17th CU config

[Chri5]

Changing my old board to 17th spec.

Have a 15w wylex board to replace the old split unit.

Old unit (done early 16th) has:-

Grd ring via RCD
Kitchen ring via RCD
Emmersion via RCD
Boiler via RCD

1st ring direct
Loft ring direct
Loft (electric) heating ring direct
Grd lights direct
1st lights direct
2nd lights and house smoke alarms direct
Cooker direct
Misc (under stairs bell xfrmr and light) direct

Was thinking the new config should be:-

Direct
40a cooker circuit (it's a socket + isolator and earth leaks)RCBO
6a 2nd floor lights and smokes RCBO
Spare

1st RCD
Grd ring-32a
Loft ring-32q
Emmersion 2.5mm radial 20a
Misc 2.5mm radial-6a
1st lights- 6a
spare

2nd RCD
Kitchen ring-32a
1st ring- 32a
Loft heating ring-20a ( 2 x 2kw heaters)
Boiler 2.5mm radial- 10a
Grd lights-6a
Spare

Fridge / Freezer is new'ish and hasn't tripped the RCD via the current config ever, so I have no plans to provide a dedicate circuit for them.


Would you do anything different ?

 

[ericmark]

I feel where duel RCD system is used rather than using RCBO for all circuits one needs to do a risk assessment and see what the risk is of danger that may arise from the failure of a single circuit such as a lighting circuit. And also reduce the possibility of unwanted tripping of RCDs due to excessive protective conductor currents produced by equipment in normal operation.

I have for last 18 years had whole house on two RCD's both 30ma at 40ms and when kids were at home and we had 6 or 7 PC's in the house the power would trip about once a month but since they have left about once every 6 months normally during atmospheric storms.

So if you have fridge and freezer on same RCD as other items it is more likely to trip but you will most likely be aware it has tripped. But if they are on their own dedicated RCBO although less likely to trip also less likely to know it has tripped.

So unless you use auto resetting type

Untitled

• ericmark
• 6 Dec 2008
• 34

then you need to strike a balance which will suit you. I would want to put any ring powering IT equipment on it's own RCBO but 18 years ago when mine was done these were not available in the way they are now.

 

[Albert]

I would agree with ericmark; Since 2004 I used RCBOs only. The one disadvantage is the price (coming down all the time), but the advantages are as mentioned and to add one more is in case of fault finding, RCBO on every circuit will clearly identify the faulty one, using split load RCDs will trip the main RCD and disconnect all the MCBs connected to it.

 

[Chri5]

I don't despute what you guys are saying, but since I'm paying for it and doing it in doors I'll avoid the 12 x £25 cost.

So is the circuit position per RCD 1 and RCD 2 as resilent as necessary, or given the option with the cu set as is, can anyone think of any better positioning ?

The lights seem to THE important part due to safety / lack of light.

Loft circuit (with all house smoke detection) via RCBO
1st floor light via RCD 1
2nd floor lights via RCD 2

The PC's and network all run via 1st floor ring, which is already on the existing RCD so I see no need to consider a high intergrity ring when all I'm doing is moving the circuit on to a new board with another RCD.

 

[londonboy]

Sorry to but in, Ericmark where did you find those RCDs? I've never seen those before, could be a good idea!.. Just thinking of the pro's and con's now ..