Clearly in security applications and where recording may be the only evidence of a crime, continuity of power is essential. A security guard may spot somebody on CCTV and raise an alarm, but the evidence is the recording itself. An Uninterruptible Power Supply (UPS) provides the continuity of power required. In this article we’ll take a HikVision DS-7732NI-K4/16P Network Video Recorder as the basis for our UPS selection. A quick look through the NVR manual and page 5 “Preventive and Cautionary Tips” recommends you use a UPS, so don’t just take our word for it.
For our purposes here we’re going to assume we fit 2 hard disks and have 12 Power Over Ethernet (PoE) devices connected to it. Our system is installed in a remote unmanned building and we require alerts in case of power failure and 2 hours of backup to allow somebody to attend site.
To specify a UPS, firstly determine the power consumption of the NVR. After trolling through a lot of specifications, some give the maximum power ratings and others give minimum power ratings. The minimum power ratings are specified without HDD (Hard Disk Drives) or PoE (Power Over Ethernet) ports. A little bit of arithmetic is required but we’ll use the minimum power level as the start. From the product data sheet take the minimum power level which we’ll call PMIN.
Eg for the HikVision DS-7732NI-K4/16P,
PMIN = 20W
Actually it is ≤ 20W (less than or equal to) but since we don’t know exactly we’ll use 20W.
How many hard disks do you have installed? Each HDD will take a maximum of 15W, so multiply the number of disks by 15. We’ll call this number PHDD.
Eg, The HikVision DS-7732 can take 4 hard disks but we’re only going to use 2 in this example. We have
PHDD = 2 x 15 = 30W
How many IP ports are PoE and how many are you using? If you’re not using PoE then skip this part. Each PoE is rated at 12½W or 15W depending on the system and this will give you a maximum figure. You may over specify this way so it may be an idea to gauge the actual power consumption of the connected devices. See the DLink website for help here. We’ll call this figure PPOE. If you have it from the attached devices then great but if not, use the number of PoE ports in use and multiply this by 15.
For example, our DS-7732 has 16 PoE devices of which in our imaginary scenario 12 are connected, so
PPOE = 12 x 15 = 180W
Now we add up all the power consumptions to get our total:
PTOT = PMIN + PHDD + PPOE = 20 + 30 + 180 = 230W
Now we have our total power we need to determine how long we need the system to run for. In some circumstances you may wish to cover for some momentary outages so a few minutes should suffice. In others you may need to have somebody remote attend site so several hours may be required. For our imaginary case, we need a minimum of 2 hours runtime.
Additionally, we need our UPS to fit into a standard 19inch rack along with our Network Video Recorder. We also require the ability to remotely talk to the UPS over a network so our HQ can be notified of a power anomaly at site.
Now we need to visit the UPS Selection Tool to find which UPS meets our criteria.
For smaller and lower powered Network Video Recorder applications, where basic protection is required, then lower cost VIX series products will work well. This is due to the fact that most NVRs will use Switch Mode Power Supplies (SMPS), or “computer type” power supplies that are suitable for use with square wave UPS. Although note that any runtimes over 30minutes should be used with a sine wave system.
Some small NVRs that are powered by a 12Vdc supply may also be powered by the iPower, offering a low-cost, zero footprint alternative.