How To Choose An Inverter For A Heating Boiler: Selection Criteria

Many modern heating systems are automatically controlled and require a constant supply of electricity to work properly. If there are regular power outages, experts recommend buying a backup generator. When the absence of electricity is rare and does not last long, it is enough to install a progressive inverter for the heating boiler.

It transforms the direct current coming from the battery into alternating current and allows the heating equipment to function fully for a certain time even in the absence of electricity. Let us have a closer look at the main characteristics of the appliance.

According to the article:

  • General characteristics of the appliance
  • Inverter power supply units
  • Design features of the product
  • How are the appliances classified?
    • The working principle of off-line units
    • How do the line-interactive units behave?
    • Peculiarities of on-line devices
  • Benefits and disadvantages of the equipment
  • Basic rules for choosing a module
  • List of popular models and manufacturers
    • Energy ETK
    • Elim-Ukraine device
    • Line-interactive deviceLine-interactive deviceLine-interactive device Line-interactive device Rucelf UPI-400-12-EL
  • Conclusions and a useful video on the subject

General characteristics of the device

The inverter is first of all a DC to AC converter. In parallel it changes the transmission amplitude and generates an output signal of suitable frequency. The device itself cannot charge the battery and monitor its current capacity.

Many modern manufacturers equip their products with accompanying elements, additional chargers and a controlling control unit. Such models are already classified as uninterruptible power supplies (UPS) and have the ability to solve a wider range of problems.

How to choose an inverter for a heating boiler: selection criteria

Boiler inverter equipment manufacturers give a big guarantee - 10 to 12 years with 600-620 active cycles and 80-83% battery discharge

Integrated into the heating system, they monitor the current presence in the network and, in case of a sudden power failure, keep the equipment fully operational for a while.

Thereby preventing the potential freezing of the water in the pipes and radiators (in winter), the breakdown of individual parts of the system and other unpleasant problems.

How to choose an inverter for a heating boiler: selection criteria

An inverter equipped with an additional battery allows the heating equipment to work long and well even in the long absence of central electricity supply

Simple, low cost products have only one direct function - to provide the boiler with energy to run for a certain amount of time. The sophisticated advanced modules have an extended potential.

In addition to their basic mission, they act as stabilizers and equalize the voltage in the system, thus protecting the equipment from overloading and failure.

Inverter power supply package

Inverters are available in several variants in the modern market of household related equipment. Some brands produce the simplest units that work only as voltage converters.

The battery is not initially included in such modules, but its connection is allowed by the design and the user can buy this element separately in the future.

How to choose an inverter for a heating boiler: selection criteria

Purchase the inverter equipment only at the regional official representative office of the manufacturer. There, in addition to the product, the purchaser will be given a warranty card for service and, if faults are detected in the first working days, the product will be replaced with a functioning one

Some types of inverter have a built-in battery of a certain, usually small capacity, but it is not possible to increase its capacity through external additional batteries.

Fixtures of this type keep the heating equipment running for a short time and mostly serve to allow the owner to properly disconnect the system from the electric Expansion of the capacity of the appliance is accomplished by the addition of external batteries. In this way the operating time is increased from a few hours to several days.

Product design features

The inverter has optimal dimensions and is shaped like a parallelepiped. It can be placed on the floor near the boiler or mounted on the wall (if the characteristics of the model purchased allow this).

How to choose an inverter for a heating boiler: selection criteria

The operating battery transmits a direct 12 V current. The inverter absorbs it and converts it to AC with the traditional 220 volt voltage and monitors the degree of charge of the battery itself

The advanced models have a control unit with a boiler switching system and a base battery inside the case. The first unit controls the power availability and switches the equipment in time to autonomous operation if the central power supply is interrupted.

The second unit (accumulator) powers all the electronic elements of the boiler for the duration of the power failure or until the charge runs out.

How are the appliances classified?

Almost all inverter devices are components of a UPS (Uninterruptible Power Supply) and have the same function - converting the direct current from the battery into alternating current.

In case of an unexpected power outage, the backup power system is activated and the heating equipment instantly switches to autonomous operation. This allows the heating system to be fully functional for a certain time period, from a few hours to a few days.

Functional principle consists of three types of units:

  • Off-line (stand-by);
  • Line-interactive (linear-interactive);
  • On-line (double conversion).

Each type has its specific characteristics and possibilities, allowing a multifarious task. After a detailed study of the characteristics of the three units, it is very easy to choose the one which is best for you.

Off-line units

Off-line model has a simple construction and is considered a stand-by unit. When the mains is functioning in standard mode and shows stability and the voltage does not \"jump\" between the extremes, the unit is \"asleep\" and does not participate in the operation of the domestic heating system.

