Backup power how-to guide

June 2016 News

Power failures are an unfortunate but unavoidable fact of life. At the very least, they prove annoying and disruptive to our work and personal lives, but in the case of a security system, the consequences can, in extreme cases, literally be a matter of life and death. In most instances, therefore, backup power is not optional, but rather an absolute necessity.

Just as every security installation is unique, so too are its backup power requirements, and it can be a tricky balancing act weighing the desire to maintain power continuity against factors such as budgetary constraints. The good news is there is an array of solutions out there to suit every need, and Hi-Tech Security Solutions consulted two experts on the subject to put together this guide covering the most important elements to consider.

Step 1: Identify critical equipment

“Mission-critical systems for each organisation and institution differ,” says Pinnsec’s MJ Oosthuizen. “A good idea is to look at the two obvious elements of access and the securing of assets, which boils down to access control and key CCTV nodes. Fire alarm systems should always be on the top of your list for any redundant power design. Data access might or might not be defined as mission-critical, depending on the particular type of institution.”

As PSS Distributors’ Shane Griggs describes it: “Determining what is the most critical equipment that needs to continue operating in the event of a power failure depends on the user. Servers carry important data, while DVRs and cameras are used for safety and security. All devices considered a necessity should be supplied with backup power.”

As if dealing with power cuts wasn’t enough to worry about, the quality of the mains power must also be considered, since imperfect or unstable power can result in not only temporary equipment failure, but possibly permanent damage. “South Africa today unfortunately has a very unstable power grid,” Griggs explains. “When I say unstable, I mean on a daily basis we experience power conditions such as surges, spikes, dips, high/low voltages and blackouts. These power conditions are terrible for any electronic equipment, therefore one should always ensure that any electronic devices such as servers, DVRs and cameras are supplied power by a UPS. Distribution board surge arresters are also becoming very popular today.”

Oosthuizen clarifies that when an AC spike occurs, there’s basically ‘too much’ power available to equipment, and usually the components are not able to process the excess, therefore causing damage. He further points out that brownouts (power dips) are more common in South Africa than what we think: “How many times have you had a slight dip on your lights, and your devices reboot after that?” he asks by way of illustrating the problem.

“During a brownout, system component power supplies are essentially starved of the correct amount of voltage, therefore causing them to fail,” he continues. “Data loss or corruption is a more common result of this. Blackouts can also cause corrupted data files if a server or DVR/NVR is in the middle of a write cycle. Determining your key requirements, or at least the operational requirements for your site, will determine where your priorities should lie.”

Step 2: Calculate total backup requirements

Once the most critical devices have been identified, determining the power required by each is a simple matter of referring to their technical specifications. However, calculating total requirements is not necessarily as straightforward as simply adding them all together. “This all depends on the type of equipment,” Griggs states. “Should your equipment be a resistive or capacitive load, then yes, it is all a matter of adding the wattages together to get your maximum consumption. Computers, servers, switches, DVRs, light bulbs and ovens are all examples of these types of loads. If your load is inductive, you would have to ask someone that specialises in the field of power, such as a qualified UPS technician or power specialist. Examples of inductive loads can be copiers, laser printers, fluorescent lighting, air conditioners, fridges, etc.

“Should you have an array of various devices and they are all a combination of resistive and capacitive loads, simply adding the wattages proves more than ample to work out the size of the required UPS, inverter or generator,” he continues. “The specifications on the products specify a maximum wattage draw of that product. Without getting into the finer detail and to keep it simple, you can take the total wattage and add 20-50% to allow for future growth.

Oosthuizen boils down this part of the process to three steps. “The best way is to check your desired devices and see what you think you can live with (or without!) over a period of, say, four hours,” he explains. “Once you have established the equipment and the wattage that they draw, do the following:

1. Add up the nameplate power (found on the device) of the identified devices. If the wattage is not listed on the device, it can be determined by multiplying the current (amps) by the voltage of the device to get the VA, which approximates the amount of watts the device will consume.

2. Multiply the anticipated VA number by 0.67 to estimate the actual power, in watts, that the critical load will represent.

3. Divide the number by 1000 to establish the kilowatt (kW) load level of the anticipated load of supply.”

Step 3: Specify the backup power equipment

Armed with accurate backup power requirements, one is ready to go about specifying the equipment in which to place the trust that it will perform reliably when it’s needed most. The choices are many, and good advice at this stage can prove priceless in the long run.

