Bad resistance readings on old conduit

[daspark]

Hi there

I recently got asked to have a look at a poor earth loop resistance reading on some sockets in a flat. The boiler man had taken the readings and told the customer to have an electrician look at it before any upgrades were done on his central heating system.

The installation consists of single core cabling around old imperial conduit, into 1G back boxes. Someone has then fitted 1G to 2G converter socket outlets.

Reading the OSG the readings for semi-enclosed fuses on a 30A fuse should be 0.9ohms. Some sockets read around 0.2ohms and others 4ohms. The resistance of two of the sockets in the kitchen come in at around 50ohms. The other two kitchen sockets have had the old back box cut out and double drylining boxes fitted over them with double sockets.

My question is...what would be the effect on the earth? The conduit has still worn with age. I tried talking to the customer on a rewire of the ring circuit but he will not go for it. Mainly asking as I have not seen this type of thing before. Has anyone else?

Would appreciate feedback. Cheers

 

[bugsy]

High impeadance due to corrosion, is it split conduit or solid, you could pull through a cpc

 

[daspark]

Split conduit. Have not tried yet, however do not think I will get earth through. It is imperial. Smaller in diameter

 

[bugsy]

split condiut's a ******* , try using plenty of yellow 77 , otherwise it looks like a rewire

 

[GrannySmiff]

Did you do any Zs tests?

 

[daspark]

Sorry. I meant solid conduit. Typing error

 

[daspark]

It was the Zs test I performed on the outlets

 

[GrannySmiff]

how was the IR?, did you check the tightness of any of the connections? could be loose.

 

[bugsy]

if its soliid and you get some help and yellow 77 might manage a cpc , are the bessa boxes accessable

 

[somersetsparks]

I would try tightening a few bushes first, and like bugsy says- if the besa boxes are accessable you might stand a chance of pulling a cpc in, Most of the installations I have seen like this have been in very good condition even after 50 odd years! You may well find that the high readings you are getting stem from one loose bush, If you can get to any besa boxes just have a good look at the general condition.
Sometimes these places have big JBs that are only accessable from the upstairs flat!

 

[Sintra]

Are there fly leads installed between back boxes and accessories?


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