Bedsit electrics peculiar wiring

[ohdearme]

Hello, in this house of bedsits there is a room where a NICEIC electrician told me that the room is supplied by a 20 amp supply and the installation was overload as there was a 32 amp ring main and a 6 amp circuit running off this supply.

The room has a heater, table top oven electric points, Sadia.

Please explain I need some not too complicated advice about why this is out of kilter.
Best regards

 

[EFLImpudence]

Well, the 20A "supply" cable is presumably protected by a 20A MCB, because that is what is required to protect the cable, therefore that is the maximum current that can be drawn (allowing for tolerances).

You, therefore, cannot have a 32A ring final (not ring main) on the circuit.

If you mean there is a 32A MCB 'downstream' of the 20A one then it will make no difference - it is just unnecessary.




If what you have reported is indeed what you were told, then it may be wise to tell the landlord or agent to employ a more knowledgeable 'electrician'.

 

[EFLImpudence]

If he said the circuit was overloaded because of the appliances used, then that may well be correct but if the 20A MCB does not trip then all would appear to be well.

Presumably you do not switch them all on at the same time.

 

[ericmark]

Since 2.5mm² cable can is the most common cable and can in the main take 20 amps, if you have a 20 amp supply it is unlikely that any overload will not fail safe. In other words the trip or fuse will open and that is the worst case scenario.

However with a 32 amp supply even if using a ring final circuit again with 2.5mm² cable the result is not quite so cut and dried. In the main it will still cause the trip or fuse to open, but there are more exceptions where you can get an overloaded cable where it does not fail safe. Where on the ring the load is placed, and the use of un-fused spurs can in some cases cause an overload where the cable over heats before the circuit fails safe.

As a result with the latter large fixed items should have their own dedicated supply. However I have lived in a caravan with just a 16A supply micro wave, kettles, ovens etc. Very rare did it trip.

 

[EFLImpudence]

However with a 32 amp supply even if using a ring final circuit again with 2.5mm² cable the result is not quite so cut and dried. In the main it will still cause the trip or fuse to open, but there are more exceptions where you can get an overloaded cable where it does not fail safe. Where on the ring the load is placed, and the use of un-fused spurs can in some cases cause an overload where the cable over heats before the circuit fails safe.

That does not apply if, as I understand the OP, the so-called 32A ring is supplied by a 20A protected supply cable.

Otherwise why would he have called it a 20A supply?

 

[ericmark]

It seems odd to have both a ring final and 32A protective device and a 20A protective device. So I am guessing something missing or wrongly reported, seems likely nothing wrong, but unless we have more information it would be dangerous to assume that's the case.

 

[EFLImpudence]

Could be similar to someone fitting a garage unit and ring circuit on a 13A spur.

 

[JohnD]

I wonder if the room has, or had, a landlord's meter.

 

[333rocky333]

Its a posiibility the 32a and 6a circuits were there first and the supply intentionally limited to 20a at a later date to stop residents taking the P.
the 32amp may be an rcbo and left in purely for Rcd protection.
we had a similar thing in student accomadation rooms in a college , the students often plugged in heaters hence tripping there room

Travelodge too had a similar set up, though used a 40 amp mcb feeding a 2 way board for each room fitted with a 6a mcb and a 32a rcbo

 

[JohnW2]

Its a posiibility the 32a and 6a circuits were there first and the supply intentionally limited to 20a at a later date to stop residents taking the P.

That's possible. However, as EFLI has implied, it's also the case that some people 'automatically' (i.e. without thinking) protect a sockets circuit with a 32A MCB, regardless of the limitations/capabilities of the supply.

Kind Regards, John

 

[ohdearme]

Than you everybody, I have some reading to do, I might come back to you.
Best
Alan