Uninterrupted for a gas heating boiler: tips for choosing a UPS with an external battery

Redundant power supplies are required when operating devices that are not desirable to be disconnected. One of these types of appliances is a gas boiler. If the power goes out, the heating is turned off along with it and the radiator batteries cool down. It will take additional energy and time for the room to reach the optimal temperature again. This can be avoided by using an uninterruptible power supply for a heating boiler.

Types and principle of work

An uninterruptible power supply (UPS) is a device designed to provide the connected load with electricity even in the event of a power failure. The principle of operation of the device is based on the ability to work in two modes: direct and autonomous.

If the voltage in the mains is in the range of 205-235 volts, the UPS operates in repeater mode. As soon as the tension goes beyond the permissible limits,

the device disconnects the input circuit, and the load is powered by a backup power supply. Rechargeable batteries are most often used as it.

Thus, a UPS is inherently is an inverter with charger. When there is voltage in the network, the load is supplied and the batteries are recharged at the same time. But if the voltage of 220 volts at the input disappears, it instantly switches to battery operation. Since the power supply unit of the boiler needs an alternating voltage of 220 volts, and on the battery it is constant, then an inverter is used to obtain the desired signal shape.

Backup power supply

Uninterruptible power supplies (UPS) are produced in various designs and types, but the main units in all models are the same. The principle of operation depends on the design type of the product, but its main provisions are as follows: variable voltage through the rectifier unit is converted into a constant, after which it is reduced to the required value for charging the battery batteries.

In the case of switching to autonomous mode, the charging circuit is disconnected, and the voltage from the battery begins to flow to the inverter. It converts a constant signal into an alternating one, which is then raised to 220 volts and fed to the output of the UPS.

That's why highlight the following blocks:

1. Input filter. The device usually uses a filter of the simplest type, consisting of a coil and capacitors. Its purpose is to prevent the penetration of noise into the electrical network and to smooth out the oscillations of the frequency converter.
2. Rectifier. The UPS uses a full-wave design. It consists of four semiconductor diodes connected by a bridge and smoothing the signal of an electrolytic capacitor designed for a voltage of 450 volts.
3. Charger. It includes a converter and a charge controller, which provide the necessary parameters for the accumulation of energy by the battery.
4. Inverter. Converts constant current to alternating current, while changing the voltage level. That is, in fact, it is a signal generator. The pulses generated by it are fed to the transformer, from which they are already supplied to the load.
5. Commutation. Designed to switch UPS operating modes. High-speed relays or field-effect transistors operating in the key mode are used as switches.
6. Output filter. Consists of inductors and capacitors. Its task is to remove parasitic harmonics from the output signal in order to bring the signal shape closer to a sinusoid.

Types of devices

All UPSs are divided into three large groups. Therefore, when choosing a UPS for a gas boiler with a battery, first of all, it is necessary to select the correct type. This is due to the fact that the electronics used in heating devices are sensitive to the shape and quality of the signal. Due to the fact that the UPS performs signal conversion, not all of its types can provide a pure sine wave at the output.

There are three types of uninterruptible power supplies:

1. Off-line (backup). This is the simplest of all types of devices and, accordingly, the cheapest. It is characterized by a non-sinusoidal output waveform when operating on battery power. Does not have the ability to adjust the frequency and stabilize the voltage. Switching from one operating mode to another takes about six milliseconds. Among its advantages are: noiselessness and low heating. The main purpose of this type is for use in home-level computer systems. In heating systems, this type of UPS is not used.
2. Line-Interactive An improved type of backup uninterruptible power supply due to the inclusion of a voltage stabilizer in its circuit. The signal is stabilized in a stepwise manner using an autotransformer. The output signal is close to sinusoidal, but there are also trapezoidal and rectangular models. It is characterized by an acceptable switching time of the operating modes. Has a high efficiency. But due to the use of a classical type of transformer in the circuit, to connect powerful devices to this type of UPS, it is necessary to increase the frequency of the signal. And this approach makes its use undesirable in conjunction with heating systems.
3. On-line (double conversion). The work is based on double signal conversion. First, alternating current is converted to direct current, and then back to alternating current. The scheme of operation of this device is built in such a way that the batteries are constantly on. Therefore, if the input signal is lost, the device does not need to switch to another operating mode. The main advantage of this type is the pure sinusoidal waveform of the output signal. In addition, the advantages include the ability to adjust both voltage and frequency. That is, it can perform the functions of a full-fledged stabilizer. The disadvantages are the low efficiency, not exceeding 94%, noise and noticeable heating. The price for such devices is 2-3 times higher than for the previous types. But at the same time, such an uninterruptible power supply for heating boilers will be the best option.

