Question-and-Answer Resource for the Building Energy Modeling Community
Get started with the Help page
Ask Your Question

Julien Marrec's profile - activity

2019-07-17 00:58:43 -0500 answered a question OpenStudio Optional Objects

If you really are interested in the reason behind this implementation, I'll try to explain exactly why. After all, the u

2019-07-17 00:18:29 -0500 commented answer OpenStudio SDK file

https://rubygems.org/gems/openstudio-api-stubs/versions/0.1.0

2019-07-16 07:08:46 -0500 received badge  Popular Question (source)
2019-07-02 12:34:35 -0500 received badge  Popular Question (source)
2019-06-24 06:55:18 -0500 received badge  Nice Answer (source)
2019-06-10 09:30:31 -0500 marked best answer Appendix G condenser water temperature reset in EnergyPlus

This question is following a thread on the EnergyPlus Support group.

Quoting Appendix G:

G3.1.3.11 Heat Rejection (Systems 7 and 8). The heat rejection device shall be an axial fan cooling tower with two-speed fans. Condenser water design supply temperature shall be 85°F or 10°F approaching design wet-bulb temperature, whichever is lower, with a design temperature rise of 10°F.

The tower shall be controlled to maintain a 70°F leaving water temperature where weather permits, floating up to leaving water temperature at design conditions.

For reference CTI rates cooling towers at 95°F DB/78°F WB with 95°/85°F condenser water temperature. That's what's used for the performance of the cooling tower in E+ too.

First question, is my design wetbulb temperature 78°F - meaning the design approach is 7°F - or is it my design day wetbulb temperature (eg: Ann Clg 1% Condns WB=>MDB) for my specific location, in my case 75.8°F meaning an approach of 9.2°F?


Second, as far as the reset strategy, I think SetpointManager:FollowOutdoorAirTemperature placed on the supply outlet of the condenser loop is appropriate.

Knowing that:

  • 85°F = 29.44°C
  • 70°F = 21.11°C

I would do something like this:

SetpointManager:FollowOutdoorAirTemperature,
    MyCondenserControl,      !- Name
    Temperature,             !- Control Variable
    OutdoorAirWetBulb,       !- Reference Temperature Type
    X,                       !- Offset Temperature Difference {deltaC}
    29.44,                      !- Maximum Setpoint Temperature {C}
    21.11,                      !- Minimum Setpoint Temperature {C}
    Condenser Supply Outlet Node;  !- Setpoint Node or NodeList Name

I'm wondering if this is the right approach and what value of Offset Temperature Difference I should use.

Should I use the calculated approach (7°F or 9.2°F) to keep a constant approach? Should I keep it at 0 and leave E+ to try and do as best as possible?

2019-06-09 17:52:24 -0500 commented question I'm using GenOpt coupling with EnergyPlus to minimize the LCC but this variable that I need to minimize doesn't appear in the .eso file of E+

Get it from the Output:Table:SummaryReports in the HTML or the SQL file (if requested). You'll have to write for eg a py

2019-05-28 01:23:25 -0500 received badge  Notable Question (source)
2019-05-21 12:30:44 -0500 marked best answer Turn off outside air for air loop during unoccupied period

In case of an office building, my system should be running 6am to 10pm, and should cycle with the load at night, except I want to make sure I don't have any outside air during the night cycle (unless economizer is activated for cooling).

Let's call my schedule HVAC Operation Schedule, and it has a value of 1 between 6 am and 10pm, and 0 otherwise

I've set an AvailabilityManager:NightCycle for the airloop an assigned HVAC Operation Schedule as fan schedule.

I figured that to turn off the outside air I should assign the HVAC Operation Schedule to the Controller:OutdoorAir.

Instinctively, I have set this schedule to the Maximum Fraction of Outdoor Air Schedule Name field. This made sense to me: if I say the maximum is zero, it should be turned off!

This doesn't seem to be doing what I want, since when cycling at nighttime, it's apparently still pulling Outside Air.

