The high-temperature heat pump is shown as a serious competitor to the traditional boiler. But we must pay attention to the parameters of operation before making that choice.
Heat pump and heating temperature
Heat pump (BC) technology operates on the basis of the refrigeration cycle. The BC works with the absorption of heat from the condenser and expels it through the evaporator. The temperature recovered from the condenser side in a standard way is to be around 45 ° C.This temperature level is appropriated for use in low temperature emitters, such as underfloor heating or low temperature radiators. Therefore, for a building with good insulation, low consumption, with reasonable heating requirements, with that level of temperature is sufficient, it allows a physiological comfort of quality and energy saving.
The high-temperature heat pump is a BC that can reach 65 ° C. As in any heat pump, operation and performance are linked to external conditions. To be clear, the same heat pump can have a COP of 3, when +7° C is given outside, while when -10 ° is given, the COP will be reduced to 2.
In the same way, the incidence of the heating temperature affects the COP: this same heat pump that presents a COP of 3, with + 7 °C of outside temperature for a heating temperature of 45 º C, presents a COP of 4 for a heating temperature of 35 ° C. The pair "from outside temperature 7 ° C - heating temperature of 35 ° C ", is often used as a basis for the presentation by manufacturers, of the values of the COP, based on the European standard EN 14511; So pay attention to this instantaneous value which should not be confused with the value of the total POPs, seasonal or annual.
The level of 60 ° C is important, but it does not cover the specific needs, especially of boilers operating in old facilities with hot water regimes of up to 80 or even 90 ° C.In this case, the heat pump can not function as a relay of the boiler, the boiler will raise the temperature to 80 ° C or 90 ° C during days of intense cold and the heat pump will begin to operate only with warmer outdoor temperatures, around 5°C.
For the heat pump to replace a boiler, it must be placed in one of the following two scenarios:
- The heat pump called "very high temperature BC" and provides hot water at 80 ° C temperature with an outside base temperature that can be between -10 ° or -20 ° C.
- The heat pump is a high-temperature BC and produces hot water at 60 ° C, for example, at -10 ° C. It covers the heating needs of the premises, due to an improvement of thermal insulation (in windows, insulating walls, ceiling, floor) that can reduce the needs and installation and is compatible with a hot water of lower temperature.
The High Temperature Heat Pump
Beyond 45 ° C, the heat pump uses for the production of hot water, the technology of "improved steam injection", to raise the temperature up to 60 ° or 65 ° C. In fact, after the condenser, a small amount of coolant is separated. Used separately, it is converted into steam and injected during the compression phase. This is the intermediate phenomenon of steam injection. The steam produced cools the compressor and increases the condensation pressure and amount of heat in the condenser without using additional energy. This is the "enhanced steam injection" technique, now well known and integrated into high-temperature BCs.
Heat pump for heating and domestic hot water
On the other hand, the fall of the COP remains an obstacle. Of course, for hot water temperature of 60 ° C, the COP is closer to 2 or 1.5, for -10 ° C. This is always more favorable than a heat emission by direct electricity with an efficiency limited to COP of 1, due to the Joule effect. Let's not forget that once the outside temperature is milder, the COP will increase to values of up to 4 and more (for +7 ° C outside).
This high temperature heat pump is therefore:
- For a building with good insulation that does not require high temperature, 60 ° C, for its emitters, of the type of radiators or underfloor heating
- For installations that require hot water at more than 80 ° C, for example, provided that the heat pump is installed as a relay of a boiler.
The high temperature heat pump
It is a heat pump with a particular technology that allows to raise the water up to 80 ° C. It works without additional electrical supply with a double Inverter circuit of R410A - R134a - associated with Inverter circulators. The efficiency of this heat pump achieves a COP of 1.7 , at -20 ° C outside, for hot water at 80 ° C and progressively at 3, at + 7 ° C outside, for heating hot water regulated at 65 ° C.
High temperature heat pump
It encompasses the renewal of the existing market when the heating temperature must irretrievably reach 80 ° C peak. The target market is the renovation of boilers producing hot water at 80 ° C; fuel boilers, gas boilers, with radiators, standard hot water emitters. This heat pump can replace a boiler. This application is pre-recommended in cases where only a replacement of the generator is possible.
The temperature of the different heating systems
It is evident that if, on a thermal plan, the thermal insulation of the walls can reduce the need and temperature of hot water, so a high-temperature heat pump or operating at a regime of 45 ° C or less, may be sufficient and in all cases, provide a better balace of its annual consumption.
The building or house has a bad energy label
Then the improvement solution is to start a very high temperature heat pump for the production of hot water at 80 ° C, or install a normal heat pump to replace the boiler. This reasoning is valid for any existing energy renewal.
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Authors: Javier Gainza
