CBECC-Com Issue - HVAC

[GoogleCodeExporter]

I’m trying to create a series of High Rise prototypes that result in 0 
compliance margin for all 16 CA climate zones. In all climate zones, I’ve 
been unable to get perfect compliant model. There is always at least a 0.1 
TDV/sf discrepancy in the DHW and sometimes a discrepancy in other end use 
categories as well.

Please review the model and provide some feedback about how to zero out these 
models. I suspect there is an issue with the mixed use space assumptions caused 
by having non-residential and high-rise residential space within the same model.

Version = 2013_3_653

Category = HVAC

Issue Summary:
List the steps taken to produce the error. For example:

1.      This model is designed to be perfectly compliant. I have run multiple 
iterations comparing the ab.xml and ap.xml model files to try to create a model 
that results in an overall budget of 0.

2.      If you open the model and run the analysis, the results are off in 4 
categories very slightly (0.1 – 0.2 TDV/sf)

3.      Please advise on what could be causing the discrepancy.

Original issue reported on code.google.com by f.le...@gmail.com on 30 Dec 2014 at 8:20

[GoogleCodeExporter]

Issue not related to bugs, errors or issues relating to the software. 

Original comment by nka...@archenergy.com on 6 Jan 2015 at 10:06

• Changed state: WontFix

[GoogleCodeExporter]

There are a few issues that I see in your High-rise Res. model that is trying 
to match the baseline to the proposed exactly:
1. Water Heaters
a. The “Office-2” space had the SHW FluidSeg Ref set to “Base HW Supply 
Seg”, it needs to be served by the water heater fluid segment “Office Hot 
Water Supply”.
b. The Solar Fraction for the Service Hot Water System should be 0.0, there is 
no solar fraction requirement for nonresidential spaces, only residential 
spaces.  The solar fraction for the Recirc System is correct.
c. It is very difficult to match the Proposed recirc water heater to the 
baseline because recirc water heaters are simulated by a CEC produced software 
that is not transparent.  That said, if you change the thermal efficiency of 
the Recirc. Water Heater from 0.78 to 0.80 the compliance margin goes to 0.0, 
assuming the above changes are included.
2. Pumps
a. Change the Control System Type of the BaseChWSystem from “Other” to 
“DDC”.
b. Update all pump values from the baseline.xml to the CBECC-Com interface.  
Include all significant figures that you see in the ab.xml.  The interface does 
not show all of the sig figs that you type in but they are stored in the .cibd 
file.
3. Fans
a. It looks like most of the fans are slightly different between the ap.xml and 
the ab.xml.  if you update all of these so they match the ab.xml exactly you 
should be able to remove the final 0.1 (kTDV/ft2*yr).

Original comment by ncz...@archenergy.com on 10 Feb 2015 at 9:40

[GoogleCodeExporter]

There are a few issues that I see in your model 
(HighRiseMF_CoolRoofAnalysis_CZ12.cibd:
1. The Chiller and Cooling tower seem to be undersized.  Some of the pumps also 
look to be undersized.  Since you have Auto-Populate Capacities / Efficiencies 
checked on the Non-Compliance Analysis tab (double click on Project:) you can 
right click on most of the capacity / flow / efficiency terms (select Restore 
Defaults) for Chillers, Towers, Boilers and Pumps to see the “recommended 
default values”.  These are great values to start with if you do not have a 
mechanical schedule or you are just trying to get a model to simulate.  After 
you get the model to simulate then you can go into the ab.xml file and pull out 
the exact capacities you want.
2. I also noticed that one of your spaces had unmet heating hours.  I think it 
was “M NE Apartment Zn”.  Click on the hot water coil for this zone, right 
click on the capacity and restore to default.  This should eliminate the UMLH 
in this zone.
3. For the Recirc DHW System the “Water Heating System serves more than one 
dwelling unit” tick box was unchecked.  This needs to be checked because the 
system is serving 79 spaces.  The tick box is just below Distribution Type on 
the Recirc. Water Heating System screen.
4. For the Recirc. annual solar fraction the value should be 0.35 if you are 
trying to match the baseline to the proposed.  I think for residential living 
spaces in the baseline model Climate Zones < 10 = 0.20 and all others climate 
zones = 0.35.

Original comment by ncz...@archenergy.com on 20 Feb 2015 at 12:18