After investigation in the documentation and confirming it by looking at the DOE Commercial reference buildings, it seems that the field I should use is Minimum Outdoor Air Schedule Name. From the docs:

Minimum Outdoor Air Schedule Name

The name of a schedule which uses decimal values (0.0 1.0). These values are multiplied by the minimum outdoor air flow rate. This schedule is useful for reducing the outdoor air flow rate to zero during unoccupied or start up hours. If this field is not entered, the minimum outdoor air flow rate either remains constant during the simulation period (Minimum Outdoor Air Control Type = FixedMinimum) or varies in proportion to the supply air flow rate (Minimum Outdoor Air Control Type = ProportionalMinimum).

I'm having trouble following the logic here... Can someone enlighten me?

2019-05-20 10:10:18 -0500 commented question Cosimulation Energyplus/Openstudio-FMU

Files are missing: to attach the files, please host them somewhere and include the links here. Thanks!

2019-05-20 03:56:41 -0500 edited question EnergyPlus EMS program line error

EnergyPlus EMS program line error Hi everyone, could someone help me with this error I`ve got in EMS in EnergyPlus? **

2019-05-13 06:04:20 -0500 commented answer Transmittance schedule for trees

Eg: here. Seems that pretty much everything comes from the "Shadow Pattern Simulator" (Robert A. Brown, 1988, see here)

2019-05-13 06:02:38 -0500 commented answer Transmittance schedule for trees

The study talks about a tree shading factor, which would be the opposite of the transmittance. The study I linked to has

2019-04-28 00:52:41 -0500 marked best answer Modeling plenum and handling floor thickness

This isn't the first thread on plenums, but I haven't found a straight answer on this particular point.

Let's say I have a floor to plenum height of 14', then some ceiling tiles (about an inch, that I'm willing to neglect), then a 3' plenum void, then a 1' concrete slab. The floor to floor height is then 18', but considering the fact that the slab is 1', I don't necessarily want to just assume the plenum void is 4' as I would overestimate the volume by a third.

How am I supposed to enter that in EnergyPlus / OpenStudio to respect both the volumes as well as the exterior wall area (and elevations)?

2019-04-23 09:38:06 -0500 marked best answer Can you load Schedule:File in OpenStudio?

Can you load a Schedule:File object in OpenStudio?

If not what's the best way to translate a csv file into an OpenStudio schedule?

In my case I've got a 8760 schedule (and some 87600 ones) that I'm not going to consider creating by hand

2019-04-23 09:38:06 -0500 edited answer Can you load Schedule:File in OpenStudio?

Update: ScheduleFile was wrapped and available to use with the API in OpenStudio 2.7.0. Here's an example on how to i

2019-04-18 10:20:46 -0500 commented question Simulation Crashes for .idf with Swimming Pool Component, no severe or fatal errors

Everything in a code block like I just did. Except our error file is too long for the post, I suggest truncating the por

2019-04-18 10:20:03 -0500 edited question Simulation Crashes for .idf with Swimming Pool Component, no severe or fatal errors

Simulation Crashes for .idf with Swimming Pool Component, no severe or fatal errors I am trying to simulate an .idf file

2019-04-18 02:17:16 -0500 commented question Simulation Crashes for .idf with Swimming Pool Component, no severe or fatal errors

@jgmodel please use a code block instead of 10 images to paste the content of the eplusout.err. A code block is somethin

2019-04-18 02:16:30 -0500 edited question Simulation Crashes for .idf with Swimming Pool Component, no severe or fatal errors

Simulation Crashes for .idf with Swimming Pool Component, no severe or fatal errors I am trying to simulate an .idf file

2019-04-15 06:55:24 -0500 asked a question EMS: Failure to read Schedule value during Warmup

EMS: Failure to read Schedule value during Warmup My end-goal is to load different Schedule values based on some conditi

2019-04-03 02:32:36 -0500 edited question Using meter:custom to aggregate output variable data

Using meter:custom to aggregate output variable data I'm having trouble getting the meter:custom object to work with som

2019-04-02 03:42:13 -0500 edited answer How to run OpenStudio in SketchUp 2017?

OpenStudio will automatically install itself to Sketchup 2017/2018 only if you install it AFTER sketchup. See the troubl

2019-04-02 03:41:48 -0500 answered a question How to run OpenStudio in SketchUp 2017?

