How to bleed air from the heating system of a Navien boiler

Self-diagnosis system

The purpose of automatic self-diagnosis and protection systems is to detect and correct various breakdowns at the moment they occur. After fixing any kind of defects, the equipment stops, with a breakdown code displayed on indicators or LCD screens. Finding problems in equipment that is not equipped with self-diagnosis is much more difficult, although the procedure for checking the internal filling does not change. Self-diagnosis allows you to quickly identify and find faults in the Navien boiler.

During the search process, the system sends requests to numerous sensors and nodes: all received results are analyzed and stored. If serious breakdowns are detected, a report about them is instantly transmitted to the indicator board. Initially, such systems were developed for gas workers, since they make it much easier to troubleshoot a Navien gas boiler and fix them. However, if you have minimal skills in servicing boiler equipment, you can repair Navien appliances on your own. Before you begin self-repair, you need to check whether the warranty period has expired. If the warranty is still valid, it is better to send the boiler to a service center for a free repair.

Causes of malfunctions

For a Navien gas boiler, faults are concentrated in several probable areas:

1. problems with the coolant;
2. ignition does not work;
3. there is no fuel (gas) supply.

First, before planning a visit to the service center or estimating the cost of repairs, you should try to analyze the possible causes of the indicated error. This is, first of all, a failure in the automatic system receiving a signal about the normal flame level in the igniter. Further search for the probable source of the malfunction will lead to the ionization sensor (failure), gas pressure in the system (valve closed by mistake, no supply), problems with the grounding loop.

You can start by inspecting the flame sensor: it should be clean, free of deposits and dirt. If this is not the case, the sensor is cleaned and then they try to turn on the boiler. At the same time, check the position of the valve at the gas inlet to the unit and the grounding connection.

Practice shows that in most cases these simple manipulations will allow you to do without calling specialists and the cost of diagnostics.

Important. Before you begin troubleshooting any problems yourself, you should carefully study the error code, check its compliance with the manufacturer’s classification, and only then try to solve the problem.

What malfunctions occur

To repair the Navien heating boiler yourself, you need to read the special manual. It will help not only decipher the type of breakdown, but also eliminate it in the most effective way.

List of problem codes with the Navien boiler and their interpretation:

• 01E. The device overheated, and this was recorded by the temperature sensor.
• 02E. Indication of an open circuit in the flow sensor and a drop in the coolant level in the circuit.
• 03E. The signal confirming the presence of a flame has disappeared. In this case, the combustion can continue.
• 04E. This code has the complete opposite meaning of the previous designation: in this case, there is confirmation of the flame, although in fact it is absent. E
• 05E. Failure of the circuit responsible for controlling the degree of heating of the coolant in the heating system.
• 06E. This code also indicates a malfunction of the temperature sensor (the circuit is closed).
• 07E. Signal about failure of the temperature sensor in the DHW circuit.
• 08E. Malfunction of the Navien gas boiler in the same unit due to a short circuit.
• 09E. Alert about fan failure.
• 10E. The appearance of malfunctions in the smoke removal system.
• 12E. Flame extinguishment in the burner.
• 13E. The heating circuit flow sensor has shorted.
• 14E. Gas has stopped flowing from the main line, which is why the Navien boiler does not turn on.
• 15E. A general indication of errors in the operation of the control board, without specifying the problematic element.
• 16E. The equipment has overheated.
• 18E. Malfunctions in the operation of the smoke exhaust sensor.
• 27E. Air pressure sensor (APS) malfunctions.

The manufacturer itself does not provide any instructions for repairing the Navien gas boiler. The calculation is made that repair activities are the responsibility of service centers exclusively. In our country, people’s thinking is somewhat different, so many of them are accustomed to troubleshooting household appliances on their own.

Malfunctions of heating boilers

A dirty heat exchanger is a common reason for the lack of hot water in the DHW circuit.
Common boiler breakdowns include:

• coolant leak;
• water hammer;
• after turning on the burner, the lock is activated;
• the burner does not turn on;
• fuel burns unevenly, in waves;
• soot is formed;
• decreased productivity;
• During operation of the burner, the ignition is switched on;
• soot forms on the walls of the chimney and combustion chamber.

To resolve a problem, you must first determine the cause of the problem.

