Dear Joe,
This is my “favorite” 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 we’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 “go�to” expert on this topic.
I’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, there’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.
That’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
www.whiteboxtechnologies.com
(o) (925)388-0265
(c) (510)986-2683
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