Old circuit, low insulation resistance readings - REPLACE?

Joined
25 Aug 2014
Messages
94
Reaction score
0
Location
Essex
Country
United Kingdom
Just had an electrical safety inspection done of the house.

Been told that in various places circuits have low insulation resistance ratings (this is going to be rated as a 2 - serious concern, doesn't need addressing immediately).

Also informed that the circuits are generally old, although there is a mixture of copper, color coded and aluminium wiring.

Plus, the fuse box is not up to a modern standard, lacks the switch which stops you from being electrocuted if you drill into a cable.

Should I have the house completely rewired?
 
Sponsored Links
... Been told that in various places circuits have low insulation resistance ratings (this is going to be rated as a 2 - serious concern, doesn't need addressing immediately). ... Also informed that the circuits are generally old, although there is a mixture of copper, color coded and aluminium wiring. ... Plus, the fuse box is not up to a modern standard, lacks the switch which stops you from being electrocuted if you drill into a cable. ... Should I have the house completely rewired?
The person who undertook the inspection is probably the best person to advise on that.

I would personally say that the low insulation resistance (assuming it's low enough to worry about) probably should at least be investigated (and rectified as necessary). I'm rather surprised that there is aluminium wiring in a domestic installation (and I don't know what 'colour coded' means - does it perhaps mean 'old' {pre-2004} colours?). The last point (lack of RCD protection) is not uncommon, even though not ideal.

From what you say, it sounds as if a re-wire might be the best solution - but, as I said, it's only really someone 'on site' who can advise you properly about that.

Kind Regards, John
 
... Been told that in various places circuits have low insulation resistance ratings (this is going to be rated as a 2 - serious concern, doesn't need addressing immediately). ... Also informed that the circuits are generally old, although there is a mixture of copper, color coded and aluminium wiring. ... Plus, the fuse box is not up to a modern standard, lacks the switch which stops you from being electrocuted if you drill into a cable. ... Should I have the house completely rewired?
The person who undertook the inspection is probably the best person to advise on that.

I would personally say that the low insulation resistance (assuming it's low enough to worry about) probably should at least be investigated (and rectified as necessary). I'm rather surprised that there is aluminium wiring in a domestic installation (and I don't know what 'colour coded' means - does it perhaps mean 'old' {pre-2004} colours?). The last point (lack of RCD protection) is not uncommon, even though not ideal.

From what you say, it sounds as if a re-wire might be the best solution - but, as I said, it's only really someone 'on site' who can advise you properly about that.

Kind Regards, John


I asked the guy, he wasn't adamant that I should, and he certainly didn't volunteer the suggestion, but he agreed that it might be a good idea to do.
 
I asked the guy, he wasn't adamant that I should, and he certainly didn't volunteer the suggestion, but he agreed that it might be a good idea to do.
I rather feared you would say something like that. Ideally, you could do with another opinion or two.

Kind Regards, John
 
Sponsored Links
The whole idea of an electrical installation condition report (EICR) is to tell you what is required. If you need to come onto a forum to ask questions then it would seem it’s a very poor report.

Small aluminium cables were used for a very short time in the days of Ian Smith, but are today only used with large cables and with special cables which don’t require the "switch which stops you from being electrocuted" (RCD).

Both with old aluminium and rubber insulated cables yes it’s a rewire of those circuits but the newer PVC cables it’s rare for the cable to need renewing it’s more likely where cables connect to sockets and dampness has got into the box. Also items like immersion heaters which have not been isolated during a test can cause low readings.

In general any code 2 items need correction quickly within a week or two but code 3 items cover such a huge range of faults there is no real answer as to how quick or even if ever they need correction.

We do not simply say low insulation resistance we actually give results so 500 kΩ for example may be cause for concern and further investigation is required but 50 kΩ would likely mean considering turning off that circuit. It would depend on how long the circuit was and what it feeds but without actual figures no one can really start to work out how bad it is.

However the fact you have asked the question clearly you are not happy with the report and you it would seem have some concern as to if it's really as bad as he makes out.

So give us some real figures and let us then see if we would agree with what the guy says.

Nearly every house wired before 2008 will have some codes raised not all make it dangerous.
 
Low insulation is a fault that will occur in a damp or dirty socket. The fault could be just 1cm long in one place.

