Does anyone have a handle on how PSZ reheats to control space humidity? I can tell that it does some kind of sub-cooling and reheating because when you use DX-Furnace systems or Air to Air Heat Pump systems in an energy model and then include 50% maximum humidity, both the yearly cooling and heating energy used increases. However, the amount of heating and cooling energy used to control humidity in the PSZ-DX-Furnace energy model is significantly larger than the amount of heating and cooling energy used to control humidity in the PSZ-Air to Air Heat Pump energy model. In both energy models, the DX cooling EIR is 0.2451 and the heat pump heating EIR is 1.0 and the furnace EIR is 1.0.

The amount of yearly heat used when no humidity control is present is 40 Mbtu for the PSZ DX-Furnace and 24 Mbtu for the PSZ-HP.
The amount of yearly heat used when 50% humidity control is present is 98 Mbtu for the PSZ DX-Furnace and 35 Mbtu for the PSZ-HP.

The yearly cooling increases associated with humidity control in each model show the same pattern but the differences aren't so large. The envelope, weather file, people count, osa, etc. are the same in both models. The eQuest/DOE-2 documentation on humidity references MAX-COND-RCVRY which is a variable that no longer appears to be use.

If anyone knows how PSZ works to control humidity, please contact me.

Thanks.

Kathryn Kerns
Systems Specialist
BCE Engineers, Inc.
| Ph: 253.922.0446 | Fx: 253.922.0896 |