server connections

[Electro-tech]

If there are high earth currents , you should clamp to know exactly what you are dealing with, as a server cabinet in arms reach of a service pipe etc; could provide a path to earth via that person.I would say that the 300mA RCD would be good to keep there in case of fire and as to risk to persons the 30mA rule would apply if persons could come in contact with the equipment.Also the method of installation of the circuit of the industrial socket dictates whether need for RCD or specifically labelled/ under supervision etc. I would be also be concerned as to the earthing integrity of each workstation back to the server room.If all earthing is common, then you may need to segregate the circuits involved and this way you may find parallel paths contributing to your earth leakage at the server.

 

[123cool]

[FONT=&quot]Telectrix [/FONT][FONT=&quot]& [/FONT][FONT=&quot]Malcolmsanford [/FONT][FONT=&quot]I[/FONT][FONT=&quot] know that safety device designed to protect against personal electric shock and Fuses / MCB’s protect only the installation and final appliances; they are not suitable for personal protection from electric shock. Many believe that it is voltage that can kill whereas in actual fact it is the current that causes a shock and can prove fatal. The actual amount of current that can cause death is very small. In fact its just 50mA (milliamps), much less than the 3A fuse you may have fitted in your plug.To simplify, just 1/20th of an amp can kill an average person. All above mentioned I believe and agree but what can I do if the power supply tripped at 30mA and IT people not understand the risks, what you will do if you are in my position??? [/FONT]

[FONT=&quot] Electro-tech unfortunately the server rack not earthed [/FONT]irate: and what do mean by parallel paths contributing to your earth leakage at the server??? [FONT=&quot] [/FONT]

 

[malcolmsanford]

Seeing as you are lecturing to me perhaps you should read regulation 531.2.4 concering RCDs and their use in conjuncture with circuits that produce Protective conductor currents.

Also if you deem yourself sufficently knowledgeable to lecture at least research your subject matter. The actual amout of current that can kill is less than 50mA, which is why for additional protection against shock, a 30ma RCD is used. In fact a defibulation of the heart can take place at 10mA, which is why in the industry and mostly in schools and research facilities we use a 10mA RCD.

You clearly are the adage a little knowledge is dangerous, and by removing a device design to protect against shock, and replace it with a device designed to protect equipment shows this. Please though carry on with this situation if you feel this is the correct path.

Becasue the installation is badly designed, you decide that the way to go is not to correct the design but to change it's parameters to make the installation dangerous. Same as I assume if you could not fit a piece of work into a circular saw the answer would be to remove the safety guard.

 

[nickblake]

If an industrial socket is installed specifically for a server normally in a locked or restricted access room ,the circuit is designed correctly access restricted to skilled and compitant persons ,risk assesed then there is no need for RCD protection ,it when there is a possabilty that some one using equipmet thats of a higher risk ie outside , cleaners with vac etc , agree with malcome on this one , its all about risk ,

 

[123cool]

[FONT=&amp]Malcolmsanford why the power source tripped @ 30mA?????
[/FONT]

 

[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