Frequently asked questions

Find out our frequently asked questions, which you can conveniently find by different topics.

Maalämpö – vianmääritys

Failures in technical equipment usually occur without a warning – and ground source heating equipment is no exception. Failures in ground source heating equipment often manifest themselves as unexpected problems in heat distribution, but also as alerts given by the equipment.

Do you suspect there might be something wrong with your ground source heating equipment? Take a look at these frequently asked questions – the answer might be found below!

  1. Look for a problem code on the ground source heating pump control panel and write it down. Check whether the heat pump has a software restart or reset function. If it does, restart the system. If the equipment does not have a reset function or a software restart does not solve the issue, switch off the device from the main switch and wait for 5 minutes before switching it on again.
  2. If the fault reoccurs after start-up, then it is probably a fault that requires an acknowledgement of the overtemperature protector, for example.
  3. Be sure to check both the power supply fuses of the ground source heat pump at the property’s power room as well as the fuses of the actual ground source heat pump.
  4. If the fault persists, contact maintenance. When contacting maintenance, be sure to report the problem code and the measures you have already taken with the heat pump.
  1. Check if the equipment is in failure (point A).
  2. Check the heating curve settings and the current setpoint.
  3. Check whether the pump has gone into summer stop mode or lowered mode.
  4. Check that the room thermostats are open and set correctly.
  5. Clean the waste collector on the heating side. See cleaning instructions in this video.

  1. Check the heating curve settings and the current setpoint.
  2. Check if the equipment is in failure (point A)
  3. Check that the 3-way valve is working properly. In the heating mode, one branch should point towards position B.
  4. If you have a cooling coil unit, see section G
  1. Check whether the accumulator is in failure.
  2. Check whether domestic hot water production is on. (See the manual for your equipment – you can find the manuals in our data bank)
  3. Check the domestic water production setpoint. (See the manual for your equipment – you can find the manuals in our data bank)
  4. Has there been an increase in water consumption? Temporary increases in consumption may cause domestic hot water to cool down. Check the hot water temperature and wait until sufficient amount of hot water corresponding to the setpoint has been produced.

Check the position and setting of the thermostat. The cooling of a single room means that the room thermostat has been set incorrectly or the thermostat is defective.

Overpressure alert:

  • Check that the heating circuit’s thermostats are open.
  • Check the heating circuit pressure from the pressure gauge
  • Check if the waste collector on the heating side is blocked; see the instructions in the video.

Underpressure alert:

  • Check the collector pressure from the pressure gauge.
  • Check that the collector shut-off valves are open.
  • Check if the collector’s waste collector is blocked; see the instructions in the video.

Alarm contact active / Overheat protector alert:

  • Acknowledge the overheat protector of the flow-through resistor. Note! Remove the red resistor cap in order to acknowledge the overheat protector. The instructions can be found in this video


Sensor temperature alert:


  • Check the controller display to see whether the sensor reading could be correct.
  • If the sensor shows readings that are significantly incorrect (at least tens of degrees), the sensor is likely to be broken. Contact maintenance and report the problem code shown on the equipment display.

The equipment is not working

  1. Check whether the remote control has batteries that work.
  2. Check that power has been turned on for the coil unit at the main switch.
  3. Check that the fuses are OK.


The equipment works, but doesn’t provide enough cooling

  1. Check from the device display whether the ground source heat pump receives a cooling request.
  2. Check that the fan filters are clean (open the coil unit housing to check this). (See the equipment manual for more information – you can find the manuals in our data bank)
  3. Check for any obstructions in the airflow of the unit.
  • Check that the coil unit fan is running


The majority of failure situations can be resolved by following the instructions above. In many cases, locating a fault requires a little familiarity with the equipment, but it is not difficult when you get to know the basic functions of your ground source heating equipment.

Ground source heat terminology

We have compiled in our ground source heat terminology the most common terms used for ground source heat and its utilisation including explanations. Check out the key ground source heat terminology so that you know what we’re talking about.