Built-in pump malfunction

The reason for the lack of hot water may be a clogged built-in pump.
An important part in the heating system is the circulation pump. The quality of heating and the functioning of hot water supply depend on its uninterrupted operation. There are several signs and causes of breakdowns:

• The unit makes uncharacteristic sounds. This occurs due to oxidation of the shaft, the entry of a foreign object into the structure, problems with the power supply, air in the pipes, dry running of the mechanism, and the appearance of cavitation.
• After turning on the boiler, the pump does not start. Perhaps there is no power supply, the fuse has tripped.
• After a short period of time after switching on, the structure switches off: limescale deposits in the stator shell.
• Hot water does not turn on in a double-circuit boiler.

Also, the reasons for poor operation of the circulation pump are poor pressure in the system, wear of the bearing, which causes additional vibrations in the line, and low pressure.

To troubleshoot problems, you need to check the presence of electricity, clean the pipes and other elements, replace failed parts, and remove foreign objects from the system.

The heat exchanger is clogged

You can clean the heat exchanger from scale using a solution of citric acid and an electric charge.
Heated gases are transported through channels, which are collectively called a heat exchanger. The design features are that the walls of the artery simultaneously serve as partitions of the water circuit, along which the coolant constantly moves, heating the metal surface. The combustion process is associated with the intense release of flue gases, partly consisting of soot and tar, which create a deposit inside the boiler, on the chimney. Therefore, the manufacturer recommends regularly cleaning the equipment at least once every 30 days and during the preparation of the device for the heating season.

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When soot settles on surfaces, the performance of the mechanism decreases, fuel consumption increases, and the risk of costly breakdowns and internal fire in the contaminated area increases.

Chemical cleaning of bithermal heat exchanger

Washing is carried out without dismantling the heat exchanger; to perform the procedure, you will need a booster with a volume of 20-30 liters. Before starting work, it is necessary to drain the coolant from the heating system using a Mayevsky tap.

Fill the booster reservoir with the flushing solution, and lower the hoses into the container, the free ends of which are connected to the heat exchanger pipes. Liquid movement is possible only under the action of a circulation pump; it must be connected to one of the hoses.

The ends of the hoses must be put on the heat exchanger pipes, and the free ends must be placed in a booster with flushing liquid, connecting the circulation pump. Work can be performed without removing the heat exchanger

It would be ideal to connect a reversible pump with the ability to change the direction of fluid flow. All that remains is to start the boiler for heating at a set temperature of 50-60 degrees and leave for 15 minutes, periodically changing the direction of circulation.

Chemical cleaning of the secondary heat exchanger

Flushing the secondary heat exchanger of a double-circuit gas boiler can be performed in a similar way to flushing a bithermic heat exchanger. However, you need to take into account that the secondary heat exchanger is easily removed, so you can improve the quality of cleaning by dismantling it.

To gain access to the heat exchanger, it is necessary to dismantle the front panel of the unit and move the control unit to the side. The heat exchanger is secured with two bolts at the bottom, which can be easily removed by unscrewing them.

It is most effective to place the heat exchanger removed from its original location for washing in a container with a salt-dissolving solution and boil it. Instead of a suitable household product, you can use a 20% citric acid solution.

Good results can be achieved by boiling the secondary heat exchanger in a washing solution

When cleaning any heat exchanger, the final stage is rinsing with clean water. This measure is necessary to remove traces of a chemically aggressive substance and stop its effect on the walls of the heat exchanger.

There is another way to clean the heat exchanger - hydrodynamic. Its implementation requires special equipment and pressure control at each stage of cleaning. Therefore, without special knowledge and skills, doing it yourself can be dangerous.

Regular cleaning of the heat exchanger will avoid the need to use very aggressive compounds and will make it possible to extend its service life. It is recommended to clean the heat exchanger annually at the end of the heating season.

Problems with the heating circuit

The pump must be selected according to the requirements of the heating circuit.

Malfunctions in the operating mode of the heating circuit are not always associated with a malfunction of the main heating element. If the boiler works, but does not heat the batteries, the reason must be sought in the wiring itself.

List of main heating circuit malfunctions:

• the filter on the return line or the needle tap (Maevsky tap) is clogged;
• insufficient power of the circulation pump;
• the rules for installing a heating circuit with natural circulation have not been followed.

Any of the above problems must be resolved before the start of the heating season. Otherwise, the room may be left without heat for several days, since the repair involves completely draining the coolant.

