It seems what I've said had touched some nerves. That was not my intention, and I was trying to point out something that seems puzzling to me.
When I said "red herring", I was referring to your earlier comment that I was having troubles because I didn't have any DesignDay objects, which then motivated
Jeremiah to tell me how to insert design days in my files. But then, we both agree that the file in fact did have design days all along, which was why I told Jeremiah
that it (the absence of design day objects) was a "red herring". I'm sorry if you were offended by that description.
I've inserted other comments below to make it clearer to what I'm referring.
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 5:39 PM, YuanLu Li wrote:
I finally took a look on the Web at the DDY for CZ15RV02 and found that its 99.6% criteria had exactly the same max. temperature as what I had derived (17.8C), the only difference being that I had a diurnal swing of 17.8C and the Web version had 0 C. Since CZ15 is the high desert, I would question more the latter than the former. But given their overall similarity, I find it hard to believe that it's my Design Day definition alone that's creating this problem. Besides, if the Design Day definition is different, shouldn't the
I did not use your DesignDay data, because I did not agree with the content.
When I overwritten them with the correct one, the warning were different.
I should have said that you IDF did not use the DesignDay sizing simulation.
I showed you in the DOS listing, that your design day warming up was not performed.
It is not a red herring as you have described.
If you do not use the DesignDay object correctly, please do not claim that the EPlus choke the autosizing.
You do have DesignDay object specified, but they were not correct.
If you do not accept, it is fine with me and you need not read on.
The DesignDay data were extracted from the .epw file using statistical rules and condition that will prevent situations such as your -74 and 200°C temperature. Some of the causes were in your zone and system sizing objects. Do not blame the EPlus for warning you.''
autosizing routine just return a different capacity, and not fail ? I also think you're giving too much credence to the DDY (which are not extracted from the EPW). There are no fancy tricks in their derivation beyond making sure that the climatic parameters not violate physical reality.
I think you're missing my point and turning it around 180 degrees. What I'm saying is that the Design Day conditions for different buildings in the same location are not necessarily the same. A low-mass building with a lot of west-facing windows will experience its design load in the fall, while a high-mass building with a lot of internal loads may experience its design load in the summer because temperatures are high.
In the original design, the design day sizing is always done first to get the maximim heating and cooling load for the building. Then the user is allowed to add HVAC, etc. Because the current user were never told these procedures, by using point and click. to get a report.
The user does not even know what is the zone temperature after the simulation. I come to this conclusion, because a user seldom ask for the output variable for zone mean air temperature in their IDF.
"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."
This statement is false. Are all the DesignDay data for the same building at different loacation the same? Never. Your reference building has a different epw for each climatic zone, and therefore have different DesignDay data for every zone.
"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)."
This is true, because the user does not know why sizing is required and cannot find or do not know how to generate a DesignDay object correctly. By naming it the coldest day does not mean that it is the correct coldest day data.
That's not what happened. What's happened is that the autosizing routine is failing to find any solution, thus aborting the program. If it's just a matter of proper sizing, the program should return an improperly sized equipment, and I will then see underheated/undercooled hours. The autosizing routine should only fail if the psychrometrics are
When EPlus use the Coldest day data for sizing in the other Sizing object format, it knows what field to use and what to ignore. It is smarter than the way you transferred the numbers into the three fields, without knowing other requirements.
You are doing the annual simulation without the proper sizing (I am not saying DesignDay sizing because there are other option mentioned by Linda.) and experienced your fatal crash.
out of physical reality. Otherwise, i.e., if the climate conditions are realistic, it should just tell what is the capacity of the system under those conditions. You shouldn't be blaming the victim.
I'm talking about doing LOADS for the entire year to find out what is the peak load over the year, use that peak load to size the equipment, and then repeat the simulation with that system sizing."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."
That is why there are two simulation control in EPlus. I do the LOAD first and then do the others and not necessary HVAC. There are many other things you can do in EPlus.
Once the maximum values are entered in the IDF, the LOAD run is not needed any more. If you do not run the LOAD first, you do not know the system capacity you need.
"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. "
If you do not manually enter the maximum condition, the EPlus will find these again by doing a LOAD, and then proceed with the zone, system, and plant sizing. LOAD is not done at avery time step as you may have assumed. Autosizing is not done at every time step either.
Now I can say that you're wrong. 0.4% criteria means that the peak hourly temperature is exceeded 0.4% of the time over the time period studied. The percentage of days with
"The other way, of course, is to pre-process 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."
This is already done for you in the .stat file. DesignDay data are compiled from these data. There are so many of them, because it simplify your choice for down sizing. 0.4% means, that there are so many days that the conditions will exceed these data. But it is only a statistical calculation.
peak hourly temperatures that exceed this temperature will tend to be less, often much less, because high temperatures are often clustered, i.e., a hot day may have 4 hours exceeding the peak hourly temperature.
TMY are real data, just that the year is a composite of months from different years picked to be the most representative of the long-term weather. If you looked at a TMY file, the years are indicated for every month.
The weather man can tell you that he cannot predict more than a few days. TMY is not real and is only for those who wanted to compare the findings in the report. Your building cannot change the weather.
