Looking for opinion on whether this scenario is compliant

[The Ghost]

Went to daughters house to replace a couple of broken sockets and did a Zs and RCD test after replacing. CU was replaced and notice on it said inspected 2015. Plastic dual RCD 30 ma/Main switch 60947-3 isolator. System is TT. (100ma RCD?)
Zs at socket was 11.75 ohms L-PE 2.64 ohms L-N. No bonding present to services. Suggested my daughter might get the council in to check it out. Had a phone call today and electrician said it is all compliant! He also said it disconnects in 0.37ms and I asked to talk to him he would not. He said I was just trying to make money, if only he knew? Apparently he fixed the bonding in a few minutes.
I said to my daughter tell him it should be 0.2 (the property is not cross bonded as in the exception to table 41.1) he said that was the case 20 years ago and I needed to get up to date. Okay!
I must confess to be a little bit taken aback by this and thought I would do a sanity check with the forum members. I do have Amd 3 BS7671 by the way i.e. 2382-15 so I think I am up to date.
Essentially I am of course concerned for my daughter, and what appears to be possibly a cavalier attitude. I told my daughter to get a copy of the report and tests so we await that. Am I being concerned over nothing or just plain stupid??? Tin hat on.

 

[Dillb]

Who arranged the work and who were the certs issued too?

Is she the homeowner or just a tenant?

 

[Strima]

The 0.37mS time for the RCD would comply at both 1x and 5xIn so would pass.

As for plastic board in 2015 all depends on when the installation was designed, might be the council has a generic design for those properties.

 

[Wilko]

Sorry but what disconnects what in 0.37 ms?

 

[The Ghost]

Sorry but what disconnects in 0.37 ms

I presume the RCD test.

Who arranged the work and who were the certs issued too?

Is she the homeowner or just a tenant?

Tenant, the council arranged the work and presumbaly got the cert, my daughter did not.

 

[magnoliafan89]

Ive been told that 100ma isnt sufficient enough now amd that it needs to be 30ma. If its a tt system surely the zs at the socket is ok??

 

[Dillb]

I presume the RCD test.
Tenant, the council arranged the work and presumbaly got the cert, my daughter did not.

You should contact the council then and express any concerns as they ordered the work.

 

[The Ghost]

The 0.37mS time for the RCD would comply at both 1x and 5xIn so would pass.

Ok so what about table 41.1 TT?

 

[Andy78]

I doubt the RCD trips in 0.37ms, or 0.37s. A more likely result is 37ms.

 

[The Ghost]

zs at the socket is ok??

Well as I read it with 80% rule 1.06 on 32a yes?

 

[buzzlightyear]

considering it could be council proprty ,then your daughter should contact them .and rectify the damaged sockets .not you Vort .you had no write to do such work unless you have their writen consent.

 

[The Ghost]

daughter should contact them

She did and no response and with a toddler and boy there I thought...well change it.

 

[westward10]

0.37ms, that is quick what meter did he have.

Beaten to it

 

[The Ghost]

You should contact the council then and express any concerns as they ordered the work

Exactly what happened and the above is the result.

 

[Dillb]

She did and no response and with a toddler and boy there I thought...well change it.

How did she contact them? Write a letter and send it recorded delivery. Theres a good chance they will be more likely to give a suitable reply.

 

[The Ghost]

0.37ms, that is quick what meter did he have.

To be clear when I checked the RCD I got at x 1 37ms at x5 13 ms

 

[The Ghost]

How did she contact them

Online system and the only way you can contact housing repairs.

 

[Wilko]

Just for fun
L-N at 2.64 Ohms implies 0.95x230/2.64x0.8 = 66A so it's good to disconnect B10 or C6 on a short .

 

[westward10]

The rcds are providing fault protection so the only issue is bonding??

 

[The Ghost]

Sorry but what disconnects what in 0.37 ms?

Yes, well chinese whispers I was quoting verbatim, however we must all assume what was meant is 37ms which is the same as what I got. But TT?

 

[telectrix]

then the disconnection time is compliant (200mSec.).

 

[The Ghost]

Ok then I am worrying about nothing. Good.

 

[Strima]

Ok so what about table 41.1 TT?

That’s for over current protective device disconnection not RCDs.

 

[littlespark]

Keep at them about the broken sockets, and the day before they say they're coming, go back and replace with the old ones.
But then, youll be sitting with broken sockets in your shed for the next 4 years

 

[Adam W]

So everything is RCD protected and the CU was compliant when it was installed.
Cross bonding is no longer necessary.
The water and gas supplies should be bonded unless the pipes are plastic.

 

[Gavin John Hyde]

When you say council @Vortigern do you mean a housing association? if so and its curo you can contact the head honcho victor da cunha and he will actually personally respond to emails and deal with any issues like this! one of the few decent chief exec's i have come across, most of the housing associations around the west country are quite decent, Bristol council are one of the few in the region who still own there own properties, have done work for them.. they are slow paying and quibble over silly little things in the price and everything is as cheap as possible. Would not do contract work for them again.

 

[The Ghost]

do you mean a housing association

Mmmm not sure now you ask!

 

[The Ghost]

That’s for over current protective device disconnection

Yes thats fine so I am testing socket and get Zs of 11.75, compliant or no? (RFC 32A)

 

[Dillb]

Yes thats fine so I am testing socket and get Zs of 11.75, compliant or no? (RFC 32A)

You will usually get higher Zs values ok a TT than a T-N system. What is the Ra valie?

 

[westward10]

Frankie??

 

[The Ghost]

the Ra

Did not test Ra, just wanted to change sockets and get council to check basically.

 

[Gavin John Hyde]

What is the Ra valie?

If it is anything like the rods I have measured the last few weeks then the readings will be much higher than normal.

 

[telectrix]

That’s for over current protective device disconnection not RCDs.

Wrong..... if you look below table 41.1, it specifically mentions RCDs.

 

[Wilko]

Sorry if I've missed something, but B32 won't trip "instantly" with that L-N impedance. Hopefully appliances are protected by 13A fuses but a short in the cabling would cook for a while, I think.
And stepping out on the edge a bit further, I don't think the ring is intact

 

[The Ghost]

Ok so still, 11.7 ohms Zs on RFC any thoughts? 60898 MCB 32a B

 

[Strima]

Wrong..... if you look below table 41.1, it specifically mentions RCDs.

But if you rely on an RCD for fault protection you must ensure the fault currents are significantly higher than the rated residual current of the RCD.

As RCDs are used for additional protection then the timings for those must comply with table 3A in appendix 3.

Leaving you to ensure that the PSSC of the installation will disconnect the OCPD within the stated times of 41.1.

 

[Strima]

Ok so still, 11.7 ohms Zs on RFC any thoughts? 60898 MCB 32a B

Using a 30mA RCD for earth fault protection then your maximum permitted Zs is 1667 ohms.

But what was the PSSC for the circuit? Only this measurement will tell you if the OCPD will disconnect within 0.2 seconds.

For a 32 amp B type 60898 you need a current of 5x the device rating for a disconnection time between 0.1 and 5 seconds. i.e. 160 amps.

 

[Strima]

Infact looking at one of your earlier posts with you L>N of 2.64 ohms that will give you a fault current of 87 amps which will disconnect in roughly 40 seconds so it will not comply.

How far out in the sticks is her house and what was the voltage reading?

 

[telectrix]

agreed. the RCD will comply with a L-E fault, but not with L-N. for a L-N reading of 2.64, must be a bloody long circuit.

 

[westward10]

Doesn't need to comply across L/N as no values are given for this scenario. We need to know the L/N reading at source.