So, why doesn’t the boiler heat the batteries if everything worked fine over the previous years? The reason is a dirt plug that has formed on the heating circuit filter and completely blocks the coolant flow. It can be solved simply - the water is drained from the pipes or its circulation is blocked using bypasses, and the filter is cleaned. To prevent a recurrence of such a situation, it is necessary to completely replace the coolant with parallel flushing of the entire circuit.

In a gravity system, the slope of the pipes is key.

The second reason why the boiler works but the radiators are cold is the insufficient power of the circulation pump. The performance of the device is not enough to pump the entire volume of coolant in a timely and efficient manner. Or the heating system in the house has branches that are located at a significant distance from the pump. As a result, the circulation pump overheats, the heating equipment operates with excessive energy consumption, and the radiators remain cold. The solution is to change the coolant pumping device to a more powerful one.

If the house has a two-pipe heating circuit with natural circulation of water, and during the heating season it is often noticed that the boiler is on and the radiators are cold, then the reason lies in non-compliance with the slope of the main line. According to regulatory documentation, only a pipe slope of 10 mm per linear meter in a heating system with natural circulation will ensure normal coolant movement. The result is uniform heating of the batteries throughout the house. If there is no slope, the coolant stagnates, which negatively affects the temperature of the radiators. The problem can be solved by completely redoing the wiring.

Modulation errors on the burner

To heat running water, in most cases a boiler power close to maximum is required. In modern boilers, the burner power is regulated over a wide range. The adjustment occurs by changing the amount of gas supplied by the gas valve. The amount of adjustment is determined by the control board depending on the operating logic and settings. The process can be observed visually by the height of the flames on the burner.

If the boiler settings are set to 100% boiler power in DHW mode, but visually the flames on the burner are weak, or obvious interruptions are visible, then you should check:

• setting the gas valve (static and dynamic gas pressure)
• control board

Such checks should only be performed by a qualified person.

Three-way valve

A three-way valve is installed in boilers with two heat exchangers. When a signal is received from the flow sensor, the electronics gives a signal to the valve and the heated water from the first heat exchanger is sent to the second heat exchanger, where the heat is transferred to the passing tap water. If, for example, no actual switching occurs (the valve is faulty), then the coolant will continue to circulate in the heating circuit and no heat transfer to the hot water circuit will occur.

If, for example, a valve only partially closes the heating circuit due to a malfunction, then there will be problems with insufficient heating of hot water, since part of the heat will go to the heating system.

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Problems with the flow sensor

A possible reason why a gas boiler may stop heating water is a problem with the flow sensor. The device is a small fan that rotates under the influence of water flow. As a result of rotation, a signal is sent to the control board to heat the water. Due to clogging, the fan may stop rotating.

You can clear the blockage without dismantling the device. To clean it, just open and close the water supply tap several times. If such actions do not give the desired result, you will have to remove the sensor and clean it.

To do this you need:

• Disconnect the gas boiler from the electrical network;
• Turn off the water supply tap;
• Drain the water from the unit.

Typically, the flow sensor is secured with a bracket, by removing which you can easily remove the device. The assembly is removed completely; to remove the inner part, you need to turn the parts in the groove. During disassembly, you should clean the filter mesh and remove the turbine.

Often, turbine blades are covered with a layer of rust that needs to be thoroughly cleaned. If you remove the three clamps, you can remove the turbine itself to clean the internal plane of its landing. Now all that remains is to reassemble in reverse order.

When disassembling the flow sensor, you need to clean the filter and turbine blades

If cleaning the flow sensor does not bring the desired result and there is no hot water, you will have to replace the entire assembly.

No need to heat

The first step is to clean the heat exchanger. At home, it is common to use citric acid, toilet bowl cleaners and special liquids (if available). Before cleaning the Navien gas boiler, you need to dismantle the heat exchanger and pour a suitable solution into it. After a short pause, it is washed out with high pressure of water.

A similar procedure should be carried out with the DHW circuit heat exchanger if problems are observed with heating hot water. In case of particularly contamination, it is easier to install a new exchanger. To prevent scale build-up, it is recommended to have a system for cleaning and softening your tap water.

