Re "So how is it more economical?"
Let's say you put a 20A 80% breaker on each available leg.
Case 1) 120/240 single phase, 3-wire (L1, L2, N):
120v x 80% x 20a x 2 hots = 3840va
3840va / 3 wires = max 1280va delivered per installed wire
Case 2) 208Y/120 three-phase, 4-wire (L1, L2, L3, N)...
There are various relays which can be used to protect against single-phasing, including ANSI 46 Reverse-phase or phase-balance current relay; ANSI 47 Phase-sequence voltage relay; and ANSI 48 Incomplete sequence relay.
Note that many (most? all?) solid-state overload devices now also provide...
Re "So, it sounds like your installation is not code compliant": I should rephrase that....
The grounding installation you describe is not recognized by NEC, nor by TIA. It may or may not be code compliant.
Additional grounding may or may not be required by NEC -- it is entirely possible that...
I believe IEC/BS EN 62305 (Lightning Protection) Part 4 (Electronics Devices) might well require it. If you don't have access to 62305, Furse publishes a nice (and free) guide to 62305:
http://www.furse.com/ps/eel/index.cgi?a=getpg&p=Product Catalogues&b=furse
NEC would generally not recognize a water pipe as a grounding method at any point further than 5' from the location of its entrance to the building - see NEC 250.52(A)(1) adn 800.100(B)(2). I believe this is generally due to the concern that pipe joints may not be very electrically conductive...
The battery is the weakest link in a UPS system. It would make much more sense to parallel 3 batteries on one UPS, that would be much more reliable than 3 UPS's on one battery.
And as DanEE suggests, it'd be even better to have two UPSs, each with their own battery, feeding dual-cord (dual...
I'm a bit scared to answer your question and won't really attempt to do so. But I'd advise against connecting the grounds between two separate systems without giving that some serious consideration first. My advice would be to ground to only one of the two systems in question. If you are...
You can view the complete 2008 NEC (and other earlier revisions) on nfpa.org:
https://www.nfpa.org/catalog/services/Login/login2.asp?npg=http%3A%2F%2Fwww%2Enfpa%2Eorg%2Fonlinepreview%2Fonline%5Fpreview%5Fdocument%2Easp%3Fid%3D7008SB
It's free, it will cost you nothing more than an email...
NEC 250.162 requires DC systems from 50-300v to be grounded. To the best of my knowledge, your 24VDC system is not required to be grounded in the US. Any metallic non-current-carrying metal parts (conduit, etc) would need to be grounded per NEC 250.169; it's unclear if you have any such...
Re. stainless steel tubing/conduit/raceway/etc -- To the best of my knowledge, there is no UL-listed stainless steel tubing/conduit/raceway available anywhere on the market, which would make it an automatic violation of NEC. My understanding is that when people say they've installed SS conduit...
Is there any disconnect for the motor? Or do those breakers only disconnect the controls? If not, you will need an additional local disconnect per 430.102 unless you fall under one of the exceptions to 430.102. That disconnect would most likely be placed just ahead of your single-point...
The ground conductor run from the equiopment to the main service entrance may be a long high-impedance run -- it might be fine for safety's sake, but you might get enough voltage developed on the long ground & neutral wires to cause problems with the operation of the communications equipment...
I wouldn't address it at all as the EOR -- I'd get a fuse vendor or the switchgear vendor to address it. But the vendors will probably refuse to address the issue using fuses due to the issues rbulsara has pointed out.
You may find that, unless you can find some listed combination of series...
Wikipedia has an interesting article on "horsepower", there's way more definitions for horsepower than I would have ever guessed. CV is defined in there -- it is not a metric unit, it is an obsolete French unit previously used in automotive marketing.
http://en.wikipedia.org/wiki/Horsepower
