What Form Factor UPS Do I need?
UPS are available in several formats including desktop, wallmount, rackmount, tower and floor standing. The topology of the UPS and its size, limits the form factors available.
| UPS Topology | Form Factors |
|---|---|
| Offline (standby) | Desktop, Wallmount, Tower |
| Line Interactive | Desktop, Wallmount, Tower, Rackmount |
| Online | Desktop, Wallmount, Tower, Rackmount, Floor Standing |
If you want to use an Offline UPS for rackmount applications, then the UPS can sit on a suitable rack shelf.
When selecting the UPS form factor consideration should be given to the physical space available for and required by the UPS and the total weight loading. It is good practice to leave sufficient space around the UPS for airflow and cooling. A UPS is not 100% efficient and so there will be some heat generated from its operation. Batteries are also endothermic (absorbing heat) when charging and exothermic (generating heat) when discharging. A reasonable working space is also required with good access for UPS service and maintenance, and future battery replacement.
Safe manual handling is also an important aspect. In general, the maximum recommended weight that one person should lift is 25kg for men and 16kg for women. These limits are guidelines, and should be observed but the shape of an object such as a UPS can also play a part in how safely they can be managed. For UPS systems, a 2-person team and lifting or trolley arrangements may be required to place the UPS and its battery packs inside a room or server cabinet.
The physical size of the UPS system and its battery packs will also dictate location. For any rack mount UPS, the available U-height within a server cabinet will an important consideration. UPS depth should also be considered to ensure the server cabinet maximum internal depth is sufficient.
In a server rack, the UPS should be installed at the bottom of the rack due to its weight and batteries. In terms of temperature rise, the higher the location within a server rack, the higher the temperature and for lead acid UPS batteries, a 20-25°C (or less) ambient inside the rack is recommended to ensure battery life and performance. If in doubt the UPS should be installed with its own external temperature sensor (if available) or a suitable environmental monitoring system installed.
Location distance to the UPS load to be protected should also be considered. Longer cable runs can lead to voltage drop (and potentially interference) and it is good practice to install the UPS as close to the loads to be protected as possible.
In Centralised UPS installations, where a single UPS power a complete room or facility, such as a server room or data centre, additional power distribution should be considered alongside installation of a UPS maintenance bypass. For reference a decentralised UPS installation is one where each location has their own UPS i.e. one UPS per server rack or data cabinet.