On 30/06/2018 11:47, Fredxx wrote:
On 30/06/2018 08:15, ARW wrote:
On 29/06/2018 21:51, John Rumm wrote:
On 29/06/2018 00:19, wrote:
On Monday, 25 June 2018 01:08:08 UTC+1, tabbyÂ* wrote:
Current fusebox has several fuseways each feeding a meter then a 2
way fusebox which powers each rented room. Plan is a new CU & new
secondary 2 way CUs, the meters will be retained. The question is
how may RCD protection be implemented. If done in the main CU with
an RCBO, a trip results in a room losing all power including
lighting. If done in the secondary small CU, the cable from main CU
to meter to secondary would not be RCD protected. This wiring is
surface clipped direct. Neither of those options strike me as fully
satisfactory. How's good to do this?
NT
OK, some questions.
Does there need to be separate rcd protection for lights & sockets
so lighting isn't lost when sockets trip?
Ideally, yes
Since SP RCBOs don't disconnect N-E faults, I presume the whole
install still requires 2x DP RCDs. Can these be 300mA time delayed
or must they be 30mA?
If there are additional downstream 30mA trip devices, then they can
in theory be 100mA type S devices. However you won't then be able to
achieve discrimination with the RCD protecting the submain feeds to
the meters. So you are no nearer a workable solution.
So that leaves you needing either 2 DP RCBOs per room, or two
conventional 30mA RCDs and two MCBs (likely 6 ways in total per room).
The cheapest option may be a small CU for the head end - Type S RCD
on its incomer, then 4 x regular MCBs for your submain feeds.
It would probably be a a lot cheaper and easier to use a hi integrity
dual split load CU with a 100mA main switch, 4 MCBs for the rooms fed
from the mains switch and to use the 30mA RCD supplies for the
communal areas and just fit a 2 way garage CU in each room.
Won't that mean the feeds to each room will not be 30mA RCD protected
and will need to be surfaced wired, or in SWA.
Do you need the lighting in a HMO room to be on a separate RCD to mains
outlets, or is the light in the landing on a different RCD circuit
sufficient?
As it's a TT supply then a 100mA RCD and surface mounted cable is fine.
There is no requirement for the lights and sockets to be on seperate
RCDs apart from inconvenience in the case of a trip.
The communal lights should be on a separate RCD to the rooms.
--
Adam