Re: [EnergyPlus_Support] Fatal error with sizing of AC coil, what could be the problem?

[Joe Huang <YJHuang@xxxxxxxxxxxxxxxxxxxxxxxx>]

Jim, Yuanlu, and Richard,

Interesting to hear that this is your "favorite" EnergyPlus error.  If 
it's a systemic or reoccurring error, that would tell me there's 
something faulty in the EnergyPlus sizing algorithm, or at least for 
certain conditions.

Looking at the comments from Yuanlu and Richard, who reported that the 
file ran fine using either no weather file or for some other location, 
this problem seems related to the weather file used.   What I used was 
CZ15RV2 (here attached in Zip form), which is the standard California 
Energy Commission weather file for Climate Zone 15 for the desert areas 
in Southern California. The file is also available from the EnergyPlus 
Weather web site under California.

I appreciate your suggestion about simply shutting off the AC in 
December, but I thought this error was caused in the sizing routine, not 
the simulation. Perhaps someone should explain to me in brief how and 
when EnergyPlus does its sizing calculations.  Isn't it done using the 
DDY file?

I get back to the reported outlet air temperature of -74 C  in the err 
report.  This is so out of normal that it makes me question the 
algorithm.  I looked at the weather file and the lowest temperatures are
still above 0C , so what drives EnergyPlus to derive such a 
out-of-bounds result?  This reminds me of the problems I had 5 years ago 
when some runs were failing, with zone temperatures exceeding 200 C.
I attributed those to iterations going haywire, but here I'm wondering 
if it' a problem in the psychrometrics.

I would ask Yuanlu and Richard to try the IDF again with the CZ15RV2 
file, and see if the same error occurs.

Joe

Joe Huang
White Box Technologies, Inc.
346 Rheem Blvd., Suite 108D
Moraga CA 94556
yjhuang@xxxxxxxxxxxxxxxxxxxxxxxx
www.whiteboxtechnologies.com
(o) (925)388-0265
(c) (510)928-2683
"building energy simulations at your fingertips"


On 3/16/2012 6:46 AM, Jim Dirkes wrote:
>
> Dear Joe,
>
> This is my â??favoriteâ?? EnergyPlus error!
>
> Essentially, EnergyPlus is convinced, with good reasons, that DX coils 
> are not rated to operate outside of the range shown in your errors, 
> which corresponds to about 300-450 cfm/ton.  (The acceptable range 
> widens for operation).
>
> Part of the key here is that weâ??re talking about the coil rating 
> conditions.  For autosizing, E+ assumes the same rating and operating 
> conditions.
>
> Richard Raustad of the E+ Help desk is approaching sainthood for his 
> patience in answering many of my questions and bearing with my 
> frustration on this issue, and is probably the â??go?toâ?? expert on this 

> topic.
>
> Iâ??m trying to think what may cause an autosized file to trip this 
> error and not coming up with too much.
>
> ·You are using a reasonable-to-generous delta T of 10.4C / 18.7F, 
> although ASHRAE 90.1 would like you to use  11.1 / 20.  Increasing 
> delta T should help.
>
> ·The error, however, occurs in December.  If your weather file is a 
> northern hemisphere location, thereâ??s no reason a cooling coil should 
> operate.  Perhaps you should schedule it off.  The schedule for this 
> in a full year simulation is tricky because TMY weather patterns (and 
> winter warm periods) differ, but it may work out for you since the 
> error occurs during warmup?

