Hi all,
I'm working on a data centre energy model and have a question about modeling the supply air temperature to the white spaces.
I'm using DesignBuilder as energy modeling software.
According to ASHRAE the supply air temperature needs to be sized at a dT of 11,11 degrees C, and a supply air temperature reset of 2,8 degrees C under minimum cooling load conditions according to section G3.1.3.12.
In DesignBuilder there are three locations where this can be added to the model and I'm wondering if my reasoning and approach are correct here.
The set point temperature in the whitespaces is set at 37 degrees C. So a dT of 11,11 would mean a supply air temperature of 25,89 degrees C.
Climate zone is 4A.
First location is at the HVAC zone level.
The default setting for cooling sizing is a set up to temperature difference and the dT is 11,11 degrees C. Which is according to ASHRAE and I didn't change any inputs here.
Second location is at air loop level.
The central cooling design supply air temperature here is set to 25,89. This directly impacted the sizing of the cooling coils in the AHU.
The default setting was 12,22 degrees C, raising this number to 25,89 reduced the size of the cooling coils by around 30%.
Third location is at the air loop setpoint manager.
The setpoint manager default values are a minimum setpoint of 14,89 and a reset to 17,67 degrees C.
I've changed this to 25,89 and 28,67 degrees C to have a dT of 11,11 compared to the 37 degrees C set point and the 2,9 degrees C reset.
This changed more than doubled my fan energy consumption compared to default settings.
I'm wondering if I interpreted ASHRAE correctly here and if my settings are correct.
Especially the third step had a large impact on the results as changing this value in the setpoint manager more than doubled my Fan energy consumption so wondering if the approach is correct.
Could anyone please confirm if my approach is correct or if I need to adjust some settings?
Kind regards,
Boris Jonjic