Hello list,
I thought the dehumidification calculation would be a relatively straightforward calculation for QUEST, however, I have some results that are a bit puzzling.
I have a simple all-electric packaged VAV system that serves living quarters of an in-patient clinic. The system has 50% OA and uses an economizer. The system is designed to heat and dehumidify air only (no cooling, none of my zones have cooling schedules). My dehumidification set point is 60% RH. The building is located in Chibougamau, Quebec (quite north) where cooling and dehumidification requirements are relatively small, but still exist. According to the SS-N report, the maximum RH is never surpassed for my system.
This is all fine and great until you start digging a bit deeper into the hourly results of the system in question. In my hourly data report I have the following variables : Total central heating/cooling coil outputs, dehumidification reheat heat output, return air humidity ratio, mix air humidity ratio, humidity ratio of air leaving cool coil, Moisture added or removed from air for (de)humidification, and maximum humidity set point. The strange thing I noticed is that my return air humidity ratio and mix air humidity ratio NEVER surpass my maximum humidity set point, yet I still have loads on my cooling coil during the summer, and moisture removed from the airstream. Furthermore, I noticed that there are 815 hours during which there is a load on the cooling coil, but no humidity is removed from the airstream whatsoever (mix air humidity ratio = humidity ratio of air leaving cool coil). My team here has experienced these results in more than 1 simulation that have a system with only dehumidification requirements on the cooling side.
So my questions are:
1. How does eQUEST control the maximum humidity allowed in the supply airstream?
2. How could one possibly explain a cooling load/consumption without any cooling schedules in any of the zones supplied by my system and zero moisture removed from the air?
Any insights would be much appreciated!
Many thanks.
[Bouthillette Parizeau]
Jason Ng_ing. M.Sc.A.
jng at bpa.ca
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