HVAC tab in model data Simple and Compact HVAC
The effect of hot water consumption (hot water taps, showers etc) on building energy use can be included in your thermal model by switching on DHW on the HVAC tab.
When using Simple and Compact HVAC, Domestic Hot Water (DHW) is modelled in DesignBuilder by using hot water consumption rates based on the activity in each zone. DHW hot water consumption is defined on the Activity tab and the definition of the hot water generating equipment is described below) is defined on the HVAC tab.
Three types of DHW are available:
1-Boiler - heat is supplied by the same boiler used for heating the building
2-Gas - gas-fired hot water system
3-Electric - electric immersion heater
The temperature of the water supplied to the taps.
The temperature of the water delivered to the building. This can be approximated to the annual average outside air temperature.
The operation schedules define the timing of the hot water draw off when the Timing HVAC + natural ventilation operates with occupancy option model option is not selected. The profile of hot water consumption in the EnergyPlus simulation is calculated from l/m2-day data (gal/ft2-day in IP units) entered on the Activity tab by first calculating the number of operation hours per day ('Typical hours per day').
When using a Compact schedule to define DHW operation DesignBuilder calculates the 'Typical hours per day' based on the day in the year which has the most operation hours. Fractional hours operation are added as fractions. A 30 minute timestep through the year is used to perform this calculation.
When 7/12 schedules are used the typical occupancy hours per day is determined from January/Monday data.
When typical
workday schedules are used, this is simply the number of hours occupied
during the working day.
The DHW volumetric consumption rate supplied to EnergyPlus is calculated as:
DHW (m3/s) = DHW (l/m2-day) x 0.001 x m2 / (Typical hours per day x 3600)
Note: the zone DHW operation schedule is also used in Detailed HVAC when the default 1-Simple HVAC Detailed HVAC Activity data setting is made.
A range of DHW types can be selected but note that different types of DHW system do not affect results in EnergyPlus simulations, apart from 1- Same as HVAC which causes heating CoP and fuel to be taken from the heating system. Other options all give the same results.
1- Same as HVAC
2- Dedicated DHW boiler
3- Stand alone water heater
4- Instantaneous DHW only
5- Instantaneous Combi
6- Direct (or off-peak) electricity
7- Heat pump