Consumer Unit Advice

[PaulS]

Okay, tracked the earth cable to a black box where the overhead cable enters the system. The black box has the service fuse and the only other info on it is: AEI Series 5, 80/100A Type IIb, is this an ELCB?

 

[plugwash]

how many earth cables are there to the black box

if there is only one then it sounds like your system is PME not TT

at a socket mesure the resistance between the neutral and earth pins with a multimeter

if its less than an ohm your supplly is definately not TT

 

[kai]

My readings came to 0.4. ohms, on the farthest socket on the circuit.

That reading Included the submain resistance between the intake room on the ground floor, to my third floor flat as well! (PME/TN-C-S).

Should that reading be close to R1+R2, if the circuit was wired in Twin and Earth (which it is)?

 

[PaulS]

Guys, just found a crusty old tag stuck to the side of the meter that states that it is connected to a PME system.

I guess this means the MK split load box would be okay.

Incidentally the reason for using a seperate CU for the heaters is because they are connected to the white meter.

Your help is really appreciated.

 

[plugwash]

yeah the mk split load will be fine then

 

[Damocles]

Just a point to consider guys: If this had been a TT installation without any RCD, then putting in a new CU with no RCD would not have made things worse from the safety point of view. Putting in one with a 30mA on some circuits instead of on none would definitely have made things safer. So have a care in considering what is scary. I don't consider making things safer than they used to be is scary. It would still have been a relatively simple job to divert the meter tails and insert a separate 100mA RCD before the CU.

The only scary bit I see might be if someone removed an existing 100mA RCD without realising why it was there.

 

[ban-all-sheds]

Just a point to consider guys: If this had been a TT installation without any RCD, then putting in a new CU with no RCD would not have made things worse from the safety point of view.

True, but it would not have been compliant, and we are only just over 3 months away from the point where compliance becomes a legal requirement, so I don't think it is unreasonable to say that you "must" have a whole-house RCD.

Putting in one with a 30mA on some circuits instead of on none would definitely have made things safer.

Indeed.

So have a care in considering what is scary. I don't consider making things safer than they used to be is scary.

What I meant really was not that the action itself, or the resulting situation would have been scary, it was the generic situation of how easy it would have been for someone, through ignorance, to do the wrong thing.

As it turned out it wasn't TT, but I'm disappointed that nobody thought to check...

 

[Damocles]

I notice it's quite easy sometimes to give the main advice about something, but miss a detail where there might be an unusual but important problem.

I don't regard breaking building regulations as scary. Particularly as I remember that in general alterations to a property which make it more compliant with regulations than it used to be are not frowned upon. Building regulations are in theory open to negotiation, though the council may not see it that way. Going to war on a pack of lies is scary.

Again, I say that even installed in ignorance the likelihood is that the new installation would have been better than the old. Legalities aside, this is a good thing.

It does illustrate that it is a good idea to look carefully at what you have got already before you change anything.