There is no hot water in the wall boiler. Boiler does not heat hot water

Reading time: 2 min

Gas boilers are designed to create comfortable living conditions. Double-circuit units provide the living space with heat and hot water in the tap. But it happens that a working boiler heats water poorly and does not provide the necessary comfort.

The degree of efficiency of the entire heating system depends on how the boiler works. If there are malfunctions in the gas boiler itself, then this can adversely affect the efficiency of the entire system and cause excessive consumption of energy resources.

What happens when the boiler stops heating water? Let's analyze the causes and ways to solve this problem.

How does a boiler work?

For a clearer understanding of the situation, you need to understand the principle of operation of the boiler. Double-circuit gas wall-mounted boilers such as Baksi or Ariston consist of several components. In the gas part, the incoming fuel is burned, the water part provides the supply of heated water from the heat exchangers to the heating system, the smoke removal part is responsible for the removal of combustion products outside the dwelling.

After the boiler is started, the pump is turned on, providing the necessary water level in the system and the gas supply valve opens. The coolant moves in the heat exchanger, which is heated by the flame of the burner. The thermostat monitors the temperature in the room, temperature sensors monitor the readings on the supply and return pipelines. Also, indicators of fuel pressure, coolant in the circuits, the presence of traction and combustion are taken.

Depending on the user's settings, temperature sensors adjust the water heating mode. The sensor on the return pipe turns off the boiler, depending on the achievement of the required temperature set for the return. However, the system pump does not stop running until the heat exchanger temperature drops.

This is to prevent the water from boiling in it. As soon as the coolant cools down to the limit level, the electronics will send a signal to turn on the water pumping and the gas valve. The whole process will start over.
When a tap is opened in the mixer in a double-circuit boiler, a flow sensor reacts, which tells the electronics to switch the three-way valve to the DHW heating mode.

Turning off the hot water tap switches back to heating mode. Some manufacturers provide for the heating of both heat exchangers during periodic switching.

The boiler does not heat water for heating

So, let's consider the main reasons why a gas boiler does not heat water for a heating system and what to do about it:

• airlock. It is necessary to examine the heating system for the presence of air in the radiators. To eliminate this problem, you need to install an air vent. The principle of its operation is similar to the operation of an expansion tank, but it is able to maintain pressure in the system. Use an air vent to bleed air from the system. It is important to inspect the valve itself for mechanical blockage - scale may be present there;
• corrosion in radiators. You can determine the blockage of heating devices by draining water from the system. If the water flowed dirty, then it is necessary until visually clean water appears;
• connection errors. Hot water may not flow if the diameter of the pipes is not the same as provided for by the project or instructions. It is necessary to check the compliance of the pipeline, the correct connection and the quality of the installation of valves;
• insufficient network pressure. You should try to add water to the heating system, as there may not be enough pressure to trigger the automatic ignition of the burner;
• the presence of scale in the heat exchanger. The first sign is the prolonged heating of the coolant and the heating of the batteries. It is necessary to get rid of deposits and carry out boiler water treatment. To do this, you need to disassemble the boiler, and dismantle the heat exchanger assembly.

Before this, you need to shut off the flow of gas and water to the device. Then, flexible connectors from the pump are connected to the heat exchanger and it is washed with a composition with a special cleaning agent, which can be purchased commercially. After that, the parts are washed with water.

It is important to understand that the addition of chemicals to the coolant prevents and reduces the appearance of deposits on parts. But before using the reagents, you need to read the instructions for the boiler, since some manufacturers, such as Ariston, Electrolux, Buderus, Navien or Arderia, do not provide for the use of chemical additives in the coolant. In this case, you can use water purification filters or distilled water.

Some manufacturers allow the use of antifreeze instead of water in the heating system. This substance can be used in the following boilers: Baxi, Vaillant, Proterm, Beretta, Korea Star. However, it should be understood that each manufacturer recommends using their own antifreeze;

• filter clogging. If the filter screens are clogged with mechanical debris, the radiators can also warm up poorly. Therefore, the filter should be regularly checked and cleaned by rinsing with water. If clogging occurs too often, then such a part must be replaced;
• wrong setting. First of all, with little or no heating, it is necessary to check the settings of the control unit. Insufficient temperature may be set and the gas does not heat the water;
• malfunctions of pumping equipment. If the pump power is not enough to ensure good circulation, then it may turn off when it overheats. This can happen when the DHW circuit is turned on;
• improperly selected heating devices. If radiators with inappropriate heat transfer parameters and design are installed in the system, this can also lead to weak heating;
• incorrect slope of pipelines. Most often this problem occurs in systems with natural circulation. Regulatory documentation specifies that the slope of the pipes should be from 10 mm per meter of pipe. In case of non-compliance with these requirements, circulation may be disturbed and, as a result, there will be no heating due to the low coolant flow.

The boiler does not heat hot water

In addition to the lack of heating of the heating system, it happens that the gas boiler does not heat the hot water circuit.

