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Eric,<br>
<br>
The coils in the DOAS are not intended to condition the zones, they
are only for tempering the OA to "room neutral" or slightly below
room conditions. If your DOAS heating coil is set to 75F then it is
fighting with the DOAS cooling coil set at 70F, which is located
directly AFTER the heating coil (see schematic below). So with your
settings if the supply air > 70F the DOAS cooling coil is
energized; if supply air < 75F the DOAS heating coil is energized
so the 75F air off the heating coil will have to be cooled back down
to 70F. <br>
<br>
Your assumptions on the controls are a bit off too. The DOAS never
has zone heat priority. In other words all required zone heat comes
from the terminal heating coils only, during both occupied and
unoccupied modes. The function of the DOAS is to ONLY temper the OA,
never to heat the zones (see sequence below).<br>
<br>
<img src="cid:part1.06070507.06010108@swbell.net" alt=""><br>
<br>
Suggest you set the DOAS heating coil several degrees LESS than the
DOAS cooling coil, something like 65-68F. The HAP Help system has
schematics of each of the systems showing the relative placement of
the coils in the DOAS along with sequences of operation for the DOAS
and the terminal units. Here is a cut and paste of that information:<br>
<br>
<title>Terminal Unit Systems</title>
<script language="JavaScript" title="BSSC Special Effects" src="ehlpdhtm.js"></script>
<p class="Body-Normal"><span style="FONT-WEIGHT: bold;
TEXT-DECORATION: underline; x-text-underline: normal">A.
Operation of Terminal Units</span></p>
<p class="Body-Normal"><span style="FONT-WEIGHT: bold;
TEXT-DECORATION: underline; x-text-underline: normal">A-1.
Occupied Period Operation</span></p>
<p class="List-Normal">1. Continuous Fan Operation</p>
<p class="List-1-Indent">a. The terminal supply fan runs
continuously. </p>
<p class="List-1-Indent">b. If the zone thermostat calls for
cooling, the cooling coil operates to maintain zone conditions. </p>
<p class="List-1-Indent">c. If the zone thermostat calls for
heating, the heating coil operates to maintain zone conditions. </p>
<p class="List-1-Indent">d. If the zone thermostat does not call for
cooling or heating, neither coil operates but the supply fan
continues to run in order to ventilate the zone. The zone
temperature floats in the deadband between cooling and heating
setpoints.</p>
<p class="List-Normal">2. Cycled Fan Operation</p>
<p class="List-1-Indent">a. If the zone thermostat calls for
cooling, the terminal supply fan cycles to meet the cooling
demand. Air is provided at the design cooling supply temperature.
The supply fan is on only as long as necessary to meed the demand
and then turns off.</p>
<p class="List-1-Indent">b. If the zone thermostat calls for
heating, the supply fan cycles to meet the heating demand. Air is
provided at the design heating supply temperature. The supply fan
is on only as long as necessary to meed the demand and then turns
off.</p>
<p class="List-1-Indent">c. If the zone does not call for cooling or
heating, the fan is off.</p>
<p style="MARGIN-TOP: 0px; MARGIN-BOTTOM: 0px" class="Body-Normal">
</p>
<p class="Body-Normal"><span style="FONT-WEIGHT: bold;
TEXT-DECORATION: underline; x-text-underline: normal">A-2.
Unoccupied Period Operation</span></p>
<p class="List-Normal">1. Continuous or Cycled Fan Operation</p>
<p class="List-1-Indent">a. If the zone thermostat calls for
cooling, the terminal supply fan cycles to meet the cooling
demand. Air is provided at the design cooling supply temperature.
<!--kadov_tag{{<spaces>}}-->
<!--kadov_tag{{</spaces>}}-->The supply fan is on only as long as
necessary to meed the demand and then turns off.</p>
<p class="List-1-Indent">b. If the zone thermostat calls for
heating, the terminal supply fan cycles to meet the heating
demand. Air is provided at the design heating supply temperature.
<!--kadov_tag{{<spaces>}}-->
<!--kadov_tag{{</spaces>}}-->The supply fan is on only as long as
necessary to meed the demand and then turns off.</p>
<p class="List-1-Indent">c. If the zone does not call for cooling or
heating, the terminal supply fan is off.</p>
<p style="MARGIN-TOP: 0px; MARGIN-BOTTOM: 0px" class="Body-Normal">
</p>
<p class="Body-Normal"><span style="FONT-WEIGHT: bold;
TEXT-DECORATION: underline; x-text-underline: normal">B.
Operation of Common Ventilation (DOAS) Unit</span></p>
<p class="Body-Normal">When the terminal unit system is configured
with a common ventilation (DOAS) unit, the ventilation unit
operates as follows:</p>
<p class="Body-Normal"><span style="FONT-WEIGHT: bold;
TEXT-DECORATION: underline; x-text-underline: normal">B-1.
