Heating that stops at night does not necessarily mean there is a fault with the boiler or heat pump. Often, operating hours, nighttime temperature setbacks, or a mismatch between different controls are to blame. Other times, the lower outside temperature reveals a problem that is not noticeable during the day. For an accurate diagnosis, determine whether the installation is turning off, displaying an error, or running without heating effectively.

1. First check the thermostat and night schedule

When the interruption occurs at roughly the same time every night, start with the settings. A programmable thermostat may automatically switch to economy mode, lowering the desired temperature. If the room remains warmer than the new setting, the heating stops normally until it is needed again.

  • Check the current time, day, and weekly schedule.
  • Look for "eco," "sleep," away, or frost protection modes.
  • Compare the desired temperature with the room temperature displayed.
  • Check for a low battery indicator or lost connection on a wireless thermostat.
  • See if there is a second schedule on the boiler, heat pump, or control app.

For a brief test, select manual mode according to the manual and increase the desired temperature slightly. Observe if a heating demand is displayed and if the installation responds. Do not turn the setting to the maximum: it does not necessarily accelerate heating and makes assessment difficult.

Also check the position of the thermostat. If it is affected by a fireplace, an electrical appliance, or warm air from another room, it may cut off the heating while the bedrooms remain cold. In an apartment building, first confirm the shared hours with the building manager.

2. Distinguish between shutdown and insufficient heating

At the time of the problem, look at the unit's screen without removing covers. Is it on? Is there an error code? Does it indicate heating mode, standby, or hot water production? This information is more helpful than the general observation that "the radiators have gone cold."

If the screen is off, visually check the external power switch and the indicator for the corresponding circuit in the electrical panel. Do not open the panel and do not repeatedly reset a circuit breaker or residual current device (RCD) that trips. Repeated tripping requires an inspection by a licensed electrician.

If the unit is running but the house is getting cold, consider a different possibility: nighttime heat losses may exceed the available output at current settings. This does not prove that a larger unit is needed. Compensation, water circulation, or power limitation in night mode may be involved.

Note whether all rooms are affected or just one. When a room remains cold while others are heating, a local problem with the valve, zone setting, or flow distribution is more likely.

3. Water pressure, circulation, and radiators

In water-based installations, low pressure can cause a safety shutdown. Read the pressure gauge or electronic indicator and compare the value with the manufacturer's instructions for the specific installation. There is no single correct pressure for all systems: it is affected by the network height, layout, and water temperature.

Record the pressure when the system is cold and when it is running. Large fluctuations, frequent need for refilling, or water from the safety valve require technical investigation. They may be related to a leak, expansion vessel, or other hydraulic problem, without this being confirmable from a single reading.

  • Look for visible traces of water under the unit and near accessible connections.
  • Check that the known radiator valves have not been closed by mistake.
  • Observe if gurgling sounds are heard or if some radiators remain cold.
  • In a zone installation, check the controls without interfering with solenoid valves or wiring.

Do not refill water blindly and do not attempt to bleed the system while the installation is very hot. Refilling or bleeding should only be done if intended for the user, you know the procedure, and you follow the manual. Continually adding water is not a leak repair.

A problem with the circulator, a clogged filter, or insufficient flow can also lead to a shutdown due to overheating. Cleaning hydraulic circuit filters and working on the circulator are technician tasks.

4. Potential causes according to the heating source

Natural gas or oil boiler: A burner lockout may be related to fuel supply, ignition, flame detection, or flue gas exhaust. Record the exact error code. For oil, check only the accessible level indicator, if present. Do not open fuel lines and do not attempt combustion adjustments.

Condensing boiler: In severe cold, an exposed section of the condensate drain may freeze and cause a lockout. A visual check from a safe point is sufficient. Do not disconnect pipes and do not use an open flame or boiling water. Repair and protection of the route require proper technical handling.

Heat pump: In cold and humid weather, it performs periodic defrosting of the outdoor unit. A temporary reduction in heat output, water, and steam during defrosting may be normal. Prolonged inability to heat, persistent ice, or an alarm should not be automatically attributed to defrosting.

Also, check if a silent operation mode is active that limits performance. Remove only loose objects around the unit, without coming into contact with the fan or elements. Do not break ice with tools.

5. When to stop checking and call a technician

Call a technician when the interruption recurs, an error appears, the pressure drops systematically, or there are leaks and unusual noises. Resetting is permitted only as described in the user manual and provided there are no signs of danger. If the error returns, do not continue to reset and do not bypass safety devices.

If you smell gas, do not operate electrical switches, plugs, or flames. Move away from the area and contact the gas network's emergency service or 112 from a safe location. If a carbon monoxide detector is triggered or if headaches, dizziness, or nausea occur near a combustion appliance, go immediately to fresh air and seek emergency help. Carbon monoxide has no odor.

For a more effective check, keep a photo of the error code, device model, time of interruption, thermostat settings, and pressure readings. Note if the hot water is working and if the heating returns by itself in the morning. These limit unnecessary tests.

Frequently Asked Questions

Why does the heating stop every night at the same time?

First, check the weekly schedule, nighttime setback, shared hours, and hot water scheduling. A constant time often points to automation, without ruling out a fault.

The thermostat shows heating but the radiators are cold. What does this mean?

The indicator may only show a heating request. It does not confirm that the burner, circulator, or zone valve is operating. Check the unit's screen for additional information.

Should I turn off the heat pump completely at night?

There is no single answer. In high-inertia systems, such as underfloor heating, a complete shutdown may make morning recovery difficult. Follow the settings chosen for your installation.

If it works after a reset, is the problem solved?

Not necessarily. A reset may simply temporarily clear the lockout. If the interruption recurs, record the error and request a technical check instead of successive restarts.