How to choose a UPS

An uninterruptible power supply (UPS) is used for the stable operation of equipment in the home or office, and to maintain its functioning. It helps to stabilize the voltage in the network, for example, if you connect a computer to the device, then a certain time will appear to save data in the event of a power outage. The purchase of models with a large battery capacity makes it possible to support even heating systems in a private house. It is important to understand how to choose a UPS so that it can perform its basic functions.

The structure and principle of operation of the UPS

Before deciding which UPS to choose, you need to familiarize yourself with the device as a whole, as well as the principle of its operation. Among the main components, various modules are distinguished:

• power;
• distribution;
• control;
• management;
• indication;
• accumulators.

A similar technique works according to the following principle:

• If there is a stable voltage in the network that meets certain limits, then current is supplied to the output of the UPS. This allows the internal batteries to be kept charged from an external power source.
• As soon as the light turns off, the power is lost or it can significantly deviate from the nominal power, in which case the activation of the equipment output to the inverter begins, which gives current to household appliances from the batteries.

The duration of operation is determined by the battery capacity as well as the efficiency of the built-in inverter. An important factor is the power of the equipment used, which is powered by the UPS.

UPS selection options

To understand how to choose an uninterruptible power supply, you should understand its basic parameters.

Power

When choosing the power of the UPS, one should be guided by a similar indicator, but for all equipment that will be connected. To do this, it should be understood that the power of household appliances is measured in W, and the uninterruptible power supply itself is in VA.

To understand and simplify the calculations, you will need to multiply the total power of the product by 0.8. For example, if a 600 VA model is on sale, then you can connect devices that consume 480 watts.

In addition, the starting current for the technique should be taken into account. Often, all equipment will have more power than the connected devices, by about 20-40%. For some people, it is important to connect several types of equipment at once, so you will need to allocate the nominal consumption in total for all equipment.

Efficiency

Due to this indicator, the consumer can understand how effective the UPS will be. If you choose weak devices, then the effectiveness will be low, which means that there will simply be costs without efficiency. To calculate, you need to divide the output power by the input power and multiply by 100%.

As an example of the effectiveness of UPS applications, experts identify the following parameters:

• With a UPS power of 800 W, and the main equipment, which is connected at 300 W, the use of equipment will be ineffective. About 70 W is spent on providing the equipment, from which 41% efficiency is obtained.
• A good example is that with a similar UPS, a household appliance will consume 650 watts. In this case, the ratio will be 89%.

Battery life

With this value, the user is able to determine the duration of the device when the light is turned off. The period of operation directly depends on the capacity of the batteries, as well as the load consumption. Often household models can work in a small range of 4-15 minutes, but this is enough to save data on a PC or perform other manipulations.

Connectors

When choosing a power source for yourself, you should immediately determine the number of required outputs to which the equipment will be connected. In addition, they must match the input in the home appliance. Many models have these connectors:

• To be connected to a 220 V.
• To protect network or telephone lines.
• To control the module using a PC.
• For diagnostics or control using USB, COM ports.

There may also be sockets on the case that help connect to the battery using a standard plug or IEC cable. It is possible to connect to the module bypassing the batteries.

Other selection options

Among the rest of the selection recommendations are the following:

• When considering how to choose a UPS for a computer or other equipment, you must choose different outlets. They can be European (CEE 7/4) or computer type (IEC-320-C14). It is recommended by experts to choose combined devices, since at home this type of equipment can be useful everywhere.
• In addition, you need to make sure that the case has a removable unit for battery replacement without additional effort. This is due to the fact that the average period of work is up to 5 years. If there is no such function, then the device will need to be sent to the masters for repair.
• An equally important parameter for choosing an uninterruptible power supply is indication. It helps to see the data on the operation of equipment, the remaining battery charge, as well as modes. It is often performed in the form of diode indicators on inexpensive models and in the form of a screen with detailed display of data in models of medium and high cost.
• Having at least one USB socket will help you quickly save personal data on your PC automatically. For this purpose, special software is intended, which is very convenient to use. The function helps to save unfinished work when the lights are turned off, even if there is no person nearby.
• RJ11 and RJ45 ports help protect your network or phone line from heavy loads. This function may be required by some people, it is often available even in budget equipment.
• The bypass mode bypasses the inverter inside the UPS and supplies power directly from the mains. In this case, users can carry out repair work without disconnecting household appliances from the power supply. When the grid is functioning normally, the load from the inverter can be transferred to the bypass to reduce current consumption.

Types of uninterruptible power supplies

Many versions of the UPS that can be found at the point of sale are manufactured in China. The quality is not always at its best, so it is important to understand the best brands and types of devices. Experts advise using equipment from trusted companies that guarantee high quality:

• APC;
• Powercom;
• Ippon;
• P-Com.

Below are the main types used at home with all the pros and cons. This will make it possible to disassemble which UPS to choose for a computer or a boiler.

Reserve

Such models are the simplest and most common among the possible options. Most of them are used for computers, but other devices can also be connected. It is often customary to use switched-mode UPS for PCs, since they can compensate for the shortest network drops. This is due to the small amount of energy stored in the internal capacitors.Since the minimum delays during the transfer of current from the mains to the battery are not critical, backup models can be used.

