Can I use a UPS for emergency power during rolling blackouts?

Yes, you can, but it isn’t cheap when it comes to repetitive daily power failures and thus not always the best option to use a UPS on its own.

A UPS can supply ANY load if it is sized correctly; however, it comes with a price tag and a backup battery that requires replacement every few year depending on use and number of discharges.

What can I power with my UPS?

When looking for a UPS system to backup your house, office or factory, you need to consider only the most essential items to put on it to keep your UPS inverter size as small as possible and hence the purchase price as low as possible.

Firstly do NOT add things like air conditioners, washing machines, pool pumps, hairdryers, fridges, stoves and all other heating and cooling devices.

A short and simple rule is that anything for heating or cooling either goes on to a generator backup or you use the sun or gas, for instance, the sun to heat water and gas to cook or heat your home and office.

Only put on your UPS sizing list critical items like electronics, PC’s, home and office audio visual equipment and screens and maybe a few LED lights for safety both at home and in the workplace.

Can a UPS power a motor or pump?

If you want to put any device on the UPS inverter that uses a motor or pump, you need to consult with your Standby Systems specialist so that it can be calculated into your inverter sizing. This is because when a motor or pump starts, it does not have what is called a soft start; so the supply to it has to provide up to ten times more power to start than when it is running. This is called the startup current, and it is vital to take this into account when sizing a UPS. The current power drawn from the UPS inverter while the load is running is called running current (Power).

Even your home PC when it starts up, will draw power of about 300 watts which will then drop to about 100 watts in a few seconds.

Why is calculating the startup current important?

Catering for the startup current is essential when sizing a UPS; otherwise, it will keep beeping UPS inverter alarms on every startup, and keep going on to UPS bypass. The inverter could blow up, and it will probably not be able to supply the startup current under power failure conditions, meaning the whole load will be dropped and go off.

It’s because of startup current that the UPS inverter is often only running at below 50% of its rated power capacity because it is sized to cater for the startup currents when those types of loads are connected to its inverter output, even your PC does this!

Where can I buy my UPS System?

In South Africa, the typical household language at braais and functions is:

What inverter system do you use?

Although the choice of available backup power product is very vast, when you consider purchasing a UPS system, you should also look at the availability of African based spare parts and technical knowledge.

Many a UPS user has purchased his dream backup system to cater for rolling blackouts only to find out in a year or two that the supplier either no longer exists or doesn’t have the spare parts and technical ability to repair the system.

The familiar words “uneconomical to repair” are a popular excuse by the sellers of these systems, when, in fact, it should mean “unable to repair.”

It is essential when buying a UPS system that you purchase from a well-known outlet that has been in the UPS business for decades and knows the market, the products, and their areas of use as well as possessing the technical expertise and personnel to repair these products in years to come.

There are many cheaper products other than the real brand names like AROS and RIELLO from Standby Systems in Africa. Many a user has been caught out in the long term with a product that they can’t be repaired. This includes a growing list of some well-known chain store outlets and retailers, selling cheap Chinese imports at excessively high prices with no local after-sales support and repairs.

What is the difference between short run-time and long run-time?

In the past, a UPS was there to cater for bad power, switching spikes and short power failures. This has drastically changed because of the ageing ESKOM power grid the common ESKOM practice of load shedding, which results in regular rolling blackouts that last for weeks at a time.

The UPS user is thus faced with the choice of whether to go with a UPS that has a short backup time and a standby generator – this means that the UPS battery backup will supply the UPS load while the generator is starting, making the transfer between mains and generator power for the load seamless.
Go with a long battery backup that will carry the inverter load for several hours, as happens with rolling blackouts.

Before deciding, it is important to understand the following about batteries:

  • 1. ALL batteries have a fixed. They have a guarantee of generally 12 months. Do NOT confuse the guarantee with design life.
  • 2. All batteries have an expected life use, called a design life, which is based on a long list of parameters which include the operational environment temperature, the number of discharges it experiences, and how much power is used of its reserves before it recharges. In short, batteries start to age and weaken from the moment they are put into use.
  • 3. All batteries that are discharged every day need to be sized completely differently from batteries that discharge now and again, even if both sizings are for the same period.

If you choose a long backup battery bank, the biggest portion of costs, by far, will be the battery portion.

Remember that the battery starts to age and degrade from day 1 of use and that, depending on its design life expectancy (which is usually about 3, 5, 8 or 10 years), it will fail eventually, either when that life expectancy is achieved or partially achieved due to regular use.

Most batteries used in long-run applications have a 3 to 5 year design life, so the user must be aware, upfront, that in as little as 12 months this battery, no matter what make or who the supplier is, depending on how its size is worked out for your application, will need a full replacement, if it is being discharged every day.

Of course, a full replacement battery bank of long runtime batteries comes with a hefty price tag.

In Summary

A short backup time UPS with a generator combination is still the lowest cost, long-term, for total cost of ownership and technically the best solution for long term emergency backup power.