Computers on an rcbo

[Albomofo]

Hey, wondering if anyone can help. I am installing ring circuits in a school for IT use. I know that comptuers leak current to earth and was wondering how many before a 30mA rcd trips. I have the number 8 in my head. Anyone know??

 

[Zeespark]

Do a ramp test on the RCBO and an earth leakage test on the IT equipment. Do schools specify 30mA or 10mA RCBO's?

AndyGuinness

---------- Post Auto-Merged at 17:20 ---------- Previous post was made at 16:55 ----------

In fact, thinking about it, are you competent enough to be wiring installations at a school with such a small grasp of what an RCBO is and how it is tested?

AndyGuinness

 

[fletchflash]

bit harsh Zee! dunno if that OP really demenstrates such a serious lack of knowledge of RCBO testing

I think 8 is the max number of PC's you can have on each circuit. However, as far as Im aware, this would be for a circuit with a high integrity earth. A normal ring circuit on an RCD would nuisance trip.

Others can probably give a better answer than me. Theres a section in the regs too me thinks

 

[Zeespark]

If the OP was just researching the ins and outs of the mechanics of RCBO's and RCD's My tack and tone would have been a lot different Fletch. It just worries Me that He wiring in a school with the knowledge of RCD's and RCBO's that He appears to have. If I have offended anybody I apologise.

AndyGuinness

 

[Doc Hudson]

The actual leakage from any particular piece of IT equipment will be down to the manufactures design and components used. Not all computers leak the same amount. The traditional CRT monitor was a prime culprit for a lot of leakage. Things like laptops, with double insulated PSU's don't even have a CPC connection to leak down. I think you would need to test some of the actual equipment to be used. I have in my mind the figure of 3ma being the amount some items can leak, which is where the figure 8 come from, as 10 would theoretically give you your 30ma trip current.

Doc H.

 

[Megaohm7]

A ramp test would tell you approx how many milliamps the device will trip so the device is a 30mA, it might trip at 26mA for e.g. Now you need to measure the earth leakage of every computer and add them up. It's the power supply of the computer that leaks current. Those earth leakage testers cost a small fortune too for a decent one. Unless Meggermark is doing some deals at the moment. I know he has done in the past but it's this economic downturn that's affecting everyone.

 

[M107]

I put a radial in for a school IT class last year & the school specified 30mA rcbo. I did highlight the potential problem but it turns out the class only has flat screens/keyboards & rodents in the class & the drives are in another room on a dedicated non rcd circuit....

I did how ever put in a larger csa cpc as a ring & used dp cpc termial outlets (I know a larger csa isnt required but belts & braces was the thinking & I had a roll of 4mm g/y singles to get shot of:innocent) .

 

[Evans Electric]

I read in an IT article that computers use the earth connection to dump data which makes me think that leakage levels will up and down like a *****'s drawers.

 

[batty]

We have four computers and other computer equipment in our house and leakage from any other equipment like fridges etc and never had the RCD trip yet so it may not be a problem unless you have about 20. Just put more circuits in to be on the safe side.

 

[fletchflash]

read in an IT article that computers use the earth connection to dump data which makes me think that leakage levels will up and down like a *****'s drawers.

ho ho!

A ***** dropping her drawers to dump data