Question-and-Answer Resource for the Building Energy Modeling Community
 | 1 | initial version |
The ASHRAE 90.1 Large Office Prototype models (https://www.energycodes.gov/development/commercial/prototype_models) are being updated for the upcoming 90.1-2019 savings analysis. We are making changes to the cooling tower modeling strategies on tower design/sizing and operational control inputs. There are differences between 90.1-2010 App G G3.1.3.11 and later editions, for example 90.1-2016 G3.1.3.11. Since the design and controls specified in the newer editions are not in the prescriptive requirements yet, we decided to use the following 90.1-2010 App G rules:
The condenser water design supply temperature is either 85 deg. F or 10 deg. F approaching design wet-bulb temperature with a temperature rise of 10 deg. F
The tower is controlled to maintain a 70 deg. F leaving water temperature.
When using CoolingTower:VariableSpeed to implement these rules, we found the following built-in limitations in EnergyPlus The design inlet air wet-bulb temperature to be lower than 20 deg. C, this limit is set in the IDD. The design inlet air wet bulb temperature bounds for the CoolToolsCrossFlow model are -1.00 and 26.67 deg. C. The approach temperature to be lower than 1.11 deg. C or higher than 11.1 deg. C
So, if you'd like to follow this method, the notes above might be helpful.
Thanks,
Jian