The most common cause of this negative phenomenon is the critical formation of scale in the heat exchanger.

After all, the scale has a structure that limits the passage of the coolant, as well as taking away its heat. This is due to the thermal conductivity of salt deposits - it is much lower than the thermal conductivity of the metal from which the heat exchanger is made. Therefore, the boiler does not heat hot water well.

It is also possible that a piece has moved away from the salt deposit, blocking the flow completely, which leads to a complete cessation of the supply of hot water.

The next reason that the boiler does not heat water is the malfunction of the flow sensor.

Structurally, the sensor is a bladed device through which water flows, which is a condition for its operation, because it sends a signal about the presence of a flow to the electronics, which, in turn, starts heating the water again. It happens that the sensor is clogged, but it can be cleared of blockage without removing it.

The device has the shape of a cylinder and is located near the circulation pump. To start cleaning, open and close the tap near the sensor. In case this does not help, then it should be unfastened and removed, manually cleaned and replaced. If this does not help, then the sensor is most likely defective and needs to be replaced.

The reason for the lack of water in the DHW circuit may be a faulty three-way valve.

It is designed to shut off the heating system when the hot water tap on the mixer is opened. If the valve does not work, the boiler does not switch to DHW heating from heating water to heating. The first reason for its failure may be a blockage of corrosion products, which must be disposed of.

If this does not help, then the valve should be replaced. It is also possible that the hose system and filter are contaminated. This problem is barely noticeable on the heating circuit, and on the hot water circuit it will be more noticeable. These items need to be cleaned.

During the operation of a double-circuit gas boiler, each user will encounter certain problems associated with the operation of the hot water circuit. These problems are inevitable. They always appear, regardless of the manufacturer of the boiler and its heat exchanger, on the design features of the boiler; It doesn't matter if the boiler is wall-mounted or floor-standing. Often the boiler starts to heat hot water poorly or does not heat it at all. Especially when you use multiple points at the same time. Let's talk in this material how to get rid of this problem forever.

In any room where a double-circuit gas boiler is installed, whether it is an apartment, a country house or an office, there are certainly several places that are water intake points: a washbasin in the toilet, a shower in the bathroom, a sink in the kitchen. All these points are connected to the hot water circuit of the boiler.

What happens when hot water is turned on at one point of intake

The double-circuit boiler is set to maintain a certain temperature in the hot water circuit. When hot water is turned on at one of the points:

• for some time, cold water continues to flow from the tap, which stood in the pipe before it was opened,
• the heating of the boiler is turned on, while it takes a certain time for it to reach the set temperature,
• after a few seconds, heated water enters the pipe and begins to move to the intake point,
• a few more seconds are needed for hot water to reach the point of intake,
• an additional few seconds are necessary due to the fact that the incoming water seems too hot to the consumer, and he regulates the water supply to the mixer.

Thus, at least a few seconds pass from the moment the hot water tap is opened to the moment the water supply starts at a comfortable temperature. The farther the water intake point is from the boiler, the longer this period of time.

All this time, the user cannot fully use the water and it will be that the boiler does not heat normally hot water. It waits for the moment when water arrives at a comfortable temperature. Meanwhile, water that is not comfortable for the user simply goes down the drain.

Unproductive water consumption can range from a few liters to tens of liters, depending on how far the water intake point is from the boiler.

What happens when hot water is turned on at the same time at two points of intake

The scheme becomes more complicated if, during the use of hot water at one point of intake, it becomes necessary to turn it on at another point, for example: when the shower in the bathroom is turned on, it becomes necessary to wash your hands in the washbasin of the toilet. In this case:

• the rate of use of hot water increases sharply, its consumption increases,
• there is a weak pressure of hot water;
• the flow of cold water into the boiler increases,
• a drop in the temperature of the boiler heat exchanger leads to the fact that the water temperature at the first point of intake ceases to be comfortable,
• a few seconds are needed to turn on the automatic boiler for heating,
• a few more seconds to ensure that both users at two points of the fence can use water at a comfortable temperature.

All this time, both users cannot fully use hot water. She comes intermittently. Unproductive consumption of water, uselessly going down the drain, increases dramatically.

What if one of the users turned off the water? In this case, the consumption of hot water drops sharply. A temperature jump occurs on the heater of a double-circuit gas boiler. As a result, the temperature of hot water rises sharply at the point of intake, which continues to work. The user cannot fully use the water, it goes into the sewer until the automatics work on the boiler, and the water of the desired temperature begins to flow to the user in a stable mode.

Since such situations are repeated several times every day, the unproductive consumption of hot water is increasing every day. At the same time, one should not forget about the discomfort that users experience during moments of unstable hot water supply.

Ways to solve the problem

The problem can be solved in ways that require significant investment, for example:

• use with a boiler
• purchase of a new boiler with a built-in boiler.

However, there is a way that is less expensive, but very productive - inserting an electric storage heater into the hot water circuit. Moreover, for this purpose, any standard heater with a volume of 30 liters is quite suitable, regardless of the manufacturer.

