How the safety automatics of gas boilers work

Gas boilers are a typical home appliance that supply hot water and warmth all year round. These systems are convenient and comfortable, but they also carry some risk, especially in terms of safety. It is essential to comprehend how gas boiler safety automatic functions operate in order to protect your home and property.

Every gas boiler has a sophisticated safety feature system built in to identify and stop possible risks. These safety automatics act as a buffer against a variety of problems that might occur when the boiler is operating, such as gas leaks and overheating. These safety features keep your home safe by using a combination of sensors, valves, and control mechanisms. They operate nonstop.

Monitoring the flow and combustion of gas is one of the main jobs of safety automatics in gas boilers. Strong safety precautions must be taken because gas leaks represent a serious risk to people’s lives and property. When abnormalities or leaks are detected in the gas flow, automatic gas valves and pressure sensors quickly cut off the supply.

Additionally, safety automatics are essential in avoiding boiler system overheating and pressure buildup. Elevated temperatures and excessive pressure have the potential to cause disastrous malfunctions, presenting significant hazards to the boiler and its surroundings. Together, pressure relief valves and temperature sensors control the boiler’s internal conditions to guarantee constant, safe, and effective operation.

Safety automatics not only identify and avert impending threats, but they also add to the gas boilers’ long-term dependability and toughness. Through the constant monitoring of multiple parameters and timely intervention, these features serve to alleviate wear and tear on vital components, thereby prolonging the boiler’s lifespan and decreasing the probability of expensive repairs.

Ultimately, keeping a safe and comfortable home requires an understanding of how gas boiler safety automatics operate. Understanding the inner workings of these systems will help you recognize the value of routine maintenance and the need to act quickly in the event of any malfunctions or warning signs. Your gas boiler can provide dependable heat and hot water for many years to come with the right maintenance.

Automatic units of floor standing boilers

The great majority of gas boilers that are freestanding have safety automatics that run on a non-volatile external power source. In three emergency scenarios, automation devices are required by normative documents to cut off the burner’s and igniter’s gas supply:

1. Main burner flame extinction due to blowing out or other reasons.
2. When in the chimney channel there is no or sharply reduced natural draught.
3. Natural gas pressure drop in the main line below the critical level.

As a point of reference. All varieties of gas boilers must be able to perform the specified functions. Protection against overheating is a fourth level of safety that many manufacturers include. Based on the sensor signal, the valve shuts off the gas supply to the main burner when the coolant temperature reaches 90 °C.

Non-volatile automatics of the following kinds (brands) are used in different models of gas floor standing boilers from different manufacturers:

• Italian units EuroSIT (EuroSIT) series 630, 710 and 820 NOVA (heating units "Lemax", "Zhitomir 3", Aton and many others);
• Polish devices "KARE" (heat generators "Danko", "Rivneterm");
• American devices of automatic regulation Honeywell (heaters of Zhukovsky plant of "Comfort" line);
• domestic products of ZhMZ, SABK, "Orion", "Arbat" firms.

The most popular automatic brands, which are frequently fitted on identical hot-water boilers, are mentioned below. For instance, Zhukovsky Plant outfits low-cost AOGV units with ZhMZ-manufactured safety units, medium-priced heat generators with EuroSIT devices, and high-end models with Honeywell automated valves. Let’s examine each group in isolation.

Gas valves of SIT Group brand

When it comes to boiler unit automatics, EuroSIT safety units are the most widely used and dependable. Companies that supply natural fuel, such as those who are replacing outdated gas equipment in boilers like KChM and AGV, recommend them. Function flawlessly in conjunction with Polidoro, Iskra, Vakula, Thermo, and other micro-flame burners.

The three models that were utilized have the following exact names:

• 630 SIT;
• 710 MiniSIT;
• 820 NOVA.

As a point of reference. The 630 and 710 series were discontinued by SIT Group because they were deemed outdated. The 820 NOVA, 822 NOVA, 840 SIGMA, and 880 Proflame gas valves (battery operated) have taken the place of the replacement heating boiler safety automatics. However, it’s not difficult to find the older products on sale.

