CBECC-Com Issue - HVAC

[GoogleCodeExporter]

Version = 2013_3_653

Category = HVAC

Issue Summary:

I am running a computer room HVAC only simulation with DX CRAC units for two 
8,500 computer room suites at 100W/SF. I think there is an issue with the 
baseline sizing run when it convers to the CRAH  / chilled water baseline 
system for a computer room load this large per the ACM. It looks like the 
baseline sizing run fails because there is no heating hot water boiler capacity 
being put in.

Also when running a computer room model I could have one zone with 20 units, it 
looks like the limit is 10. This is not practical for large data centers.

Original issue reported on code.google.com by f.le...@gmail.com on 20 Oct 2014 at 11:46

Attachments:

• image003.jpg

[GoogleCodeExporter]

Changing owner to David.  I haven't run this yet, but I can see that if the 
baseline system map calls for a boiler, but there is no heating load because of 
the high internal loads, then the error above might occur.  Can we a) remove 
the boilers if the sizing result is zero capacity or b) put in a small minimum 
size?  The cibd file is in the issue tracker files folder on google docs.

Original comment by rhedr...@archenergy.com on 21 Oct 2014 at 4:56

[GoogleCodeExporter]

Retaking ownership.  Will add fix in HVACPrimary-Boilers.rule

Original comment by rhedr...@archenergy.com on 21 Oct 2014 at 6:00

[GoogleCodeExporter]

Added rule changes to ensure that boilers and chillers will have non-zero 
capacities.  However, David you are correct, the baseline is getting a System 
5.  Changing ownership to David. 

Original comment by rhedr...@archenergy.com on 21 Oct 2014 at 11:00

[GoogleCodeExporter]

I've identified the issue and locally implemented updates to resolve this 
issue.  Testing today and will commit rule updates today.  The bug stems from 
this being CompType = "NewMechanical".  

Other issues with this model:
- The fan control method is VSD, but the AirSys:Type is 'SZAC'.  For proper 
simulation of a SZVAV system, select AirSys:Type = "SZVAVAC".  A warning to 
alert users of this will be added in v3b
- There is not air economizer, which results in significantly more cooling 
energy than the baseline.
- The model includes some extra FluidSeg objects for the SHW system.

I'll post an update once I've tested and committed rule updates, as well as any 
possible work-around for this issue.

Original comment by da...@360-analytics.com on 23 Oct 2014 at 7:26

• Changed state: Discussion

[GoogleCodeExporter]

The root cause of this issue is a bug that results in creating baseline, 
non-process AirSystems and related FluidSystems for buildings that only have 
process space area. The extraneous systems are not connected to zones and 
therefore have 0 capacity, which results in the baseline simulation failing. 

Rule updates to fix this issue have been committed at r2690. 

Unfortunately, the only workaround using v3 is to:

- evaluate using the Proj:CompType = "NewComplete", and set the proposed 
lighting and envelope performance to match the baseline.
- include at least one non-process, conditioned "dummy" Space/ThermalZone. 
Could be very a very small zone with a small system that does not greatly 
influence the overall compliance result.

Original comment by da...@360-analytics.com on 24 Oct 2014 at 1:08

• Changed state: Fixed

[GoogleCodeExporter]

Sent to user:
Your model has found a couple of bugs which will be fixed in version 3b, due to 
be released in mid-November.

In the meantime, a workaround to avoid the issue is to:
- evaluate using the Proj:CompType = "NewComplete", and set the proposed 
lighting and envelope performance to match the baseline.
- include at least one non-process, conditioned "dummy" Space/ThermalZone. 
Could be very a very small zone with a small system that does not greatly 
influence the overall compliance result.

A couple of issues were noted with your model.  
- You specified an air system of type SZAC, but the fan is variable speed with 
VSD control.  For proper simulation of a SZVAV system, select AirSys:Type = 
"SZVAVAC".  A warning to alert users of this will be added in v3b. 
- There is no air economizer, which results in significantly more cooling 
energy than the baseline.
- The model includes some extra FluidSeg objects for the SHW system.  You 
should include only one supply segment and one makeup segment.  Additional 
segments may cause problems with the simulation, although we’re not sure as 
this has not been tested.

Original comment by rhedr...@archenergy.com on 24 Oct 2014 at 4:28

[GoogleCodeExporter]

Sent to user, example file in GD:

Christian,
My name is David and I work with Roger on the CBECC-Com development team.  I 
outlined this work-around for Roger, however, after giving it more thought, 
there is one specific detail that is important to know if you plan to use this 
to keep moving forward with evaluating your design:

The additional "dummy" space/zone/system needs to serve a 'Residential' zone.  
Attached is an modified version of your model that includes the additional 
example components needed, as well as updates to other inputs that I touched on 
in my original response provided to Roger. 

As Roger mentioned, fixes to the bug your model identified will be included in 
the Nov release, so hopefully you can wait for that update. 

Thanks for submitting your model for review,
David

Original comment by da...@360-analytics.com on 24 Oct 2014 at 4:57