No earth!

[tigerpaul]

Hello folks!

I tested a 300 year old cottage on Friday, wiring dates back to the 70s. It has 2 CU's, both 6 way wooden backed Wylex boards fitted with 3036 fuses.
The main switch feeding both CU's is the oldest 4293 RCD I have ever seen rated at 60A, tripping current is not marked but on a ramp test it tripped at 330mA.

There are a load of faults on the installation but the one that concerns me the most is there doesn't appear to be supply earth at all. Feeding the meter is a supply cable with only Line and Neutral, then whats looks like 25mm2 tails through the RCD to a henley block which then feeds the 2 CU's.

There is a bond at the water stopcock, 4mm2 max, and I am getting 0.08 ohms between that and the CU earth bar. No earth cables are labelled in the earth bar.

Ze at the CU's is 110.8 ohms!

What would you put on an inspection report regarding this?

I am thinking the only way forward is to recommend a new split load DB, new bonding to the water stopcock, possibly they will need an earth rod installing into the ground?

Talk about opening a can of worms! Like I say this is a 300 year old building, and its in a right state, full to the rafters with clutter.

What would you fellas put in your report about it?

 

[DurhamSparky]

i would write what you found... no earth , undersized bonding....

dont just make it up as the building is old...!

 

[Octopus]

Insufficient earth = C2
Slow tripping RCD = C2
4mm bond to water = C2

Should it be TT?

Thats about it IMHO

 

[Strima]

I think a call to the DNO would be in order to see if they have any record of earthing for this property. 99% certain they'll say bang a rod in as the old utilities pipes may have been used for the earthing.

With an upfront RCD it could point to a TT system, you could try a temporary rod to try and get the Ze down and ramp test the RCD again.

I could be talking complete balls though as it's Sunday and my head is a little fuzzy...

 

[tigerpaul]

Also I am trying to find the breaking capacities of the 3036 fuses, I've follwed this link -

Wiring Matters - 2008 issues - IET Electrical

and all I can find is it will be either 1kA or 2kA, depending on the category of duty! How am I supposed to know which one it is?!

A bit more backround to this job. The owner needs this report done for his house insurance company, so I'm telling it how it is, rather than glossing over anything as I'm fully aware it's my name on the bottom of the report if any disaster happens.

In terms of my report, I'm considering what work is required to bring this installation up to scratch.

 

[tigerpaul]

Old Wylex 3036 Consumer Units made offlammable material
Henley block below both DB's is notfixed to wall
Old RCD main switch has no labelstipulating tripping current. Ramp test shows it tripping at 330mA
No apparent earth at installation
Protective Bond to water supplyundersized

DB1/1 Unable to obtain loop impedanceat socket in Study due to Error 4 (Voltage between N-E)

DB1/2 Unable to secure socket and spurto back boxes due to severe corrosion by flood damage
DB1/2 N-E insulation resistance = 0.4Meg ohm

DB1/4 Two cables leaving fuseway

DB1/5 Strands removed from cable tofacilitate connection into neutral bar of DB
DB1/5 LED indicator on pull cordisolator not functioning

DB2/1 Circuit not located, suspected tobe supplying area where old kitchen was located. Fuse removed on 15[SUP]th[/SUP]June 2012

DB2/1 Insulation Resistance results (M ohm)
L-N = >500
L-E = 40.0
N-E = >500

DB2/2 Numerous points spurred off of asingle point of the ring main without fusing down
DB2/2 Socket in Greenhouse not suitablefor humid environment
DB2/2 Socket in shed has cracked front
DB2/2 Insulation Resistance results (M ohm)
L-N = 0.12
L-E = 0.21
N-E = 0.36

DB2/3 Unable to obtain end to endresistance of cpc due to Error 5 (Excessive noise)
DB2/3 Only one cpc at socket in study
DB2/3 Unable to obtain loop impedanceat landing socket due to Error 4 (Voltage between N-E)
DB2/3 Insulation Resistance results (M ohm)
L-N = >500
L-E = 160
N-E - >500

All in all, his house is in a right sorry state

 

[Risteard]

DB1/4 Two cables leaving fuseway

Not a defect.

 

[Strima]

Old Wylex 3036 Consumer Units made offlammable material
Henley block below both DB's is notfixed to wall
Old RCD main switch has no labelstipulating tripping current. Ramp test shows it tripping at 330mA
No apparent earth at installation
Protective Bond to water supplyundersized
etc, etc, etc

All in all, his house is in a right sorry state

Remedial work will keep you off the streets for a while... :lol:

 

[jonnyboy1]

To be honest I would be telling the customer a re wire is essential is this case.

 

[Plonker 3]

To be honest I would be telling the customer a re wire is essential is this case.

Why?

Until the OP has actually called into look into defects then there is no need for this, all low readings could be down to items that haven't been found during the EICR.

 

[Strima]

To be honest I would be telling the customer a re wire is essential is this case.

Not necessarily, there could be easy fixes for most of these faults. Could be just down to poor installation and selection of accessories for their environment.

 

[jonnyboy1]

Not necessarily, there could be easy fixes for most of these faults. Could be just down to poor installation and selection of accessories for their environment.

I'm mainly taking about the age of the installation very old and needs upgrading and the 3036 boards needs replacing as a matter of urgency IMO. The op stated no main earth but a 4mm to the water service, so what wil happen under fault conditions, where will the fault current travel?? It will use the 4mm as a path to earth- possibly. So I'm my view if it was my job I would tell customer of pros and con's for rewire but definetly advise it 100%, again which is only my opinion

 

[tigerpaul]

I called the ECA technical helpline today, and what I gleaned from that is;

The service provider do not actually have an obligation to provide an earth. The old water utility pipe may have been used in the past but now whats really needed is a earth rod. The maximum Ze then would be 200 ohms! (quite high actually)

All final circuits will require 30mA protection. (most likely a dual RCD board)

The protective bonding requires upgrading to a minimum of 6mm2

Of course, putting 30mA protection on the final circuits will stop some of them from staying on. Those faults will need fixing as well.

All the other faults will need tracing and sorting too.

If it was an empty house, I wouldnt mind, but its like that programme "Obsessive Compulsive Hoarder" Ha ha!

 

[somersetsparks]

What I would do for a cheap job -
2 x30ma 100a RCDs, one feeding each board. -
Whack a stake or 2 in (I would get the thread together ones and try to get 10 ohms or less, although this may prove impossible.)
The low IR readings are almost certainly something or some damp accessory still in circuit.
Run new bond In.
Plus of couse all your other minorish faults.

That RCD may well be an old 500ma (girt grey thing?) mainly for fire and earth fault protect
Just some ideas

 

[Engineer54]

tigerpaul... Old Wylex 3036 Consumer Units made offlammable material

​

Never seen an old wooden frame Wylex catch fire yet. ...not one!! Seen plenty of modern plastic CU's in molten blobs on the floor though!! lol!! Those wooden frames were made from seasoned and treated hardwood, you could hold a flame to them for several minutes and they still wouldn't burst into flames!!!