You just noticed that your heat pump runs all the time, and you’re wondering why. In fact, there are several reasons for this problem. Here are 7 possible causes and solutions.

1. Extreme Temperatures

Winter: Heat pumps operate efficiently down to around -15°C to -25°C, depending on the model. When the mercury falls below this limit, the heat pump loses efficiency and runs continuously in an attempt to maintain indoor heat. If your unit no longer heats sufficiently in very cold weather, it may be in defrost mode, or it may be operating in overdrive.

Solutions :

• The first thing to do is check that your heat pump is adapted to Quebec winters (some models adapted to our northern climate operate down to -30°C).
• Make sure the outdoor unit is not covered with snow or ice, as this can obstruct heat exchange and force the machine to work harder.
• If your unit is designed for a maximum of -15°C, use a supplementary heating system (electric baseboard heaters, fireplace, etc.) on the coldest days.

In summer: If the heat pump runs continuously in hot weather, it’s probably struggling to reach the required temperature. Poor insulation or an undersized unit may also be to blame.

Solutions :

• Close blinds and curtains during the day to reduce heat entering the house.
• Make sure the outdoor unit is well clear and in the shade to maximize heat exchange.
• Make sure there is no refrigerant leak (see point 4).

2. Dirty Filters or Lack of Maintenance

A dirty filter blocks air circulation, reducing the efficiency of your heat pump and causing it to run longer than necessary.

Solutions :

• Clean the indoor unit filters every 4 to 6 weeks during periods of heavy use.
• Be sure to check and replace the furnace filter of a central heat pump according to the manufacturer’s recommendations.
• Make sure air ducts are free of obstructions and clogging.

3. Sensor or Thermostat Problem

If the thermostat or a temperature sensor is incorrectly calibrated, it may not correctly detect the ambient temperature, preventing the unit shutting down.

Solution :

• Check that the thermostat is displaying the correct temperature by comparing with an independent thermometer.
• Make sure the operating mode is set correctly (Heat in winter, Cool in summer, and Auto for ventilation).
• Reset the thermostat by switching off the power supply for a few minutes.
• If the problem persists, consider replacing the thermostat or temperature sensors.

4. Refrigerant Leak or Shortage

A refrigerant leak causes a drop in performance, forcing the heat pump to run non-stop without managing to heat or cool effectively.

Solutions :

• Check whether the unit is taking longer than usual to heat up or cool down.
• If you notice abnormal icing on the outdoor unit in the summer, this may indicate a lack of refrigerant.
• Contact a certified technician to detect and repair any leaks.

5. Poor Home Insulation

If your home lets in too much heat in the summer or loses too much heat in the winter, your heat pump will have to compensate by working longer. Poor insulation may explain why it never stops.

Solutions :

• Add insulation in the attic, walls and around windows to limit heat loss.
• Seal air leaks (doors, windows, electrical outlets).
• Use thermal curtains in winter and solar protection in summer.

6. Electrical or Mechanical Problems

A blocked relay, tired compressor, faulty outdoor fan or faulty reversing valve can prevent the heat pump shutting down properly.

Solutions :

• Listen to your heat pump: if it hums constantly without pauses, it may be a worn relay or compressor.
• Call in a professional for annual maintenance to check the condition of all components.
• If your heat pump is more than 10-15 years old, a major breakdown may be imminent. Repair or replacement may be necessary.

7. Heat Pump Undersized

A heat pump that’s too small for your home has to work harder to reach the set temperature. And when temperatures drop or rise sharply, it can’t keep up with demand, forcing it to run non-stop.

Solutions :

• Check the BTU capacity of your heat pump and compare it to the surface area of your home.
• If it’s too low, consider adding a second wall unit or a more powerful model.
• Improve insulation to reduce energy demand.

When to Call in a Professional?

You have checked your outdoor unit, the state of the filters, the thermostat and the problem persists? If your actions can’t solve the problem, you need to act as soon as possible by consulting an expert like the certified technicians at Entreprises MPH, who can identify the cause of the malfunction and correct it.

Or, if need be, suggest the heat pump that’s right for your home and your budget.

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Whether it’s for repair, maintenance, the purchase of a central heat pump or a wall-mounted heat pump, or for installation, our know-how, our licenses and our concern for satisfaction ensure optimal service.