economizer (controller:outdoorair) operation based on cooling signal from thermostat

Issue overview

• I always thought economizers operate only when the zone is in (or thermostat is calling) cooling mode. Below is one of the economizer manual found from the web.

• and lately I have noticed that that might not be the case for EP's economizer (controller:outdoorair).
• Maybe I need to know the reason why it was implemented in that way.
• But also would like to know if this could be a potential fix to the EP.

Details

• I've been working on modeling stock of buildings (ComStock) that reflect some realistic variability.

• One of the variabilities is overnight operation and we have buildings (=models) that ventilates 24/7.

  • so fan can run overnight
  • ventilation can happen overnight as well

• for a system without economizer, the above case only introduces minimum OA requirement overnight. so, basically OA damper is fixed to minimum position as shown below.

• but when we add an economizer to this same model, then economizer basically opens up OA (because OAT can be cold at night in many regions) even though zones are not calling for any cooling.

• the behavior that we want to see eventually after adding an economizer is to let economizer introduce (1) minimum OA when no cooling is called overnight but (2) do economizing when cooling is called overnight.

Checklist

Add to this list or remove from it as applicable. This is a simple templated set of guidelines.

• Defect file added: link to a zip file including two idfs (with and without issue) and one weather file
• Ticket added to Pivotal for defect (development team task)
• Pull request created (the pull request will have additional tasks related to reviewing changes that fix this defect)

Start with the attached defect zip, comparing the two IDF files and weather file around Controller:OutdoorAir operation. Trace how the controller responds overnight when the fan runs without a cooling call. Done means minimum outdoor air is maintained without cooling demand, while economizing occurs when cooling is called.