Technical characteristics of Navien gas boilers

Navien is one of the leading manufacturers of boiler equipment from South Korea; its products are in demand in many countries around the world and are of guaranteed high quality. The model range is widely represented by both single and double-circuit units, including:

• turbocharged;
• atmospheric;
• condensation

Recently, electric boilers of this brand have also appeared. The manufacturer places special emphasis on the fact that Navien gas boilers are in no way inferior to competitors in terms of technical characteristics, and most importantly, they are maximally adapted to domestic conditions with their unstable pressure, differences in the gas main and electrical network.

Unfortunately, in practice, a situation occurs when an error code is displayed on the information display of the unit and you need to decide what to do next.

Troubleshooting error 03

There were some obstacles in the way of the signal about the presence of flame entering the system. The cause of this malfunction of the Navien boiler may be a cessation of gas supply or a failure of the flame presence sensor in the burner. Often, problems of this type arise after repairs to a gas pipeline. Error 03 is also displayed when problems occur with ignition.

Elimination procedure:

• Checking the gas supply.
• Testing the serviceability of ignition.
• Cleaning the ionization sensor (it often gets dirty).

When using liquefied gas, you must ensure that the gearbox is in good working order. If the boiler is fully operational, the cause of error 03 may be improper grounding.

Typical Navien Ice boiler breakdowns

Although the devices in this series are famous for their impeccable performance, they sometimes fail. When installing a Navien Ice boiler in your home, it is recommended to arm yourself with information about its most typical faults (there are not very many of them). For example, for the 24 K model, the most typical error is 10. The design of this double-circuit boiler uses a closed combustion chamber, which leads to periodic problems with smoke removal. Most often this happens due to fan breakdowns, which need to be replaced from time to time.

Typical malfunctions of the Navien gas boiler also include error 02: it indicates rapid heating and equally rapid cooling of the boiler. This usually occurs due to the appearance of air pockets in the circuit system or due to a breakdown of the flow sensor. All air must be bled from the heating circuit.

Navien boiler error 02

Error 02 is caused by the heating circuit flow sensor located at the outlet of the main heat exchanger. If nothing prevents the movement of water in the CO circuit, after turning on the pump, the sensor contacts close and the signal is registered by the control unit, otherwise error 02

.

The following main reasons can be identified:

• low pressure in the heating system (to control the pressure, Navien boilers are equipped with a dial pressure gauge located on the front cover - you need to check and, if necessary, feed the system to 1.2-1.5 bar)
• failure of the flow sensor (to check, measure the resistance of the sensor before and after turning on the pump)
• no circulation in the heating circuit
• control board is faulty

Lack of circulation means that for some reason the coolant cannot move normally through the heating pipes. Obstacles can be: clogged cleaning filters, freezing of a section of the pipeline, closed taps around the perimeter of the heating system, the presence of an air lock or a malfunction of the pump.

To remove air, you can try to start the boiler in a special test mode, after first opening the air vent valve on the pump. To activate the test mode, you need to turn off the boiler and move switch No. 1 on the DIP-Switch block of the board to the ON position. We will discuss the testing of actuators in more detail in a separate article.

We recommend watching a video in which one of the users simulates error 02 on a Navien boiler:

The control board is faulty

This error, which is difficult to accurately diagnose, is designated by code 15E. It is almost impossible to understand how the control board works without special education. The most correct algorithm of action in such a situation is to invite a specialist who can use testing to determine and eliminate the causes of the problem.

The place where the Navien gas boiler is repaired is chosen by the foreman: in particularly difficult cases it is necessary to transport the boiler to a service center. To avoid problems of this type, it is strongly recommended to equip the supply networks of the Navien boiler with a voltage stabilizer.

How to remove air from a heating system

First you need to determine where the air lock is located. This can be done in the following way: lowering the temperature in the devices, tapping the system elements or listening to the characteristic sound in the pipes.

Once the location of the air lock has been determined, it is necessary to find an air vent that is closest to the highest point along the direction of movement of the coolant. In order to get rid of air, it is necessary to turn on the system make-up.

But there are times when it is impossible to determine the location of the airlock. In this case, you need to seek help from specialists:

1. As the pressure in the system increases and the temperature increases, the plug will either be removed using automatic devices or moved to a place where it can be found.
2. If you hit the pipes hard, it is possible that the resulting air will move. But this method does not always give results.

If airing often occurs during the period of use of the heating system, then it is necessary to find and eliminate the cause of its occurrence.

