[EnergyPlus_Support] ASHRAE fun - ODA mixing Damper (economizer action)

["Jean marais" <jeannieboef@xxxxxxxxx>]

I am using a setpointmanager:mixedair to control (partly...the other control is the ODA requirements) the mixing damper, to help deliver the air at the setpoint temperature.

Q) If neither heating or cooling is needed and the setpoint changes linearly between 13 and 33 deg C, I assume the ODA damper will try and hold the average (23 deg C).

Background (ASHRAE appx G modeling):
I have a naturally ventilated building without "mechanical" cooling:
1) the "mechanical" ventilation requirement of both proposed and baseline models is zero, as the ventilation is done via windows in both proposed and baseline models.
2) the proposed model includes the baseline system for cooling which jumps on when the "natural" cooling via windows cannot hold setpoint (all be it never as we can set the setpoint for cooling high enough...although I prefer to keep with the intent of 90.1 to provide cooling when user thermal comfort is in jeopardy...bearing in mind that statistical users 10% "dissatisfied" are at different temperatures, i.e. more extreme, in naturally ventilated spaces...ASHRAE 55, AM 10).

Note: The cooling system includes the entire cooling system...possibly with economizer, heat recovery, etc.

Q) G3.1.2.4 Fan System Operation
Will the baseline and proposed fans both come on continously during occupied hours? As the minimum "mechanical" ODA is set to zero, this fan will basically be mindlessly blowing air in circles during the non-heating occupied hours.

My opinion is that fans should be set to cycle to meet loads in both models.

As G3.1.2.4 is a baseline requirement, the best outcome for credit would be to set the proposed case to cycle and the baseline case to be continous during occupation hours.

*************************************

So technically I must set the limits of the setpoint manager to my clg/htg zone setpoints +-11degC, i.e. (50/22) --> (39/33)...obviously my cooling air delivery setpoint can't exceed my heating air delivery setpoint. So the max zone clg setpoint would be limited to 43 deg C. --> (32/33)...Ha, ha, ha!

enjoy reading that one a couple of times.



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