HVAC tab in model data - Simple HVAC
You can enter details on the cooling system including the maximum capacity (at zone level).
This item is shown with a green background as it is used in Cooling design calculations only. The data is normally used to group zones together that are served by the same AHU. This allows the cooling capacity of the AHU to be calculated on the Cooling design screen.
By default DesignBuilder provides a single Cooling system called Default and all zones are allocated to it. You can create new Cooling systems and select them in the same that any other component such as a glazing system would be created and selected. Cooling systems have no data other than a name.
The Cooling capacity can either be entered by hand or can be Autosized using the Cooling Design Calculations. If, immediately prior to a Simulation the Cooling capacity has not been entered (neither by hand nor from a previous Cooling Design Calculation) then a Cooling design autosizing simulation is started to calculate the capacity. The Plant sizing building model option controls the way this works.
You can change cooling capacities by hand if you wish but you should bear in mind that, by default, if Model Options change, all heating and cooling capacities are reset to zero. Set the Plant sizing model option to '2-Manual' to avoid this happening.
When using Simple HVAC you can specify the cooling supply air conditions of the air. This data is used for simulations only - cooling design calculations have a specific equivalent setting on the Cooling design calculation options .
The minimum dry-bulb air temperature of the air supplied for cooling the zone (in °C or °F).
The minimum humidity ratio (kg of water per kg of dry air) of the cool supply air. The default is 0.0077 kg-H2O/kg-air which corresponds to a 10C (50F) dew point. You should be careful to enter a value that is a valid condition, i.e. it is under the 100% saturation line on the Psychrometric Chart.
Select the type of fuel used to generate the cooling energy - choose from:
| Interface Fuel Name | Fuel in results |
| 1-Electricity from grid | Electricity |
| 2-Natural Gas | Gas |
| 3-Oil | Oil |
| 4-Coal | Solid fuel |
| 5-LPG | Bottled gas |
| 6-Biogas | Bottled gas |
| 7-Anthracite | Solid fuel |
| 8-Smokeless Fuel (inc Coke) | Solid fuel |
| 9-Dual Fuel Appliances (Mineral + Wood) | Other |
| 10-Biomass | Other |
| 11-Waste Heat | Other |
You should select 1-Electricity from grid you wish the results displayed in DesignBuilder to agree with those calculated by EnergyPlus directly for District cooling and displayed on the Summary tab of the Simulation screen.
The cooling system coefficient of performance is used to calculate the fuel consumption required to meet cooling demand. The value represents the total seasonal efficiency of the entire cooling system and should include the effect of all energy consumption associated with building cooling such as fan and pump energy, chiller inefficiency, control equipment etc.
Cooling system CoP data is specified by zone so you can model different cooling efficiencies in each zone. But generally you should access this data from the building level and allow zones to take on building default.
Note: for all systems, cooling setpoint temperatures are defined on the Activity tab.
This schedule data is used in conjunction with the cooling setpoint temperatures on the Activity tab to define the time-varying cooling setpoint schedule in the zone. The operation schedule defines the times when full and setback setpoints should be met and the setpoint data on the Activity tab define the actual setpoint values. See Defining setpoint temperature schedules for more on this.
Note: the zone cooling operation schedule is also used in Detailed HVAC with the default 1-Simple HVAC Detailed HVAC Activity data setting.