Radial Into Ring Questions

[steve.mack]

So while doing the usual re decorating, I've been changing all the plugs/sockets etc and I've come across this..

We have a 2.5mm Ring main protected by a 32A RCBO

The conservatory (which was built many years ago), has been connected as an unfused radial into the ring main but only in 2.5mm. The cable run length is about 10-15m max.

The radial..
The conservatory radial has 2 x 1.5KW panel heaters on 13A fused spurs. It has 1 X fused spur at 6amp for the lights/ceiling fan @65W max consumption. Then unfused on the radial is a total of 4 X Twin sockets.
Then... Also off the radial is an unfused spur going into the garden into armoured cable and some plugs with an RCD socket about 30metres across the garden.

Now factoring in worst case scenario, we only use the heaters in winter (both on it comes to approx 13amps and they use run back timers so can't be left on by acciident) and never at the same time we would use the garden power outlet for lawn mowing. The 4 double sockets are also only really there for convenience, we use 2 of them with a stereo and phone chargers at the most.

What's my best way forward with this? I can't connect them to the ring main without massively distruptive work taking place due to french doors in way.

Do I add in a 20Amp RCBO/MCB single way consumer unit into the conservatory to protect the radial? I'm guessing this is outside the scope of what I can do as DIY though? If I get an electrician to do it, would that be an acceptable solution? If so how close should the new 20amp fuse be to where it connects to the ring main, could we install it where the wiring comes into the conservatory (approx 1m from the plug/ring it's spurred from)?

 

[flameport]

13A FCU where the cable connects to the ring, or where the cable enters the conservatory.

 

[EFLImpudence]

What is on the ring circuit?

If it's not the kitchen, you could change its RCBO to 20A (or 25A if available for your consumer unit).

As for position of additional single way unit - anywhere from spurred socket to first socket on the spur.

Perhaps it is outside of your scope as you won't have the test equipment and an electrician should be engaged.

 

[donrkebab]

The conservatory radial has 2 x 1.5KW panel heaters on 13A fused spurs. It has 1 X fused spur at 6amp for the lights/ceiling fan @65W max consumption. Then unfused on the radial is a total of 4 X Twin sockets.
Then... Also off the radial is an unfused spur going into the garden into armoured cable and some plugs with an RCD socket about 30metres across the garden.

I would suspect you have excessive volt drop and loop impedance, this would effect the safe operation of protective devices and would therefore be dangerous. You need a qualified electrician to check this out and to provide an acceptable solution.

 

[steve.mack]

Thanks for the quick responses... the funny part of this is that we had the consumer unit changed 3 months ago and the electrician told me the conservatory was fine (I didn’t know this radial bit though so he assumed on the ring main).

He tested everything for voltage drops and z values whatever they are, it’s all on the test sheet and he said everything was fine. Should he have picked up on it being a radial?

I couldn’t drop the rcbo to 20amp, the rings are split left and right hand side of the house and it’s a big house, luckily this isn’t the kitchen side though, but I have a quite a bit of electrical equipment plugged in on this side (not excessive but with those heaters on, but probably it will draw more than 20amps total I think, it’s connected to 3 bedrooms, loft conversion, boiler, 2 living rooms and conservatory).

We have a brand new Hager metal rcbo cu

 

[steve.mack]

13A FCU where the cable connects to the ring, or where the cable enters the conservatory.

The heaters at 230v calculate to just over 13amps to me though, so it wouldn’t be enough?

 

[steve.mack]

I would suspect you have excessive volt drop and loop impedance, this would effect the safe operation of protective devices and would therefore be dangerous. You need a qualified electrician to check this out and to provide an acceptable solution.

Fyi, I plan to buy a petrol mower imminently so these RCD protected plugs will soon be defunct anyway. I did start wondering about voltage drop over that distance but I’ve not stuck a multi meter on it to check

 

[EFLImpudence]

The heaters at 230v calculate to just over 13amps to me though, so it wouldn’t be enough?

They will be rated at 240V so at 230V will be lower amperage.

Anyway - 0.04A

 

[steve.mack]

Just found something else sorry...
The outdoor plugs are connected to an external/waterproof consumer unit with a 10amp mcb inside, this is connected to the 13amp fused spur I previously thought was the only connection. Looks like the consumer unit has been used to protect an old exterior light too as there’s another 6amp in mcb in there too

 

[steve.mack]

They will be rated at 240V so at 230V will be lower amperage.

Anyway - 0.04A

Yup true, sorry I think I was using 230V because of something I read in another thread. Still a bit too close for comfort if the whole room relies on a 13A fuse

 

[flameport]

Still a bit too close for comfort if the whole room relies on a 13A fuse

13A fuses do not fail at 13A.

We have a brand new Hager metal rcbo cu

Were there any certificates provided with it?
The mess of a circuit you have found should have been located and fixed/altered when the CU was installed.

 

[steve.mack]

13A fuses do not fail at 13A.



Were there any certificates provided with it?
The mess of a circuit you have found should have been located and fixed/altered when the CU was installed.

I’m sure they won’t fail at 13A... however surely it’s not good practice to have 13A going through it before I plug even a phone charger in?

No certificates with the house, all the cabling is old black/red only the small outdoor CU is done in brown/blue so shows how long it’s been like this.

We have the cert for the CU install we had done that’s all

 

[AndyPRK]

I guess when you run 14-15A thru them they get hot and damage the fuse holder contacts.


Is this the same style as you have now?

https://www.ebay.co.uk/itm/HAGER-AD...982770?hash=item2a8cddf4b2:g:6YcAAOSwSRpZsQeE

 

[steve.mack]

I guess when you run 14-15A thru them they get hot and damage the fuse holder contacts.


Is this the same style as you have now?

https://www.ebay.co.uk/itm/HAGER-AD...982770?hash=item2a8cddf4b2:g:6YcAAOSwSRpZsQeE

Yes, that looks the same. I guess that's an easier fix overall to lower the 32A rcbo to a 25A one?

 

[AndyPRK]

Yes