Sensors measure temperature, pressure, etc. The operation of the heat pump is adjusted on the basis of the sensor measurements.

Automation controls the operation of the heat pump’s compressor, circulation pumps and other peripherals based on the measurements.

The kilowatt-hours (kWh) used in a year to heat a house and domestic water. The energy requirement includes the total electricity consumed by all of the electrical appliances in the house.

The indicative energy requirement distribution of a detached house could be, for example: heating 52%, domestic electricity 28%, domestic hot water 20%. In a ground source heated detached house, the production of heating and domestic hot water typically takes up 60% of the energy, and the domestic electricity takes up the rest.

The room sensor measures the indoor temperature of the property.

The effect of the room sensor on the adjustment result. If the effect is big, room temperature alterations have a greater impact on the adjustment result.

The expansion coil is a heat exchanger that transfers the heat collected from the ground to the refrigerant. In the expansion coil, the refrigerant turns from liquid into steam.

The inverter, or the frequency converter, can be used to control, for example, the heat pump’s compressor to reach the appropriate speed.

Cascade connection means connecting several heat pumps to operate in the same system such that they can be adjusted as one.

The heat pump uses the heating energy collected from the brine circuit. Usually from heat wells, horizontal piping to a field or other “residual” heat, for example, from exhaust air or some process.

A compressor increases the pressure of the vaporised refrigerant, simultaneously raising its temperature.

Refrigerant is a heat exchange agent used in the cold process. The state of the refrigerants used in heat pumps changes during the different stages of the process from liquid to gas and back.

A charging pump transfers the heating energy created by the heat pump to heat domestic water or the property.

A condenser transfers heat from the refrigerant to heat the property or domestic water. The condenser also changes the state of the refrigerant from gas to liquid/a mixture of liquid and steam.

A dirt filter collects debris from water or brine. If the filter is blocked, circulation water pumps are unable to circulate water or brine in the system.

Seasonal Coefficient of Performance, or SCOP, indicates the efficiency of the ground source heat pump better than COP (see Coefficient of Performance) because it takes into account the variations between different heating periods.

SCOP is calculated for four different heating periods because the temperature intervals applied to the calculation, the basic temperature measurements and the dimensioning loads are seasonal.

In addition, geographical climate zones are taken into account when calculating the heat coefficients of ground source heat pumps. In northern Europe, the calculation of a heating period heat coefficient is based on the climate conditions of Helsinki.

For example, the Gebwell Aries 6 inverter ground source heat pump (0°/35°) has a SCOP value of is 5.6. The corresponding SCOP value of the Aries 12 ground source heat pump is 5.8.

The ground source heat pump’s heating output is measures according to the building’s heating requirements either as partial or full power.

A heating circuit refers to a heating network or a part thereof, for example, the underfloor heating used to heat a house and garage heating may be separate (= heating circuits).

Heating water circulates in the heat pump and the heating network. Usually, heating water is also used to heat domestic water.

The heat recovery liquid is approx. 25-30% ethanol (i.e. spirits) that has been denatured, or made undrinkable using an additive. Normal water cannot be used as a heat recovery liquid because it would freeze in the ground source heat pump’s expansion coil and hence break the heat exchanger. The freezing point of the heat recovery liquid is below -15 Celsius.

A heat collection pump that circulates the heat recovery brine from the heat collection circuit to the expansion coil and back.

See charging pump.

The Coefficient Of Performance, or COP, of the heat pump is usually referred to as efficiency. COP indicated the ratio of the consumed and produced energy. The COP of an air source heat pump indicates how efficiency the consumed electrical energy can be converted into heat energy.
Formula: The heat energy received from a ground source heat pump (kW)/the electrical energy consumed by a ground source heat pump (kW) = COP. For example, COP 5 means that a 1 kW input power produces 5 kW of heat energy. The higher the figure, the more energy-efficient the device is.
You can reach the COP rating by conducting the measurements at a temperature of +7 degrees. Because of this, COP alone will not always yield reliable information about the functionality of a heating device, for example, in sub-zero temperatures.
When comparing COP ratings, it is a good idea to confirm the standard and conditions used in the calculation. The previously used SFS-EN 255 standard gives a better COP value than calculations performed using the official SFS-EN 14511 standard.
For example, the Gebwell Aries 6 inverter ground source heat pump’s COP (0°/35°) is 4.8. The corresponding COP value of the Aries 12 ground source heat pump is 4.9.

