server connections

[123cool]

[h=2]nickblake :coolgleamA: [FONT=&amp]why the power source tripped @ 30mA?????[/FONT][/h]

 

[Electro-tech]

123cool ."Electro-tech unfortunately the server rack not earthed irate: and what do mean by parallel paths contributing to your earth leakage at the server??? " A main earthing terminal in common to various circuits including your industrial plug earth may have earth leakage before you connected this I/Plug supply. So your PDU Supply is earthed and all equipment is earthed via the PDU. If any mains supply cable fail and touch the cabinet frame then- What ?? Maybe overkill but have earth bonded each panel and equipment.Rather than relying on screw or Bolt contact for continuity of earth. Other than the above I have to agree with Nickblake but at least if the cabinet was earthed that would reduce the risks to personel.

 

[malcolmsanford]

It is most likely tripping because you have an accumilation of circuit protective currents.

On each Server/blade/switch/computer you will have a filter that enables to cut down on what is called "noise". This "Noise" is interference for the want of a better word, from other pieces of equipment on the installation. A by product of this filter is high protective currents, which is the modern term for earth leakage. Each piece of equipment will leak a few milliamps and the build up of these could cause your 30mA RCD to trip. This is why I referenced you to regulation 531.2.4 and the design of circuits that have these protective conductor currents, it may turn out that you would need to split the circuits and have more than 1 RCD.

A healthy 30mA RCD will trip at anything from 22-30mA, that RCD you have replaced may have been a faulty one and be tripping at well below this, a way to check this is to carry out a Ramp test, that will give you a value at what the RCD trips at.

As I said before as this seems to be a commercial/industrial situation and that plug is specific for your server, you may be able to do away with any RCD protection at all, but only under certain conditions which a designer/electrician will be able to ascertain. I still think it was fool hardy of you to just replace the 30mA device with a 300mA device as you are not competant to really say why a 30mA was used.

 

[123cool]

Electro-tech and malcolmsanford thanks for your help and really I want to save IT people life:74:. So, already I gave the contractor instruction to start test the earth current and I asked from the store to purchase ramp test to use it by our electricians but are there any other reasons caused this tripping like using the extensions since I noticed many of them in the server room , moisture or dust?????
malcolmsanford please can you more explain why with industrial outlet no need to use RCD ??? do you mean that you connect the industrial outlet to distribution board by MCB only ????

Thanks & Regards

 

[malcolmsanford]

Yes moisture would cause an RCD to trip as well.

Do your electricians on site who your going to buy this ramp test for(?) not know the the BS 7671-2008 regulations?

Regulation 411.3.3

 

[Electro-tech]

Just a thought does any Extension trailing sockets have surge protection.A standard surge protector passes the electrical current along from the outlet to a number of electrical and electronic devices plugged into the power strip. If the voltage from the outlet surges or spikes-- rises above the accepted level -- the surge protector diverts the extra electricity into the outlet's earth conductor. Equipment fed through Power Distribution Units have similar filters of components connected to earth. I am glad you are going to test this earth leakage problem.Thanks for your reply !

 

[Engineer54]

I Think the important here, for the protection of persons, is maintaining a maximum a 50 volt touch voltage in this room/cabinet/area. If the 300mA RCD device/Ze achieves or betters that value it should be fine.

We have often needed to use adjustable level RCDs, very expensive by the way...lol!!! Ones we used were adjustable from 30mA thru to 1A they were also equipped with adjustable time delays, that was generally left on Inst' as they were not being used for discrimination purposes...

 

[123cool]

I asked from the electrician to measure the earth leakage current and he found it 60mA so how come no body get :banghead: electrical chock???

 

[Electro-tech]

Source being touch voltage .

 

[123cool]

Electro-Tech , so long as the earth wire existed no body will get chock until damged in the earth wire happened , Also , I understand that only good earthing can be provided in server room so no harm to install 300mA or 100mA RCD for more protection and safety and also to avoid the tripping problems , and we have to accept this high leakage current level from UPS and the servers , but , why in the regulation no cleared mentioned that no used of RCD with UPS or servers?????

thanks & regards

 

[Electro-tech]

If continuity of the earthing conductor was lost the server cabinet or associated metal work if earthed would be carrying as you say 60ma. So if metal work touched and passed through somebody to earth they would get a shock.If all metal work is bonded then the shock potential will be the same wherever touch is possible.However if you have satisfied the Regs 543.7.1.2 etc ,adding a 100ma can only help the situation.Also, as long as this 60 ma leakage current is not adding to leakage at the Main Earthing Terminals and other points where the shock potential could occur in another part of the building. Maybe a earth continuity monitoring system would guarantee connection to earth.