When a personal computer is connected to this unit, a person gets a few minutes in stock to save important data or unfinished work. In addition, when the light is turned off, it will be possible to correctly close programs and turn off the PC.

The reserve type is suitable for a stable network where there are no current surges or they are minimal. If used in networks with constant interruptions, the batteries will quickly discharge and fail. Therefore, they will need to be replaced. On average, the price of such a device is in the range of 2.2-4 thousand rubles.

Pros:

• The design is one of the simplest.
• Affordable cost.
• Low electricity costs for maintenance.
• Virtually silent operation.

Minuses:

• There is no built-in current stabilizer, so it is not recommended to use the models in case of constant network failures.
• The battery cannot be quickly recharged in the event of frequent switching, and therefore the battery life is reduced.
• The switch is activated in approximately 6-20 ms, which can have negative consequences for some household devices.

Line-interactive

These models are considered better than conventional backup sources. They are characterized by stable functioning. Inside, manufacturers install an automatic transformer that can stabilize the voltage by compensating for its fluctuations. Switching between mains and battery is reduced to a minimum due to the installed inverter with converter. They are also connected to the output channel.

The main distinguishing feature of this type is that the nature of current consumption does not change during the stabilization of the voltage before it is distributed to the connected devices. The principle of operation is the same as for backup devices. In the presence of power supply and voltage, power will be supplied from the mains. As soon as the light is cut off, power is conducted by the inverter from the battery, and the input switch will open. In addition, if there is current, but it does not correspond to the rating, then the equipment switches and stabilizes the current without using a battery.

Line-interactive options are best suited for places where the current does not differ much from the nominal. The price of this device can be completely different, starting at 2,500 rubles and going up to 177,000.

Pros:

• Large price range, which will allow you to select options for certain parameters at an affordable price.
• The highest efficiency of the device in comparison with other types. The efficiency of this device is at the level of 96-98%.
• At the output, a sinusoidal voltage is given, which allows to reduce voltage drops, as well as pulses as a result of switching charging from the mains and the battery.
• Provides power to household appliances even with reduced or increased current in the network without switching to battery operation. This helps to significantly extend battery life.
• During operation, the housing is minimally heated, and a minimum of structural parts are involved in the operation. This solution helps to increase the level of reliability and increase the life time.

Minuses:

• Switching power supplies is carried out within 6 ms.
• Medium protection when comparing double conversion options.
• Poor performance for noise filtering or current suppression.

With double converter

Such devices allow you to convert energy 2 times. Initially, the alternating current is completely converted to direct current, after which any distortions are eliminated with transfer to alternating current. If the parameters of the alternating voltage do not correspond to the required rating, then the device operates on battery power, but the switching is almost instantaneous. During this process, the inverter is powered through capacitors, which provide a constant supply of output current to the devices.

In addition, models in this segment can stabilize power. The devices are considered the most expensive on the market. The starting price is 16,000 rubles and ends with 171 thousand rubles.

Pros:

• At the output, you can adjust the frequency, as well as make a partial conversion.
• Small weight and size.
• In spite of the load, the power is compensated.
• When there are strong current fluctuations in the network from standard indicators, the devices rarely operate on batteries.

Minuses:

• High electricity consumption.
• Substantial heat release, for which it is necessary to consider the removal.
• Many elements are installed inside, and with an increase in their temperature during the operation of the UPS, the reliability and durability of the devices decreases.
• Average efficiency compared to line interactive UPS. Based on the specific model, the efficiency is 85-92%.

Which uninterruptible power supply to choose

There are some simple guidelines for choosing that will make it easier to find a product. So, we choose a UPS for a boiler, computer and other equipment:

• In the case of low power equipment, for example, a PC or a fax machine, you can buy backup UPSs, which give a small margin of time after a power outage.
• If the PC is gaming or powerful, then you should take sources that will be 30% stronger than the power indicators of the computer.
• For a gas-fired boiler with electronics, which is needed to maintain all heating, devices with a capacity of about 40% more should be used for the reserve.
• For comfortable operation, it is better to choose products that have the ability to quickly replace the battery without outside help. Their durability is small, usually 3-5 years.
• For heating boilers, pumping equipment, backup models are suitable, but in this case a voltage stabilizer or other devices that protect against heavy loads, for example, relays, should be used.
• Double conversion models can be connected to boilers without the use of stabilizers. The same is permissible with the line-interactive technique, since the devices automatically equalize the voltage. The output should be a sinusoidal waveform.
• In a country house or a private house, where various boilers, pumps and other equipment are actively used, it is better to buy a line-interactive UPS, you can put a constant operation if the power is calculated correctly.

Frequent mistakes of buyers

If you make a mistake with the choice and purchase of an uninterruptible power supply, then there may be a problem with frequent battery replacement. This is because the voltage is constantly jumping, so inexpensive devices will often switch to battery operation, which will reduce battery life. It is in this case that it is better for a person to choose options of the linear-interactive type.

Often, users quickly buy equipment, but you need to carefully calculate the total power of all devices, otherwise, if the UPS is overloaded, it will not work, but will turn off.

In order not to be disappointed in the choice, remember that double conversion models are loud, therefore, they can cause trouble after the start of operation. The described tips and basic parameters of the UPS will help you choose a model for a PC, pumping equipment or boilers.