Very confused by electrician

[Ken P]

I had some concerns about the installation at my house so I paid for an EICR. When the electrician was down he told me that some of my cables were really problematic and that the garage was at immediate risk of fire and needed disconnecting. He said I’d need a partial rewire costing £500, which seemed a lot, so I asked my son in law to speak to him. My son in law owns an Air Conditioning company and has a reasonable amount of electrical knowledge, and when he spoke to the electrician the electrician got flustered and couldn’t answer any of his questions. He then left my house, despite having previously agreed to do 2 repairs for me.

He’s now sent me the report over email and it doesn’t have any faults or recommendations on it. I’m very confused. Is the resistance to
My shower and my garage so dangerous I need a rewire or does it seem ok please. I’m very confused

 

[oldbutnotdead]

That R1+R2 for the garage definitely needs investigating. If you are running high-current items in the garage (tumble dryer, welder, big compressor) then try not to until said investigation.
Not seeing anything extraordinarily on the shower circuit.

 

[Murdochcat]

On the schedule the R1+R2 for the garage circuit looks out of place versus the Zs

Nothing else suggests work is required.


Does the report say satisfactory or unsatisfactory ?

 

[Ken P]

The report says satisfactory, which is confusing seeing as he told me I was at risk of having a fire, and needed £500 work doing immediately.

 

[Murdochcat]

The report says satisfactory, which is confusing seeing as he told me I was at risk of having a fire, and needed £500 work doing immediately.

I think you should get another spark to check the circuit to the garage

And if the test results differ a lot then come back here

 

[ericmark]

At 4.95Ω with a type B MCB to trip in the required time it would need an MCB rated 9 amp or less. I can't see the size or type of MCB listed, which seems odd.

 

[Ken P]

At 4.95Ω with a type B MCB to trip in the required time it would need an MCB rated 9 amp or less. I can't see the size or type of MCB listed, which seems odd.

I’m really sorry but I don’t know what that means exactly, but I think you mean the rating of the switch on the circuit, which is 16 amps. Sorry if I’ve misunderstood

 

[ericmark]

A MCB has the thermal overload trip figure, and a letter which says how much more current it will need to trip the magnetic part of the trip, so B = 3 to 5 times, C = 5 to 10 times, and D = 10 to 20 times.

So down to ohms law so a B16 MCB would need 5 x 16 = 80 amp to trip it on the magnetic part of the trip. So 230/80 = 2.875 Ω we give a 5% safety margin so 2.73 Ω.

Since there is a RCD this is the line - neutral reading which is important and the 0.50 Ω seems OK, but seems to be some thing odd, the figures don't seem to match up. Maybe the garage is TT, but if so it should say so.

 

[Risteard]

At 4.95Ω with a type B MCB to trip in the required time it would need an MCB rated 9 amp or less. I can't see the size or type of MCB listed, which seems odd.

At 4.95 Ohms it would be highly indicative of a loose connection, which should be resolved. But that's if we take it at face value.

Do people seriously conduct (R1+R2) testing during periodic inspection and testing, where the installation is already energised? Live (Zs) testing is perfectly adequate to verify cpc continuity for this purpose.

 

[flameport]

The EICR is fiction.

No observations on an older installation = impossible. There will be plenty of things which don't comply now just because BS7671 has changed since it was installed.

All insulation resistance values >999 off the scale = impossible. Only seen on 100% new cabling and accessories which have never been exposed to any dirt, moisture or use. Even on new installs it's possible to have values which are less due to things such as moisture from plaster and other building works.