Jeremiah,
It turns out that I did have two DesignDay definition in the file, so that was a "red herring". The conversation has now shifted to my Design Day being faulty, even though it was labeled as a HeatingDesignDay. My contention, though, is that no matter what are the design day conditions, unless they're outside of physical reality, EnergyPlus should not choke in its autosizing calculation (please see my previous post for details).
I think that design day calculations have been overstressed and mystified to some degree. They're largely a carry-over from the old days before simulations were
available and engineers picked a "design temperature" to manually calculate the size of equipment to put in (I always liked the joke I heard from a former DOE
staff, who opined that most contractors use the "door method" , i.e., "whatever equipment fits through the door"). "Design temperatures" has since morphed
into "design days" , "monthly design days", "5-day design sequences", etc., so maybe eventually we will just do an annual simulation (or multiple year simulations). To me, the biggest limitation of the "design day" concept is that it assumes all buildings will experience their peaks under the same conditions, which we all know is not true.
Your suggestion of having the simulation program automatically choose the peak days presents some difficulties for EnergyPlus. DOE-2 can do this because it simulates LOADS and HVAC in sequence, so by the time it gets to the system simulation, it knows which days have the highest heating and cooling loads and sizes the HVAC accordingly. EnergyPlus, however, does LOADS and HVAC in the same time step (but still in sequence within the time step), so it would not know the peak days unless it were to repeat LOADS twice. The other way, of course, is to preprocess the weather file but then you'll have the worst of both - no coupling with the building, and no knowledge of weather outside of what's in the weather file.
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 3/17/2012 11:59 AM, CleanTech Analytics 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 12Begin Day of Month 21End Month 12End Day of Month 21Day of Week for Start Day WinterDesignDayUse Weather File Daylight Saving Period YesUse Weather File Rain and Snow Indicators Yes
Name coolBegin Month 7Begin Day of Month 21End Month 7End Day of Month 21Day of Week for Start Day SummerDesignDayUse Weather File Daylight Saving Period YesUse Weather File Rain and Snow Indicators Yes
Jeremiah D. CrossettCleanTech Analytics503-688-8951This 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"
>
>
__._,_.___
Primary EnergyPlus support is found at:
http://energyplus.helpserve.com or send a message to energyplus-support@xxxxxxxx
The primary EnergyPlus web site is found at:
http://www.energyplus.gov
The group web site is:
http://groups.yahoo.com/group/EnergyPlus_Support/
Attachments are currently allowed but be mindful that not everyone has a high speed connection. Limit attachments to small files.
EnergyPlus Documentation is searchable. Open EPlusMainMenu.pdf under the Documentation link and press the "search" button.
![]()
Your email settings: Individual Email|Traditional
Change settings via the Web (Yahoo! ID required)
Change settings via email: Switch delivery to Daily Digest | Switch to Fully Featured
Visit Your Group | Yahoo! Groups Terms of Use | Unsubscribe
__,_._,___