Hey, just a clarification! As I've only come across DOAS system with All air exhaust with no return. Only in case of an ERV we use the return to get back the energy from used air. Basically, AHU's deals with supply air stuff( OA+RA), DOAS are just 100% OA without return mixing into it. Please advise if my thought about this topic makes sense. Great videos BTW, appreciate your time and effort!
If I used VFD to reduce the CFM from the DOAS, how would that impact the de-humidification and cooling of the units? Our units supply 10,000 CFM each to the room but we only need 6000-7000 CFM each. We do not want to compromise on the de-humidification and cooling. What are your thoughts?
If the airflow is reduced the sensible and latent cooling would also be reduced. The beam can likely be sized to offset the lost space sensible cooling but the space latent cooling is done by the preconditioned air coming from the AHU. The amount of latent cooling reduction will depend on the performance of the AHU cooling/dehumidifying coil at the reduced face velocity.
Ideally buildings are maintained under a positive pressure to minimize infiltration. We generally see a balance between the required outside air, toilet/general exhaust and required air flow to maintain positive pressure (or exfiltration) of the building. In cases where this is unbalanced, we see a relief air system installed (this can consist of a barometric hood on the roof or exhaust fan powered system) in order to maintain building pressure.
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Hey, just a clarification!
As I've only come across DOAS system with All air exhaust with no return. Only in case of an ERV we use the return to get back the energy from used air. Basically, AHU's deals with supply air stuff( OA+RA), DOAS are just 100% OA without return mixing into it. Please advise if my thought about this topic makes sense.
Great videos BTW, appreciate your time and effort!
If I used VFD to reduce the CFM from the DOAS, how would that impact the de-humidification and cooling of the units? Our units supply 10,000 CFM each to the room but we only need 6000-7000 CFM each. We do not want to compromise on the de-humidification and cooling. What are your thoughts?
If the airflow is reduced the sensible and latent cooling would also be reduced. The beam can likely be sized to offset the lost space sensible cooling but the space latent cooling is done by the preconditioned air coming from the AHU. The amount of latent cooling reduction will depend on the performance of the AHU cooling/dehumidifying coil at the reduced face velocity.
what is this setup or program you write on
We use the program Explain Everything.
we call this OAC in the philippines
How would you depressurize a building with DOAS system?
Ideally buildings are maintained under a positive pressure to minimize infiltration. We generally see a balance between the required outside air, toilet/general exhaust and required air flow to maintain positive pressure (or exfiltration) of the building. In cases where this is unbalanced, we see a relief air system installed (this can consist of a barometric
hood on the roof or exhaust fan powered system) in order to maintain building pressure.