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

On Sat, Mar 17, 2012 at 5:46 PM, Dru Crawley <dbcrawley@xxxxxxxxx> wrote:

Jeremiah,

You can let E+ select the design day. Just cut/paste ALL the design days from the .DDY file that is in the .ZIP with the .EPWs. It includes all 18 annual design days--with the appropriate peak (coldest/warmest) month (may be Dec/Jan/Feb or July/Aug/Sep). EnergyPlus will autosize on the largest zone and system load.

As Linda notes, they will be adding monthly design conditions -- in low-energy buildings I've found that the cooling peak may occur in September -- lower sun angles, etc.
Dru
On Sat, Mar 17, 2012 at 2:59 PM, CleanTech Analytics <jeremiah@xxxxxxxxxxxxxxxxxxxxxx> wrote:
Joe,
To use a design day file you have to download the weather file bundle and copy/paste the design day files of your choice to your IDF. I do not like this method because it allows me to choose what days to design to, and I would rather the software choose that for me. As a work around for this I like to arbitrarily set the "sizing period use weather file" object, to the dates below, then run the simulation, then use the timestamped peak heating and peak cooling days from the output "table" and change the sizing period weather file days to match the peak.. The whole idea of design days, in my opinion should be done away with in the next version of E+, and the sizing period weather file days should be modified to automatically choose the peak heating and peak cooling days for sizing, but that is up to the E+ team to decide, and possibly there is some incomprehensible reason why the design day option is provided rather then the more strait forward peak weather file days approach is not taken..

Name heat

Begin Month 12
Begin Day of Month 21

End Month 12
End Day of Month 21
Day of Week for Start Day WinterDesignDay

Use Weather File Daylight Saving Period Yes
Use Weather File Rain and Snow Indicators Yes

Name cool
Begin Month 7
Begin Day of Month 21

End Month 7
End Day of Month 21
Day of Week for Start Day SummerDesignDay

Use Weather File Daylight Saving Period Yes
Use Weather File Rain and Snow Indicators Yes

Jeremiah D. Crossett
CleanTech Analytics
503-688-8951
www.cleantechanalytics.com

This document may contain valuable information proprietary to CleanTech Analytics which is private and confidential. It may not be shared, copied, stored or transmitted in any form without the prior written consent of CleanTech Analytics
On Fri, Mar 16, 2012 at 4:02 PM, Joe Huang <YJHuang@xxxxxxxxxxxxxxxxxxxxxxxx> wrote:
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"
>
>