming cable.

It is quite possible that dodgy looking clamp is not doing a good job, hence the raised loop impedance.

The majority of my out of spec Ze readings have been down to such a dodgy connection.

Let's face it, they weren't designed to do that job.

 

[JohnW2]

I am strongly disagreeing with your ridiculous assertion that

It seems fairly unlikely that the DNO-supplied earth is significantly 'high resistance'.

I would have thought it was obvious that this was what I was disagreeing with this, judging by my comments:

Yes, that seemed obvious, but I had to wonder because I couldn't (and still can't) really understand what you were/are so strongly disagreeing with, and you now even call my statement 'ridiculous'.

Is your issue perhaps over my word "significantly"? IF (as many people seem to) one considers the maximum 'acceptable' Ze with TN-S to be 0.8Ω, then, in the OP's case (Zs = 1.19Ω), and with a guessed R1+R2 of the final circuit, the Ze might well be only about 30% (maybe less) over that 0.8Ω figure- and that's what I was regarding as 'not significantly high'.

Is your strong disagreement with my (now 'ridiculous') statement' simply because you would regard such a figure as 'significantly high''? If so,I guess that, as so often, we are probably only arguing or disagreeing, about semantics.

 

[securespark]

I'm not sure if I am "left-brained" (as Mrs S calls me - I am left-handed and she right and she says I reason differently to her), but quite simply I do not agree about your statement.

I am strongly disagreeing with you that it is unlikely that the DNO earth will have a significantly high resistance.

Ridiculous may have been a little harsh, but I thought you were almost dismissing the possibility.

In my experience, I have regularly found DNO earth connections with varying degrees of high resistance.

Personally, I have always reported all Ze readings above 0.35 or 0.8 to the DNO and they have all been rectified, resulting in a much lower reading.

 

[JohnW2]

I'm not sure if I am "left-brained" (as Mrs S calls me - I am left-handed and she right and she says I reason differently to her), but quite simply I do not agree about your statement.

I'm sure your brain is fine - if anyone's brain is 'wrong-sided',it's probably mine I personally regard you as one of the more 'level-minded' people here!

I am strongly disagreeing with you that it is unlikely that the DNO earth will have a significantly high resistance. Ridiculous may have been a little harsh, but I thought you were almost dismissing the possibility. In my experience, I have regularly found DNO earth connections with varying degrees of high resistance.

Ah, maybe I've twigged the problem!
Did you perhaps read my statement as a general one, hence meaning that I felt it was unlikely that any DNO earth would ever be 'of high resistance'? If so, I agree that such would be a ridiculous suggestion (it happens all the time, sometimes with very high resistance), and I would also 'strongly disagree' with such a suggestion (and might well also callit 'ridiculous')

To be clear, my comment was not a general one, but one which related specifically to the OP's situation -in which we know that the Ze must be appreciably less than 1.19Ω. As I've said, you may disagree with my word "significantly", but I certainly would not regard a figure of 'appreciably less than 1.19Ω" as being 'very high' (in relation to thee 0.8Ω figure), would you?

Kind Regards, John