VSD with SP Reset Curve

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What NACM Section(s) are relevant to this issue?
5.7.3.2 Supply Fans

Explanation of issue:
The NACM curve 'VSD with static pressure reset' has coefficients that match the 
Advanced VAV Design Guide "Perfect" SP Reset curve.  It seems more appropriate 
to use the "Good" SP reset curve for multizone (MZ) VAV systems.

Proposed resolution:
Revise same from 'VSD with static pressure reset' to VSD with Perfect static 
pressure reset'.  Update rules to indicate this curve is used for SZVAV and 
relief fans only
Add additional curve called 'VSD with Good static pressure reset' from Advanced 
VAV Design Guide. Update rules to use this curve for supply/return fans in 
other MZVAV systems that use SP Reset.

Please provide any additional information below.
These are likely the rules that will be used for 90.1 PRMRM. See GC issue 863 
for reference. I agree with PNNL that it is more appropriate to use the 'Good' 
SP reset curve for MZVAV systems.

Original issue reported on code.google.com by da...@360-analytics.com on 4 Dec 2014 at 9:53

[GoogleCodeExporter]

I'll review. I agree in principle but would like to look at the curves to 
confirm.

Do we have an input/option for a Boolean as to whether DDC to the zone is 
specified? If it isn't, they can't do the reset and should be penalized for it.

this should be an easy fix once I verify. 

Original comment by JohnJArent on 11 Dec 2014 at 11:35

• Changed state: Discussion

[GoogleCodeExporter]

Yes, we check that a zone w/ DCV specified is served by a ventilation system 
with:
a) 'DDCToZone' control if it is a multizone system
b) An economizer if it is a single or multizone system.

Original comment by da...@360-analytics.com on 11 Dec 2014 at 11:58

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I reviewed the curves (Source: 
http://taylor-engineering.com/downloads/guides/EDR_VAV_Guide_5-2-07.pdf)  and 
agree with this change.  

The standard design curve would then follow the "Good SP Reset Curve", with 
coefficients of:

This is based on a plenum airfoil fan on a system curve through 0.5 in.
"Good SP Reset VSD Fan" = CURVE-FIT
 TYPE = CUBIC
 INPUT-TYPE = COEFFICIENTS
 OUTPUT-MIN = 0
 OUTPUT-MAX = 1
 COEFFICIENTS = (0.040759894, 0.08804497, -0.07292612, 0.943739823) 

The proposed design curve is not entered directly by the user, but rather 
selected based on the ControlType.

If ControlType = "DDCToZone" then
    Use GoodSPReset curve above
Else
    Use the NoSPReset curve

The default curve to use if DDC to Zone level is not specified is unchanged 
from before. Change required to Appendix 5.7 for this. I'll review and verify 
if any changes are needed to the ACM RM.

David, I don't fully understand comment #2. By "DCV" do you mean "DDC"? The 
desired rule is that DDC control is the standard design, but the proposed is 
not required to have it in the 2013 Standards since it is not mandatory. The 
DDC is the baseline and provides benefits through static pressure reset for 
fans and DP reset for pumps for CHW systems.

Original comment by JohnJArent on 12 Dec 2014 at 6:59

• Changed state: Resolved

[GoogleCodeExporter]

Re #2, yes sorry, I read DCV somehow.  In answer to your question, yes, the 
user must specify they have 'DDCToZone' to get SP Reset. PNNL asked for 90.1 
compliance to have another check box so the user must specify 'DDCToZone' and 
check a box that they are actually using SP Reset to get the GoodSPReset curve. 
That is:

If ControlType = "DDCToZone" AND StaticPressRstCtrl = TRUE
Then
    Use GoodSPReset curve above
Else
    Use the NoSPReset curve

Let me know if you'd like to have this extra check included in CBECC-Com for T24

Original comment by da...@360-analytics.com on 12 Dec 2014 at 7:11

[GoogleCodeExporter]

David, yes, I think PNNL has a good idea with actually having to check SP 
reset, if they have DDC controls, and not automatically assume they have 
demand-based resets just because they have DDC.

If they don't have DDCtoZone controls, there are a couple options for handling 
this in the UI, both acceptable. One is to flag an error if they select 
GoodSPReset when DDCtoZone is not selected. Another option is to restrict the 
list of available control options from the dropdown list in the UI if "Other" 
is selected as the ControlType.  The second option is probably a bit more work, 
but would be a little more user-friendly as it would prevent some runtime 
errors that occur before the sim runs.

Original comment by JohnJArent on 12 Dec 2014 at 7:50

[GoogleCodeExporter]

Rules to use GoodSpReset fan curve merged to trunk @ r2970

Original comment by da...@360-analytics.com on 24 Jan 2015 at 9:06

• Changed state: Fixed