From time to time we receive questions on our Support Desk asking how to model refrigerated spaces in DesignBuilder. This Top Tip explains the process involved in cooling a zone down to a constant temperature of -20°C using Detailed HVAC.

1. Start with a new single zone Detailed HVAC model with all default settings.
2. On the Activity tab, set the Cooling and Heating Setpoint and Setback temperatures all to -20°C.
3. On the HVAC tab, set the Cooling operation schedule to "On 24/7".
4. Load the "District Heating and Cooling, FCU 4-pipe" HVAC template.
5. Navigate to the HVAC zone and remove the Fan coil unit included by default in that template and replace it with a Zone water to air heat pump. Connect the coils up to the demand side of the District cooling and heating plant loops.
6. On the HVAC zone dialog change the Cooling design supply air temperature input method to "2-Temperature difference" and accept the default difference of 5°C.

With these settings your zone will be cooled to a constant -20°C. 

The aim here is to model the effect of chilled areas on surrounding spaces. Whilst this method will give you a reasonable rough estimate of energy consumption, you can improve the accuracy of that by modifying the equipment efficiencies in DesignBuilder or even conducting a more detailed analysis in EnergyPlus outside DesignBuilder.

Note that in DesignBuilder v7.1 it will also be possible to model refrigerated spaces in Simple HVAC.