Fitting an isolator to ring main

[Thingy]

Hi

I am installing a completely new ring main for an office at home which will be running quite a few PCs & all the gubbins that go with them, scanners, printers etc.
What I want to do is have a handy switch that will isolate everything on that circuit - can someone advise me what to use & how it should be connected into the circuit - I don't want to flip the MCB in the CU every time as it's not particularly handy)

TIA
cheers

 

[Lectrician]

Either use a 30amp switch, feed this with 4 or 6mm cable from the CU MCB, and the ring ends go on the output side of the switch.

A better way is to use a contactor, and switch the contactor with a normal switch (possibly a key switch). This is a little more expensive, but a better job.

Also, for these computers, you should be installing a high integrity earthing system. This is because computers, by their nature, leak substantial current to earth when in use.

2 Radial circuits switched by a four pole contactor, with the earths linked at the end of the two radials would provide a good solution.

 

[plugwash]

id use a 45A shower switch because of the rather large switch on surges

6mm from CU to switch
then start your 2.5mm ring from the switches outputs

 

[Thingy]

Thanks guys - I think I can sort it from that info

cheers

 

[ban-all-sheds]

id use a 45A shower switch because of the rather large switch on surges

Or something like this:

Or just get a 4-pole DIN rail mount isolator and a small enclosure in which to mount it...

 

[plugwash]

im not sure breaking both halves of the rings seperately is the best idea in this case

the thing is that all the poles may not switch at exactly the same time so one half of the ring could take most of the switch on surge

 

[Lectrician]

im not sure breaking both halves of the rings seperately is the best idea in this case

the thing is that all the poles may not switch at exactly the same time so one half of the ring could take most of the switch on surge

I think BAS was referring to two radials.

 

[ban-all-sheds]

I think BAS was referring to two radials.

No I wasn't.

im not sure breaking both halves of the rings seperately is the best idea in this case

the thing is that all the poles may not switch at exactly the same time so one half of the ring could take most of the switch on surge

I was working on the basis that people who make TP+N isolators make PDS that they make & break all 4 contacts as near to simultaneously as possible....

And even if not, any starting surge would be so short lived that it couldn't possibly damage the cable.

 

[plugwash]

probablly not but you know what the worst thing about SMPSUs is

as the voltatage DECREASES the current INCREASES

 

[ban-all-sheds]

That's not the worst thing - it's the best thing - it's the whole point....

Anyway - a room full of kit all "on", suddenly powered up via the circuit being energised, would trip the breaker before it damaged the cable.

 

[andy]

Anyway - a room full of kit all "on", suddenly powered up via the circuit being energised, would trip the breaker before it damaged the cable.

computers with an ATX PSU wont all start when the power is turned on tho

 

[plugwash]

depends how you set things in the bios

 

[Lectrician]

Getting heated and technical.

Stick to the basics for these guys on here

I dont think he is fitting a 30man call centre in his attic.

 

[shaggy]

Lectrician, you said:

This is because computers, by their nature, leak substantial current to earth when in use.

Can you explain that for my benefit please? If there's a lot leaking to earth the rcd would trip?

 

[ban-all-sheds]

Lectrician, you said:

This is because computers, by their nature, leak substantial current to earth when in use.

Can you explain that for my benefit please?

Hope L won't mind me butting in. The type of power supply common in computers uses a form of transient suppression that, as a side effect, leaks current to earth. Not a lot, but it adds up. See this: http://www.tlc-direct.co.uk/Book/7.8.1.htm

If there's a lot leaking to earth the rcd would trip?

Possibly, although it's unlikely that you'd have enough high leakage gear to do that, but it could be enough when added to a minor fault in, say, a cooker or immersion heater, to push an RCD over the edge.