Air-source heat pump

Abstract

An air source heat pump wherein heat is extracted from air at ambient temperature in an evaporator ( 4 ) and heat is rejected at a higher temperature in a condenser ( 2 ); further comprises an auxiliary heater ( 7 ) arranged to preheat the ambient air when required to prevent deposition of frost on the evaporator. The combustion heater may be a gas fired boiler, arranged to heat recirculating water for supplying heating radiators and wherein the flue gases mix with the ambient air before it passes over the evaporator.

1 . An air-source heat pump wherein heat is extracted from air at ambient temperature by an evaporator and heat is rejected at a higher temperature by a condenser; the heat pump further comprising an auxiliary heater arranged to preheat the ambient air when required to prevent deposition of frost on the evaporator; the auxiliary heater being a combustion heater, and flue gases from the combustion heater mixing with the ambient air before it passes over the evaporator; and a heated fluid circuit passing through condenser and through the combustion heater. 
   
   
       2 . A heat pump according to  claim 1 , wherein the auxiliary heater is arranged to operate when the temperature of the ambient air falls below 5° C. 
   
   
       3 . A heat pump according to  claim 2 , wherein the auxiliary heater is arranged to operate when the temperature of the ambient air falls below 2° C. 
   
   
       4 . A heat pump according to  claim 1 , which is arranged to monitor the evaporating pressure or temperature and to apply sufficient heat by means of the auxiliary heater to prevent the evaporator operating at a pressure which would allow frost to form on the evaporator. 
   
   
       5 . A heat pump according to  claim 1 , arranged to operate such that water of combustion from the flue gases condenses as liquid on the surfaces of the evaporator, thereby recovering latent heat of evaporation. 
   
   
       6 . A heat pump according to  claim 1 , wherein the combustion heater is a gas fired boiler. 
   
   
       7 . A heat pump according to  claim 6  wherein the gas fired boiler is of the condensing type. 
   
   
       8 . A heat pump according to  claim 1  wherein heat is rejected at a temperature in the range 30-35° C. for direct air heating or under-floor heating. 
   
   
       9 . A heat pump according to  claim 1  wherein heat is rejected at a temperature in the range 50-55° C. for heating water as the heated fluid. 
   
   
       10 . (canceled)