OpenStudio will automatically install itself to Sketchup 2017/2018 only if you install it AFTER sketchup. See https://nr

2019-04-02 02:54:42 -0500 commented answer How to run OpenStudio in SketchUp 2019?

OpenStudio will automatically install itself to Sketchup 2017/2018 only if you install it AFTER sketchup. See https://nr

2019-04-01 08:29:17 -0500 edited answer Metric Reports in Open Studio

IGRETEC (@Julien THIRIFAYS) and EffiBEM (disclaimer: that's my company) have contributed the open source addition of SI

2019-04-01 08:28:59 -0500 edited answer Metric Reports in Open Studio

IGRETEC (@Julien THIRIFAYS) and EffiBEM (disclaimer: that's my company) have contributed the open source addition of SI

2019-04-01 08:28:31 -0500 edited answer Metric Reports in Open Studio

IGRETEC (@Julien THIRIFAYS) and EffiBEM (disclaimer: that's my company) have contributed the open source addition of SI

2019-04-01 08:27:53 -0500 edited answer Metric Reports in Open Studio

IGRETEC (@julien-thirifays) and EffiBEM (disclaimer: that's my company) have contributed the open source addition of SI

2019-04-01 05:58:23 -0500 answered a question Metric Reports in Open Studio

IGRETEC and EffiBEM (disclaimer: that's my company) have contributed the open source addition of SI units to the results

2019-03-21 11:57:17 -0500 edited question open studio app and Hi res Screen

open studio app and Hi res Screen Hi, I installed Open Studio but - as you can see - there is a resolution problem with

2019-03-21 11:56:14 -0500 edited question open studio app and Hi res Screen

open studio app and Hi res Screen Hi, I installed Open Studio but - as you can see - there is a resolution problem with

2019-03-21 11:54:52 -0500 commented question OS simulation failure due to energy management system

Can you share your model? You can host it somewhere and post a link to it.

2019-03-21 11:54:30 -0500 commented question OS simulation failure due to energy management system

Can you share your model?

2019-03-21 11:52:44 -0500 edited question OS simulation failure due to energy management system

OS simulation failure due to energy management system I was doing an OS simulation. It failed and this is what it showed

2019-03-21 11:52:22 -0500 edited question File does not exist after simulation call

File does not exist after simulation call Greetings everyone, I am using TRNSYS and genopt for optimizing the life cycl

2019-03-20 09:41:43 -0500 commented question Any ideas to correct this GenOpt 3.1 error?

I'm not a TRNSYS user. Given that you use TRNSYS and not E+, the resolution cannot be the same, so I suggest opening you

2019-03-08 07:00:29 -0500 commented answer Alternate ways of opening an E+ .sql file

Please do use an URI to set it to read-only instead to avoid problems when reruning simulation while sql file is open in

2019-03-08 06:59:48 -0500 answered a question Alternate ways of opening an E+ .sql file

Please do yourself a favor and never use conn = sqlite3.connect(sql_path), as if you try to rerun your simulation while

2019-03-06 06:39:52 -0500 edited question Admin: Please delete

Understanding Files ---------- Deleted Content ------------

2019-03-06 06:39:32 -0500 edited question Admin: Please delete

Understanding Files ---------- Deleted Content ------------

2019-03-05 08:52:01 -0500 edited question Swap construction set by command line interface

Swap construction set by command line interface Hello, I want to simulate several cases of external wall thickness chang

2019-03-05 02:35:42 -0500 commented question How to set the leaving and entering water temperature of water-to-water heat pump in energyplus

Could you please retag your question using existing tags and the software you're using? Also a little bit more of contex

2019-03-01 12:00:56 -0500 received badge  Nice Question (source)
2019-03-01 04:19:52 -0500 commented question Restrict tag choice to existing tags instead of adding the please-use-existing-tags tag? And what qualifies as an existing tag?

Actually better yet: go upvote the feature request on the Github askbot-devel#564

2019-03-01 04:18:12 -0500 commented question Restrict tag choice to existing tags instead of adding the please-use-existing-tags tag? And what qualifies as an existing tag?

Cf askbot feature request here, which didn't get any traction since 2015. If you happen to have an Askbot account with s