Conditioned Fresh air & Heat Load Calculation

[Rajgo]

Hello,
I am new to this forum & i have a question on head load calculation.
shall we consider already conditioned outside fresh in heat load calculation (i.e. conditioned fresh air is provided by FAHU & while calculating heat load for rooms, should we need add this fresh air load to indoor system).

Please share opinion on this.
-Raj

 

[ZDR1985]

No need to add the fresh air load. It is already handled by the FAHU.
If there is no FAHU and you require fresh air inside your building, then your total load to size your AHU will be fresh air load plus your building load.

 

[dbill74]

You would never include outside air load as part of the "room" load calculation. Unless you are bringing in unconditioned air directly into your space.
Your room/space load consists of internal heat sources such as lights, computers, people; and external heat sources such as solar loads through roof, walls and windows.

However you need to include outside air loads when sizing and selecting your air handling equipment. Where and how the outside air load is handled depends your choice of system to use. When you use a FAHU and introduce the discharge to RA side of the main AHU (mixing with RA from rooms), you change the state of the air entering the main AHU from a state where RA is mixed with unconditioned OA.

Bill