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The boiler heat pump produces hot waterA compact system for preparing domestic hot water is represented by boiler, heat pump, air (Series Air Combo).

The heat removed from the air, enhanced by the heat pump, is directly transferred to the accumulation of hot water below. 

The required air can be drawn in from the installation room, from a nearby room or directly from the outside through a ducting: during the design phase, it must be ensured that the air used falls within the operating range of the heat pump (- 10 ° C-43 ° C) and that it is not sucked up by too dusty or polluted environments. 

Produce domestic hot water with a heat pumpLa thermal power to devote to the production of sanitary hot water, depends on the type of production, if snapshot or with backlog.

In systems with heat pump is to choose the production with accumulation in order to avoid Frequently ignitions e shutdowns in correspondence of the peaks of demand, counterproductive for the compressors of the unit.

The most widespread system provides for a tank accumulation, the capacity of which must be sized appropriately, equipped with a serpentine heat exchanger in which circulates the water that is heated by the heat pump. 

La power required to achieve and maintain the desired water temperature, can be dispensed is at the request of the tip, both in the absence of request being stored in the accumulation heat.

La power the generator and the volume accumulation are inversely proportional because the greater the requirement instantly satisfied the smaller the required volume

Vc = ((Qm * Dp * (Tm - Tf) / (Dp + Pr)) * ((Pr/ (Tc-tr)) = Liters accumulation

P = ((Qm * Dp * (Tm - Tf) / (Dp + Pr)) * = 1 Watt generator

dp: Tip life (h);

Qm: Maximum hourly demand hot water (l);

tm: Operating temperature hot water (° C);

tf: Temperature of the cold water from the aqueduct (° C);

tc: Temperature of hot water storage (° C);

Pr: Duration of the preheating (h). 

As a criterion to be followed in the choice of sizing parameters you should not exceed in either the volume of the storage nor in the power of the heat pump.

For the temperature of aqueduct reference can be made atf = 10 ÷ 15 ° C, while the temperature of use assumes tm= 40 ° C.

For the production temperature of the hot water must consult the operating limits of individual heat pumps, it being understood that this temperature may vary in the range of 50 ÷ 55 ° C; accordingly to the temperature of accumulation reference is made atc= 48 ÷ 50 ° C.

Also the duration of the period of preheating has its importance for the proper sizing; usually assume dp= 1 ÷ 3 h.

If you want to do the insights on boilers for heat pump, You can find valuable information

Sizing of the heating time

Swimming pool heating

The pools contain large masses of water that must be kept at a controlled temperature, whether they are located in theopen or closed.

The temperature at which to bring and keep the water depends on the type of activities that must take place in the pool and on the degree of comfort desired in the following table are identified ranges of temperature for different types of reservoirs.

In the heating of swimming pools, there are two different times: start-up system e maintenance. The start-up system is the increase in water temperature from the value of the aqueduct to the value of use.

This operation takes place during the first start-up of the pool and subsequently whenever necessary to empty the tank for the normal operations of maintenance and hygiene.

The time in which it can be made the start-up system varies from 24h up to 96 h.

Type of pool

Temperature ° C

competitive pool 22 24
light sport / leisure 24 28
children's pool / warm up 28 30
swimming pools for therapeutic use 29 30

Water temperatures for different types of pool

Calculation of heat loss of the pools 


The shorter the time to reach steady greater the power required to the generator accordingly it is advisable to opt for a longer time: the power start-up system exceeds that required for the maintenance of a share greater the smaller is the time of start-up system.

Once reached the desired temperature, this must be maintained so we need to deliver a continuous heat input equivalent to the sum of the dispersions of the entire pool: this is the maintenance phase. The heat loss a pool is due to several factors:

  • Evaporation from the surface of the water;
  • radiation towards the external environment;
  • convection produced by the contact between the air and the water;
  • transmission through the walls of the basin;
  • flow rate of water daily change.

