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PTAC - Mech Ventilation and Humidity control (DesignBuilder)

asked 2018-03-13 04:02:10 -0500

RicardoPereira's avatar

I am using a simple HVAC up to now, I have to use the default setting for the HVAC system, I can change only the boiler efficiency and the fuel for the boiler, therefore I am creating a "base case" where my building has a poor energy and comfort performance. Those are the instructions for my task. I noticed that the PTAC model in the simple HVAC comes with mech ventilation off and no humidity control. After running the simulation I found that my humidity levels are way off the limits I set (40-60%). For every change I make on the HVAC system, I have to include an equipment cost and deduct it from my budget. I was wondering if you could help me with some opinions on how much would cost me to "turn on" the mech ventilation on my PTAC units and "tun on" the humidity control as well. Because I need to improve my performance of the base case and I have a limited amount of money. Maybe it is the case that I am not fully getting the PTAC unit and how it works.


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answered 2018-03-14 08:45:25 -0500

mikesweeney's avatar

PTACs don't typically specifically have humidity controls, but if you lower the supply air coming off the PTAC it may reduce the humidity issue. You can also, in Detailed Mode, play around with the "Design inlet /outlet air humidity ratios" on Cooling Coil, which may increase the latent capacity sizing.

Regarding the mechanical ventilation portion, you can check the "Outdoor air supply" box on the "Edit PTAC Unit" dialog in Detailed HVAC. Then you should be able to specify a flow.

Speaking of Detailed HVAC, it seems like this issue warrants switching into it from Simple HVAC. I seldom use the Simple HVAC module other than for purely massing/daylight-type studies.

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Asked: 2018-03-13 04:02:10 -0500

Seen: 451 times

Last updated: Mar 14 '18