Combi heating system and control method

Abstract

A system that includes a hydronic heat pump; an indirect storage tank (IST) configured to heat potable water stored therein; an air handler unit (AHU) configured to heat an enclosure; a hydronic loop configured to direct hydronic flow between the hydronic heat pump, the IST and the AHU; a temperature control system comprising a space heating thermostat configured to control an air temperature in the enclosure and one or more IST thermostats configured to control a temperature of the potable water in the IST; and a control system comprising control logic configured to control operation of components of the combi heating system among a plurality of predetermined operating modes, in response to an operating call from the temperature control system.

What is claimed is: 
     
         1 . A combi heating system comprising:
 a hydronic heat pump;   an indirect storage tank (IST) configured to heat potable water stored therein;   an air handler unit (AHU) configured to heat an enclosure;   a hydronic loop configured to direct hydronic flow between the hydronic heat pump, the IST and the AHU;   a temperature control system comprising a space heating thermostat configured to control an air temperature in the enclosure and one or more IST thermostats configured to control a temperature of the potable water in the IST; and   a control system comprising control logic configured to control operation of components of the combi heating system among a plurality of predetermined operating modes, in response to an operating call from the temperature control system, the plurality of predetermined operating modes comprising a space heating (SH) mode, a water heating (WH) mode and a combination (combi) mode configured to provide a combination of space heating and water heating,   wherein, in response to the operating call, the control system is configured to (i) select a mode among the plurality of predetermined operating modes, (ii) activate the hydronic heat pump, (iii) control operation of one or more of the AHU and IST and (iv) control operation of the hydronic loop in accordance with the selected mode; and   responsive to receive a termination of the operating call from the temperature control system, the control system is configured to at least one of, after said termination:
 a) continue operation of the hydronic heat pump after said termination until a predetermined condition is met, 
 b) redirect any heat energy remaining in the hydronic loop after said termination to one of the AHU and the IST, and 
 c) continue operating the AHU to output any heat energy remaining in the hydronic loop after said termination. 
   
     
     
         2 . The system of  claim 1 , wherein the control system is configured to minimize on-off cycles of the hydronic heat pump and maximize a length of on periods of the hydronic heat pump.