Interesting EICR

[Manator]

I had an interesting EICR rush job today, the report had to be supplied as soon as the testing was carried out.

I gave an unsatisfactory result, as there were many C2 codes given, however I thought it may be a useful exercise if I posted the findings here and let people have a say.

The test was carried out on a Victorian house and the supply was TNS. I suspected due to some very old MK plug type fused spurs that the property was rewired probably early 1960's.

A new meter was fitted, and supply from the HED to meter was 25mm from the meter to DB 16mm tails and 6mm main earth.The properties main fuse carrier was unmarked and although I suspect a BS 1361 this was not verified.

There was no gas bonding and no water bonding. Before the DB was a 63 amp 0.1A BS 4293 in an enclosure.

The distribution board was an old wylex rewirable fuses with 6 circuits. 5 of these circuits were wired in Vulcanised Rubber.

Insulation tests on the vulcanised rubber;

Cooker = >500 M hms

Sockets = L-E 273 L-N 257 N-E 244 M hms

Lighting = 2.08 M hms

R1=R2 on sockets =0.93   Zs = 1.08

Ze = 0.79

The lighting circuits had no earth present and all the switch plate back boxes had plastic lugs, all the lights with the exception of the kitchen light were 1960's type bakolites with glass domes and porcelain lamp holders.

The immersion heater was wired to a fuse spur in the kitchen and terminated at exit into a 30 amp junction box with flex to the immersion heater. This heater was situated at the rear with no access to test.

Now I have given a few examples and some of the above were C2's.

I would like to see if anyone can give me a C2 that is not quite as obvious from the details above. The information is there. Do not worry it is not a test, and I acknowledge that people code differently.

 

[ProDave]

First observation, that's bloody good I/R for VIR of that age, the low reading on the lights probably shows the effect of heat at the light fittings.

 

[Manator]

@ProDave I must admit I was really amazed at the results. The owner of the house by the way is an Electrical Engineer with a Bsc and I think was testing me out.

 

[Andy™]

any insulation fall off when you looked at it?

 

[Manator]

No Andy, I did rub a bit where I could get to it and it was fine and still had some flex in it. Although I did not want to disturb it too much.

 

[Essex1]

I will play  opcorn

front end RCD - C3

No 30mA RCD protection to sockets likely to feed outside equipment - C2

No main bonding - C2

No cpc in lighting circuit - C3

Inaccessible immersion heater - C2 (age of install chances are no thermal cutout and plastic tank)

You got to be in it to win it eh?

 

[binky]

just been rewiring the lighting of a house last re-built and wired around WW2 - bomb damaged. Old VIR sockets tested OK, the meter tails were felexible in some places and fragile where they had been bent. Whole house run in steel conduit and never been touched since - little old lady resident for decades. Lighting had developed a fault - didn't care to trace it and fiddle with the old cable. So old it has fuses in the neutrals....

 

[Adrian]

What size was the CPC on the sockets ? if 1mm not suitable for 30 amp 3036

Light flexes single insullated?

 

[Manator]

Good observation Adrian, as all the cables are imperial sizes this does have an effect on the outcome.

Lighting was equivalent to 1mm

Sockets was equivalent to 4mm (just over but near enough)

The CPC of the sockets was equivalent to 1mm, however I did not have a vernier on me so I opted for 1mm rather than risk saying 1.5mm.

 

[Adrian]

Zs to high on sockets from memory 1.09 for 30 amp 3036

Sorry just in 

 

[Manator]

Zs is too high Adrian but I tested at 1.08 and the actual maximum is just a little lower than that.

 

[Phoenix]

Sockets was equivalent to 4mm (just over but near enough)

The CPC of the sockets was equivalent to 1mm, however I did not have a vernier on me so I opted for 1mm rather than risk saying 1.5mm.

That seems a little odd to me, just over 4mm² would put it at 7/036 which translates at 4.59mm² but the cpc should be 7/029 (translates as 2.9mm². Even 7/029 which was normally used for rings had a 3/036 cpc (1.97mm²)

It wasn't until they tried to go metric that things got screwed up and it took them the best part of a decade to realise that 1 wasn't actually at least half of 2.5!!

 

[Manator]

@Phoenix you are correct, and I had to double check whilst on site. The VIR cable is over 55 years old and the cpc was not of the size I expected to see when compared to later PVC cables.  The latest tables produced for this cable was 1966 ( 14th edition) and even then the cpc was as you say.

 

[Rob_the_rich]

Is the fact that the meter supplier put in 25mm tails from HED to meter suggestive of a 100A cutout fuse? Or do they always fit 25mm?

Edit; also imm heater into fused spur, not designed for continuous load.

 

[Manator]

The HED is the older type (not metal) but with a fuse carrier in the neutral, this is freshly sealed up and the meter is one of the new ones with inbuilt isolator ( a little red flag thingy)

I think all the meter guys now only carry 25mm, I doubt that they would have changed the main fuse but as always I would never assume. Getting an answer from the energy supplier and the DNO was fruitless. I just hope there is a link in the neutral fuse link :innocent

 

[Andy™]

could always take it apart to look, then go running to the press that someone machined a solid link the same as a fuse to bypass it

 

[Phoenix]

Anyway, My guess at some of the code 2s (although I have used my crystal ball on some of these and presumed what I cannot know for certain, etc)

* Lack of main protective bonding

* The IR on the lighting, given the other readings, it says to me that if a fitting is taken down, the crispy insulation may fall off. Also is that to earth? without a cpc that suggests some kind of strange fault.

* The kitchen light? - Unearthed flouro batten?

* "Spark cover" from the wylex board is probably absent

* Lack of 30mA RCD to sockets reasonably expected to be used for portable equipment outside

* No safety stat to immersion when the header tank is plastic (though it could be galv in a place that old?)

*4293 enclosure - fails to meet ip4x on top surface by a long margin?

We perhaps should not get caught up in the weeds too much, its clear the recommendation is going to be to re-wire the place, anything else is just dragging out the inevitable, so best to avoid wasting too much time and money on the details!

 

[Manator]

@Phoenix Overall that is not a bad assumption, I just wished I had a better camera on my phone.

The C2 that I wanted people to spot was the immersion heater, I have seen people miss this on many EICR reports.

The 4293 if you noticed was a 63A 0.1A so its a 100mA RCD which is a current operated earth leakage RCD.

The insulation on the lighting was not disturbed at the light fittings but I concurred that the insulation had indeed broken down at all the light fittings due to 55 years of heat. Any light fittings changed would or could make the cable useless for future use. The socket circuit failed the max Zs for the breaker and as it is a 100mA RCD could not be trusted to operate within any time if in contact with any person.

As I say it is not a test, just a useful exercise. My main issues were with the reduced cpc of the cable, I am trying to find out if this was normal as in just after the war was the cpc reduced to save money? I am not sure but would like to find out. I am going back to the property and will take my verniers with me on the next visit to double check.

 

[Essex1]

Errrrrrr. See post #6

 

[ProDave]

The only one I question is the immersion heater.

An EICR only tests parts you are able to examine without dismantling the building.  As you could not see the immersion heater, you made an assumption. How do you KNOW that last week someone hadn't opened up the space, fitted a new immersion and closed it up again.

While there is a strong suspicion it may not have a safety trip, as you can't actually see it, in my mind it can only be a FI "requires further investigation" or dare I say it a LIM?

Off to get my tin hat.