Hi there,
I fully understand the fresh air loads section when completeing the fresh air load design info however I have never understood the input required within the Design data section.
Why do some comments have "0" within the resultant supply air temperature input?
What effect does changing this do?
Would it be relevant for for the bwlo which is what I am trying to apply the prgram to
Application. A single supply from AHU to serve rooms with fresh air. Some have FCUs within the rooms, some do not. I wish to determine the fresh air load for the AHU cooling coil and will specify a temp (will be changed from 26) and will include a specified humidity from my hand psych. chart.
The building loads from the results I can use to understand the internal gains and subsequently possible use some of that across a heat rejection coil.
What is the importance of inputting a temperature (or indeed leaving at "0") in the [design data, room design temperature {resultant} supply air temperature]. I have never been able to find decisive instructions on this?
A swift repsonse would be most welcome please. Also, as this is the first time I have used the bentley communities forum / discussion board would welcome an email confirmation as to how to return / find any response please.
Many thanks in advance.
Hi Richard,
Changing the Supply air temperature here will affect the resulting air flow rate required to keep maintain room design temperatures. The following section from the manual may be of some assistance:
A supply air temperature is specified. This will be used to compute the required air flow rate to rooms, assuming a central all air system. The supply air temperature must be below the room temperature. Do not try to use an outside temperature as the supply air temperature - use the summertime temperatures program if the building is fresh air ventilated and not air conditioned.
Shane Regan | Principle Building Performance Support EngineerHevacomp to OpenBuildings - A complete guide for every user | Bentley Communities
Shane,
Thanks do much; I have read the excerpt before although it still remains unclear in my mind,,,,,,what exactly is this temperature? I know what the other temperature is as attached (being the supply air off coil temp but in the attached situation (fresh air only AHU) what is the design data supply air temperature?????
Comparing the above image to that for 'No additional fresh air' on our Wiki should help to clarify, as below. This only considers the Supply Air Temperature you are referring to - i.e. the air temperature of the local fan coil units:
In the case of the 'Conditioned Primary Fresh Air', this local cooling still exists, but there is also a fresh air requirement that is being managed by central plant.
The local cooling coil temperature is defined by the Supply air temperature in the room design data, and the temperature of the primary fresh air from central plant is defined in the Fresh Air loads.
Thank you for confirming. I did suspect this although there is no definitive explanation from Bentley anywhere. Thank you so much, that puts my mind at ease.