Question-and-Answer Resource for the Building Energy Modeling Community
 | 1 | initial version |
In general the latent cooling rate is getting calculated as Richard mentioned. Here are the details of how the latent load is getting calculated, when you have a humidistat. Case 1 - Non-OA system, no dehumidification load: In this case the Zone Predicted Moisture Load to Dehumidifying Setpoint Moisture Transfer Rate [kgWater/s] is a positive value. The supply air humidity ratio is whatever is specified in the ideal loads component. Return values are same as the zone values. The latent cooling rate is calculated from this. Case 2 - Non-OA system, yes dehumidification load: In this case the Zone Predicted Moisture Load to Dehumidifying Setpoint Moisture Transfer Rate [kgWater/s] is a negative value - i.e. there is a latent load on the system. The supply air humidity ratio is set to a value that will satisfy this latent load. Return values are same as the zone values. The latent cooling rate is calculated from this. In this case the Supply Air Latent Cooling Rate is same as the predicted moisture load (Moisture transfer rate x latent heat of vaporization). Case 3 - When OA is used: In this case the supply air humidity is decided as above. The latent cooling rate calculations are based on these supply conditions and the mixed air conditions. So the cooling rates are different from the predicted load (unless the OA is the same exact condition as return air).