We won’t bore you with the specifics of how EuroSIT automatic devices are made; instead, we will use the example of a basic 630 series unit to quickly explain the basic working principle:

1. When you turn the handle to the "ignition" position and press from above, you forcibly open the solenoid valve, allowing gas to flow to the pilot burner (igniter). You click the button of the piezo element, which produces a spark that ignites the wick.
2. Holding the main knob for 30 seconds, you allow the thermocouple to warm up with the igniter flame. The thermopile generates a voltage (EMF) of 20-50 millivolts that locks the solenoid in the open state. Now the knob can be released.
3. Set the main knob to the desired position and thus supply gas to the main burner. The latter is fired up and begins to warm the heat exchanger with the heating system water as shown in the diagram below.
4. When the water reaches a certain temperature, a capillary sensor is triggered, gradually closing the second valve – thermostatic valve. The fuel supply to the burner device is stopped until the sensor cools down and the valve plate opens the way for gas. The igniter continues to burn in the standby mode.

Note: In older automatic modifications, the heat generator needed matches to start because they lacked temperature sensors and ignition units.

A diaphragm valve, acting as a pressure regulator, is in charge of the device’s regular gas supply. The fuel channel closes and the boiler emergency shutdown occurs when it drops below the predetermined value. Other circumstances may also result in failure:

1. The burner and the wick heating the thermocouple go out. Voltage generation is stopped, the solenoid valve closes the fuel passage.
2. If the draught in the chimney is suddenly lost, the sensor placed in this channel overheats and breaks the supply circuit of the electromagnet. The result is the same – the fuel supply is blocked.
3. In heaters equipped with overheating sensors, the electric circuit is broken after the water reaches the temperature of 90-95 °C.

The user cannot restart the boiler for one minute following the emergency shutdown caused by the gas automatics; the fuel supply cannot be restored sooner. The tutorial video demonstrates the system’s operation in clear detail:

Differences between the 710 MiniSIT and 820 NOVA models

These units function on the same principle as their predecessor, the 630 series. The modifications made to the 710 MiniSIT automatics are entirely positive:

• 2 buttons "Start" and "Stop" are placed separately together with the solenoid valve;
• The main handle only turns the thermostat stem and regulates the coolant temperature;
• ignition unit with piezo igniter button is built into the body of the product;
• the basic equipment of the device includes a bellows-type temperature sensor with capillary tube;
• Gas pressure stabilizer added.

As a point of reference. The spark igniter was not anticipated in the initial iterations of the 710 series.

The most recent 820 NOVA product line has undergone changes to increase throughput capacity, stability, and dependability. We wish to highlight two enhancements that are significant in the eyes of the users:

1. The product is equipped with a connector for connecting a room thermostat and weather-dependent automatics. Now the heating unit is able to maintain the air temperature in the apartment.
2. There is a modification with its own power source – thermogenerator, mounted on a bar next to the pilot burner, as shown in the scheme. The principle of operation is similar to a thermocouple, but the value of the generated EMF is much larger.

It makes sense to discuss Honeywell automatic gas valves in this section as they operate on a similar principle. Their primary distinction is the higher throughput capacity, which enables the units to be used in large-capacity (30–70 kW) boilers.

Polish automatics "Kare"

Few manufacturers install Polish safety systems on their gas boilers. The simple explanation is that although the product is more costly than domestic boiler automatics, it is not as reliable as products from Germany, Italy, or the USA.

The product is referred to as a "system" since it is comprised of multiple blocks, but the overall concept of operation stays the same:

• gas filter;
• valve – gas pressure regulator;
• Separately there is a thermostat with a regulating handle;
• membrane thermostatic valve;
• piezoelectric igniter button.

Capillary tubes are used to connect nodes and sensors to one another. It is essentially the same SIT or Honeywell device, disassembled into individual components. This is a benefit: replacing parts is more affordable and convenient.

Products of domestic firms

As you can see, boiler automation—manufactured in the former USSR—does not incorporate any novel approaches or cutting-edge innovations. Three safety functions—turning on the thermocouple’s electromagnet by voltage (EMF), opening the diaphragm gas valve, and breaking the circuit with the draught sensor—are all accomplished using the same principles.

The design of the units from the SABK, "Orion," and ZhMZ (Zhukovsky Zavod) brands cannot be explained in detail. The simplest gadget, lowest price, and lowest dependability define the products on the list. Nearly every year, thermocouples burn out. As a result, the thermostat abruptly turns off and ignites the burner, which occasionally sounds like a micro-explosion.

