On Thursday, October 24, 2013 7:35:28 AM UTC+1, Tim Watts wrote:
I would advise not putting all the larger RCBOs (32A rings, heaters) next to
each other - apparantly localised heat build up is a problem. I left a 1
module gap every 2-3 on mine and the middle RCBO is a low current one
(lights).

I asked MK about this long ago, after he wibbled for a bit, I pointed out diversity must surely apply in domestic installs.

GCH fails:
- 14+ RCBO in a row, 11x 32A with 3x 6A at the end.
- Even if #2 & #3 are feeding 32A continuous you only have 16A left on an 80A fuse.
- RCBO heating is thus localised with nearby breakers running cooler.

E7 NSH is the heaviest domestic load:
- NSH are a fixed heating load, so fuse rating is the limit.
- Even 80A is spread over 6x 16A RCBO, each feeding a 13A 3.4kW NSH.
- RCBO heating above IIRC 40oC will reduce their actual trip rating, but not below 13A in 7hrs.

For domestic it should be quite ok, even on a 100A supply.

Whereas multiple 50A RCBO instant water heaters in a commercial environment may create a problem whereby the ambient is higher (nearby DIN transformer, timer motor) and the RCBO do not get time to cool down due to duty cycle.

An increased number of RCBO may actually reduce local heating - because loads may be better distributed across more RCBO re multiple final circuits.