Heating Loads

Heating Loads implements ASHRAE Heat Balance Method procedures for the calculation of room heating requirements and the sizing of heating equipment.

Steady-state room heat losses are calculated in the absence of casual and solar heat gains. The calculation optionally includes the effects of mechanical and natural ventilation air exchanges.

 

The time, day and month of the heating loads calculation can be chosen. Ensure that the time chosen matches a heated period in the modelled building.

Results are presented (in the program Vista as tables or graphs of room or zone heat loss, broken down by heat loss mechanism. Losses can be expressed on a floor area or room volume basis. Room temperatures are also displayed. The data may be exported to other applications such as spreadsheets and word processors.

For a description of the calculation methods used in ApacheLoads see ASHRAE Heat Balance Method Calculation Methods.

 

Tick this box to include a Heating Loads calculation when you click on Calculate.

Air exchanges specified in Space Data are divided into three categories: infiltration, auxiliary ventilation and natural ventilation. Any infiltration air exchanges are included unconditionally, but auxiliary and natural ventilation air exchanges may be switched on or off at calculation time.

Tick this box if you wish to include Space Data auxiliary ventilation air exchanges in the Heat Loss calculation.

Air exchanges are specified in Space Data in terms of a Maximum Value and a Variation Profile. In Heat Loss the Variation Profile requires interpretation because the calculation does not involve the time variable. The assumption is that the exchange rate takes the Maximum Value unless the profile is ‘Off continuously’ or a formula profile (which is not supported by Heating Loads), when it takes the value zero.

Tick this box if you wish to include Space Data natural ventilation air exchanges in the Heating Loads calculation.

Variation Profiles for natural ventilation are interpreted as for mechanical ventilation.

Tick this box if you wish the analysis to make allowance for the sky shielding effects of local shades and shading objects analysed by SunCast. Under heating design conditions the sky temperature will be below the ambient air temperature, and shielding surfaces from the sky therefore has the effect of reducing heat loss.

If you tick this box the heating loads calculated for Apache Systems will include the internal gains specified for each space.

If you tick this box, and Include internal gains? is also ticked, the diversity factors assigned to the gains will be appiied for the heating load analysis.

If you select ‘Yes’, and Include internal gains? is ticked, gains wlll be saturated, meaning that when their modulating profiles are evaluated, all values greater than zero will be adjusted to 100%.

If you tick this box the heating loads calculated for Apache Systems will include the Domestic Hot Water demand for each room.

Select ‘Use peak values’ to set DHW demand to the peak value in the room, or ‘Use time settings below’ to set it according to the demand at the indicated time of day and year.

The profile settings specify the time, month and week day for which the heating load analysis is to be performed. These settings determine the availability of heating, and in some cases the setpoint values. In the case of annual profiles the profile are evaluated for the indicated weekday in the central week of the month.

Click on this button to start the ASHRAE Loads Calculation.

Click on this button to leave the ASHRAE Loads dialog and save the data.

Click on this button to leave the ASHRAE Loads interface.