Polyvalent heat pump – efficient heating and cooling 

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Published: 30 April 2021


Dimos Vasilakis, YORK

Tighter building controls are restricting the use of typical air conditioning systems with low GWP refrigerants. Dimos Vasilakis, indirect sales manager at YORK, explains what other options are available for energy efficient climate control.

The polyvalent heat pump, also known as a 4 pipe system, is an intelligent and effective solution for customers who have both simultaneous cooling and heating requirements, and the possibility for potable hot water use. The units are notoriously versatile as they adapt well to various types of systems. 

This versatility, plus the fact that the units are designed to reach energy efficiency at high levels, means that they are a popular choice for the hotel industry. The units can be tailored to adapt to the ambient temperature and the guests’ comfort level.  

The simplest ways to build this system are by using the following combinations:
  

  • a chiller and a boiler
  • a chiller + heat recovery and a boiler (to limit the use of the boiler in summer) 
  • a heat pump + heat recovery and a boiler 

Range of solutions 

American manufacturer York offers a wide range of flexible solutions for 4 pipe heat pumps in connection with enhanced vapour injection (EVI) technology. EVI involves injecting refrigerant vapour into the middle of the compression chamber. This procedure significantly boosts capacity and efficiency as well as reducing the capacity drop in cold ambient temperatures. The heat pump’s operational envelope is increased to produce 65°C water with operation in ambient temperatures ranging from -20°C to 43°C.

4-pipe heat pumps (above)

The P4U units feature four hydraulic connections and are used in most modern 4-pipe hydronic systems. Two connections are related to the hot water circuit, and two are related to the cold water circuit – both heat and cool respectively, with very high energy efficiencies because of the energy recovery taking place. This means that both hot and cold water is available year-round. 

1. User water heating: The unit behaves like a normal air/ water heat pump in heating mode, using the finned heat exchanger as the evaporator and the (A) plate heat exchanger to generate hot water.
2. User water cooling: The unit behaves like a normal air/water chiller in cooling mode, using the finned exchanger as the condenser and the (B) plate heat exchanger as the evaporator.
3. Simultaneous user cooling + heating: The unit behaves like a water/water heat pump, using the plate heat exchanger (B) as the evaporator and the plate heat exchanger (A) as the condenser. 

Domestic hot water production (above)
The P4S units have been designed to meet the needs of 2 + 2 pipe systems (two low pressure hot water or chilled water pipes and two domestic hot water pipes) throughout the year.

The units are supplied with two exchangers, one dedicated to the production of cold and hot water and one dedicated to domestic hot water production only (DHW).

1. User water heating: The unit behaves like a normal air/ water heat pump in heating mode, using the finned heat exchanger as the evaporator and the (A) plate heat exchanger to generate hot water.
2. User water cooling: The unit behaves like a normal air/water chiller in cooling mode, using the finned exchanger as the condenser and the (B) plate heat exchanger as the evaporator.
3. Domestic hot water production (DHW): The unit behaves like a normal air/water heat pump in heating mode, using the finned heat exchanger as the evaporator and the plate heat exchanger as the condenser. (B) (a special DHW heat exchanger that works with a higher set point).
4. User water cooling + DHW production: The unit behaves like a water/water heat pump, using the plate heat exchanger – (A) as an evaporator and the plate heat exchanger (B) as a condenser for DHW production.

YORK