I.T room

[steptoe]

You have said 3 things there that if you put 60 PCs on 2 circuits with RCD protection, you would not keep the RCD from tripping as I think you have forgotten or you didn't know that the PSU on the PC has leakage due to the filter circuit in the PSU. Therefore you should be looking at 10 PCs per circuit as you may have approx 2.5mA leakage per PC by the time you take the base unit and monitor into account.

would agree,

except 8 per circuit, allows for some leakage/error.

whether RCD protected or not I would still do 8 points per circuit, helps with the segregation too, just a lot more circuits,

tho Im not so sure about being totally able to do away with RCDs in a school enviroment where kids are using electrical equipment.

 

[musicspark]

rcd requirement can easily be designed out

how?

 

[Andy™]

wired in trunking, and sockets under supervision. no RCD req'd

 

[kme]

Alternative; IF the point about sockets within a school environment does necessitate RCD protection, is to fit RCD socket outlets to the trunking...........

KME

 

[Lee321]

how?

also not for general use. i.e if the sockets are only to be used for pc's and not anything else

there are even sockets available with the earth pin turned through 90

 

[musicspark]

[quote name='Andy

 

[Lee321]

I am having difficulty here as a circuit with more than 10mA total would appear to require a cpc not less than 4mm.As both 2.5 and 4m T&E have 1.5 cpc, does this not mean that either could be use - subject to load, start up and voltage drop?

Also would any more than four units per circuit (10mA) not require an additional 4mm cpc to be incorporated?

Any other interpretations?

then it rules out using the 2.5 and 4.0mm t&e

 

[kme]

If it`ll be in trunking, singles may be an option........

 

[Lee321]

If it`ll be in trunking, singles may be an option........

 

[Lee321]

saw a nice solution to this sort of job all on dado.

a 32a 4mm radial supply to the dado terminating in a 32a double pole switch

then a ring from this to the sockets.

worked very well logistically where dado had to stop/start etc

lots of pc suites i've seen have the db in the room too

 

[kme]

lots of pc suites i've seen have the db in the room too

Good point. So have I, come to think of it.......

O/P - sub to the new room, and singles in trunking from contactor adj. D/B?

 

[steptoe]

Alternative; IF the point about sockets within a school environment does necessitate RCD protection, is to fit RCD socket outlets to the trunking...........KME

good solution, but maybe running to a lot more expense due to the number,

needs working out IMO as to this particular install.

Good point. So have I, come to think of it.......O/P - sub to the new room, and singles in trunking from contactor adj. D/B?

for this amount of points maybe the most economical at this time without further input.

sorry for not quoting the original suggestor of this idea, I will go back and thank you.

 

[Andy™]

I am having difficulty here as a circuit with more than 10mA total would appear to require a cpc not less than 4mm.As both 2.5 and 4m T&E have 1.5 cpc, does this not mean that either could be use - subject to load, start up and voltage drop?

Also would any more than four units per circuit (10mA) not require an additional 4mm cpc to be incorporated?

Any other interpretations?

543.7.1.3 (iii) - you could have a 2.5/1.5 T&E radial, and then a 1.5 single from last point back to DB.

or a 4/1.5 radial, and a 1.5 single back to DB

 

[Andy™]

another thought - where will the network cables be going? you may need compartment trunking to seperate mains from data

 

[musicspark]

[quote name='Andy

 

[Andy™]

no. 2.5 twin has a 1.5 earth, so you also use a 1.5 single.

4mm twin has a 2.5 earth, so you use a 2.5 single.

 

[musicspark]

[quote name='Andy

 

[Lee321]

do we not require minimum 4mm cpc if leakage exceeds more than 10mA total per circuit?

 

[spinlondon]

do we not require minimum 4mm cpc if leakage exceeds more than 10mA total per circuit?

Isn't that only when there is a single protective conductor?

 

[Lee321]

Isn't that only when there is a single protective conductor?

don't think so spin

so 2.5mm singles L & N and 4mm earth

as long as VD is covered