PSZ Dehumidification reheat?

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Hello,

Hoping someone can help me out here. I am modeling a PSZ heat pump with
ERV as a DOAS. It is supposed to dehumidify to keep RH below 60%. It
appears to be doing this currently based on the hourly reports. However, I
need to also model an electric resistance coil that will reheat the
dehumidified air back up to 73F. Does anyone know how I can accomplish
this with PSZ? I've tried making "ZONE-HEAT-SOURCE" electric resistance,
but this does not seem to have any effect at all. I also thought about
applying preheat to the zones served by the DOAS but it states in the item
description that preheat is appled to the mixed air flow, not just outside
air so that won't work for me. Any recommendations?

Thank you,
Mike C

via Equest-users's picture
Joined: 2016-07-15
Reputation: 400

Hi Mike,
With a PSZ, your ZONE-HEAT-SOURCE will only get applied at your subzones (non-control zone(s)). The heat pump will operate to satisfy both the control zone thermostat and the humidity requirement based on the RH of the return air. For a DOAS heat pump PSZ serving multiple zones, the supply air temperature at the control zone will vary considerably on a sub-hourly basis as the heat pump cycles between cooling and heating mode to prevent overcooling the zone, but reheat can be used to keep the SAT to the subzones relatively constant. Give this input a try to get you close to your description:
"DOAS me no questions" = SYSTEM
TYPE = PSZ
HEAT-SOURCE = HEAT-PUMP
ZONE-HEAT-SOURCE = ELECTRIC
MAX-SUPPLY-T = 73
MIN-SUPPLY-T = 55
MAX-HUMIDITY = 60
REHEAT-DELTA-T = 18

Regards,
~Bill

William Bishop, PE, BEMP, BEAP, CEM, LEED AP | Pathfinder Engineers & Architects LLP
Senior Energy Engineer

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via Equest-users's picture
Joined: 2016-07-15
Reputation: 400

Thanks for the input Bill. This is actually very similar to how I have my
system set up right now. My issue is that if I have ZONE-HEAT-SOURCE as
electric with 18F DT I will get the same exact results as if I have
ZONE-HEAT-SOURCE as "Not Installed." My PSZ DOAS is only attached to my
dummy space... could this be why?

via Equest-users's picture
Joined: 2016-07-15
Reputation: 400