Heat Pumps - How they work

A Heat Pump transforms heat from a low temperature level into heat at a high temperature level at which it can be used for heating purposes. Even in wintertime with temperatures far below 0°C a Heat Pump can take energy from the environment.This is performed by an endless “cooling” cycle. The cooling liquid evaporates at a very low temperature and takes a substantial amount of energy from the ambient air, when changing from a liquid to a gas phase.


The compressor - compresses this Refrigerant gas and thus brings it to a high temperature level. The hot gas then condenses, in a condenser, or heat exchanger, where it transforms into a liquid state and gives off the heat to the water that is to be heated. The refrigerant working fluid is then expanded when passing through an expansion valve with a resultant reduction in temperature, so that the circular process can continue over again.  The Heat Pump extracts stored solar heat from the environment - air - and delivers it, plus the driving power in the form of heat to the hot water circuits.

Coefficient of Performance (COP)

COP = amount of heat energy delivered ÷ drive power (kW) consumed.

The coefficient of performance (COP) indicates the delivered amount of heat, relative to the drive power required.

A coefficient of performance of 4 therefore means that four times the used electrical energy is available as usable thermal output. The coefficient of performance is an instantaneous value.
The “System COP” is the yearly performance figure results from the usable energy in relation to the electrical driving power required for the entire heating period. It is the average integrated value of all COP values accumulated over a period of a year. 

The temperature lift determines the COP

In all cases the Coefficient of Performance (COP) depends on the temperature difference between the heat source and the heat use: The lower the required temperature lift is, the more efficient and economical the Heat Pump works. Therefore the optimal design of the entire installation is very important.

Working Liquid / Refrigerant

Substances are suitable as working liquids or refrigerants if they have high specific energy content and need a high level of energy for evaporation.   In our new millennium only substances free from chlorine are permitted. These do not have any ozone-depletion-potential (ODP = 0) and R134a as well as R410a, fulfil these conditions.

Metran Heat Pumps use the inflammably safe refrigerants R134a and R410a only. The Esther oil used is thereby biologically degradable. This means the Heat Pumps can be installed at any location and without any restriction.   In contrary, Heat Pumps with flammable media however, have restrictions and numerous safety guidelines to follow.