ECN Forum Forums General Topics of the Trade Non-US Electrical Systems & Trades Deriving Neutral

Yes, it is called TN-C(ombined).

I'm avoiding delta/wye transformers so as not to have a phase shift issue. Delta/delta on the input, the UPS outputs a delta/wye current in sync with the delta input, then a wye/wye step-down xfmr on the output to maintain the 0 phase shift and keep the delta centered about ground.

If I did anything, it would be to tear out all the delta bus duct for the maint bypass and static bypass circuits and put in 4-wire wye from the switchboards, but that's going to really kill the budget if I have to do that. If TN-C is OK, though, (sure makes it easy, Wolfgang! I don't suppose you recall the code that authorizes it? I have a google translation of the italian codes, but it's a bit... difficult) we'll likely just grandfather in the existing installation and let IEC supercede NEC in this case- after all, it's working fine now, and we're not changing anything by swapping out the old switch with a new one. Nice to be able to do that sort of thing

I don't know what specific loads are on the panel, it's never an issue if we go back 1:1. My boss was putting a rush on us to get in and out to cut travel costs, and I didn't get as full of a survey as I'd like- made a check list so this doesn't happen next time!

[This message has been edited by SteveFehr (edited 08-10-2006).]

Erm... I guess you have to keep in mind one thing: there is NO such thing as a European code! Every country has its own (sometimes fairly different) codes!
So something that is perfectly legal in Germany might actually be illegal in Austria and vice versa!

Example: in Germany most people recommend to have some receptacles (like refrigerator, freezer) on a circuit without RCD (ground fault) protection. In Austria that's completely illegal - all receptacles have to be RCD protected.

Generally TN-C seems to be limited to wires 10mm2 or larger in most European countries to avoid thee dangers resultung of PEN breaks.