“I normally look at the value of the equipment, how bad the power is in the area and how valuable the stability of the equipment is,” Griggs advises. “Considering a 1000 VA UPS as an example, an offline UPS may cost in the region of R700, a line interactive UPS R900, an online double-conversion UPS R3000, and an online double-conversion, transformer-based UPS R11000. All four do the same in principle, but they all have different levels of protection.

“You have two options when it comes to electronic equipment: either a UPS or a combination of UPS and generator. The reason for this is generator power may be unstable at times and cause surges, spikes, dips or high/low voltages; this needs to be regulated by using a UPS. Important to note is that the voltage regulator on some generators is not enough protection to regulate the voltage.

When it comes to the ratings that are most important, Griggs continues: “Wattage is important. Once you have the wattage, you can work out the VA; the calculation is wattage divided by the power factor of the UPS. Power factor depends on the type of UPS and should be included amongst the specifications of the UPS. Should a UPS have a 0.8 power factor, and the wattage draw is 500 W, it would mean that 625 VA UPS power is needed to supply power to the equipment.

“When it comes to resistive loads, your current draw is usually as specified on the name-plate rating. Capacitive loads are normally specified by the manufacturers as a maximum wattage rating, although the true load might only be 20-50% of what is specified. An inductive load also specifies the maximum current draw, however it does not specify the inrush current on startup of the equipment, which can be up to ten times the specified rating,” he warns.

Expanding on the topic of generators, Oosthuizen says the most important thing to remember is that not all are made equal. “Modern electronics are delicate devices and a power source that spikes all over the place is likely to fry that expensive HD TV on your wall,” he points out. “The two main types are standby generators and portable generators. Standby generators are big, fixed into position and take over supplying you with power when Eskom goes down. They’re expensive to install, but the idea is that you carry on as normal and don’t notice load shedding at all. Most household appliances require an alternating current (AC) power supply, which is what the spinning motor in an electric generator creates. But if you plug, say, a TV directly into a petrol generator, the fluctuation in the supply produced by the generator is likely to fry it.

“In an inverter generator, the AC power produced by the engine – which is likely to fluctuate in output dramatically and damage sensitive electronics – is pushed through a rectifier and turned into DC energy. This is then passed through a second circuit which flattens out the load and turns it into a nice, steady stream of power. It’s then passed through an inverter which turns it back into AC electricity. A suitably sized online ups will assist in serving as a current stabiliser for the period it takes the generator to start.”

Step 4: Installation

When it comes to installation, many would feel most comfortable leaving it to the professionals, but this is not always necessary, as Griggs explains. “It depends on what is purchased,” he says. “Should it be a plug and play system, installation is straightforward and a professional installer is not needed. If the unit is a plug and play unit, but the battery pack needs to be built, I would suggest a professional installer. Batteries are very dangerous and the DC voltage can cause very serious bodily harm, not to mention fire. Please note that any unit above 3 kVA needs to be hardwired to a distribution board, which can only be done by a qualified electrician.”

Oosthuizen advises to “keep in mind that whichever solution you opt for, your valuables, sometimes devices that are not fully paid for, should be protected and powered by the result of your decision. To opt for getting a professional to install rather than a quick DYI solution, more often than not changes the result from an expenditure to an investment.”

Step 5: Maintenance

Having gone to so much effort and expense, the ultimate tragedy would be to allow the lack of a proper maintenance regime to undermine a backup power system’s ability to do its job when it’s needed most.

“UPSs should be serviced at least once a year, ensuring that at all times the unit is fully functional and ready for any power conditions that may arise,” says Griggs. “Batteries should be cycled once every four to six months; the ideal is to have a periodic schedule. If the batteries have not been used, then we suggest switching off the power to the UPS, running the batteries down to battery low (the UPS will let you know when it is on battery low) and switching on the power. This assists with the longevity of the batteries. Another important factor influencing battery life is temperature: it is vital that the batteries operate in room temperatures in the region of 20°C.

“Generators at businesses or in complexes should run weekly for about 15 to 20 minutes. This will keep the generator in tip-top shape and will ensure that there are no problems in the event of power failures. Generators used in residential environments should run at least once a month to ensure the unit is always operational for when needed,” Griggs concludes.



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