>
> ·There is a simple EMS method for turning off DX coils when the 
> outdoor temp exceeds a specified value; very handy for minimizing 
> warnings about operating your DX coil during cold weather and 
> producing sub-freezing outlet temps.
>
> Thatâ??s all I can think of for now.
>
> *The Building Performance Team
> **James V. Dirkes II, P.E., BEMP , LEED AP
> *1631 Acacia Drive NW
> Grand Rapids, MI 49504
> 616 450 8653
>
> *From:*EnergyPlus_Support@xxxxxxxxxxxxxxx 
> [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] *On Behalf Of *Joe Huang
> *Sent:* Friday, March 16, 2012 4:10 AM
> *To:* EnergyPlus_Support@xxxxxxxxxxxxxxx
> *Subject:* [EnergyPlus_Support] Fatal error with sizing of AC coil, 
> what could be the problem?
>
> Hello,
>
> I have a small project to translate a large number of eQUEST input 
> files to EnergyPlus IDF. I have developed
> a procedure that seems to work, but in a few cases I have encountered 
> a Fatal error in the HVAC system sizing
> that persists even when I set the Rated Cooling Capacity, Sensible 
> Heat Ratio, and Air Flow Rate all to "autosize".
>
> The *.err file shows the following :
>
>   ** Severe  ** Sizing: Coil:Cooling:DX:SingleSpeed "EL1-SYS1-PSZ-M.S 
> DX COOLING COIL": Rated air volume flow rate per watt of rated total 
> cooling capacity is out of range.
>   **   ~~~   ** Min Rated Vol Flow Per Watt=[4.027E-005], Rated Vol 
> Flow Per Watt=[6.656E-006], Max Rated Vol Flow Per Watt=[6.041E-005]. 
> See Input-Output Reference Manual for valid range.
>   ** Severe  ** For object = Coil:Cooling:DX:SingleSpeed, name = 
> "EL1-SYS1-PSZ-M.S DX COOLING COIL"
>   **   ~~~   ** Calculated outlet air relative humidity greater than 
> 1. The combination of
>   **   ~~~   ** rated air volume flow rate, total cooling capacity and 
> sensible heat ratio yields coil exiting
>   **   ~~~   ** air conditions above the saturation curve. Possible 
> fixes are to reduce the rated total cooling
>   **   ~~~   ** capacity, increase the rated air volume flow rate, or 
> reduce the rated sensible heat ratio for this coil.
>   **   ~~~   ** If autosizing, it is recommended that all three of 
> these values be autosized.
>   **   ~~~   ** ...Inputs used for calculating cooling coil bypass 
> factor.
>   **   ~~~   ** ...Inlet Air Temperature     = 26.67 C
>   **   ~~~   ** ...Outlet Air Temperature    = -74.52 C
>   **   ~~~   ** ...Inlet Air Humidity Ratio  = 1.125000E-002 kg/kg
>   **   ~~~   ** ...Outlet Air Humidity Ratio = 1.000000E-005 kg/kg
>   **   ~~~   ** ...Total Cooling Capacity used in calculation = 
> 362778.00 W
>   **   ~~~   ** ...Air Mass Flow Rate used in calculation     = 
> 2.783088 kg/s
>   **   ~~~   ** ...Air Volume Flow Rate used in calculation   = 
> 2.414784 m3/s
>   **   ~~~   ** ...Air Volume Flow Rate per Watt of Rated Cooling 
> Capacity is also out of bounds at = 6.6563684E-006 m3/s/W
>   **   ~~~   **  During Warmup, Environment=CZ06RV2 COLDEST DAY FROM 
> WEATHER FILE, at Simulation time=12/28 00:00 - 00:15
>   **  Fatal  ** Check and revise the input data for this coil before 
> rerunning the simulation.
>
> The *.idf file shows the following :
>
>  Coil:Cooling:DX:SingleSpeed,
>    EL1-Sys1-PSZ-G.S DX Cooling Coil,  !- Name
>    S1-Sys1-PSZ-FaQ3,        !- Availability Schedule Name
>    autosize,                 !- Rated Total Cooling Capacity {W}
>    autosize,                !- Rated Sensible Heat Ratio
>    3.172176,                !- Rated COP {W/W}
>    autosize,                !- Rated Air Flow Rate {m3/s}
>    ,                        !- Rated Evaporator Fan Power Per Volume 
> Flow Rate {W/(m3/s)}
>    EL1-Sys1-PSZ-G.S Mixed Air Outlet,  !- Air Inlet Node Name
>    EL1-Sys1-PSZ-G.S Cooling Coil Outlet,  !- Air Outlet Node Name
>    Car_48TM012-Cool,        !- Total Cooling Capacity Function of 
> Temperature Curve Name
>    SDL-C78,                 !- Total Cooling Capacity Function of Flow 
> Fraction Curve Name
>    Car_48TM012-EIR-,        !- Energy Input Ratio Function of 
> Temperature Curve Name
>    SDL-C93,                 !- Energy Input Ratio Function of Flow 
> Fraction Curve Name
>    VarSpeedCyclingPLFFPLR;  !- Part Load Fraction Correlation Curve Name
>
> I'm particularly bothered by the unrealistically low outlet air 
> temperature. Has anyone encountered this problem?
> Since I've already set everything to autosize, I'm stuck on how else I 
> can fix this problem.
>
> Any help or observations would be much appreciated.
>
