Ideas?

[M107]

Evening all,

Well I have a customer that has a 7.5 tonne wagon with the rear end being a command centre thats stacked out with IT equipment (10 servers / 5 plasma + smart screens / sky / sat link + dish + server / 6 pc screens / 10 laptops + docking stations / cctv + recorder / 2x 16 port 3com hubs / 2x 3Kva ups / 1x 1.5Kva ups).

The unit does have an on board genny (50Kva limited to 20K at the moment) + battery bank with inverter that are on a split charge system, but when at its depot the wagon is plugged in to the mains via a landline (sy 4mm 3 core) to 32amp BS EN.60309-2 outlet that is rcd protected.

Yep the problem is the rcd trips when everything is fired up when on the landline, not to good when they are wanting to charge the ups/batteries.

The supply is TN-s but as this isnt strictly a distribution circuit & the outlet can be used by unskilled/supervised persons the rcd should stay, but the customer wants do do away with the rcd to stop the intermittant tripping when the IT kit is in use.

My idea is to install a lock off isolator with padlock on the circuit & label the circuit as a dedicated circuit for this vehicle only so only the crew of the vehicle can use the outlet & bin the rcd..........what do ya think.....or any other ideas are welcome.

need another beer Guiness DrinkGuiness DrinkGuiness DrinkGuiness Drink

 

[SPECIAL LOCATION]

One presumes this is due to high earth leakage current through the IT stuff?

Do you know how much current is flowing though the earth?

wouldn't a higher rating RCD fix it,, e.g. 100ma Not 30ma?? ?:|

or have I missed the point somewhere???? ?:|

 

[kme]

Could you provide the wagon with P/N, and effectively utilise the wagon as TT, or Class 2?

Or am I talking nonsense?

The lock off idea would work, though.....

 

[SLIPSHOD & SLAPDASH]

The Rcd reg is for sockets rated under 20A.

I suppose this equipment is not actually outside

 

[Nicky Tesla]

maybe something to do with getting power from the landline (80v as i recall when being rung up)which could put an imbalace down to earth somehow....just guessing.

 

[Evans Electric]

I.d guess it was the IT equip. causing currents to flow in the earth wire too, a mass of equip. raises the level over 30mA . Its a pain in the buttress, and will be cropping up more and more with al the RCBOs going in methinks.

As Specs says , a 100mA RCD might do it or a type B time delay might cope with the spikes(if thats what they are)

Does it actually require an RCD ? What if you attatch an earth lead to the truck and scrap the RCD ?

Ducking into my foxhole !!

Deke

 

[M107]

I suspect it is the IT equipment producing high protective conductor currents on start up as the rcd tests ok on its own (1x = 12mS 5x = 8mS), I've not measured anything on the wagon as yet, doing that week after next when it's back at the depot.

I did mute with customer the idea of using an S type rcd, but the customer is thinking of binning the rcd to do away with the problem altogether, so long as the regs can be satisfied of course.

Will let you know what the outcome is.

 

[danny7299]

can some one explain to me why the IT gear would cause a problem? also why on a IT ring main do you need bigger earth cable? ... what size do you put in?

Cheers

 

[Nicky Tesla]

can some one explain to me why the IT gear would cause a problem? also why on a IT ring main do you need bigger earth cable? ... what size do you put in?Cheers

The larger earth directly to the IT equipment is for a CLEAN EARTH

Any spikes on the normal cct cpc can cause problems with IT equipment. The spikes are larger on the normal cpc due to the higher resistance to earth and other equipment on the equipment causing the spikes.

Everytime a Computer deletes something for example, it dumps it down to earth causing mAmps to flow to earth. So a lot of IT equip deleting at the same time, will cause a higher mAmp flow. Its not just deleting that does this.

 

[kme]

The power supplies have inherent earth leakage - an office with a number of computers can have quite high currents circulating on the CPC.

The size required is usually best calculated during the design of the circuit - i.e. what is the type & rating of the cct, and how much current is the CPC needing to carry IN NORMAL SERVICE.

HTH

KME

 

[kme]

The larger earth directly to the IT equipment is for a CLEAN EARTHAny spikes on the normal cct cpc can cause problems with IT equipment. The spikes are larger on the normal cpc due to the higher resistance to earth and other equipment on the equipment causing the spikes.

EH?????

Everytime a Computer deletes something for example, it dumps it down to earth causing mAmps to flow to earth. So a lot of IT equip deleting at the same time, will cause a higher mAmp flow. Its not just deleting that does this.

And you are HONESTLY going to tell me that you believe what you have just typed????

What nonsense!

 

[danny7299]

so how much does one computer produce? so you can work out how big and earth you need?

also how do you get clean earth... do i have to ask the wife to get the feather duster out?

 

[kme]

Everytime a Computer deletes something for example, it dumps it down to earth causing mAmps to flow to earth. So a lot of IT equip deleting at the same time, will cause a higher mAmp flow. Its not just deleting that does this.

Mrs. KME is asking:

"Do we put flowers there"?

 

[patspark]

i could be talking ********

osg page 67

7.6.2 (i) (ii) (ii)

hope it helps if it dont read opening line again

 

[Nicky Tesla]

i ant got the osg yet but clean earths are well documented in IT

 

[Mr Sworld]

IT equipment produces high earth leakage currents, so large amounts of kit will push the earth leakage over 30mA so the RCD thinks there is a fault on the system and trips.

I too would do away with the RCD on a 32A c/form supply OR swap with a 100mA or 300mA.

Computers dumping stuff down the earth when they delete something! Honestly Nicky, you don't half talk some tosh sometimes....

 

[Nicky Tesla]

IT equipment produces high earth leakage currents, so large amounts of kit will push the earth leakage over 30mA so the RCD thinks there is a fault on the system and trips.I too would do away with the RCD on a 32A c/form supply OR swap with a 100mA or 300mA.

Computers dumping stuff down the earth when they delete something! Honestly Nicky, you don't half talk some tosh sometimes....

I talk tosh do I......What on earth is the reason for putting in a 100mA or 300mA RCD in this situation. Is the Zs too high? protection for sockets HAS to be 30mA and trip at less than 40mS so an S type is no good either.

The best thing would be seperate rcbos but are any of these sockets for use for equipment to be used outside?

 

[Mr Sworld]

I talk tosh do I......What on earth is the reason for putting in a 100mA or 300mA RCD in this situation. Is the Zs too high? protection for sockets HAS to be 30mA and trip at less than 40mS so an S type is no good either.The best thing would be seperate rcbos but are any of these sockets for use for equipment to be used outside?

Protection for sockets UPTO 20A has to have an rcd on it. This is a 32A c-form!

 

[Nicky Tesla]

not a 100mA RCD

 

[patspark]

the wiring of every final circuit having a protective conductor

current likley to exceed 10mA must have high inegrity protective

conductor connections

complying with one or more of the following

(i)a single protective conductor having a cross-sectional area not less

than 10mm 543.2/543.3

(ii)

a single copper protective conductor having a csa not less than 4mm

the protective conductor being enclosed to provide additional protection against mechanical damage for example within a flexible conduit

(iii)

two individual protective conductors each complying with section 543

the ends being terminated independently

(iv)

earth monitoring or use of a double-wound transformer