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Interview with Giacomo Benassi, Research & Development Manager of Galletti Spa

As of Saturday 26 September 2015, regulations establishing new energy labelling and Ecodesign requirements for hydronic heat pumps intended for space heating and domestic hot water production entered into force across Europe. We interviewedGiacomo Benassi, Research & Development Manager of Galletti Spa, on this subject.

Mr. Benassi, what do these new regulations consist in? «Both regulations fall within the framework of European ERP (Energy Related Products) legislation, which establishes the minimum requirements, in terms of seasonal energy efficiency and noise levels, which hydronic heat pumps intended for space heating and domestic hot water production must meet in order for these products to be placed on the EC market. The energy efficiency requirements extend to units with a rated output of 400 kW and noise level limits to 70 kW units. This information is partly summarised in graphic form on a label (mandatory up to an output of 70 kW) affixed to the product, as is already the case, for example, for domestic air-to-air direct expansion heat pumps (split system)».

Where do Galletti heat pumps stand within the energy classes defined by the ERP Directive? «Galletti heat pumps rank at the top levels in terms of seasonal energy efficiency, corresponding to classes A+ and A++ depending on the type of model and application, which confirms the high quality of the product. The design of Galletti heat pumps is completely in line with the requirements of the ERP Directive: in fact, our Technical Department has always set maximizing efficiency and thus saving energy as its main objective, thanks also to the selection of top quality brand components and the fact that the programming of the control software is developed within the company».

What are the elements that influence the seasonal efficiency of a heat pump most? «Seasonal efficiency depends largely on the capability of modulating output based on the load requirements of the room to be air conditioned. Galletti’s multi-compressor and inverter solutions represent the cutting edge when it comes to seasonal energy performance thanks to the high levels of efficiency under partial load conditions, which, within the period of operation considered, corresponds to the most common situation. It is well known, in fact, that a heat pump almost never works under the rating conditions, though these are usually what the unit is sized for. It is essential to adjust the heat pump taking account of the location where it is installed and the indoor units in the system: the controllers installed as a standard feature in all our heat pumps ensureclimate adjustment with a sliding set point. This function contributes significantly to saving energy within the period of operation considered, since a reduction in the outlet temperature of the water delivered to the indoor units is obtained with variations in the outdoor air temperature. When the output demanded by a building decreases, we can lower the outlet water temperature while ensuring thermal comfort and making a significant contribution to energy savings. Plus it should not be forgotten that distribution also plays a fundamental role in achieving high seasonal energy efficiency: decoupling the primary and secondary circuits gives us the possibility of controlling capacity in the secondary circuit and switching off the primary circulation pump of the heat pump when the set point is met. All of our heat pumps can be configured to operate according to these system layouts».

Do the seasonal energy performance data provided according to Ecodesign specifications express real heat pump performance? «On this point, the rules seem to have reached the objective only halfway. The successful half lies in the principle of the calculation method: standardizing the calculation method (according to standard UNI EN 14825) makes it possible to obtain a measure of seasonal energy performance that can be used to compare, for example, different models of heat pumps by different manufacturers. This result is helpful to designers and end consumers. The unsuccessful half, on the other hand, is tied to the fact that the inputs of the calculation method consider only average conditions, in which there is only one climate profile (Strasbourg climate), and this precludes a real estimation of the consumption of heat pumps installed in other locations, with the risk that the actual performance of the unit will be underestimated. Furthermore, when a heat pump is compared with a traditional heating system (fossil fuel fired boiler) in terms of the cost and energy savings, the performance of the heat pump is strongly penalized by the temperature distribution of the Strasbourgclimate profile, characterized by a design air temperature of -10°C, which does not take into account all the climate profiles of southern European locations. In order to overcome this limitation, Galletti provides designers with a software tool, SENECA (Seasonal Energy Efficiency Calculator), developed in collaboration with the University of Bologna, which makes it possible to calculate the seasonal energy performance of our heat pumps in both the heating and cooling modes for all major locations throughout Europe, based on the temperature profiles provided by standard UNI TS 11300. In addition to this, SENECA enables a comparison to be made between using a heat pump and more traditional generators, showing the cost and energy savings that can be achieved or the optimal configurations in dual-mode systems designed for cold climates. Another possible implementation of European legislation is to consider the contribution of heat recovery in multifunctional heat pumps, that is, to take into account the increase in efficiency when the unit is required to produce cold water (for the indoor units) and domestic hot water. It should further be highlighted that the data obtained using these calculation methods are more valid for relative comparisons among different heat generating systems (heat pumps or heat pumps plus boilers); the absolute value of energy consumption (kWh of thermal energy produced and electricity consumed) cannot be the real value for at least two reasons: the first is that local weather conditions undergo changes on small time scales (meteorological ones, precisely), whereas the legislation establishes profiles on a climate scale (longer than a meteorological scale); the second is that adjusting the room temperature set points or hot water temperature set points is sufficient to see energy consumption change as a consequence».

Can you give a few examples of the seasonal energy efficiency of your products? «I’d like to show the benefit that can be obtained in terms of the seasonal coefficient of performance (SCOP) by increasing the number of output modulation steps. Let us take two high-efficiency heat pumps as our reference, the LCX141HS, equipped with 2 compressors and 2 refrigerant circuits, and the LCX144HS, equipped with 4 compressors and two refrigerant circuits. We can simulate the seasonal energy performance or SCOP (according to UNI EN 14825) considering an outlet water temperature of 35 °C and the climate profile of Bologna (according to UNI TS 11300). In the figures below, we can compare the relationships between a building’s energy signature (output required in relation to changes in the outdoor air temperature) and the output the heat pump can deliver based on its capacity control steps.

Figure 1: LCX141HS heat pump

Figure 2: LCX144HS heat pump

As can be seen from the two figures above, a heat pump with 4 compressors has a significantly higher ability to adapt output than a unit with 2 compressors; the SCOPs are 3.60 in the case of the LCX141HS and 4.00 in the case of the LCX144HS: this confirms an increase of about 10 % in the SCOP».

How should we interpret the energy label?

Legenda:

I: Supplier’s name or trademark;

II: Model identifier;

III: The water heating function and declared load profile;

IV: The water heating energy efficiency class under average climate conditions;

V: The annual electricity consumption in kWh in terms of final energy and/or the annual fuel consumption in GJ in terms of gross calorific value, under average, colder and warmer climate conditions;

VI: European temperature map displaying three indicative temperature zones;

VII: The sound power level indoors;

VIII: Pictogram indicating operation of the heat pump during off-peak hours (if provided for).