The heat curve determines the temperature of the heating water used by the ground source heat pump to heat the property. Usually, the heat curve has a specific inclination or several points, for example, if the outdoor temperature is -20 degrees, underfloor heating should be set somewhere between 30 and 35 degrees.

A heat well provides cooling energy to heat the property. In other words, ground cooling means that brine cooled in the heat well is used to cool down the property, for example, via a fan or ventilation.

An output pipe refers to the pipeline leading somewhere, for instance, the heating output pipe is the output pipe of the heating circuit.

The power (kW) of the electricity used by a ground source heat pump drawn from the mains in the nominal conditions. For example, the nominal input power of a Gebwell Aries 6 inverter ground source heat pump (0°/35°) is 0.78 and the nominal input power of an Aries 12 ground source heat pump (0°/35°) is 1.36.
(0°/35°) means the input powers in the examples were calculated in conditions where the temperature of the heat source, i.e. the brine circuit, is 0 degrees and the heat pump sends water in 35 degrees to the heating circuit..

A partial-power heat pump has enough capacity to heat the house at reasonably cold weather. In extreme cold, the pump’s internal heating resistors produce the extra heat required.
When acquiring a partial-power ground source heat pump, the amount of the required electrical energy increases, which slightly reduces the depth of the energy well. When getting a heating system, it is a good idea to investigate the effects of the ground source heat pump measurements on the total costs.

An expansion tank levels the liquid volume variation caused by the heating, cooling or brine circuit’s temperature differences.

A soft starter is usually a switch that replaces the contactor and starts, for example, the heat pump’s compressor such that the start does not create a loud click.

A fan converter is a device with a liquid-air heat exchanger and a fan. The fan circulates the room air through the heat exchanger. Fan converters are used for heating and cooling distribution. There are also combo devices that can both heat and cool.

A buffer tank compensates the running cycles of the heat pump and acts as a heat storage in pumps equipped with a change-over valve when the heat pump is heating water.

See Seasonal Coefficient of Performance

Published by Suomen Standardoimisliitto, the SFS-EN 14511 standard sets the principles according to which the energy calculation of heat pumps intended for heating or cooling room spaces is made. The coefficient of performance, or COP, of heating devices is calculated in accordance with this standard.

An immersion heater that heats the water in the tank.

A valve that only allows flow in one direction.

The energy requirement is the maximum of kilowatts required to heat the building and domestic water on the coldest day of the year.

In the cold process, superheating supply is the phase where the refrigerant does not contain steam but it is entirely gasified. A superheated refrigerant is hotter than the boiling temperature.

Desuperheating supply means that there is another heat exchanger before the condenser (= the de-superheating supply heat exchanger) that gives off a smaller amount of energy at a higher temperature, for example, to heat domestic water.

See buffer tank.

A heat pump that is measured at full power has enough power to heat a property even in extreme cold without having to produce the extra heat using heating resistors.

An outdoor sensor measures the temperature outdoors. The outdoor sensor is usually installed outside the house, usually on the north wall. The outdoor sensor sends the temperature information to the heat pump, which adjusts the heating of the property according the outdoor temperature and the set heat curve.

The change-over valve turns the water flow to heating domestic water or the water circulating in the heating system.

The ratio of the energy consumed and created by the heating system in a year, taking into consideration both heating and the production of domestic hot water.
Now that you are familiar with the terminology, you can read more about the operating principle of ground source heat.
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