You keep insisting that I was responsible for the "nonsense condition", by which I guess you mean the -74 existing temperature, but that was what EnergyPlus derived,.
"Your suggestion of having the simulation program automatically choose the peak days presents some difficulties for EnergyPlus." (This is not my suggestion. In the seather file sizing mode, EPlus know how to pick the max and min for heating and cooling.))
"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.. "
Eplus can do this, if you use the correct object. (See the manual or Linda's reply on the similar topic.) No need to have more format as yours
"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."
This is not true. If you are in California simulating buildings in California, you only need to compile the DesignDan object once for your lifetime (may be, if that is you do not relocate.)
If you know the location, you can run a DesignDay sizing without the weather file. That was what I did. How do I come up with the LA International DesignDay? I look for a location on the same Latitude. It is the earth tilt angle with the sun that change the OD temperature in the annual cycle.
As I said in my previous mail, that the dry bult temperature is at 2 pm, range is the temperature between 2 pm and 5 am. The wetbulb is the RH at the MDB.(Max. dry buld)
This is for Summer, and the sky clearance is 1.
For Winter, the DryBulb and the Wetbulb should be the same, and the range is zero, because the skyclearance is 0. (Cloudy the whole day) You did not know and did not follow this rule for the DesignDay data construction.
Where or how do you choose the data by the software? .epw annual TMY data? I already said this data is not local and current.
I use the everage for the previous 24 hour as the day everagy, then customize the DesignDay data. You can then verify your building material entries, etc.
"That design day was never intended for sizing cooling equipment, but it seems that EnergyPlus merrily goes through all the design days specified, and perhaps picks the result with the largest capacity ? There's nothing wrong with that in principle, but in application if the design algorithm returns a nonsense value and then quits, then it does become a problem for the user."
This statement is false. SummerDesignDay object or cooling schedule is for Summer cooling, and Winter cooling, if you have too much internal load. The nonsense condition was entered by you, and got a warning.
I entered a design day condition that's physical meaningful: 17.8C max, 17.8C diurnal swing, 6.7% RH, etc. It's the program that's giving me back a
exiting air temperature of -74 C. I would be at fault only if I had entered something that's faulty, like a dew point higher than the dry bulb, RH over 100%.
It also amuses me that you insist my design day criteria extracted from the actual weather file must be faulty and causing EnergyPlus to fail, and then say
that you don't even need to know the weather to do design day calculations! So what is it? Is the design day criteria supercritical or just a number you
can pull out of the air ?
I guess I missed that explanation.
"As the contractor who developed the new standard weather files for California (as well as ASHRAE's new IWEC2 weather files), I believe I'm fairly familiar
with climate conditions and design day criteria, especially in California, and having lived here for 40 years, I am aware that California is a long state.
The problem is not the design day data I entered was faulty, but that the EnergyPlus sizing routines are failing under certain climate conditions. This should not happen."
This means that you are over confident. I have already explained why your Winter designDay object data was not correct, and it triggered the extreme conditions.
Well, I don't know if we got anywhere in this longer than anticipated e-mail stream. In case there's anyone with the patience to read till here, I'll just conclude that
I mentioned that California is a long state, because that make the choice of weather station easier. At that latitude there were only one weather station. You preferr the zone weather file. I would never have the need to use it.
"It's not unusual, definitely not impossible, that on the coldest days there is no variation in air temperature, or that the wetbulb equals the drybulb."
If you developed the weather file, you should know why you or your staff has done that in the .ddy or .stat.
On the other hand, if one forced the cloud to be opaque, why should the ODT change. When the ground is covered with snow, it is always 0°C, why does not it flow the wind chill.
Wetbulb equals the drybulb simply means thet the RH is 100% at MDB. Nothing special.
"If EnergyPlus persists on doing sizing calculations for cooling with design days that are specified for heating, then its sizing algorithm should take into account these psychrometric possibilities rather than to blame the user for having inappropriate design day definitions. (This is your assumption. Zsz looks for the heating and cooling loads and not the DesignDay time or object data.)
Alternatively, if the combination of the algorithm and input data returns something that's outside of reality, i.e., RH > 100, as happened to me once in testing an evaporative cooler model, the algorithm should guard against it and return something that is physically possible."
200°C was by the RH out of range. The EPlus continued and gave you a warning. The fatal crash is from another number you have entered or changed. It has gone.
I think it is time for me to leave too. Bye.
I don't think an autosizing routine should fail when the input design day criteria are within physical reality. I still don't understand the logic for doing cooling sizing
calculations with the winter design day, but if you are to do it, you should make sure that the equations and performance curves are up to the task, or constrained
enough to produce reasonable results.
Dr. Li
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
CC: jeremiah@xxxxxxxxxxxxxxxxxxxxxx
From: YJHuang@xxxxxxxxxxxxxxxxxxxxxxxx
Date: Sat, 17 Mar 2012 13:57:37 -0700
Subject: Re: [EnergyPlus_Support] Fatal error with sizing of AC coil, what could be the problem?
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"
>
>
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