Integrated heat pump in AHU

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Hi,

I'm investigating to incorporate an integrated heat pump (electrical) in a Air Handling Unit. The AHU heating and cooling coils are connected to a borehole field through heat pumps. The integrated heat pump would start in case of the boreholes are exhausted and need time to generate: It is a back up system. I'm modelling this system on DesignBuilder. Do you have an idea how I can incorporate it?

Thanks in advance,

Nassim