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

There is a list in the input/Output ref. manual on what variable can be autosized.

If you fix one or two values to some components, the autosize process may fail or given some unpredictible results.

It is difficult detect, because not all the number shown on the component objects are used.
Therefore, I use the DesignDay sizing and no weather file as the first simmulation.

You did not list the Zone mean air temperature in the output variable, but many others. Therefore, you have no idea which zone is having problem. The zone names are in the warnings. Comparing the ODT and the Zone MAT can easily show whether heating or cooling is having problem.

I also list the schedule value. This is because not all the designDay type are completed in the compact schedule.

Why you cannot simply pick a weather file data and use it in the DesignDay objet has been explained in my last reply. There is another input syntax to use the Coldest Day in weather file directly. I did not do that because I did not have the weather file at the testing time.

The ZoneSizing object provides information for the IDF to size each zone without the designDay sizing. So be careful with the value in it and do not change them from the default example values, unless you already have problems and directed to change by the error file. For example, 12.5°C or 14°C as a cooling air supply temperature may be too low for a zone without reheat.

Most of these are commo sense numbers. My rule is to use the real equipment values, when in doubt.

DesignDay sizing provides the maximum heating and cooling for that day to provide the design zone temperature requirement with any equipment. Equipment sizing is not done.
It is actually using the IdealLoadsAirSystem.

When you added the HVAC equipment then the sizing are computed again to meet the zone requirement and the mximum environment requirement.

Then you replace the capacity with the real equipment to generate the report.

Dr. Li

To: EnergyPlus_Support@xxxxxxxxxxxxxxx
CC: yli006@xxxxxxxxxxx
From: YJHuang@xxxxxxxxxxxxxxxxxxxxxxxx
Date: Fri, 16 Mar 2012 16:02:08 -0700
Subject: Re: [EnergyPlus_Support] Fatal error with sizing of AC coil, what could be the problem?

Yuanlu,

This is getting confusing, and maybe I'm just revealing my unfamiliarity with EnergyPlus. If I don't have DesignDay specified in the input file, then what does EnergyPlus do when capacities and flow rates are entered as "autosize" ? With DOE-2, the program has already completed the Loads simulation, and knows the days with the highest heating and cooling loads and uses those to "autosize" the equipment. How does EnergyPlus do it? I guess I'll have to look in the documentation, as I've been lectured.

What do you mean that "you cannot simply pick a day in the weather file to ... autosize and then run the annual simulation" ? I thought that was the whole purpose for "autosizing". True, you may get a somewhat different size than from a Design Day calculation, but from everything I've seen that's a pretty small effect and certainly cannot be the reason why EnergyPlus is quitting at this point with an exit temperature of -74 C!

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 1:20 PM, YuanLu Li wrote:

Actually, the problem is that you do not have DesignDay objects in the file.

You cannot simply pick a day in the weather file and use it to size or autosize and then run the annual simulation without designDay sizing.

In fact, you did not even run the sizing day in your IDF simulation control. I know, OS and some other third party software can do it and is doing this all the time with lots of warnings.

Dr. Li

To: EnergyPlus_Support@xxxxxxxxxxxxxxx
CC: jim@xxxxxxxxxxxxxxxxxxxxxxxxxxx
From: YJHuang@xxxxxxxxxxxxxxxxxxxxxxxx
Date: Fri, 16 Mar 2012 10:52:37 -0700
Subject: Re: [EnergyPlus_Support] Fatal error with sizing of AC coil, what could be the problem?

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 “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 <mailto:yjhuang@xxxxxxxxxxxxxxxxxxxxxxxx>
> www.whiteboxtechnologies.com <http://www.whiteboxtechnologies.com>
> (o) (925)388-0265
> (c) (510)986-2683
> "building energy simulations at your fingertips"
>
>