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The problem with the Smart-UPS units is they're not really that good at stabilising the incoming transients. I had big problems a year or so ago with a VideoWall supply which had PCs fed via individual UPS. If I recall they were Leibert 'powersur'. The in-rush currents of associated lighting...

I had similar on some supposedly class2 IP45 bathroom lights. They were no more class2 then my granny. Had to earth the things in the end. Just as well they were bought for IP rating and not class rating. Shouldn't be allowed to get away with calling them class2.

Only on solid core (WF etc) not on air spaced dielectric cable unfortunately.

Sounds like you need to look for a more robust UPS supply to cover the Racks & Machine Rooms. The harmonics issue can be measured direclty for each rack supply if you get somone in with the kit. Do you use small UPS units? or when you say UPS do you mean you have a dedicated UPS room fed from...

The problem here is your wants and theirs are not the same. You want to believe the existing set-up is safe as it hasn't malfunctioned yet. But without proper testing of the installation you can't tell. They want to ensure that the system they're supplying is safe, and that their work isn't...

In use or not, what you're bonding for is to counter the possibility of introducing another 'earth' potential into the premises. so if someone touches it they may have a better path to earth than via the MET. So you bond it as soon as it comes into the area to ensure it's at the same potential...

Yep use the normal JBs and if you're worried about bugs and spiders nesting then you can seal the entries with low-modulus acetoxy or similar filler.

Yea but Lec we've all been on the wrong end of their fancy installations.... still trying to figure out that TN-C-S(CNE) & TT combo down my way.... called the engineer back today and he was all embarassed for having said it'd be PME if under 0.35ohms. Promised he'll get someone out to go and...

Yep, good to see so many familiar faces. Trundled over from Novo the other day for a peek. Still won't be burning up all my on-line time on here...... but boy it's way better than slewedphrix. And doesn't shut down just because they can't find a fork-lift driver or label sticker :roll:

Yea but they may have been expensive biscuits. :wink:

Without the van or the like my 'go it alone' costs were £12.5k last year. Each year we have to get our kit calibrated at about £60 +vat per piece of kit. If we register with the NICEIC year one will be +£1000 and each year after about £500, with certificates costing about £15+VAT for 25 or you...

That's the case with singles Lec, but if it's in a house or the like the mains cables will probably be T&E so there is a continuous 240V insulated barrier between the cables (the outer sheathing)so this complies with BS7671. But if at all poss from an EMF interference point of view I look on...

and you read that in which part of his question? I'm not going to assume anything about someones desire for info from the fact it's an arguement down the pub. Surely he needs as much info as he can use to outwit his pub mate?

And answer said it in one specific example ....no. a fire can start from as little as 80mA tracking along a cable. Most fuses will not blow with just 80mA unless you also manage to get a decent increase in the load, beyond the fuse rating. So although fuses may help they won't prevent a fire if...

Another cause not related to cable size; Class2 equipment developing an internal fault. ie; TV line output transformer windings insulation collapsing, increased heat and resistance but until it goes dead short the fuse may just cope. there are HT voltages inside a TV so there is greater...