search

kbenne / cbecc

Automatically exported from code.google.com/p/cbecc
0 stars 0 forks source link

Revision to Controller:OutdoorAir default #844

Closed GoogleCodeExporter closed 9 years ago

GoogleCodeExporter commented 9 years ago 
Describe the translation issue or enhancement:
Creating this issue for tracking resolution to the lab system UMLH and related 
issue.

Reviewing detailed hourly simulation results for multizone laboratory systems, 
it was found that minimum flow and OA schedules were not being respected. 
Additionally, UMLHs were observed and could not be mitigated with increasing 
capacities, pointing to a control issue with system controls.

KB traced the root cause to be the default Controller:OutdoorAir specification 
for Heat Recovery Bypass Control Type. Using BypassWhenOAFlowGreaterThanMinimum 
results in air flow rates inconsistent with other control specifications; using 
BypassWhenWithinEconomizerLimits corrects this. This appears to be an E+ bug 
and an issue has been filed with that team. In parallel to the investigation, 
additional E+ SPMs were added to the SDD/OS translators (see issue 840) to 
determine if these SPMs would help resolve the issue. However, once the default 
Heat Recovery Bypass Control Type was revised, the SPM that the yielded proper 
control of the Laboratory system remained SPM:Warmest.

Original issue reported on code.google.com by da...@360-analytics.com on 4 Nov 2014 at 7:22

GoogleCodeExporter commented 9 years ago 
In testing of the new Controller:OutdoorAir default with other test models, 
changes in the results of a few system types was noted.  These were identified 
in the following models:

060012: This model illustrates a commercial kitchen MUA system.  Similar to lab 
systems, the OA flow rates are controlled to follow zone exhaust. Revising the 
Heat Recovery Bypass Control Type fixed a previously unidentified discrepancy 
in the outdoor air flow rates (see image). The change increases the energy use 
of the kitchen ventilation system (both fan and heating), however, the change 
is appropriate.

090012:  Revising Heat Recovery Bypass Control Type unexpectedly increased the 
energy use of SZVAV systems in this and other other test models. The increase 
in energy is associated with greater OA flow rates during certain hours (see 
image below). Also, the control of SAT/airflow is more scattered that what was 
identified in previous review (see issue 677 for reference).  

To mitigate the unexpected increase in energy consumption, I recommend adding 
an exception to the new Controller:OutdoorAir default for SZVAVAC and SZVAVHP 
systems. That is, using BypassWhenOAFlowGreaterThanMinimum for 
AirSys:Type=SZVAVAC or SZVAVHP. This update should revert the control of this 
system type back to what was previously reviewed.

Original comment by da...@360-analytics.com on 4 Nov 2014 at 7:49

Attachments:

GoogleCodeExporter commented 9 years ago 
Attached is a 1 zone SZVAV model that was used to test the SZVAV control scheme 
(see issue 677). I tested this model with both Heat Recovery Bypass Control 
Type specification and found no difference in results.  

However, if an OA flow requirement is added to the model (without economizer), 
I am seeing a difference in energy results, with the WEconoLimit option using 
less energy.  

Adding an economizer, the difference in energy use flips, withe OAGTMin option 
using less energy.

The differences in energy use are not huge. Reviewing the results for this 
model and the 090012 model (also with SZVAV), I am seeing the EUI difference is 
consistent, roughly 1-2 kBtu/ft2/yr.  However, until this change is better 
understood, I recommend sticking with the BypassWhenOAFlowGreaterThanMinimum 
method for SZVAV.

Original comment by da...@360-analytics.com on 4 Nov 2014 at 10:56

Attachments:

GoogleCodeExporter commented 9 years ago 
https://github.com/NREL/OpenStudio/commit/0ee8c51a34c68e03a8343b8f9575f950d16f1b
f9

Original comment by kbe...@gmail.com on 5 Nov 2014 at 5:04

GoogleCodeExporter commented 9 years ago 
Tested the changes; results as expected. SC will commit updates to CBECC repo; 
closing issue.

Original comment by da...@360-analytics.com on 7 Nov 2014 at 1:01

GoogleCodeExporter commented 9 years ago

Original comment by da...@360-analytics.com on 7 Nov 2014 at 1:02