[Equest-users] Appendix G Baseline Systems 6 and 8 - supply air temperature controls?

Robby Oylear robbyoylear at gmail.com
Fri Nov 22 08:47:23 PST 2013


Bill,

Seems like too big of a guess to me.  If the ASHRAE 90.1 committee
specifically wanted your supply air temperature reset priority to be
airflow first, it seems like that would be simply and explicitly stated.  I
don't have a copy of the User's Manual for 90.1 in front of me.  Perhaps
there's further explanation of the meaning of G3.1.3.14 in that document.

In my experience with these systems, I've never been called on my setting
of TEMPERATURE-FIRST in system 6 & 8 baselines, so it's likely a moot
point.

-Robby


On Fri, Nov 22, 2013 at 6:45 AM, Bishop, Bill <bbishop at pathfinder-ea.com>wrote:

>  Robby,
>
> My initial interpretation of G3.1.3.14 was similar to yours – of course
> the SAT is constant at the design condition. But then why bother saying,
> “The supply air temperature setpoint shall be constant at the design
> condition”? Since G3.1.3.14 is about fan power and air flow rate, it makes
> sense that this refers to the design flowrate. My guess is that the intent
> is for cooling controls to reset the airflow (to save fan energy, since
> that’s what G3.1.3.14 addresses) before resetting the temperature. That
> strategy can be modeled in eQUEST using RESET-PRIORITY = AIRFLOW-FIRST as I
> showed below. TEMPERATURE-FIRST can reset the temperature up at the “design
> condition” flowrate.
>
>
>
> ~Bill
>
>
>
> *From:* Robby Oylear [mailto:robbyoylear at gmail.com]
> *Sent:* Thursday, November 21, 2013 4:18 PM
> *To:* Bishop, Bill
> *Cc:* equest-users at lists.onebuilding.org
> *Subject:* Re: [Equest-users] Appendix G Baseline Systems 6 and 8 -
> supply air temperature controls?
>
>
>
> I'm not sure I follow your interpretation on G3.1.3.14.  The supply air
> temperature setpoint is constant at the design condition regardless of
> whether you reset airflow or temperature first.  At the design condition
> there will be no reset occurring because you're by definition, at design.
>  I've always interpreted that whole section of G3.1.3.14 to be referring to
> the terminal unit fans only.
>
>
>
> TEMPERATURE-FIRST makes the most sense to me for accomplishing G3.1.3.12,
> but I may be biased as in a marine climate resetting temperature up
> increases economizer hours dramatically.
>
>
>
> -Robby
>
>
>
> On Thu, Nov 21, 2013 at 10:28 AM, Bishop, Bill <bbishop at pathfinder-ea.com>
> wrote:
>
> I also created an input file template for System 6 which could be used for
> System 8 with some modification. Comments/mods are welcomed.
>
>
>
> $ *********************************************************
>
> $ **                                                     **
>
> $ **                Performance Curves                   **
>
> $ **                                                     **
>
> $ *********************************************************
>
>
>
> "G3.1.3.15 VAV Fan Curve fPLR" = CURVE-FIT
>
>    TYPE             = CUBIC
>
>    INPUT-TYPE       = COEFFICIENTS
>
>    COEFFICIENTS     = ( 0.0013, 0.147, 0.9506, -0.0998 )
>
>    ..
>
>
>
>
>
> $ *********************************************************
>
> $ **                                                     **
>
> $ **               HVAC Systems / Zones                  **
>
> $ **                                                     **
>
> $ *********************************************************
>
>
>
> SET-DEFAULT FOR ZONE
>
>    TYPE = CONDITIONED
>
>    MIN-FLOW-RATIO   = 0.3           $ Per G3.1.3.14
>
>    ZONE-FAN-KW/FLOW = 0.00035       $ Per G3.1.3.14
>
>    ZONE-FAN-RATIO   = 0.5           $ Per G3.1.3.14
>