Obvious place to look is sockets near the back of the washing machine or on damp single skin walls or on wet walls where the guttering is overflowing.

This obviously needs the power off, a suitably competent person.
The right sort of meter with a meg ohms range.

The ring main can be disconnected at various sockets to prove the fault in one direction or the other. Then when the fault is found replace the faulty section or socket.
 
Low insulation is a fault that will occur in a damp or dirty socket. The fault could be just 1cm long in one place.

Obvious place to look is sockets near the back of the washing machine or on damp single skin walls or on wet walls where the guttering is overflowing.

This obviously needs the power off, a suitably competent person.
The right sort of meter with a meg ohms range.

The ring main can be disconnected at various sockets to prove the fault in one direction or the other. Then when the fault is found replace the faulty section or socket.

Useful, I had someone round today, an electrician who reckoned that the person taking the readings most likely didn't connect all the plugs and appliances (e.g. unscrewing lightbulbs, fittings were very dusty with no finger marks).

I mean, if all the readings mean is that someone didn't do their job properly they don't mean anything do they?

Anyway, i'll get someone to replace the fuseboard and then test again, properly, and see if we can identify offending wires/appliances/sockets.

This kind of thing is a job for Sherlock Holmes.
 
Anyway, i'll get someone to replace the fuseboard and then test again, properly, and see if we can identify offending wires/appliances/sockets.
That's probably the wrong order to do things in. I think you ought to discuss with your chosen electrician how best (including what order) to tackle the various tasks.

Kind Regards, John
 
Anyway, i'll get someone to replace the fuseboard and then test again, properly, and see if we can identify offending wires/appliances/sockets.
That's probably the wrong order to do things in. I think you ought to discuss with your chosen electrician how best (including what order) to tackle the various tasks.

Kind Regards, John

An electrician who I spoke to this afternoon said just that.

I mean he gave me two choices.

Test the sockets again and try to identify the areas giving the low resistance readings, before replacing the fusebox.

Or just replace the fusebox, which needs replacing anyway, and then do the tests.

In some way, given that the fusebox is really old, and needs replacing anyway, I figured it would be better to do it the way I suggested?
 
An electrician who I spoke to this afternoon said just that. ... I mean he gave me two choices.
Test the sockets again and try to identify the areas giving the low resistance readings, before replacing the fusebox.
Or just replace the fusebox, which needs replacing anyway, and then do the tests.
In some way, given that the fusebox is really old, and needs replacing anyway, I figured it would be better to do it the way I suggested?
I don't think so, and I'm not convinced that the electrician was 'thinking straight'. ... If there are problems with the wiring etc., it's at least possible that when he replaces the Consumer Unit (presumably with a modern one with RCDs), problems might arise (e.g. the RCDs immediately tripping), which would possibly leave you stuck without electricity until the wiring/insulation resistance/whatever problems are sorted.

Kind Regards, John
 
An electrician who I spoke to this afternoon said just that. ... I mean he gave me two choices.
Test the sockets again and try to identify the areas giving the low resistance readings, before replacing the fusebox.
Or just replace the fusebox, which needs replacing anyway, and then do the tests.
In some way, given that the fusebox is really old, and needs replacing anyway, I figured it would be better to do it the way I suggested?
I don't think so, and I'm not convinced that the electrician was 'thinking straight'. ... If there are problems with the wiring etc., it's at least possible that when he replaces the Consumer Unit (presumably with a modern one with RCDs), problems might arise (e.g. the RCDs immediately tripping), which would leave you stuck without electricity until the wiring/insulation resistance/whatever problems are sorted.

Kind Regards, John


Cheers for that,

I'm seeing a few more electricians tomorrow, so I'll see what they throw into the mix.
 
[
Test the sockets again and try to identify the areas giving the low resistance readings, before replacing the fusebox.

Or just replace the fusebox, which needs replacing anyway, and then do the tests.

In some way, given that the fusebox is really old, and needs replacing anyway, I figured it would be better to do it the way I suggested?

You need to do the tests and resolve the defects before installing the new consumer unit. Otherwise they may not be reconnected if they are faulty, or the fault may cause intermittent tripping problems.
 

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.


Are you a trade or supplier? You can create your listing free at DIYnot Local

 
Sponsored Links
Back
Top