Set an HVAC project's design conditions

Space loads and air systems are calculated on the project's outdoor design conditions: where the site is, its cooling, dehumidification and heating design conditions, and the monthly design days the cooling load is worked on. Design Conditions is the first station of the HVAC chain, and the only place they are set.

1. 1

   Choose the HVAC project under System in the spec sheet, or choose New HVAC project to start one.

2. 2

   Under From the library, type a town, country or WMO number in Find a weather station, choose the station under Weather station, then choose Copy in.

3. 3

   Check the copied figures, fill in anything still blank, and choose Save design conditions.

The Outdoor design states beside the sheet follow what is on screen, saved or not: the site pressure from the elevation, and the humidity ratio, enthalpy, relative humidity and dew point of the cooling design condition.

Copy in replaces what is on the sheet with the station's location, cooling, dehumidification and heating design conditions, monthly design days and citation.

• –A percentile you have already typed is kept, and Kelvin copies the station's figures at that percentile. Where the percentile is blank, it takes the first one the station lists.
• –If the station doesn't list the percentile you typed, that group comes back blank. Clear the percentile and choose Copy in again.
• –The ground temperature is never copied, and Copy in clears one already typed. Enter it afterwards, and add its source to the citation.

The station's figures are copied into the project, not linked to the library. If the library is corrected later, this project's numbers don't move. The Source block keeps the station the figures came from, marked copied, not linked. If you change a copied figure, update the Citation to say where the new figure came from.

If there is no station for the site, or the library can't be loaded, type the figures in. The sheet won't save without a Citation saying where they came from.

• –Location: a name, latitude (negative south of the equator), longitude, Elevation and UTC offset (standard). Use standard time, not daylight saving: AEST is 10. Loads are reported in local standard time.
• –Cooling design: the Annual percentile, Dry bulb, Mean coincident WB and Daily range.
• –Dehumidification design is optional. Fill all three cells or none. Kelvin shows its humidity ratio and enthalpy and prints it in the report; no load on the HVAC stations is calculated at it.
• –Heating design: the Annual percentile and Dry bulb. Ground temperature is optional: it is the temperature under a slab at the heating design condition. Without it, floors and walls in contact with the ground are left out of the heating load.
• –Monthly design days: for each month, the design dry bulb and MCWB, their daily ranges, and the clear-sky optical depths τb and τd. Fill a month completely or leave it empty. Space Loads needs at least one complete month.

Tick Chilled or heating hot water plant under Water plant to add the hydronic stations (circuits, plant, pipe sizing, pumps, and expansion and volume) to this project's chain, after Fans.