<div dir="ltr"><div dir="auto"><div>Dear Nathan, </div><div dir="auto"><br></div><div dir="auto">Thank you for quick response. </div><div dir="auto"><br></div><div dir="auto">The project is a residential building and the ventilation is through the system. To meet the ventilation requirement with <b>intermittent</b> operation mentioned in <b>ASHRAE 62.2-2010,</b> the system need to run atleast 30 minutes in each hour. From this the question is come for sub-hourly operation.</div><div dir="auto"><br></div><div dir="auto">I am thinking of an approximation which I want to put for expert opinion: </div><div dir="auto">A PVVT system can be modelled with minimum air flow ratio to 50% with continuous fan to approximate cycling and minimum operation time for ventilation. The reduction of low speed based on cooling/ heating load can be similar to intermittent operation where the system is running for fractions of an hour (similar pattern as in intermittent operation in my earlier mail). </div><div dir="auto"><br></div><div dir="auto">Please let me know your thoughts and/ or other work around.</div><div dir="auto"><br></div><div dir="auto">Thank you.</div><div dir="auto"><br></div><div dir="auto">Regards,</div><div dir="auto">Mayank Bhatnagar<br><br><div class="gmail_quote" dir="auto"><div dir="ltr">On Thu, Apr 4, 2019, 7:29 PM Nathan Miller <<a href="mailto:nathanm@rushingco.com" target="_blank">nathanm@rushingco.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
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<p class="MsoNormal">Assuming you have another system/method responsible for providing ventilation to the units, I’d model it more or less the way you have, but I’m not clear from your description that you have all the settings correct for a cycle-on-demand
system. In the climate zones I usually model in there would be hours where the fan does not run at all, but that’s obviously highly depending on T-stat settins and ambient conditions.
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<li class="m_-1359447782634332785m_-7207796201416492845m_6406353398219464293MsoListParagraph" style="margin-left:0in">Coolin fan schedule should be something that is all-zeros (meaning the system never HAS to run). This essentially means the unit thinks it is in “night/unoccupied” mode all the time.<u></u><u></u></li><li class="m_-1359447782634332785m_-7207796201416492845m_6406353398219464293MsoListParagraph" style="margin-left:0in">Select Cycling fan control, and intermittent operation (looks like you did that)<u></u><u></u></li><li class="m_-1359447782634332785m_-7207796201416492845m_6406353398219464293MsoListParagraph" style="margin-left:0in">Night Cycle Control should be “Cycle On Any”. Since you already told the system it is ALWAYS in night-mode (meaning it’s not forced to run), then fan will remain off until temps in
the space drift out of dead-band mode, and then system will turn on fans and condition the space until temps are satisfied, and then shut off agin. With settings above, partial hour fan operation is allowed.
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<p class="MsoNormal">You said you want to know if you can “create schedule to restrict cycle off on sub-hourly”. I’m not clear what you mean. If you want the fan to be prevented from only running for partial hour you can use Continuous instead of Intermittent
Indoor Fan Mode. <u></u><u></u></p>
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<b><span style="font-size:9.0pt;font-family:"Verdana",sans-serif;color:#6f1200">Nathan Miller, PE, LEED AP BD+C</span></b><b><span style="font-size:9.0pt;font-family:"Verdana",sans-serif;color:#632423"> –
</span></b><i><span style="font-size:8.0pt;font-family:"Verdana",sans-serif;color:black">Mechanical Engineer/Senior Energy Analyst</span></i><b><span style="font-size:9.0pt;font-family:"Verdana",sans-serif;color:#632423"><u></u><u></u></span></b></p>
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<p class="MsoNormal"><b>From:</b> Equest-users <<a href="mailto:equest-users-bounces@lists.onebuilding.org" rel="noreferrer" target="_blank">equest-users-bounces@lists.onebuilding.org</a>>
<b>On Behalf Of </b>Mayank Bhatnagar via Equest-users<br>
<b>Sent:</b> Thursday, April 4, 2019 9:31 AM<br>
<b>To:</b> <a href="mailto:equest-users@lists.onebuilding.org" rel="noreferrer" target="_blank">equest-users@lists.onebuilding.org</a><br>
<b>Subject:</b> [Equest-users] How intermittent fan operation works<u></u><u></u></p>
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<p class="MsoNormal">Dear all,<u></u><u></u></p>
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<p class="MsoNormal">I am working on a residential project in which the indoor units fan is cycling with load. For this, I have modelled as PSZ HP (as designed) and changed indoor fan mode from continuous to intermittent operation. My first question is whether
it is correct to model intermittent for system with cycling or should I model different system. <u></u><u></u></p>
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<p class="MsoNormal">Additionally, as per definition of intermittent operation : The indoor fan operates as in CONTINUOUS, but only for that fraction of the hour required for space heating or cooling. I want to check how many hours it is cycling as I assumed
that the eQUEST is working on hourly timestep. By extracting hourly report of fan cycle ON for continuous and intermittent operation, the hourly profiles are:<u></u><u></u></p>
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<p class="MsoNormal"><img border="0" width="452" height="271" style="width:4.7083in;height:2.8229in" id="m_-1359447782634332785m_-7207796201416492845m_6406353398219464293_x0000_i1025" alt="image.png"><u></u><u></u></p>
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<p class="MsoNormal">From the figure, it appears that fan is running maximum 60% of an hour in intermittent operation whereas 100% in continuous. As it is providing results in sub-hourly basis, is it possible to create schedule to restrict cycle off on sub-hourly?<u></u><u></u></p>
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<p class="MsoNormal">Thank you.<u></u><u></u></p>
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<p class="MsoNormal">Regards,<u></u><u></u></p>
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<p class="MsoNormal">Mayank Bhatnagar<u></u><u></u></p>
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