Aİr to aİr heat pump unİt(rooftop) desİgn

Hello guys,

I have a question.

I design air to air industrial heatpump unit(Rooftop packaged units).
We use constant speed compressors and thermostatic expansion valves.

I have doubts to size and calculate the indoor coil because ıt works as an evaporator and a condenser.

If I size it as a evaporator then ıts inside volume will be little to work as a condenser.
Because once I experienced this situaiton and the pressure goes to so high quickly in the heating season. I think this happens because of insufficient volume of indoor coil.

What can you advice me?