> I've attached the full IDF with this e-mail: 
> OfL-w06-v96-hDXGF-cMsr-mNE-ILtg-FixtPwr-Prim-48in100wT12RefESMg100w-48in55wT8RefEl55w_2.idf 
> .   The weather file used is CZ15RV2.epw .
>
> Joe
> Hello,
>
> I have a small project to translate a large number of eQUEST input 
> files to EnergyPlus IDF. I have developed
> a procedure that seems to work, but in a few cases I have encountered 
> a Fatal error in the HVAC system sizing
> that persists even when I set the Rated Cooling Capacity, Sensible 
> Heat Ratio, and Air Flow Rate all to "autosize".
>
> The *.err file shows the following :
>
>   ** Severe  ** Sizing: Coil:Cooling:DX:SingleSpeed "EL1-SYS1-PSZ-M.S 
> DX COOLING COIL": Rated air volume flow rate per watt of rated total 
> cooling capacity is out of range.
>   **   ~~~   ** Min Rated Vol Flow Per Watt=[4.027E-005], Rated Vol 
> Flow Per Watt=[6.656E-006], Max Rated Vol Flow Per Watt=[6.041E-005]. 
> See Input-Output Reference Manual for valid range.
>   ** Severe  ** For object = Coil:Cooling:DX:SingleSpeed, name = 
> "EL1-SYS1-PSZ-M.S DX COOLING COIL"
>   **   ~~~   ** Calculated outlet air relative humidity greater than 
> 1. The combination of
>   **   ~~~   ** rated air volume flow rate, total cooling capacity and 
> sensible heat ratio yields coil exiting
>   **   ~~~   ** air conditions above the saturation curve. Possible 
> fixes are to reduce the rated total cooling
>   **   ~~~   ** capacity, increase the rated air volume flow rate, or 
> reduce the rated sensible heat ratio for this coil.
>   **   ~~~   ** If autosizing, it is recommended that all three of 
> these values be autosized.
>   **   ~~~   ** ...Inputs used for calculating cooling coil bypass factor.
>   **   ~~~   ** ...Inlet Air Temperature     = 26.67 C
>   **   ~~~   ** ...Outlet Air Temperature    = -74.52 C
>   **   ~~~   ** ...Inlet Air Humidity Ratio  = 1.125000E-002 kg/kg
>   **   ~~~   ** ...Outlet Air Humidity Ratio = 1.000000E-005 kg/kg
>   **   ~~~   ** ...Total Cooling Capacity used in calculation = 
> 362778.00 W
>   **   ~~~   ** ...Air Mass Flow Rate used in calculation     = 
> 2.783088 kg/s
>   **   ~~~   ** ...Air Volume Flow Rate used in calculation   = 
> 2.414784 m3/s
>   **   ~~~   ** ...Air Volume Flow Rate per Watt of Rated Cooling 
> Capacity is also out of bounds at = 6.6563684E-006 m3/s/W
>   **   ~~~   **  During Warmup, Environment=CZ06RV2 COLDEST DAY FROM 
> WEATHER FILE, at Simulation time=12/28 00:00 - 00:15
>   **  Fatal  ** Check and revise the input data for this coil before 
> rerunning the simulation.
>
> The *.idf file shows the following :
>
>  Coil:Cooling:DX:SingleSpeed,
>    EL1-Sys1-PSZ-G.S DX Cooling Coil,  !- Name
>    S1-Sys1-PSZ-FaQ3,        !- Availability Schedule Name
>    autosize,                 !- Rated Total Cooling Capacity {W}
>    autosize,                !- Rated Sensible Heat Ratio
>    3.172176,                !- Rated COP {W/W}
>    autosize,                !- Rated Air Flow Rate {m3/s}
>    ,                        !- Rated Evaporator Fan Power Per Volume 
> Flow Rate {W/(m3/s)}
>    EL1-Sys1-PSZ-G.S Mixed Air Outlet,  !- Air Inlet Node Name
>    EL1-Sys1-PSZ-G.S Cooling Coil Outlet,  !- Air Outlet Node Name
>    Car_48TM012-Cool,        !- Total Cooling Capacity Function of 
> Temperature Curve Name
>    SDL-C78,                 !- Total Cooling Capacity Function of Flow 
> Fraction Curve Name
>    Car_48TM012-EIR-,        !- Energy Input Ratio Function of 
> Temperature Curve Name
>    SDL-C93,                 !- Energy Input Ratio Function of Flow 
> Fraction Curve Name
>    VarSpeedCyclingPLFFPLR;  !- Part Load Fraction Correlation Curve Name
>
> I'm particularly bothered by the unrealistically low outlet air 
> temperature. Has anyone encountered this problem?
> Since I've already set everything to autosize, I'm stuck on how else I 
> can fix this problem.
>
> Any help or observations would be much appreciated.
>
> I've attached the full IDF with this e-mail: 
> OfL-w06-v96-hDXGF-cMsr-mNE-ILtg-FixtPwr-Prim-48in100wT12RefESMg100w-48in55wT8RefEl55w_2.idf 
> .   The weather file used is CZ15RV2.epw .
>
> Joe
>
> Joe Huang
> White Box Technologies, Inc.
> 346 Rheem Blvd., Suite 108D
> Moraga CA 94556
> yjhuang@xxxxxxxxxxxxxxxxxxxxxxxx <mailto:yjhuang@xxxxxxxxxxxxxxxxxxxxxxxx>
> www.whiteboxtechnologies.com <http://www.whiteboxtechnologies.com>
> (o) (925)388-0265
> (c) (510)986-2683
> "building energy simulations at your fingertips"
>
> 


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