What’s going on with this radial

[John tomo 1972]

Called to a property which has just been sold to do an EICR
The sockets down stairs including the kitchen were on a 16a 2.5 radial the issue being the Zs for the first couple of sockets were about average readings but the last few and the sockets in the kitchen went from 0.90 ohms to 1.19 ohms. Personally I wouldn’t put a kitchen on a radial but that’s just my preference. But why the higher than normal results could it be a case of more than one spur from a socket That’s giving me high readings also 16a is just not cutting it. The property had an EICR done a few months ago but no concern over higher readings on socket radial for the down stairs sockets including the kitchen being on a 16a 2.5 cable your comments would be appreciated

 

[davesparks]

The Zs readings will naturally increase the further from the CU you get, 1.19 doesn't sound like a problem on a 16A MCB off the top of my head.

 

[John tomo 1972]

Do you think the kitchen being included on this radial would no occurre trip issues with it only being 16a

 

[Deleted member 26818]

Maximum allowed is 2.73 Ohms.
1.75 for 20A.

 

[westward10]

What were the average readings.

 

[John tomo 1972]

0.56 / 0.60

 

[magnoliafan89]

Slightly loose terminals??

 

[gazdkw82]

It's a radial, the further away from the protective device the higher the reading will be. However a sudden jump (like you have here) is a sign of loose termination/bad connection/large distance between 2 points etc.

It's still compliant but worth investigating if it's close to the last (lower reading) point.

 

[l4urence]

Is the cpc 1mm or 1.5 - maybe a mix of both plus older wiring plus changes - otherwise connection loose or a hidden connection box.

 

[Risteard]

Maximum allowed is 2.73 Ohms.
1.75 for 20A.

2.185 Ohms surely for a 20A Type B device.

 

[telectrix]

2.30, before corrections for temp. and Cmin. ( Cmin correction then gives 2.185.

 

[John tomo 1972]

What about the kitchen ,it is running of f it as well 16a would this be enough or should I suggest putting a separate feed in.

 

[Electric Magic]

What about the kitchen ,it is running of f it as well 16a would this be enough or should I suggest putting a separate feed in.

Depends on the load, in most cases one 16A radial is unlikely to provide enough power for a kitchen. Also, 1.19ohms, if there are no poor connections and assuming you are talking about 2.5mm2 twin and earth means the circuit is about 60m long at that point (off the top of my head might be a couple of meters out) and volt drop may well be over 5%

EDIT just noticed you said Zs not R1R2 so my calc and point about volt drop may not be valid, what's the Ze?

 

[John tomo 1972]

0.20 the thing is I’m not comfortable with the fact downstairs sockets and the kitchen are all on a 16a what do you think.

 

[telectrix]

cut kitchen out of existing radial. leave that for the downstairs sockets, then new 4mm radial or 2.5mm rfc for kitchen. if rfc, you can probably re-use a lot of the existing kitchen wiring.just make it into a rfc.