How to choose a UPS for the boiler

In one of the previous articles, we considered several options for providing gas heating boilers with uninterrupted power supply. The most rational, in terms of economy, is the use of a UPS uninterruptible power supply, where the battery is used as the energy source.

Today, in the Uninterruptible Power Supply-UPS market, there are 3 main types of devices - on-line, off-line and line-interactive UPS. In this short article we will try to figure out what is the difference between these devices, which one is better, the advantages and disadvantages of each of the devices.

Before we begin to analyze the advantages and disadvantages of the UPS, you must determine the degree and importance of the equipment that will power the UPS.

In order to determine which device you need, answer a few questions that will facilitate the further selection of the UPS.

1) For what other equipment, in addition to the gas boiler, the constant availability of electricity is necessary. Such equipment can include additional circulation pumps for the heating system, alarm, etc., that is, equipment that ensures the life of the house.

2) For a more accurate selection of the UPS, you need to know the quality of the electricity. To be precise, the upper and lower thresholds for voltage, how much and how often the light “jumps”.

3) It is necessary to know the power of the equipment that will “power” the UPS. When calculating power, we must not forget about induction loads. Such loads include, in particular, motor-circulation pumps. At the time of starting, the engine consumes 3-6 times more current. Most UPSs are designed for short-term overload, but still it is better to be safe and take the UPS with a margin of 25-35% of the planned capacity.

4) Determine the approximate battery life of the equipment from the UPS, the final cost of the equipment directly depends on this. Indeed, 80% of the cost of a UPS is a battery (battery), on which, in fact, depends on the duration of battery life.

Consider UPSs from simple to more complex models.

UPS off-line. Of the listed devices, these are the simplest and cheapest models. The principle of operation is approximately the following: when the voltage in the network disappears or exceeds the permissible limits, the UPS switches to battery. When a voltage appears in the network, the device automatically switches from the battery to the network. The switching time for the UPS is 10-15 ms, which practically does not affect the performance of consumers.

Such UPS consists of an inverter that converts the constant voltage of the battery to 220 V, and a network voltage controller. Most off-line converters operate on mains voltages in the range of 170-270 V. Such converters do not have a voltage stabilizer, so the voltage at the output of the device is the same as in the network.

If the mains voltage constantly “jumps”, the UPS will constantly switch to the battery, which significantly reduces the service life of both the batteries and the device itself. UPS In addition, as practical experience with these devices shows, not all UPSs off-line work correctly with gas and diesel generators.

Line Interactive UPS. This is the middle segment among UPSs both in price and in work. Functionally linear-interactive UPSs perform the same function as off-line inverters, but the device already has a voltage stabilizer, which makes using the device safer for devices that are powered by a UPS.

Depending on the model of the UPS, the voltage in the network can range from 170 to 270 V.Like off-line UPSs, not all line-interactive UPS models work normally with generator sets.

Online UPS. There are no shortcomings of the two previous UPS models. In the on-line UPS, the input AC voltage is converted to constant, regardless of its quality, then the constant voltage is converted to stabilized alternating voltage.

A huge advantage of these models is that online UPSs work perfectly with generator sets, which is especially important where often and permanently disconnect electricity and where mini-power plants are used as an alternative source of electricity.

These devices are quite complex in design, which could not affect the final cost of the device. The use of this type of UPS is justified where voltage surges are undesirable, where equipment is particularly sensitive to the quality of the power server, medical equipment, etc.

Summing up everything that is written above, you can decide on the choice of UPS for boiler equipment (gas and solid fuel boilers). In most cases, an off-line or line-interactive UPS is sufficient. But if electricity is often and permanently turned off and a generator set is used as an alternative source of energy, then it is better to use online UPSs. In any case, before purchasing a UPS, consult a specialist.

Sergey Seromashenko

Installation of the inverter for the boiler on the video: