Metrel eurotest xe & UPS odd readings???

[chocca]

Hi all,
I'm testing an unoccupied office block and I'm having some major grief with my tester trying to get Zs readings.

The place was a call centrre for a computer related firm and as well as the normal supply it has a gert UPS in the plant room (p.resumably to keep the servers etc up and running). I've no problems with the "ordinary" DB's, the meter works fine. Try and get readings off the ones that are "backed up" though and the metrel throws a right wobbler. Phase 1 tests ok but try phase 2 or 3 and the LCD display suddenly shifts to the "memory" screen and the thing bleeps like a banshee.
(For those without experience of this model it only works on 230v so you've to treat a 3 phase board as 3 x single phases)



There's no info with the UPS but it appears the supply goes in and the backed up boards are fed from it. I've seen UPS systems before where the mains/UPS are separate and get switched in as required but I've no experience of this permanently in-line type.

Any ideas ?


I dropped an email to metrel technical but haven't had a reply (surprise??) and I'm running out of time.

TIA, Rich

 

[malcolmsanford]

Hi there Chocca I know your not on so it's difficult to get an handle on what you mean

There are a couple of things though you saying that these units are "in-line" and not via an Automatic Transfer Switch (ATS) which would lead me to thing that they are the small rack mountable type, about 10KVa

You then go on th say that they feed "back up boards". If these are actual Electrical Distribution Boards then I have the larger stand alone 200KVa plus type of unit in mind and these would be feed via an ATS

Which ever units you have, you could be getting this problem with your testing because of the inverter system inside the UPS. The meter is reading "noise" on the circuit and it is registering this as an error.

The bigger 200KVa system via an ATS should not give you problems as the ATS should be triple pole and should isolate all conductors until there is main failure

The smaller in lines one normal have switch modules built into them, but again there is normally separation either by transformer or electronics.

It would be interesting to see what makes the UPS are

 

[chocca]

Hi, sorry for being as clear as mud :-( lol but that's early mornings and pressure for you!

There's 2 of the units and they're 300Kva made by chloride IIRC. Big beasts leastwise.

I've spoken to the landlords rep this morning and he's arranging for the guys who normally service the things to come out and shut them down - the building's been empty for 3 years and, along with the hot water and heating, everythings running and costing money. I suspect you're right regarding the inverter, they used to cause problems on early digital meters when they were fitted to control motors back in the good old days.

Coming from a chemical plant background I'm more used to back-up generators etc where each supply is separate and there's no crossover of any kind.

I didn't mean the boards were back-ups, just that they were fed via the ups as well as the mains, whereas the rest of the boards are fed from the mains only. I reckon that in the event of a major power failure they didn't want the staff to be able to see to get out, so the only power available was to the screens and keyboards and the staff would have to stay and man them ;-)