While spare parts are readily available and reasonably priced, appliances should be closely monitored and serviced on schedule after their initial years of use. The following video provides an example of troubleshooting a common ZhMZ automatic malfunction:

In understanding how the safety automatics of gas boilers work, it"s crucial to grasp their vital role in ensuring your home"s safety and the efficient functioning of your heating system. These automatics serve as guardians, monitoring various parameters like gas pressure, temperature, and flame presence. If any of these parameters deviate from the safe range, the automatics swiftly intervene, shutting off the gas supply to prevent potential hazards such as leaks or fires. This proactive approach not only safeguards your property and loved ones but also extends the lifespan of your boiler by preventing damage from occurring. Understanding how these safety features function empowers homeowners to maintain a safe and efficient heating system, fostering peace of mind and comfort throughout the colder months.

Electronics of wall-mounted units

One feature of these heat generators is the electronic control of the coolant’s temperature maintenance, combustion, and ignition processes. In other words, energy-dependent automation is installed in wall-mounted gas boilers (as well as some floor-standing boilers) that run on electricity.

Vital. Even with the numerous "tricks" incorporated into the mini-boiler design, mechanics are still in charge of the safety features. Regardless of whether there is voltage in the power grid, the appliance can handle the three types of emergencies mentioned above.

The purpose of the automatic gas boiler is to maximize convenience for homeowners and apartment owners. All you need to do is press one button to turn on the heater and select the desired temperature. Let’s quickly go over the unit operation’s algorithm and the components that make it up:

1. After the specified start-up actions, the controller of the heat generator collects the readings of sensors: temperature of the heat carrier and air, gas and water pressure in the system, checks the presence of draft in the chimney.
2. If everything is in order, the electronic board energizes the solenoid gas valve and simultaneously energizes the ignition electrodes. No wick.
3. The main burner is ignited and gives full power in order to heat the heating medium as soon as possible. Its work is monitored by a special flame sensor. The controller switches on the built-in circulation pump.
4. When the coolant temperature approaches the set threshold, which will be detected by an overhead sensor, the combustion intensity decreases. Step burners go to low output mode and modulating burners smoothly reduce the fuel supply.
5. When the heating threshold is reached, the electronics will shut off the gas. When the sensor detects the cooling of water in the system, automatic ignition and heating will be repeated.

Note: The controller also activates and deactivates the fan in turbine boilers with closed combustion chambers.

The wall-mounted gas boiler’s instructions specify that because it is intended to operate in a closed heating system, the automation keeps an eye on the water pressure. In the event that it drops below the allowable range (0.8–1 Bar), the burner will extinguish and remain inactive until the issue is fixed.

There are numerous imported boilers that operate on the energy-dependent scheme, including Buderus Logano, Viessmann, and others. The master in the video will be informed in an understandable language about how the installation of electronic gas equipment is going.

Understanding how safety automatics work in gas boilers is crucial for ensuring the safety and efficiency of heating systems in our homes. These safety measures are intended to protect people and property from possible risks like pressure buildup, overheating, and gas leaks.

The thermocouple, a sensor that can identify the presence of a flame, is one of the main parts of safety automatics. The thermocouple detects the absence of the pilot light and triggers the gas valve to cut off the gas supply in order to avoid an explosion caused by an accumulation of unburned gas.

The pressure relief valve, which controls boiler pressure, is another crucial safety feature. This valve releases excess pressure if it rises above safe limits, protecting the boiler and related parts from potential harm.

In addition, contemporary gas boilers have electronic control systems that constantly track a number of variables, including gas flow, pressure, and temperature. These systems have the ability to automatically turn off the boiler in the case of an anomaly, stopping further operation until the problem is fixed.

To guarantee that safety automatics operate as intended, gas boilers must receive routine maintenance and servicing. These parts can be examined and tested by qualified technicians to rule out any possible problems and make sure they function dependably when needed.

To sum up, safety automatics are essential to the safe operation of gas boilers because they guard against potential risks and guarantee the comfort and safety of homeowners. Homeowners can enjoy reliable, efficient heating systems with peace of mind by learning how these mechanisms operate and making appropriate maintenance investments.

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