Use a water heater

A water heater embedded in the hot water circuit acts as a buffer tank. Its purpose is to equalize the temperature of hot water and smooth out possible temperature fluctuations. The storage water heater and the gas boiler heater are set to the same operating temperature.

Even if hot water taps are turned on simultaneously at different points of its intake, all users will initially receive water from the storage tank. The time spent waiting for a comfortable water temperature is reduced. Reduced waste of water.

Turning on and off the hot water supply at any point of the intake causes a temperature drop in the water at the outlet of the gas boiler. However, this water enters the lower part of the water heater, and when it leaves the upper part, the temperature jump is completely smoothed out.

Connecting the water heater through a ball valve allows you to switch to the normal gas boiler operation system at any time, which can ensure uninterrupted hot water supply in the event of a water heater breakdown.

Using a bypass jumper with a tap in close proximity to the boiler allows you to exclude the boiler from the hot water supply system. If the boiler is under maintenance, the use of the existing water heater will ensure the uninterrupted operation of the hot water supply system.

Use expansion tank

In winter, when the heating circuit is activated at the boiler, any turning on of hot water leads to the fact that it is turned off so that the hot water circuit can turn on. During the summer period, when the boiler is not connected to the heating circuit, each hot water switch-on causes the gas boiler to switch on.

Often, the user turns on the hot water faucet just to rinse their hands. The boiler turns on or switches, hot water flows through the pipes. But the user can simply not wait for it by washing his hands with cold water.

Meanwhile, frequent and useless inclusions and switching of the boiler “eat up” its service life. A possible solution is to install a small expansion tank. It is installed in front of the water heater. In the presence of such a tank, for the first time after turning on the tap, hot water enters the pipe exclusively from the water heater due to the increase in pressure in the tank. Thus, in the case of a short use of hot water, there is no need to turn on and switch the boiler.

Use recycling pump

The best option - the water heater is located in the immediate vicinity of the hot water intake points. The closer it is, the faster hot water will enter the tap, the more efficiently it is used. If this option of installing a water heater is not possible, then it is recommended to install a recirculation pump.

The pump is installed on the segment between the water heater and the hot water intake points, ensuring the slow movement of hot water through the pipes. In addition, if you insert a heated towel rail on this segment, it will perform its direct function at any time of the year, regardless of the operation of the heating circuit of the boiler.

The effectiveness of the proposed method

With a relatively small cash outlay, the installation of a water heater, expander and pump allows you to:

• save up to 25 thousand liters of water per year if a family of four lives in the apartment,
• use water at a comfortable temperature even in the case of simultaneous operation of several points of water intake,
• reduce the consumption of gas and electricity,
• extend the life of the double-circuit boiler.

One of the problems that can happen when using a double-circuit boiler. The boiler does not heat hot water. The main and most common reason why the boiler does not heat water well is the heat exchanger is clogged.

In this article I will describe how I treat this problem. Thus, you can also get out of the situation if you have a double-circuit boiler with a plate heat exchanger.

I have a well at home and the water is very hard, so there are always problems with hot water, so I use citric acid to fix the situation.

The task is this. How to deliver this acid to the inside of the heat exchanger with the least effort. I found such a way. I have a magnetic converter at the entrance to the boiler, which should remove the hardness of the water, but it does not remove it, in my opinion this is a fiction. But for me it is good that it is installed directly at the entrance to the boiler. You can see it in the photo below.

It has an American nut on it, unscrewing which you can easily pour citric acid into the inside of the pipe.

But for this you need to turn off the water. Next to the boiler I have a collector. He is in the photo below.

Now all the ducts on it are open and with one easy movement I shut off the water supply to the boiler.

All water is blocked, now you can unscrew the American on the magnetic filter. And do not forget to come up with something, from the flowing water from the boiler, there is not much of it, but it is there. I wound up the rag.

Then I pour citric acid into the inside of the pipe.

I twist the American back and open the tap for supplying tap water to the boiler.

Now it is important to understand when the acid enters the heat exchanger. Since my water tap is located a meter from the boiler, I determine whether the acid has reached the heat exchanger to taste. I just open the faucet in short jerks and taste how “sour” went, which means the entire system from the magnetic filter to the faucet is filled with citric acid.

Next, you need to turn off the tap so that your family does not drain all the acid ahead of time.

I refuel the system at night and until the morning I have it acidified. In the morning I open the water supply valve to the boiler and drain all the acid. The water will sizzle, don't be alarmed.

A question may arise, but will the acid heat exchanger not eat through? I poked around on the forum of chemists and came to the conclusion that organic acid (citric refers to it) is harmless to copper.

I use this method as needed. If you don’t like how the boiler heats water or the pressure of hot water has become weak, I take and process the heat exchanger with citric acid.

If you have polypropylene connections to the boiler, and there is no place to fill the acid, then think of something similar, it will not take much time.