[Equest-users] DOAS with dehumidification

[Sharad Kumar via Equest-users]

Hi Michael,

The dehumidification process is the process to cool the air low-to dew
point temperature and have the condensate.
The dew point temperature is even below wet bulb temperature.
Also the wet bulb temperature is a temperature below dry bulb or the normal
air temperature.
Hence if the air is having some condensate then the cooling coil is
dehumidifying the air certainly below up-to dew point and then have the
condensate.
So may be the figure 60 F that you are looking is the below temperature low
seeming to be dew point temperature or the low temperature seeming to be
for having the possible condition to have water condensate and the
condensate can be formed at low valued temperature.

The low seeming value for having condensate temperature is possibly the dew
point temperature.

Then after the condensate formation then the latent heat of water of air
(moisture plus air i.e the normal air in surrounding) is taken into the air
(moisture left as condensate and left air) then that air aftermath the
cooling and condensing process is heated up-to 74F in the room.The dummy
room temperature is meeting the set points as the set-point is as per
sensor and controllers in the HVAC to be met.
I have read it before about the unmet load hours that it is the control
issue.
If the controllers and the HVAC design and the model is perfect then there
can not be unmet load hour so possibly the air temperature is with-in the
set-points and hence resulting less unmet load hour.


Thanks,

Sharad.Kumar|Engineer.

Green Horizon Consulting LLP.

Gurgaon.

India.



---------- Forwarded message ----------
From: Michael Campbell via Equest-users <equest-users at lists.onebuilding.org>
To: equest-users at lists.onebuilding.org
Cc:
Date: Wed, 18 May 2016 08:36:42 -0400
Subject: [Equest-users] DOAS with dehumidification
Hello,

I am trying to model a DOAS that supplies conditioned outside air to
dwelling units.  It also has an ERV.  I have created a dummy zone with no
loads and made the setpoints for the dummy zones my desired heating and
cooling supply air temperatures (73F for heating and 75F for cooling).
However, the DOAS also has dehumidification in which it will operate in
cooling mode to dehumidify at >60% RH.  There is no reheat coil, so when
the system is dehumidifying, the supply air temperature should drop below
the setpoint.

Here is the issue I'm having.... when I look at my hourly reports, I can
see that the air leaving the cooling coil will drop down to about 60F at
times when the system is dehumidifying.  However, the dummy space is still
showing a space temperature of ~74F.  How is this possible?  Does anyone
have any ideas?

Thank you,
Mike C
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