17th Edition and Computer Equipment

[SteveC]

I am converting an outbuilding into an office. There will be a few lights, and a few 13A sockets on a ring main for supplying a kettle, microwave, radio etc. Occasionally, outdoor equipment such as a lawnmower or drill may be plugged into one of these sockets for short periods.

So far so good. However there will also be a second ring main, feeding an IT system (several computers, printers scanner etc). This will be run in PVC maxi trunking which will also incorporate the 13A sockets (and probably one or two network sockets). I could meet 17th edition requirements by having this IT ring main protected by an RCBO or RCCB (separate from the one protecting the other stuff). However I am nervous about supply reliability. I understand that sockets feeding computer equipment can be excluded from the requirement to protect by RCCB/RCBO. In that case I would just feed the IT system ring use a simple MCB in the consumer unit. Is this correct and, if so, what, if anything would I need to provide in the way of notices labels etc?

Or am I being too paranoid? Should I just go with an RCBO or second RCCB?

 

[sparks1234]

How much IT equipment are you putting on it?

 

[SteveC]

How much IT equipment are you putting on it?

Probably 4 computers for users, 1 server, 3 printers, 1 scanner and one or two other bits & pieces (router etc).

 

[AcB85]

What do you mean by being nervous on supply reliability, nuisance tripping?

Its all down to the load you intend the ring final to withstand at the end of the day.

Take a look at Reg 411.6, and table 41.1 (As these disconnection times still apply to IT systems)

Seems that if a continuous supply is required to the system then you need to look at installing IMD's &/or RCM's. I think its heavily circumstantial as to your clients requirements!

Alex

 

[Mac]

I would still use a 32A RCD/RCBO on the computer ring.

 

[Des 56]

You should be ok with up to six or so computors on the same ring
You can also connect the ring cpcs to form the functional and protective earthing
You could perhaps fit non standard sockets for the computors and forget the rcd for the dedicated circuit

 

[SteveC]

What do you mean by being nervous on supply reliability, nuisance tripping?

Alex

Yes it's just nuisance tripping that I'm worried about.

 

[johnsparks23]

IT suites should have a 4mm (singles) earth cable, run in a ring round the sockets, using both earth terminals on the back of the socket. This is due to high earth leakage current.
Have worked on similar jobs/installations.

 

[Des 56]

IT suites should have a 4mm (singles) earth cable, run in a ring round the sockets, using both earth terminals on the back of the socket. This is due to high earth leakage current.
Have worked on similar jobs/installations.

For a 2.5mm twin and earth ring main
The cpc of the circuit can act as both the functional and protective conductors
The total size of the conductors is less than 10mm which is the requirement when installation of a seperate functional earth conductor
The ring cpcs need to be connected to their own individual terminals at sockets and also at the consumer unit

 

[confused-fuse]

For a 2.5mm twin and earth ring main
The cpc of the circuit can act as both the functional and protective conductors
The total size of the conductors is less than 10mm which is the requirement when installation of a seperate functional earth conductor
The ring cpcs need to be connected to their own individual terminals at sockets and also at the consumer unit

i would put Uninterruptible power supply (UPS) in a IT room as well with earth tags to each ups so it if does trip the computers or server will still be online but monitors will be off UPS have mains filter in as well and warnings of spikes,jumps and mains noise
hope this helps as well with all the other info on cpc & bonding to backplate/sockets