Occupied Period Operation</span></p>
<p class="List-Normal">1. The ventilation supply fan runs
continuously to supply 100% outside air.</p>
<p class="List-Normal">2. If a ventilation cooling coil is present
and scheduled on, the coil will be energized when the duct
temperature downstream of the unit rises above the duct cooling
setpoint. The air will be cooled so the duct temperature is held
at the setpoint.</p>
<p class="List-Normal">3. If a cooling coil is present and scheduled
on, and dehumidification control is used, the unit will control
both dry-bulb temperature and relative humidity (RH) downstream of
the unit. If the temperature of duct air downstream of the unit is
rises above the duct cooling setpoint, the cooling coil will be
energized to hold the duct air at the setpoint. If the duct
humidity is above the maximum RH setpoint, the cooling coil will
provide additional cooling to lower the coil dew point, thus
condensing more moisture, and holding the duct air at the maximum
RH setpoint. A heating coil will provide dehumidification reheat
so the duct air temperature continues to be held at duct cooling
setpoint.</p>
<p class="List-Normal">4. If a heating coil is present and scheduled
on, the coil will be energized when the duct temperature
downstream of the unit falls below the duct heating setpoint. The
air will be heated so the duct temperature is held at the
setpoint.</p>
<p class="List-Normal">5. If a heating coil is present and scheduled
on, and humidification control is used, the unit will control both
dry-bulb temperature and relative humidity (RH) downstream of the
unit. If the temperature of duct air downstream of the unit falls
below the duct heating setpoint, the heating coil will be
energized to hold the duct air at the setpoint. If the duct
humidity is below the minimum RH setpoint, the humidifier will add
moisture to the air stream to hold the duct humidity at the
minimum RH setpoint.</p>
<p style="MARGIN-TOP: 0px; MARGIN-BOTTOM: 0px" class="Body-Normal">
</p>
<p class="Body-Normal"><span style="FONT-WEIGHT: bold;
TEXT-DECORATION: underline; x-text-underline: normal">B-2.
Unoccupied Period Operation</span></p>
<p class="List-Normal">1. The ventilation system is off during all
unoccupied period hours.<br>
</p>
<p class="List-Normal"><i><big>------------------------------------------------------------------------------------------<br>
Regards,<br>
</big></i></p>
<p class="List-Normal"><i><big>Craig J. Gann, P.E. LEED AP</big></i><br>
</p>
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<div class="moz-cite-prefix">On 9/10/2015 2:16 PM, Eric Rivera
wrote:<br>
</div>
<blockquote
cite="mid:5EDBEC6383A6A74CA96A08520DD10DD20204774C@SANDBINC4.sbi.smithboucher.com"
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<p class="MsoNormal">Hello All,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I’m working on an energy model for a
controls rebate for an office building in Kansas City, where I
am comparing a VRF system with a DOAS with constant
ventilation and a thermostat with 24/7 occupancy, to a
similar VRF system with DCV and ASHRAE 90.1 standard office
thermostat. <o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">The DOAS for both models have an air-cooled
DX coil with a setpoint of 70 F and a natural gas fired
heating coil with a setpoint of 75°F. The terminal units are
modeled with an air cooled DX coil with a design supply temp
of 58°F and a heat pump with design supply temp of 95°F. Both
systems model sensible and latent heat reclaim.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I would assume that under the option with
controls, during the winter months, the DOAS would heat the
building during scheduled occupied hours. Once the system
goes in unoccupied mode, the terminal units would heat the
space to the unoccupied setpoint. What is weird is that
electrical heating consumption is highest in March (See
attached for a building summary report). After reviewing the
detailed hourly system reports, I’m still not able to figure
out what would be causing a high heating load in March. My
guess would be something to do the heat reclaim. My question
is:<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">What, within the heat reclaim, be causing
the electrical heating demand in March to be so high?<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Any help would be appreciated,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Thanks,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><img
id="Picture_x0020_1"
src="cid:part2.04020407.02090608@swbell.net"
alt="cid:image001.jpg@01CCAE92.6FC59620" height="37"
width="119"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal" style="margin-top:6.0pt"><b><span
style="font-size:14.0pt;font-family:"Avenir
55";color:#2D4D5E">Eric Rivera<o:p></o:p></span></b></p>
<p class="MsoNormal" style="margin-top:12.0pt"><span
style="font-family:"Avenir 55";color:#2D4D5E">25501
west valley parkway</span><span
style="font-size:10.0pt;font-family:"Avenir
55";color:#2D4D5E"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Avenir
55";color:#2D4D5E">olathe ks 66061<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Avenir
55";color:#0070C0">direct: 913.344.0036<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Avenir
55";color:#2D4D5E">main:</span><span
style="font-family:"Times New
Roman","serif";color:#2D4D5E"> </span><span
style="font-family:"Avenir 55";color:#2D4D5E">913
345.2127<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Avenir
55";color:#2D4D5E">fax: 913 345.0617<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
<br>
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