The most important item of dispersion is evaporation and depends on the size of the mirror of water, the water temperature and the air temperature and above all by its content of steam.

For reasons of comfort in indoor swimming pools, must be:

Taria ° C = Twater + (1 ÷ 3) ° C

Relative humidity RH = 50 ÷ 60% 

The phenomenon of evaporation it is accentuated by the degree of activity in the pool: in the calculation of the evaporation fraction it is necessary to resort to corrective factors to be used according to the degree of activity. Convection losses depend on the velocity of the air on the water surface.

The losses for radiationMore difficult to assess, depending on the temperature of the surfaces bounding the pool.

The above items must be added the losses due to water flow renewal daily. For hygienic reasons the conduction of the basins requires a water flow rate of renewal of at least 5% of the volume present in the tub.

Calculate the heat demand for heating swimming pools

In the following tables show the values ​​of thermal requirement for swimming pools of different type, highlighting how the dispersions vary with the temperature of the air.

Specific dispersion of swimming pools for sports W / m2
  Air temperature (° C) / Humidity
water (° C)
23 ° C / 60% 25 ° C / 60% 27 ° C / 60% 29 ° C / 60%
22 230 190 160 121
24 - 260 230 190
26 - - 290 260
28 - - - 330

Indicative of leakage from reservoirs sports

Specific dispersion swimming pools for residential use W / m2
  Air temperature (° C) / Humidity
water (° C)
23 ° C / 60% 25 ° C / 60% 27 ° C / 60% 29 ° C / 60%
22 170 150 130 110
24 - 190 170 150
26 - - 220 200
28 - - - 240

Indicative of leakage from reservoirs residential 

In important applications such as those of sports is even more significant savings achievable by heating in heat pump. Already Annex D of Presidential Decree 412/93 indicated heat pumps as technologies for the use of renewable sources or similar electively indicated for the production of energy in buildings and facilities used for sports activities and specifically for:

  • drying air temperature in indoor and heated;
  • heating ambient air in indoor swimming pools;
  • heating tank water;
  • heating hot water for showers and changing rooms.

Energy savings for heating swimming pools

Both the powers necessary for the start-up system, as those necessary for the maintenance, may be provided by heat pumps saving in terms of Costi management compared to other heating systems up to 80%.

The state of the art envisages, in particular applications such as those of the pools the interposition between the
generator and the pelvis of a heat exchanger plates of a material able to withstand the aggression of the chlorinated water.

The hydraulic circuit must be equipped in each case of filters and prefilters to protect the system and also a system by-pass the pool side to avoid the sovradimensionameto exchanger.

If you want to do the insights on heating for swimming pools heat pump, You can find valuable information at the following links:

The savings with the new electricity tariff D1 for heat pumps is especially evident in consumers with consumption important.
The estimated cost, including the fixed fee, is approximately € 0,24 per kWh compared to the progressive D2 and D3 rates ranging from € 0,14 up to € 0,40 per kWh.

What is the real cost of the tariff D1?

To calculate the cost of your fuel consumption by applying the new electricity tariff for heat pumps, use our simulator.

-> Find out the cost for your D1 rate

 The calculation is based on Official figures of authority for electricity.

heat pump and solar thermalIn general, the electricity tariff D1 is applicable to private users who use the heat pump as a generator for the exclusive space heating.
Therefore, it is not applicable to condominiums with central heating system.

Also excluded are combined or hybrid systems (heat pump + boiler), unless the second generator is not used only in case of emergency.
In these cases, you must submit a statement by a qualified technician.

It is then possible application is installed, the only heat pump for domestic hot water production (instead you can by matching machines).

Rossato Group Srl
Via del Murillo, km 3.500, 04013 Sermoneta LT - Italy
Share capital € 200.000,00 fully paid up - no. REA LT-107494
VAT-CF IT01745300598

Opening Hours
From Monday to Friday
Morning 8: 30 - 12: 30
Afternoon 13: 30 - 17: 30