Discuss Cottage supplied by 16mm SWA 300+ yards! Trying to resolve a high Ze reading in the Periodic Inspection Reporting & Certification area at ElectriciansForums.net

Reaction score
3
Hi, while carrying out an EICR at a farm cottage on Friday i came up against a problem early on. Whilst measuring the Ze the reading i obtained was 0.97 Ohms and 27Amps Pfc.
Now the earthing system itself is quite strange. Next to the consumer unit is an old service head holding a 60A BS 88 fuse. Terminated into this is a 16mm split concentric. The live is connected into the service head and the neutrals go into a henley block. This block is where the 16mm earth going into the consumer unit is connected. The earths of the split concentric are cut off where cable is stripped for termination into the service head.
Things now get interesting.
Outside there is a meter box that the split concentric goes back to. This meter box is supplied by a 16mm 3 core SWA that travels 300+ yards underground from a new box on the edge of a field that was fitted by the SSE last year when new overheads were run to the farm.
This 16mm SWA supplies TWO! cottages. The brown core is the Live for the cottage i was in, the Black is the Live for a cottage next door and the Grey is the Neutral. The sheath of the SWA is the earth. The cores of the SWA go into blocks where they are split and each is then terminated into a switched fused isolator serving the split concentric feed to each cottage. The earths that were cut off at the service head inside the cottage - at this end are connected to the earthing terminal of the switch fuse isolator.
The readings in the cottage for the EICR were generally all ok and under the max Zs value however one ring circuit was measuring at 1.55 ohms. I imagine i could change the RCBO serving this circuit from a 32A to a 20A.
Does anyone know of what should be done here regarding the Ze exceeding the max value? Somewhat in disbelief that two cottages are supplied such a distance with a cable so small!
ThanksIMG_2992.JPG
 
Last edited by a moderator:
You can consult the supplier but as to what you can do about it, very little. I assume this is a TN-S supply where the suggested Ze should not exceed 0.80 but this is not an absolute requirement.
 
Did you take a line to neutral loop reading?
The earth clamp isn't ideal they shouldn't be used on cables unless there is something to stop it crushing the cable.
 
Hi, while carrying out an EICR at a farm cottage on Friday i came up against a problem early on. Whilst measuring the Ze the reading i obtained was 0.97 Ohms and 27Amps Pfc.
Now the earthing system itself is quite strange. Next to the consumer unit is an old service head holding a 60A BS 88 fuse. Terminated into this is a 16mm split concentric. The live is connected into the service head and the neutrals go into a henley block. This block is where the 16mm earth going into the consumer unit is connected. The earths of the split concentric are cut off where cable is stripped for termination into the service head.
Things now get interesting.
Outside there is a meter box that the split concentric goes back to. This meter box is supplied by a 16mm 3 core SWA that travels 300+ yards underground from a new box on the edge of a field that was fitted by the SSE last year when new overheads were run to the farm.
This 16mm SWA supplies TWO! cottages. The brown core is the Live for the cottage i was in, the Black is the Live for a cottage next door and the Grey is the Neutral. The sheath of the SWA is the earth. The cores of the SWA go into blocks where they are split and each is then terminated into a switched fused isolator serving the split concentric feed to each cottage. The earths that were cut off at the service head inside the cottage - at this end are connected to the earthing terminal of the switch fuse isolator.
The readings in the cottage for the EICR were generally all ok and under the max Zs value however one ring circuit was measuring at 1.55 ohms. I imagine i could change the RCBO serving this circuit from a 32A to a 20A.
Does anyone know of what should be done here regarding the Ze exceeding the max value? Somewhat in disbelief that two cottages are supplied such a distance with a cable so small!
Thanks
The maximum permitted Zs for any final circuit with a 30ma 61009 or 61008 device at its origin is 1667 ohms, so the Zs on your ring circuit is satisfactory on a 32a rcbo.
 
Did you take a line to neutral loop reading?
The earth clamp isn't ideal they shouldn't be used on cables unless there is something to stop it crushing the cable.
Hi, yes i believe my reading was the same between line and neutral. Yeah it would have been better if whoever installed this had brought it into an enclosure and used an earthing nut or something else more appropriate.
 

Reply to Cottage supplied by 16mm SWA 300+ yards! Trying to resolve a high Ze reading in the Periodic Inspection Reporting & Certification area at ElectriciansForums.net

Similar Threads

I'm practising EICRs on friendly locations as I'm still in training - technically done my 2391-52 but frankly need loads more practise. I've just...
Replies
11
Views
906
Hi everyone, i might be having to run new meter tails from meter box to consumer unit which is just under 3m run, i have used 25mm 3 core before...
Replies
6
Views
3K
All of the work described below will be completed by a qualified electrician, I am just curious and using the info for planning!! I am planning a...
Replies
13
Views
4K
  • Locked
  • Sticky
Beware a little long. I served an electrical apprenticeship a long time ago, then went back to full time education immediately moving away from...
Replies
55
Views
5K
Hopefully someone wiser than me can help explain some odd measurements I’ve taken at my own home. This is a long read, I’ve tried to give as much...
Replies
21
Views
4K

OFFICIAL SPONSORS

Electrical Goods - Electrical Tools - Brand Names Electrician Courses Green Electrical Goods PCB Way Electrical Goods - Electrical Tools - Brand Names Pushfit Wire Connectors Electric Underfloor Heating Electrician Courses
These Official Forum Sponsors May Provide Discounts to Regular Forum Members - If you would like to sponsor us then CLICK HERE and post a thread with who you are, and we'll send you some stats etc

YOUR Unread Posts

This website was designed, optimised and is hosted by untold.media Operating under the name Untold Media since 2001.
Back
Top
AdBlock Detected

We get it, advertisements are annoying!

Sure, ad-blocking software does a great job at blocking ads, but it also blocks useful features of our website. For the best site experience please disable your AdBlocker.

I've Disabled AdBlock