Fan Coefficients used for MZVAV systems

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What steps reproduce the problem?
1.Run the Medium Office Electric Standard 90.1 Test
2. Have a look at the fan coefficients for baseline and proposed building
3. The baseline uses coef for 'Good SP Reset Curve' from Advanced VAV design 
guide. The proposed building uses 'VSD with Static Pressure Reset' curve from 
the NACM.

The attached email conversation, clarified that the baseline system 5-8 would 
use  Good SP Reset curve for fan part load performance. What is the reason for 
using a different curve for the proposed?
Also- I don't see a way for a user to specify fan SP reset control in the UI. 
Is the curve used for the proposed, default for all VSD fans?

What version of CBECC-901 are you using? On what operating system?
Version 2013-3a(678) on Windows 7 OS

Please provide any additional information below.
The baseline rule for MZ VAV is correct. The proposed uses the 'VSD with SP 
Reset curve' from the performance curve library 

Original issue reported on code.google.com by supriya....@pnnl.gov on 2 Dec 2014 at 1:40

Attachments:

• [Re Single Zone VAV Fan Curves.msg](https://storage.googleapis.com/google-code-attachments/cbecc/issue-863/comment-0/Re Single Zone VAV Fan Curves.msg)

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I just ran the current 030032-OffMed-S901GElectric model with current rules and 
found that both the proposed and baseline use the same library curve: 

FanVSDGoodSpResetPwrRatio_fCFMRatio

which matches the Advanced VAV Design Guide "Good SP Reset VSD Fan" curve. Are 
you finding something different?

Currently the property AirSys:CtrlSysType is what is used to differentiate 
between systems with or without SP Reset, and therefore, this property is a key 
criteria for determining the fan curve.

Here is a general outline of the current rules if the system Fan:CtrlMthd = 
VariableSpeedDrive

For relief fans, use "Perfect SP Reset VSD Fan" curve
For SZVAV supply/return fans, use "Perfect SP Reset VSD Fan" curve
For MZVAV supply/return fans and AirSys:CtrlSysType = "DDCToZone", use "Good SP 
Reset VSD Fan" curve
For MZVAV supply/return fans and AirSys:CtrlSysType = "Other", use the "Any fan 
with VSD" curve. For the PRMRM, this curve matched the curve in Appendix G, not 
the curve with the same name in T24. I checked the 901 curve library and see 
that this curve did not get revised from when it was copied over from T24, so I 
will fix that unless you indicate otherwise.

The fan curve rules applies to both the baseline and proposed; users cannot yet 
define their own curves. 

Please let me know if these rules should be revised.

Original comment by da...@360-analytics.com on 2 Dec 2014 at 5:49

• Changed state: Discussion

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So, it looks like the user cannot specify if the proposed design uses SP reset?

Original comment by bikerose...@gmail.com on 2 Dec 2014 at 6:22

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There is currently no explicit property used to define if there is SP Reset. 

We can add one. Right now, it is assumed that if they specify 'DDCToZone' 
control, the design does include SP reset.

Original comment by da...@360-analytics.com on 2 Dec 2014 at 6:53

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SP reset is a prescriptive requirement, so the designer is not forced to 
include it. It would be better if they did not include it, that they would be 
penalized. So some trigger to indicate whether the design includes SP reset 
would be best for the proposed building. If no SP reset, then the standard VAV 
curve should be used. 

Original comment by bikerose...@gmail.com on 2 Dec 2014 at 7:23

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Here is a proposed resolution:

1) Add new property, AirSys:HasStaticPressRst, type integer (0/1)
2) In AirSystem UI dialog, add a checkbox next to AirSys:CtrlSysType to toggle 
this property. 
3) Revise rules, as follows

For supply/return fans with Fan:CtrlMthd = "VariableSpeedDrive" 

if AirSys:CtrlSysType = "DDCToZone" and AirSys:HasStaticPressRst = 1
then fan curve = "Good SP Reset VSD Fan" 
else fan curve = "Any fan with VSD" curve 

For supply/return fans with other Fan:CtrlMthd options, proposed curve is based 
on fan properties Class and CentType, and is independent of the control system 
/ SP reset.

The baseline fan curve for VariableSpeedDrive fans is always "Good SP Reset VSD 
Fan"

Original comment by da...@360-analytics.com on 3 Dec 2014 at 12:15

• Changed state: Resolved

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Started working on this and reading the PRMRM language in 3.7.3.2, Static 
Pressure Controls, the language suggests two cases where SP Reset is 
applicable; either static control based on sensors in the main trunk -or- DDC 
of terminals to reset based on zone requiring most pressure.

Question: Are these indeed two different strategies, and if so, do you want to 
distinguish between the two with different fan curves? Up to now, I've assumed 
that credit for SP Reset will only be applicable to systems with "DDCToZone", 
but the language in the PRMRM and 90.1 seems to suggest two different 
approaches to meeting the prescriptive requirement.

Original comment by da...@360-analytics.com on 4 Dec 2014 at 7:09

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This is a mistake in the PRM language. It should read:

Static pressure sensors used to control VAV fans shall be placed in a position 
such that the controller setpoint is no greater than one-third the total design 
fan static pressure. For systems with DDC of individual zone boxes reporting to 
the central control panel, static pressure setpoint shall be reset based on the 
zone requiring the most pressure.

Original comment by bikerose...@gmail.com on 4 Dec 2014 at 7:51

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So, still proceed with plan to only use 'Good' SP curve in proposed design if 
'DDCToZone' and SP Reset is checked?

Original comment by da...@360-analytics.com on 4 Dec 2014 at 9:42

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Yes, that is the proper approach. 

Original comment by bikerose...@gmail.com on 4 Dec 2014 at 10:33

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[deleted comment]

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Rules updated and committed to branch @ r2818. Branch will be merged to trunk 
on 12/5 after v3a release is wrapped up.

Switching owner to SG for tracking PRMRM updates.

Original comment by da...@360-analytics.com on 4 Dec 2014 at 11:24

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These rules merged to trunk on 12/12 @ r2843

Original comment by da...@360-analytics.com on 18 Dec 2014 at 3:53

• Changed state: Fixed