Air Source Heat Pump System

Question

Hi, 
 Wanted to clarify my HVAC system type set up. The project involves an Air source heat pump feeding a heat exchanger within the plantroom which then feeds a pre heat storage vessel. 
 The storage vessel flows runs into the Gas fired water heaters into a hot water storage cylinder which feeds the building's hot water as the heating system is electric heating. 
 Within the SBEM how would the Plantroom HVAC system type be set up? Any advice on this would be great 
 Below is how I have the Plantroom currently set up within SBEM and also an image of the drawing.

Thanks 
 Josh Healey

Shane Regan · Answer

Hi Josh, 
 It would be more suitable to direct this question to your accreditation scheme provider, as they would be much better placed to advise you on Part L design decisions such as this. For further details on Hevacomp's role with SBEM and PartL calc's please see here.