Which UPS must be used in a Data center, the centralized or the Modular ones, as in my view Modular UPS's have low heat dissipation as compared to the Centralized ones. Is this correct?
By modular, I take it you mean rack-sized UPS units. I have seen both used successfully, but in general a rack UPS strategy works well for small installations, while larger sites prefer central units. Rack units allow granular upgrades to capacity with small incremental cost, but battery swaps and equipment reliability take their toll when the number of units grows. Also, many shops cut costs by using switching units, which do not provide the power conditioning of online units. Here is a quick plus/minus list. Heat output depends on the relative efficiency of the units.
Central UPS
Plus:
Central control/monitoring
Central capacity upgrade point
Better overall efficiency
Minus:
High replacement cost
Problems affect entire data center
Rack UPS
Plus:
Small incremental purchase cost
Problems limited to single racks
Minus:
Time-consuming battery refresh
Switching units often used to cut costs
More devices = more failures
Both have serious minuses, so what should be proper way to manage these? You won't either want to have too many devices to manage or you won't even want a single error to hamper the whole DC ?
Does this also apply then when you have a small server room as well. I really would not classify what I have at home as a data center, even though I guess it really is. Would these UPS be good in that as well.
Modular UPS is too important to make do with a system that isn's quite right. Liebert APS UPS is a modular, single phase output UPS, with both single and three phase input options to provide both high availability and flexibility. This UPS offering capacity on demand with flexible power modules wich allow capacity upgrades in 5 kVA/4.5kW increments up to 20 kVA UPS.