The operation of water heating systems may be accompanied by air entering the internal cavity of pipes, radiators and the heat source. The occurrence of an air lock leads to a change in the parameters of the coolant in individual areas or throughout the heating main. Airing the boiler can lead to overheating of the heat exchanger and failure of the heating equipment. Each user of an autonomous heating system must be able to independently get rid of traffic jams that occur inside the water system.

Modern heat sources are equipped with automatic air ventilators or Mayevsky taps located in the upper part of the unit. This design solution allows you to bleed air during operating mode without stopping the process of heating the room, just like with any radiator on which a similar valve is installed.

To do this, periodically open and close the Mayevsky tap, with an interval of several minutes. The procedure is repeated until a hiss or whistle appears, indicating the release of the air lock. The appearance of sound requires holding the bleeder in the open position until the coolant appears.

Error 01

There is no need to panic, because this code quite often indicates the appearance of ordinary air pockets in the circuit or filter. The procedure for bleeding air from a Navien boiler is carried out according to standard recommendations. Next, you need to check the functionality of the circulation pump.

It is important that it rotates and that the coolant flows well through the impeller. It happens that the reason that the Navien boiler does not start is a physical breakdown of the impeller. A more complex option is problems with the circulation pump, the elimination of which requires rewinding or complete replacement of the equipment. The most reliable model of pumping apparatus is considered to be products from the Grundfos brand.

Malfunctions of Navien gas boilers and their elimination

As you know, nothing is absolutely reliable or eternal; any equipment has a tendency to fail. When learning how to eliminate error 03 issued by the Navien boiler, you should not forget about other possible failures and failures.

Sometimes these are minor faults that the owner himself can easily diagnose (and even fix). Code “01” accumulates several probable reasons for a malfunction in normal operation, such as a clogged heating circuit, a failure of the circulation pump, or a deterioration in the normal flow in the pipes. You can try to eliminate this problem by squeezing out excess air from the heating line filter. After this, you should check the pump (impeller and motor) by visual inspection and measuring the resistance of the motor winding.

With code “02”, outwardly everything seems to be working: the hot water circuit is functioning, which runs regularly from the tap, but then suddenly suddenly becomes cold. The reasons should be sought in a low water level, sensor failure, or a simply closed distribution tap. The circulation pump may also be malfunctioning.

To eliminate the error, bleed the air, check the circulation system (engine), and the position of the shut-off valves. It doesn’t hurt to inspect the sensor, but most often the reason for the malfunction of the Navien double-circuit wall-mounted gas boiler is that the system is airy.

Code “10” is characterized by problems with the fan air supply tubes: incorrect connection or damage. The same error can be caused by a clogged chimney (sharp gusts of wind); in any case, you need to start by inspecting the exhaust line for combustion products.

Coding “05” corresponds to a failure in the automatic temperature measurement. At the same time, the condition of the conductors connecting the sensor to the controller board is checked. Sometimes it is enough, without replacing the sensor, to clean the contacts or first disconnect and then connect it again.

In addition to the above malfunctions, sometimes the boiler starts to hum when the hot water tap is opened. Experts consider this problem to be typical and widespread, and attribute it to a clogged heat exchanger. The radical solution is to replace the unit, but first you can try to clean it.

A failed three-way valve, the service life of which rarely exceeds 4 years, leads to the fact that the Navien boiler does not heat hot water well (with normal operation of other systems, including the heating circuit). Solved by installing a new one.

Error 04

A little about fault 02 has already been said: it consists of a rapid rise in temperature and an equally rapid drop. The same applies to error 03. When the self-diagnosis system detects error 04, the functionality of the flame sensor and its power supply is checked. It is strongly recommended to avoid any contact of this assembly with surrounding metal elements. It happens that this code is displayed when the system board breaks down. In such cases, it is either repaired or replaced.

Errors 07 and 08

The purpose of double-circuit boilers is to provide homes with both heat and hot water. They consist of two circuits and a set of sensors. As a consequence, in this case there is not one temperature sensor, but two. One is designed to control the temperature of the heating circuit, and the second monitors the degree of heating of hot water. The appearance of codes 07 and 08 on the monitor indicates that the hot water in the Navien boiler does not turn on. Diagnosis and elimination occur in the same order as in the previous case.

