Evaporative Cooling issues

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Dear List,
I'm working on a project that is looking to compare simple PSZ rooftop
units with Direct evaporitive cooling and gas furnace. When I make the
switch, I change "HVAC system type" to Evaporative Cool then add Supply
cfm as prompted and "Evaporitive Cooler Type" to Ditect on the air side
"Cooling - Evaporitive Cooling" display mode under air side systems.

After these changes I see the expected drop in cooling energy use and a
rise in fan energy use since the baseline had small fan power and the
evaporative uses the units spec'ed fan power. The strange part is that
the heating energy rises significantly. While I made no intentional
changed to the heating side of the units I did notice that the monthly
peak demands went down while the usage went up sio the heating seems to
be running more hours after the change to evap cooling....

Should I just schedule the heater off? I would love to have a more
elegant solution.

Attached are two versions of the model before and after the change. Any
advice is appreciated.


jacob goodman's picture
Joined: 2013-09-12
Reputation: 0

Forgot to mention: I went through the historical lists and found another
modeler with this problem and the suggestion was to check humidity
controls (they are "Not Installed") , I also went through the Hourly
reports for both models and it looks like the heating is running at a
higher % of capacity in the Evap model in winter.

Also, the ventilation fans are running at a higher kW... since evap only
uses can power could this indicate winter cooling that the heaters are
fighting against?

jacob goodman's picture
Joined: 2013-09-12
Reputation: 0