Clean earth on UPS

[James Sutton]

Hello All

Within the next few weeks i am installing a small UPS in a comms room. The spec was to install a 5OA supply to feed the ups. Iam install a small Merlin Gerin TPN sub board in the comms room. There is a clean earth bar within the comms room. Would i take the earth from there for the ups or just from the MET on the sub db. The spec on the ups didnt say anything about installing a clean earth.

Any ideas

Thanks

James

 

[grantr37]

The Clean Earth is for the Data Cabinet routers and computers in there, the supplies going to them will get connected onto one of these clean earth bars, as will the suspended floor supports (if there is a liftable metal floor) and any metal frames that form the cabinets and rack holders.....
your main earth for the UPS Unit(s) should come from the incoming main earth, this will carry on through (via the UPS)in Steel wire Armour to the supply board(or supply cabinet complete with glass door) that you are fitting inside the Data Room and bonded there...
There will be a need for an earth bonding cable from a (separate )bar there to the main clean earth (or one of them) which will be a place to bond the earth going to the underfloor sockets or feeder cables supplying the Data cabinets...

I will assume that the UPS is still a reasonable size, remember correct Battery Handling procedure for setting up and also wear safety specs and Gloves...


You will need to stock up on:

6mm Steel drill bits (eg from screwfix)
10mm Steel drill bits
25mm Holesaw x a few
32mm Holesaw x a few
20mm, 25mm and 32mm Gland kits.
Go onto ebay(best place for them) and look at the 20mm +25mm Stuffing Glands in Black and also Green (handy for doing comms rooms) you might also want to stock up on Cable ties from screwfix or ebay and look at safety electrical connection(earth) stickers, along with the standard 220V stickers, and "computer do not switch off" stickers...

If you are going into a working comms room, ask for the Fire suppression system (IG55 INOGEN) to be switched off temporarily as this could be set off by drilling/dust and is extremely expensive to refill/reset(think of up to £50,000 depending on the system size)as well as possibly dangerous if you are in there when it goes, especially if it is a room wide high-pressure system...which a lot are in Data centres



Small Data rooms in low load facilities (private offices etc) are usually only cabinet interior low pressure/low volume systems...which are usually quite safe...
I think that there is quite a high chance that they will refuse to switch this system off, either because it would involve turning off the whole building/facility, or more likely they will not know how to.....

A way to get around this as a last resort is to get a gas spanner and carefully disconnect the pony firing bottle hose from the cylinder chain, this will disable the fire system in that room only .....best bet is to ask them to get their maintenance people to do it for you...this will stop the Gas suppression system from emptying if work accidentally sets off the fire alarm..

Another thing to remember is to watch out for any underfloor water sensor pads/straps and the connection wires, as if you stand on one it will cut off the coolant pumps to any floor standing air conditioning/cooling units and close the valves as well, this is incase of leaks...these are usually situated about the concrete floor next to cooling water pipes that come in from the plant room...will save you needing to get into the plant room to turn back on again...

 

[James Sutton]

Grant thanks for the advice its been a minefeild this job with regards to where we can get a supplier from landlords metering etc. Been roped into doing ohwell its all work. Yeh we have to key the gas panel into manual and isolate anyfire dectors floor level and ceiling level so the system fire as its a two stage system. We running a 10mm swa and separate earth into the new dis board located in the comms room. then we can supply the ups from that.

Thanks mate

James

 

[grantr37]

some places I have worked in the building owner is not available/is not interested and no company maintenance people will show up, but they (the day to day workers) get really noisy about the fire system when you go to turn it off.....that's where the pony bottle hose comes into play.....disconnected it will save the system from emptying.....and hopefully they won't notice as you aren't in the corridor prodding the vesda panels...

 

[tlangdon12]

Only thing I can add to grantr37's comprehensive reply is to try to do all your hole drilling of the dist board outside of the room, and be rigorous with catching any waste you have to make in the room, especially if cutting metal.

 

[tlangdon12]

Oh, just re-read grantr37's reply. He didn't mention warning labels for the fixed items fed from the UPS. I'd recommend you apply a warning label to any dist board or outlet to say it is fed from a UPS and may remain live even if the supply is isolated. Canford have the right sort of thing at:

http://www.canford.co.uk/Products/20228/52-781_UPS-WARNING-LABEL-This-equipment-is-fed-from-a-UPS-and-may-remain-live-pack-of-5

 

[Engineer54]

There are many meanings to the term ''Clean Earth'' most of which aren't clean earth's at all!!
On most the larger UPS systems for data centres i've ever been involved with, The supply comes into an isolating transformer, so the building supplies earthing system is left behind and a separate functional TT earthing system is then used to both earth the neutral point of the isolating TX and to supply the earthing arrangements within the IT/computer room(s), generally all being radial connections from a common earthing bar ring(s) around the room(s) linked back to the main distribution board within the computer room suite!!


As i say, there are as many different way's of doings things, as there are to the meaning of ''Clean Earth''!! A clean earth could even mean, an earthing connection from the main buildings MET that serves only the IT area/data centre!!

Malcolmford is an IT centre advising Engineer in Saudi, he would be the guy to ask, but haven't seen him around from just before Xmas. Maybe still on his vacation leave!! Anyone know??

 

[Rockingit]

Someone was asking after him the other day, too.

Whatever you end up with, I'd have thought that you'll be needing the UPS earth to be the same as the Equipment earth, otherwise in the event of a UPS trigger then you'll have two different earths which could lead to all sorts of interesting things.

(???)

 

[Engineer54]

Depends where the isolating TX is located, or if it's a part of the UPS system. The main idea is to stop noise and peaks/spikes from affecting IT equipment/components etc...

 

[James Sutton]

Thanks everyone for your help I really appreciate it.

Thanks

James