Dear All,

I have an office building with compartmental cooling units on each floor and hot water reheat coils and baseboards for heating. The ventilation air is supplied from a make-up air unit on the roof. This MAU has an enthalpy wheel, but no heating or cooling coils. What is the correct way to model this MAU in equest?

Currently I have modeled this MAU as it's own heating/ventilation system with a 1ft? dummy zone. The compartmental systems have been set up to receive their outdoor air from this MAU system. However, equest has the MAU pulling the exhaust air from this unconditioned dummy zone. This results in the air being exhausted at a temperature slightly higher/lower than the outdoor air leaving the enthalpy wheel, rather than at room temperature. This greatly underestimates the heating/cooling savings for this wheel. Therefore, would it be correct to break up this system and model it under the "Heat Recovery" section for the compartmental systems, with self-contained fans, rather than modeling it as a separate dedicated outdoor air system? Or how can I force my MAU system to exhaust from the conditioned zones?

Marlene Waters, B.A.Sc., P.Eng.