I'm the sole IT administrator for a company building a new facility with one MDF and two IDFs. The IDF racks already have battery backups, but I need to choose a UPS for the main rack.
The rack will contain a dual-CPU Dell server with two Intel Xeon Gold 5315Y processors, three Hyper-V virtual machines, and 8–10 drives; four 48-port PoE switches; approximately 21 UniFi cameras, six wireless access points, and 15–20 VoIP phones; dual firewalls; a network video recorder with 12–16 drives; and possibly a backup appliance, modems, and other equipment.
The current plan includes standard receptacles and a dedicated 20-amp circuit. Since construction is still underway, I may be able to request a 208-volt, 30-amp locking receptacle instead. I'm not very experienced with calculating power usage, so I'd appreciate guidance on the required UPS capacity, voltage, runtime, and suitable models.
I'm also unsure how to handle smaller 120-volt devices such as modems, cellular failover equipment, sensors, and other single-cord gear if the primary UPS uses 208 volts and rack PDUs.
5 Answers
Before selecting a model, get the rated or measured draw for each power supply and determine what will actually be powered by that circuit. The PoE switches may be a substantial part of the load, especially with cameras and access points attached. Don’t size the UPS solely by the server’s specifications or by the total of every label; real operating load is the useful number, with extra capacity reserved for startup and future changes.
Since the building is still being designed, this is a good opportunity to plan the whole room rather than only the UPS. Consider a properly grounded, floor-anchored cabinet, enough front and rear clearance, overhead cable support, and dedicated cooling or at least a reliable way to remove heat. If possible, have two locking 208-volt, 30-amp receptacles installed from separate sources or panels.
A common setup is a UPS with an L6-30 input, two vertical rack PDUs, and dual-power-supply equipment connected to both paths. One PDU can be UPS-backed while the other is connected to utility power, or both can be UPS-backed depending on the design. For single-cord critical devices, a rack automatic transfer switch can take inputs from both PDUs and provide one output.
208-volt rack UPS systems generally don’t mean that every device must be 208 volts. Most servers, switches, storage systems, and other enterprise equipment accept 100–240 volts automatically; you use the appropriate power cords and PDU outlets. Check each device’s input rating before connecting it.
For small 120-volt, single-cord equipment, you have a few options. Some rack PDUs provide compatible 120-volt receptacles, provided the UPS output and PDU are designed for that voltage. You can also use a listed rack automatic transfer switch or a small separate 120-volt UPS for non-rack devices. Avoid improvised adapters or plugging equipment into a receptacle with the wrong voltage. A separate small UPS is often simplest for modems, cellular failover gear, and miscellaneous devices, unless you specifically need them on the same battery and monitoring system.
Start by measuring or estimating the actual wattage of every device, rather than adding up the maximum ratings printed on the power supplies. Leave meaningful headroom and size the UPS by watts as well as VA. A 120-volt, 20-amp circuit is probably too limiting for this rack once the server, storage, PoE switches, cameras, and phones are all operating. If construction allows it, a 208-volt, 30-amp circuit gives you considerably more usable capacity and is the direction I would pursue.
An Eaton 9PX 2000 RT, potentially with external battery modules depending on the runtime you need, would be one reasonable starting point. Vertiv/Liebert GXT5 units are also well regarded. Runtime should usually be based on safely shutting down equipment or riding through short outages, unless the building has a generator—in which case you may only need several minutes.
I’m going to ask whether the 208-volt circuit can be added while construction is still underway. Power calculations are the part I’m least comfortable with, so I’ll inventory the equipment and measure the expected load before choosing the UPS.
For UPS brands, Vertiv/Liebert GXT5 and Eaton 9PX are solid options for this kind of small server room. Larger systems such as a 10-kilowatt 208-volt UPS are usually unnecessary unless your measured load or future expansion justifies them. An external battery cabinet increases runtime, but it doesn’t increase the UPS’s power capacity, so determine the watt load first and decide how long the rack must remain online afterward.
The cabinet is already a 48U unit and will be anchored in the center of the room. I’m still working through the cooling plan and the difference between 208/220-volt distribution and ordinary 120-volt outlets.