GSM thermostat for gas boilers Navien ZONT H-1 Navien

ZONT H-1 NAVIEN is a room thermostat with its own SIM card, connected to Navien boilers using the original Navien protocol. It allows you to control the power of the boiler burner (burner modulation), maintaining the set room temperature with high accuracy.

The device is designed to maintain temperature conditions in the house for comfortable living. ZONT H-1 Navien monitors and manages the operation of the Navien boiler from anywhere in the world through a personal web service account or the ZONT mobile application. Control commands and mode settings can be sent from a phone, smartphone, tablet or PC. The mobile application is free and available for download on iOS and Android.

Purpose

The device is suitable for Navien gas boilers of the Deluxe series*, as well as models ACE, ATMO, GA, GST, LFA, LST.

*With Deluxe series boilers (including models S, Comfort, Plus, Expert)

Thermostats operate, the firmware of which was updated at the factory after 06/23/2020. The website tvp-electro.ru presents ZONT H-1 Navien thermostats with updated firmware.

The thermostat automatically regulates the operation of the boiler in heating mode so that the room maintains the set temperature. It monitors the technical condition of the boiler and notifies when the set temperature changes, an accident occurs or the power supply is cut off. The owner of the thermostat receives notifications in the form of messages in the personal account of the web service, push notifications in the mobile application, SMS and voice messages.

It is possible to connect up to 10 temperature sensors to the ZONT H-1 Navien thermostat, as well as wired and radio sensors for various purposes, for example, leakage sensors, gas leaks, security sensors, etc. To use sensors operating at a protected frequency of 868 MHz, you must connect the ZONT ML- radio module 489.

Operating hours and schedule

ZONT H-1 Navien has 4 preset operating modes:

— “Economy” to save energy resources

— “Comfort” for a comfortable stay in the house

— “Schedule” for boiler operation according to schedule

— “Off” contains the “Anti-Freeze” function, which protects the coolant piping system from freezing (the coolant temperature will be maintained at +5°C).

It is possible to individually program the operation of 6 more custom thermostat operating modes, taking into account the outside temperature and time of day.

For the most optimal gas consumption, you can set up a specific boiler operation schedule.

Weather-dependent control algorithm

The weather-dependent control algorithm (PCA) allows you to control the boiler taking into account data on changes in temperature outside. The ZONT H-1 Navien thermostat measures the temperature in the room and controls the operation of the boiler so that the temperature inside the room corresponds to the set value.

Error 09

These fault codes are the most common. They signal that the fan has reduced its efficiency or has stopped. To accurately determine the cause, the integrity of its windings and the continuity of their resistance are checked. It is also necessary to make sure that there is an interturn short circuit. If the damage is serious, it is better to change the device. If no problems were found on the fan, you should ring the control board. This procedure will require certain skills: if they are absent, it is better to seek help from specialists from the service center.

What to do if the aspirated air leaks?

For the Atmo model range with an open (atmospheric) burner, the primary heat exchanger is made of copper.

The appearance of a leak is almost always associated with its destruction. Purchasing a new heat exchanger is not an easy and expensive task, so most often the issue is solved by soldering the fistula .

To carry out repairs, you should contact a technician from the service center, since this requires a qualified specialist who can dismantle the unit, find the fistula that has arisen, solder it properly, simultaneously rinse the heat exchanger and install it in place without damage.

The work is complex and requires the participation of a trained person.

Error 10

An indication that problems have arisen with the removal of combustion products. A potential cause is a broken fan. The condition of the chimney duct, which requires regular cleaning, deserves a separate check. It is very important that its length complies with regulatory standards. Quite often, the cause of error 10 lies in a malfunction of the air pressure sensor. The most undesirable situation is regular malfunctions of the Navien boiler board. You need to check the most harmless option, when the wind simply gets into the chimney. Naturally, you need to know what to do if the boiler blows out in a strong wind, and how to get rid of this problem.

Error 16

This code indicates that the heating equipment has overheated: in such cases, the Navien boiler hums when hot water is turned on.

Potentially possible reasons:

• Exceeding the coolant heating norm.
• Lack of fluid in the circuit.
• The control board has malfunctioned.
• The three-way valve is acting up.
• The DHW temperature sensor has failed.
• The gas supply rate has been exceeded. This reason why the Navien boiler is humming is quite rare. Its elimination is carried out by simply screwing on the valve.