If the current level drops to 175V, the unit switches the heating boiler to a battery back-up. As soon as the situation is restored, the inverter UPS reconnects the heating system back to the mains.

How to choose an inverter for a heating boiler: selection criteria

Off-line unit is ideal to work in conjunction with a gas heating boiler, but only if the central power grid has no voltage stabilization problems

Each transfer from the main power supply to the off-line and back takes no more than 10-15 seconds and has no effect on the heating equipment's functionality.

The operating range of most off-line converters is between 170-270V.

How to choose an inverter for a heating boiler: selection criteria

The advanced inverter converters are usually equipped with information LCD displays and current controllers. They have no active cooling system. This makes the operation absolutely silent and does not disturb the occupants with annoying sounds

When the voltage is constantly \"jumping\", switching from the main system to the autonomous system is too frequent and leads to rapid wear and tear of the batteries and the device itself. Stabilizers are not included with the device, so when connected, both input and output, the mains voltage does not change.

So we recommend reading our article on how to choose a voltage stabilizer for the heating boiler. Read on for more details.

Depending on the manufacturer and model, back-up appliances can effectively handle electrical equipment with a capacity of 300 to 3 500 watts. Some products are designed for cyclic operation and the ability to keep the communication parts of the heating system from freezing for a day or more.

How do Line-interactive modules behave?

The Line-interactive unit is a switch-type device and is considered the optimal version of universal equipment. The product is structurally composed of an off-line source, a converter, a switching relay and a low-frequency stabilizing device.

In standard unit operation, the heating equipment consumes the resource of the central power line. The output voltage is controlled by a stabilizer and special filters (on some models), which smooth out the resulting noise and neutralize the interference of the network to which the boiler itself is connected.

How to choose an inverter for a heating boiler: selection criteria

The gas boiler connected to a linear-interactive converter equipped with an additional external battery can operate for 8 to 10 hours (depending on the battery capacity)

Line-interactive units supply useful energy to electrical appliances for a very short period of time (not more than 20 minutes).

To provide power to heating boilers, no ordinary linear units are used, but rather advanced products with an extension function providing for the connection of an additional external battery pack. Such devices can keep the boiler running for a longer period of time (up to 10 hours, depending on the manufacturer).

How to choose an inverter for a heating boiler: selection criteria

The linear-interactive converter puts the battery into operation extremely quickly (within about 2-4 seconds). The output stream of the device can be pulsed or sinusoidal. On heating boilers specialists recommend to put the second variant

The built-in current stabilizer allows the equipment to work correctly without switching to the battery when the voltage range is extended. The device provides battery backup power and equalizes the mains voltage. The disadvantages of the products include the impossibility of current in-line frequency correction and minimum sinusoidal smoothing (not more than 20%).

Features of on-line devices

On-line devices operate in continuous mode.

The circuit diagram of the heating equipment in this variant is structured as follows:

  • central electric network;
  • inverter uninterruptible power supply;
  • heating boiler.

The principle of operation of the device is based on the repeated conversion of the general parameters of the electric network. In the first step, at the input of the inverter, the AC voltage is transformed into a stable equivalent with a value of 12 V.

Then the reverse manoeuvre takes place and at the output of the inverter unit the voltage is transformed into an AC voltage with a value of 220 V.

How to choose an inverter for a heating boiler: selection criteria

In online systems the battery has a buffering function and is constantly on recharge. In parallel, an output converter is activated inside the battery and converts the DC voltage into an alternating 220V 50Hz voltage, independent of the voltage formed at the input

The main advantage of such a system is to provide the power supply of the heating boiler with a high quality voltage. Among the disadvantages are only two positions: high cost of the converter equipment and low performance.

Benefits and disadvantages of the equipment

The inverter is convenient in that it is not tied to a certain kind of DC voltage source. The unit can be powered from a normal car battery, a generator set with a simple rectified signal principle or from UPS batteries.

If the unit does not have a built-in charger, the owners will have to personally monitor the capacity level and the degree of discharge of the unit.

The main advantages are:

  • Broad range and possibility to choose the near perfect sine wave output;
  • functional with all nominal voltage and constant current sources;
  • reasonable price in comparison with other units of similar power capacity;
  • no limitations on battery capacity increase and operating time.

Defects include criteria such as:

  • no battery monitoring;
  • the threshold setting is not subject to additional correction;
  • an external communication circuit must be installed for automatic activation in case of power failure in the accommodation;
  • high cost of \"sophisticated\" modules with a wide range of possibilities.

The final choice of a suitable device is strictly individual. It all depends on how much the voltage \"jumps\" in the network, how often the consumers are cut off from the supply by the central power system and how long they have to sit without light.

