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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
 
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davesparks

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Mentor
Arms
Esteemed
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.
 
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  • #3
Do you think the kitchen being included on this radial would no occurre trip issues with it only being 16a
 
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  • #6
0.56 / 0.60
 

gazdkw82

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Trainee
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.
 
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.
 
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  • #12
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

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Arms
Esteemed
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?
 
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  • #14
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

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Mentor
Arms
Esteemed
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.
 
I’m getting the feeling this might be a final ring broken into 2 radials - but maybe not correctly. Do you see 2 radials that could have been a ring. What you are describing doesn’t make sense. It’s factual and correct but nonsense at the same time. Your further investigation is crucial.
 
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  • #17
Thanks for your feedback guys. It very much appreciated. rfc it is. As it stands it not right in my eyes and needs sorting thanks again for the advice
 
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Thanks for your feedback guys. It very much appreciated. rfc it is. As it stands it not right in my eyes and needs sorting thanks again for the advice
 
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  • #19
I did notice a cable cut out int the kitchen and thought that myself I have asked the buyer to contact the previous owner to see if they could shine any light on any work that’s been done prior the sale
 
I’m getting the feeling this might be a final ring broken into 2 radials - but maybe not correctly. Do you see 2 radials that could have been a ring. What you are describing doesn’t make sense. It’s factual and correct but nonsense at the same time. Your further investigation is crucial.
I did notice a cable cut out int the kitchen and thought that myself I have asked the buyer to contact the previous owner to see if they could shine any light on any work that’s been done prior the sale
This is important. You might well have found the reason this is a such conundrum.
 
I’m not comfortable with the fact downstairs sockets and the kitchen are all on a 16a what do you think.
Nor would I be. Kettle and a toaster alone are likely to cause an overload and trip!
The readings for a radial are possibly ok but if a significant jump in Zs between sockets (unless long run of cable) then further investigation required as previously suggested.
As it is an EICR recommend upgrading to
 

Electric Magic

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Arms
Esteemed
Nor would I be. Kettle and a toaster alone are likely to cause an overload and trip!QUOTE]

A little pedantic of me but if it's a fairly typical kettle (3kw rating) and toaster (2kw rating) then they may not cause the MCB to trip at all as they will be pulling up to 21.73A max and (from memory so could be slightly off) MCBs must, as a minimum, trip at 1.45 times their rating in under an hour, in this instance 23.2A, so 21.73A may not be enough to make it trip ever, let alone within the 5 minutes the kettle is on.
 
I had to split a ring final in a non domestic premises last week, open cpcs which could not be rectified. Ended up with five outlets on one, seven on the other. Zs for one 0.64 the other 1.66. The low reading the first part of the circuit the high one went all the way over and back to the middle.
 
Electric Magic said - A little pedantic of me.

Just a bit I could have used 'dishwasher' and 'washing machine' as an example but you get the picture!
 
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  • #25
Thanks again for your comments. Just to update. I called the previous owner and asked if they could shed any light and after 10 minutes of uming and aring told me that he had an issue with the downstairs ring so the electrician he used cut one leg of the RFC and layed another cable to it and the rest is still on with the kitchen 16a
 
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