>    TERMINAL-TYPE    = PARALLEL-PIU  $ For all zones served by Sys 6 or Sys
> 8
>
>    ..
>
>
>
> SET-DEFAULT FOR SYSTEM
>
>    TYPE             = PIU           $ For Baseline System 6 and System 8
>
>    HEAT-SOURCE      = ELECTRIC      $ Per Table G3.1.1B and User's Manual
> p.G-23
>
>    ZONE-HEAT-SOURCE = ELECTRIC      $ Per Table G3.1.1B and User's Manual
> p.G-23
>
>    HEAT-SIZING-RATI = 1.25          $ Per G3.1.2.2
>
>    COOL-SIZING-RATI = 1.15          $ Per G3.1.2.2
>
>    COOL-SOURCE      = ELEC-DX           $ Per Table G3.1.1B
>
>    MAX-SUPPLY-T     = 92            $ Per G3.1.2.8 (20F above room heat
> T-Stat
>
>    HEAT-SET-T       = 62            $ = COOL-MAX-RESET-T plus 1F
>
>    MIN-SUPPLY-T     = 56            $ Per G3.1.2.8 (20F below room cool
> T-Stat
>
>    COOL-CONTROL     = WARMEST       $ Per G3.1.3.12
>
>    ECONO-LIMIT-T    = 70            $ Per G3.1.2.7 and Table G3.1.2.6B by
> climate zone
>
>    ECONO-LOCKOUT    = YES           $ (Seems like a reasonable baseline
> default)
>
>    COOL-MIN-RESET-T = 56            $ = MIN-SUPPLY-T
>
>    RESET-PRIORITY   = AIRFLOW-FIRST $ Per G3.1.3.12 and G3.1.3.14
>
>    COOL-MAX-RESET-T = 61            $ Per G3.1.3.12 (5F above MIN-SUPPLY-T)
>
>    OA-CONTROL       = OA-TEMP       $ Per G3.1.2.6 and Table G3.1.2.6A
>
>    FAN-CONTROL      = FAN-EIR-FPLR                    $ Per G3.1.3.15
>
>    NIGHT-CYCLE-CTRL = CYCLE-ON-ANY                    $ Per G3.1.2.4
>
>    FAN-EIR-FPLR     = "G3.1.3.15 VAV Fan Curve fPLR"  $ Per G3.1.3.15
>
>    REHEAT-DELTA-T   = 36            $ = MAX-SUPPLY-T minus MIN-SUPPLY-T
>
>    ..
>
>
>
>    $ Bill
>
>
>
> *From:* equest-users-bounces at lists.onebuilding.org [mailto:
> equest-users-bounces at lists.onebuilding.org] *On Behalf Of *Bishop, Bill
> *Sent:* Thursday, November 21, 2013 1:14 PM
> *To:* equest-users at lists.onebuilding.org
> *Subject:* [Equest-users] Appendix G Baseline Systems 6 and 8 - supply
> air temperature controls?
>
>
>
> ASHRAE Standard 90.1, G3.1.3.12 requires cooling supply air temperature
> reset for Systems 5 through 8.
>
> G3.1.3.14 requires “supply air temperature setpoint shall be constant at
> the design condition” for Systems 6 and 8.
>
> How should we interpret this and model it in eQUEST (for Systems 6 and 8)?
>
>
>
> If the “design condition” in G3.1.3.14 means “peak design flow rate”, I
> suggest the following cooling control settings:
>
> -             COOL-CONTROL     = WARMEST
>
> -             COOL-MIN-RESET-T = 56                    $ (assumes 76F
> cooling T-stat; 56F MIN-SUPPLY-T for 20F difference per G3.1.2.8)
>
> -             RESET-PRIORITY   = AIRFLOW-FIRST
>
> -             COOL-MAX-RESET-T = 61                   $ (5F reset per
> G3.1.3.12; assumes 76F cooling T-stat)
>
>
>
> Using a RESET-PRIORITY of “TEMP-FIRST” resets the supply air temperature
> *before* the airflow, which does not satisfy the G3.1.3.14 requirement.
>
> Using a RESET-PRIORITY of “TEMP-FIRST” or “SIMULTANEOUS” does not satisfy
> the G3.1.3.12 requirement, since temperature is reset well  before minimum
> cooling load conditions are reached.
>
>
>
> Does anyone have an alternative/additional suggestion or interpretation?
>
>
>
> Thanks,
>
> Bill
>
>
>
> *William Bishop, PE, BEMP, BEAP, LEED AP | Pathfinder Engineers &
> Architects LLP*
>
> *Senior Energy Engineer*
>
> [image: webCertified_logo_colorRGB72DPI.jpg]
>
>
>
> 134 South Fitzhugh Street                 Rochester, NY 14608
>
> T: (585) 325-6004 Ext. 114            F: (585) 325-6005
>
> bbishop at pathfinder-ea.com <wbishop at pathfinder-ea.com>
> www.pathfinder-ea.com
>
> P   Sustainability – the forest AND the trees. P
>
>
>
>
>
>
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