Basic rules for selecting a module

When planning the purchase of an inverter for a boiler, you should pay the closest attention to such parameters as:

  • input voltage and current;
  • level of output voltage;
  • degree of output voltage sine wave distortion;
  • actual conversion efficiency;
  • total output power.

For domestic gas boilers, 12-220 inverter units are mostly used. These units convert the constant 12 V battery voltage to a 220 V sinusoidal voltage with minimal distortion.

How to choose an inverter for a heating boiler: selection criteria

The sinusoid of the inverter output voltage should not exceed 3%. These figures mean that the waveform is close to a sine wave at most with only slight deviations towards sharp declines or cut-off peaks

You can also get a more powerful combination of units (24-220 inverter and 24V battery pack), but you must find out exactly what the maximum input current is designed for the inverter.

Only after obtaining this information should you proceed to purchase.

How to choose an inverter for a heating boiler: selection criteria

The inverters offered in the domestic market are originally designed for the low quality of electrical networks. The units have all energy surge protection features and an option allowing the user to set the upper and lower voltage limits down to a volt

The controller and control unit of popular gas boilers usually draw about 150-200W. The circulating pump, which is responsible for proper circulation of the heating fluid in the system, draws another 125-150 watts. To determine the power requirement of the inverter, add these figures and multiply by 2.5 to take into account the start-up current at start-up.

The figures should be multiplied again by 1.2 to allow for some power reserve. The data obtained should be memorized or written down. When buying an inverter, make sure that the manufacturer's stated base power is necessarily greater than the calculated figures.

List of popular models and manufacturers

Many domestic and foreign companies, firms and organizations operate in the electrical equipment market segment. Some of them produce goods under license, others develop their own technology and offer customers unique, advanced and competitive products at a very reasonable price.

Energy ETK company's device

Energy PN-500 inverter is an inexpensive practical device providing uninterrupted power supply for modern low power boilers. It is manufactured at the production facilities of ETK \"Energy\" - one of the leaders in the domestic electrical market.

How to choose an inverter for a heating boiler: selection criteria

Energy ETK inverters fully comply with all state standards and requirements applicable to household electrical equipment. The environmental safety and quality of the products is confirmed by international certification certificates issued by the company

Connecting one base battery to the device provides full autonomous operation of the fuel boiler for 6-7 hours. If a second battery is connected, the duration of operation is doubled.

The unit outputs a clean sine, helping to preserve the expensive electronic \"stuffing\" of modern heating boilers. When the operation of the central electrical system is normalized, the inverter independently switches to voltage stabilization mode and protects the boiler from sudden voltage surges.


Elim-Ukraine has been in the electrical equipment market for over 10 years and is well respected by its customers.

The devices produced under this brand have a switching power supply, an eye pleasing LED indication and show an extremely high level of efficiency (up to 98%). They provide a clean sinusoidal signal without distortion and overvoltage peaks.

How to choose an inverter for a heating boiler: selection criteria

Elim-Ukraine inverters are also convenient because they operate correctly both with gel and car batteries

Fitted with protection against overheating, general overload and deep discharge of the battery. One of the expansion options allows to connect an additional battery of any capacity to the equipment to maintain autonomous operation of the heating system even in the absence of voltage in the central mains for a day or more.

The Rucelf UPI-400-12-EL

The Rucelf UPI-400-12-EL unit belongs to the line-interactive power sources. It has a built-in stabilizer, which, in the presence of even a minimum line voltage, equalizes the current flow without involving the battery. This makes it possible to conserve battery life without overloading and extending battery life.

How to choose an inverter for a heating boiler: selection criteria

The important advantages of Rucelf UPI are the completely silent operation and efficient provision of the necessary power supply during power failure

Reasonable cost is another characteristic feature of Russian Rucelf products.

Thanks to this, customers can create a complete autonomous infrastructure to feed their heating systems during a power failure or voltage fluctuation.

Conclusions and useful video on the subject

How to correctly buy an inverter and choose the optimal capacity battery for it. How to install the equipment on the boiler and forget about power outages forever:

A detailed review of the device, operating principles and functionality of the popular pure sine wave voltage inverter model:

How an inverter voltage converter with no built-in battery inside the case behaves in operation:

Installing an inverter unit on a heating boiler allows the heating system to function correctly during intense voltage fluctuations and during a general blackout. The owners do not feel any inconvenience due to the lack of electricity and do not freeze if this unpleasant situation happens in the cold season.

In addition, the device protects the communication elements from possible breakdowns provoked by an unexpected power outage and helps the equipment to operate as long as possible and with maximum efficiency.

Have you already had experience using inverters for heating boilers? Please tell our readers which device you have chosen? What was the main reason for your choice? Are you satisfied with the operation of the device? Leave your comments, share your experiences, ask questions in the box below.

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