[Equest-users] heat recovery bug

[Billy Vreeland]

Doug, 

 

I very recently came across the same problem but haven’t been able to solve it either.  If you haven’t tried it already, one workaround you might consider is to set the COOLING‑SCHEDULE with OA temperatures below which cooling is unavailable.  This will mitigate the winter cooling you are seeing.  In my case it appears pretty helpful in making up for the bug but I haven’t looked at this approach enough to know for certain that it doesn’t cause any undesirable affects.

 

---

Billy Vreeland

DMI

35 Walnut Street

Wellesley, MA 02481

(p) 781.431.1100 x 23

(f)  781.431.1109

 

From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Doug Maddox
Sent: Wednesday, July 16, 2008 3:19 PM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] heat recovery bug

 

I think I found a bug with the ERV feature in eQuest related to temperature control.  My input is as follows:

 

   RECOVER-EXHAUST = YES

   ERV-RECOVER-TYPE = ENTHALPY-WHEEL

   ERV-SENSIBLE-EFF = 0.75

   ERV-LATENT-EFF = 0.75

   ERV-RUN-CTRL = OA-EXHAUST-DT

   ERV-TEMP-CTRL = MIXED-AIR-RESET

   ERV-CAP-CTRL = MODULATE-HX

   ERV-HX-KW =   0.207

   ERV-FANS = HVAC-SUPPLY/RETURN 

   ERV-OA-STATIC =    0.5

   ERV-EXH-STATIC = 0.5

   ERV-FROST-CTRL = USE-CAP-CTRL

 

The system shows heating savings as expected, and cooling savings during summer periods, but during winter there is a large cooling penalty.  Hourly reports show an unexpected cooling load during winter night mode operation.  If I set ERV-OA-STATIC to zero, that cooling load goes away.

 

If I change to a fan located in the ERV, the unexpected cooling load is still absent:

 

  ERV-FANS = SELF-CONTAINED

  ERV-EXH-KW/FLOW = 0.002

 

Thus, it appears that the heat gain due to friction in the heat wheel is not taken into account for the OA setpoint during night mode when ERV-FANS = HVAC-SUPPLY/RETURN.  Has anyone else seen this problem?

 

The SELF-CONTAINED option appears to be a work-around, but it is not as convenient for add-on heat wheels.

 

 

Thanks,

Doug Maddox, PE

THE WEIDT GROUP
 
5800 Baker Road
Minnetonka, MN 55345
T 802-262-1033
F 952.938.1480
www.twgi.com <blocked::http://www.twgi.com/> 
DougM at twgi.com <blocked::mailto:DougM at twgi.com> 

 

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