The boiler does not start when opening the tap: what to do?

The boiler is one of those appliances that we do not usually remember until it fails. Something common if we do not dedicate adequate maintenance. If you don’t know why your diesel boiler doesn’t start when you open the tap or why hot water doesn’t come out, it’s a good idea to know what the causes of the problem are and how to solve them.

The boiler is the hot water generation center of those homes that have one of these products installed. In general, the most common use of these boilers is to generate domestic hot water, with which we shower or wash food in the kitchen. Less common is the use for heating, through radiators. Anyway, if our boiler fails, we have a problem, no matter what we use it for.

However, before launching to call the technical service of your boiler, there are some things that you can put into practice to solve the problem. In this article, we give you some details about it, both about what to do if the boiler does not start when you open the tap and how to solve problems such as low hot water pressure or the presence of abnormal messages on the equipment screen. 

The boiler does not start when you open the tap

When we open the boiler, the normal thing is that the water is in charge of activating it and turning on the burner, to obtain domestic hot water. If this does not happen, it is normal for some type of code to appear on the screen, indicating the problem that is affecting the device. However, we list below some of the most common causes.

supply problems

For the boiler to work, three elements are necessary: ​​water, electricity and fuel (gas or diesel). If the boiler does not have water, then the heating elements will not activate, since they do not detect the passage of liquid. If what is missing is electricity, then the boiler will remain off and, obviously, it will not carry out any operation. If what is missing is fuel, there is nothing to burn, so the boiler will try to activate, but without success. This problem is solved by checking the water, gas and electricity connections and checking that everything is as it should.

lack of pressure

One of the most common reasons why the boiler does not light the burner when opening the tap has to do with a lack of water pressure. Let us think that the boiler needs a specific pressure to work , which is usually between 1 and 1.5 bars when cold. If it does not reach this level, it is possible that the circuit is discharged or there is a leak. To solve it, simply prime the circuit to recover pressure, following the instructions for your boiler. 

probe problems

Another common problem is when the boiler is activated for the radiators but does not generate domestic hot water. The boiler has a probe that measures the outlet temperature of the water. If the probe is damaged or not working properly, then it can detect that the water is at the right temperature when it is not. You can try to solve the problem by doing a boiler reset. It is also advisable to check the outlet temperature, in case it does not correspond to what it should be and is lower than necessary.

3-way valve problems

If your problem is that the water does not work with the boiler but the heating does, then the answer may lie in the 3-way valve. This is the one that manages the water traffic through a triple connection with the boiler, the domestic hot water and the water from the radiators. Check that the tap is in the correct position, since it is likely that the route that carries the domestic hot water is closed. If the key is in place, it may be damaged.

Recirculation pump problems

In this case, the problem is the other way around: we have hot water in the taps, but not in the radiators . The cause is related to the recirculation pump. When we use boilers for radiators, a pump is included in the circuit. This piece is responsible for moving the water through the circuit formed by the boiler itself, the radiators and the connections. If the pump fails, then the water does not circulate properly and the radiators do not heat. It will be necessary to check the pump, verify its condition and, if necessary, replace it with a new one.

fume problems

The boilers include a probe designed to assess the quality of the environment in which the equipment is located. If the fumes are concentrated in the area where the probe is located, increasing the concentrations of carbon monoxide, then the probe sends a signal to the boiler so that it stops working . If the smoke outlet is clogged, dirty or there is no proper gas evacuation, the boiler will not start. The solution is to clean the chimney, as well as the rest of the gas outlet circuit. Probe failure is also possible, but less likely.

And if all this fails

As we said at the beginning, these are the most common causes for when the boiler does not heat domestic water or does not start when the tap is opened. But there may be other more complex causes. If these tips do not solve the problem, then you will have to resort to specialized assistance.