The recording does not survive the cut by chance.

The job of a UPS looks obvious and it is not. What it does is not «keep the lights on»: it is give you a while of power. What you do with that while is the engineering decision, and there are two valid answers and one invalid one. Valid: hold out until a generator starts, or shut the system down in an orderly way before the battery runs out. Invalid: wait for the power to come back, because that does not depend on you.

In a video installation this weighs more than in almost any other, for a simple reason: a power cut is not the moment when the recording is least needed. Cuts cluster around storms, around faults and sometimes around a deliberate act, and those are exactly the times when somebody is later going to ask for the images. A video system that switches off with the power does not have a gap: it has the gap.

The minutes on the datasheet are measured with a particular load, which is usually a fraction of what the device can deliver. The useful question is how many minutes it gives with YOUR load, and the relationship is not proportional: twice the load gives a good deal less than half the time, so intuition misleads you towards the bad side.

And there is a surprise in what «your load» is. In the cabinet of a video installation the biggest consumer is not usually the recording server: it is the switches that power the cameras, and forty cameras with heaters on a frosty night ask for their maximum exactly when it suits you worst. Sizing the UPS by looking only at the server is the most common mistake of all.

And the runtime falls with the years: the UPS that gave more than enough in the first year can be giving half without anyone having changed anything. So the calculation is done the other way round: first how much time is needed and what for, then the real consumption of the cabinet, and last the equipment with a margin. If the number comes out tight on installation day, it is wrong.

What goes on: the server or recorder, the storage, the switches that power the cameras that really matter and —this gets forgotten half the time— everything on the path to the outside. A live recorder with a dead router cannot alert anybody, so the communications equipment and the alarm transmitter go inside.

What does not go on: the monitors at the desk, the printer, somebody's laptop charger, a fan, a heater, and in general anything with a motor or a heating element. Every watt plugged in there is subtracted from the minutes the recorder will have, and a large monitor hung on «because there was a free socket» can take an appreciable part of the whole cabinet's runtime.

It is not a theoretical rule: it is the most frequent finding when we inspect somebody else's installation. That is why the list of what is connected is left stuck inside the cabinet door, on paper and dated, where whoever is about to plug something in will see it.

And a separate warning: if the UPS already exists and powers other company equipment, the video's runtime depends on decisions taken by another department. A shared UPS with no written agreement is not a UPS for the video.

If the battery runs out and the server switches off at a stroke, three things happen and none of them is good. The recording index —the thing that knows what is recorded and where— can be left half written, and an inconsistent index is video that is on the drive and cannot be found. The file system needs checking on start-up, and on a large set of drives that can take a long time, and during that time nothing is recorded. And what the drive controller had pending to write is lost.

The difference between that and an orderly shutdown is a cable and a while of configuration: the UPS has to be able to tell the server it is running on battery, and the server has to shut itself down when a few minutes of reserve are left. With that, a long cut is a clean shutdown and a normal start-up: you lose the video of the while without power, which is unavoidable, and nothing else.

That piece is one of the cheapest in the project and the one most often missing, almost always for the same reason: the UPS was fitted by the electrician, the server was fitted by the IT person, and the cable joining them belonged to neither of them.

And it has to be tested by really pulling the power: that the server shuts down when it should and that when the power comes back it starts on its own and records again without anyone touching anything. That last one fails more installations than you would think, because many servers sit switched off waiting for somebody to press a button on Monday.

Batteries are wear parts. They do not fail all at once: they lose capacity gradually, and they lose it faster the hotter it is where they are —the same hot cabinet that punishes the switches—. The result is a device that says it is fine, because while there is mains power nothing gives the problem away, and that on the day it is asked for ten minutes gives forty seconds.

That is why the load test is not optional: really pull the power, with the installation running, measure how long it holds and write it down with the date. Two tests a year apart say more about the batteries than any indicator on the panel. And the replacement is planned: it is a line in the maintenance budget, not an incident.

What does help is the monitoring side: a management card that puts the UPS on the network and lets it raise alerts —the power has gone, it is on battery, the battery is due for replacement—. Those alerts are taken to the same place the security system's alerts arrive, so that whoever is on duty sees them and not a mailbox nobody opens. And a temperature probe in the cabinet is the cheapest part of the installation and the one that warns of the problem that eats the switches and the batteries at the same time.

In the recorder's cabinet, always, whether the installation is large or small. In the intermediate cabinets that power cameras when those cameras have to keep seeing during a cut —and that depends on what they are there for—. On the path to the outside, so that the ability to raise an alert survives. And in the cabinet where the link between buildings lives.

And the part that is not the UPS fits too, and gets forgotten: a metered cabinet strip tells you how much that cabinet really draws, which is the figure everything else is sized on.

A UPS is not a generator: it gives minutes, not hours. Where the recording has to continue through a long cut, the answer is a generating set and the UPS moves to covering the gap until the set starts. Selling hours of runtime on batteries is expensive, heavy and almost always a bad idea.

A UPS is not the building's electrical protection. It helps with the ups and downs of the mains, but surge protection is the electrician's work, and in installations with cameras outdoors it is essential: the storm that takes the equipment out almost never comes in through the socket, it comes in through the network cable from outside.

A desktop UPS is not the UPS for a cabinet with a recording server and switches: it gives a few minutes with a small load, it has no way of telling the server and its batteries run down sooner. We have found it more than once. And we would not fit it without the runtime calculation, without the list of what gets connected and without the orderly shutdown tested. A UPS fitted without those three things is an expense that gives peace of mind and does not give recording, which is the worst possible combination.

The client's IT team runs the part that is visible from the network without trouble: read the UPS status, receive its alerts, see the consumption of the strips, switch a socket off remotely, look at the temperature probe. We leave them the console, their account with their password and the alerts directed wherever they want. Battery replacement also stays in house, with the calendar we hand over: what equipment there is, with which batteries and when they are due to be looked at.

The boundary is in three things that are not console work. The runtime calculation when load is added, because every new camera and every new switch changes the minutes and that is recalculated, not estimated by eye. The orderly shutdown chain, because touching it badly leaves a system that looks protected and gets cut off dead. And everything before the socket —board, protection devices, earthing—, which is an electrician's work with their signature on it.

And if you already work with another UPS brand and have a maintenance contract, there is nothing to change. In power, even more than in networks, the brand decides little: what decides is the runtime calculation, the list of what is connected, the orderly shutdown tested and the battery calendar. We do that on the equipment you already have, and if it does not give the minutes needed, we tell you how many it does give and with what measurement, and before signing.