Criterias of choice

When choosing, you need to pay attention to the power of the UPS planned for purchase and the time of its autonomous operation. Modern boilers are necessarily equipped with a pump, and powerful models that give heat more than 25 kW, even several.

The heater in normal operation with one pumping device consumes about 150 W of energy. Therefore, taking into account the generally accepted recommendations that the power of the UPS should exceed the limit value of the boiler consumption by 25-30%, an uninterruptible power supply of 250-300 W will be needed. Accordingly, if two pumps are used in the boiler, then the power of the UPS should already be about 400-500 W.

The autonomous operation time depends on the type and number of batteries used, as well as on the power of the boiler. If only short-term power outages occur, then attention should be paid to models with two batteries with a capacity of at least 30 ampere-hours. This will allow the device to work without power from the mains for 10 minutes at a power consumption of about 150 W. And if the power outage happens quite often and for a long time, then the best way out is to purchase an uninterruptible power supply for a boiler with an external battery.

The calculation of the autonomous power supply time can be carried out according to the following formula: T = C * Ub / Pk, where:

• C - battery capacity, A / h.
• Ub - battery voltage, V.
• Рk - heating boiler power, VA.

To convert electrical power from watts to volt-amperes (VA), watts must be divided by 0.7.

But at the same time, you should be aware that although there are no special batteries for the UPS, it will be wrong to connect any battery to it.

This is due to the fact that it must not only match the voltage, but also allow the charger to charge it within an acceptable time frame. After all, the larger the capacity, the more current will be needed to fully charge the battery. So, for a battery capacity of 100 Ah, a charge current of 10 A is required, while the full charge time will be about seven hours.

In addition, it is necessary to select a device whose output waveform will be as close as possible to a sinusoid. Manufacturers usually indicate this in the documentation for their product. If suddenly the instructions say "quasi-sinus" or "approximated sinusoid", then such a UPS is unsuitable for working with a boiler.

additional characteristics

In addition to the main parameters, there are also minor ones, while for some users they may also be important. For example, the presence of a cold start function in the product will allow the boiler to start even if there is no mains voltage.

This function is very useful when using UPS for gas boiler with external battery. Since it makes it possible, during a prolonged power outage, to connect an additional set of batteries in the event of a discharge of the main one and start the heating system again. Naturally, the additional kit must be pre-charged before this.

Additional characteristics include:

1. Voltage range. This parameter characterizes the limits, exceeding which will lead to switching the UPS into autonomous operation mode. At the same time, it should be noted that if the voltage surge is quite large, then a good uninterruptible power supply will simply turn off, going into protection mode, and not a very high-quality one will burn out. Therefore, for overvoltage protection, special devices are used, for example, circuit breakers or voltage relays.
2. The number of outlets. If the power of the UPS allows, another device can be connected in parallel with the boiler. But here it should be understood that the battery life will decrease.
3. Availability of indication. The bulk of uninterruptible power supplies contain in their designs an indication of the transition to battery operation. It can be: light, sound or combined. It is best to purchase devices that allow you to adjust the degree of indication, since at night the UPS alarm can be inconvenient.
4. Execution type. Distinguish between floor and wall type.

Popular manufacturers

The range of backup power supply devices in retail outlets is very large. When choosing, they often pay attention to the country of origin, but this is not entirely correct. It is much more important to choose not by country, but by the name of the brand and model.

It should be borne in mind that even the leading companies can have unsuccessful product lines. Although well-known companies cherish their reputation and guarantee compliance with the declared characteristics of the real ones. They fully provide warranty and post-warranty support, having official representations in many countries of the world.

The most popular companies are: Phantom, Volter, Teplocom, Vir-Electric, LogicPower, SVEN. But at the same time, there are other manufacturers whose UPS models are also at the proper level. Big name companies strive to improve their products, use quality parts and conduct meticulous pre-sales tuning.

Here is a list for an example well-proven models with the ability to connect an external battery:

1. Teplocom-300 - for boilers with energy consumption up to 200 W.
2. LPM PSW-500 is a reliable uninterruptible power supply with a two-year warranty.
3. Phantom UPS-0512 is a quality pure sine wave UPS.
4. SVEN RESERVE HOME-500 - for heating systems with average power consumption.
5. VIR-ELECTRIC NB-T102 - for boilers up to one kilowatt.

Of course, you can find quite cheap options in stores, but, most likely, these will be Chinese "non-names" assembled from low quality components.