Annie Marston's profile - activity

My simulation won't run because I have 11 degenerate surfaces. We have tried to cut up all our large misshapen surfaces but that didn't help. I intersected and matched for the most part using the OpenStudio tool and hand matched and intersected those areas it didn't pick up. Ideally I would like to search for these surfaces and delete them but they don't seem to appear in the idf file. Does anyone know how I can search for degenerate surfaces?

To set temperatures and humidity ratios on coils you need to use setpoints. I know how to find these in EnergyPlus but n

I'll put this in the answer as i think it is an answer rather than a comment

I think you can do this by putting it as a request variable in the meters output (I know meters has building total elect

The work around I can think of is modelling the DOAS with a variable volume fan and putting a schedule into the fan obje

what software are you using? Also a DOAS doesn't need to have an energy recovery wheel. Putting setpoints on the cooling

You could calculate the RH for the absolute worst condition, highest temperature at 12g/kg, then at lower temperatures t

Are you saving a sketchup version of your model as well as an openstudio version? This can often cause all sorts of issu

Have you autosized anything in the component such as capacity, flow rate etc... it might be that the autosized fields ar

I was wondering what people use as their tolerance for unmet load hours for LEED, this has been touched on before in some of the previous questions but I think it is a really interesting subject as you can't submit LEED EAp2 credit without getting your unmet hours down below 300 and with only 50 hours difference between the baseline and design case, the rules are very strict.

In EnergyPlus we can specify our tolerances and the default is a delta T of 0.2°C which is a very tight tolerance for unmet load hours. I have spoken with others and some software packages set their unmet load hours tolerance to around 1.8°F (1°C). The difference between these two values is enormous when it comes to deciding whether a zone has its tolerance met. Specifically, does anyone have any guidance from LEED as to what value to use. Clearly we could all use a delta T of 10°C and have no unmet hours but the systems are likely not doing what they are supposed to and the points would vary wildly.

If you know your upper air temperature in the space and your humidity ratio you can calculate the maximum relative humid

Have you checked the controls in your Controller:OutdoorAir, often this can be set incorrectly causing issues with your

I ran my model in EnergyPlus and I am getting this error on one of my files, it uses a single speed DX cooling coil and a single speed DX heating coil. I have used both these objects and the curves that go with them before but not got this error. Does anyone know where I should be looking or what this really means. I have copied the curves from the examples files and pasted them in.

I appeciate anyone who can help me solve this mystery

I have been using the "heatExchanger:AirToAir:SensibleAndLatent" object and the "OutdoorAir:Mixer" object in EnergyPlus and I have started to realised things have been going a little bit strange with this combination. When I look at the temperatures flowing through these two objects I get some odd results. I have a DOAS system and so the return air from the zones should not mix or come into contact with the supply air, other than through the heat exchanger. In EnergyPlus however if you have a heat exchanger then you must have an outdoor air mixer (I believe and am happy to be corrected on this). The temperature of the supply air coming into the heat exchanger and the air leaving the heat exchanger are as I would expect. However, when the air enters the outdoor air mixer from the heat exchanger it mixes with the return air from the zones and the temperatures leaving the OAM and into the AHU change, they go up in the winter and down in the summer, over stating how effective the heat exchanger actually is.

My question is: How can I stop this from happening? Is there something in the controller than can stop the air mixing in the outdoor air mixer, is there something in the "heatExchanger:AirToAir:SensibleAndLatent" object to stop this from happening?

All and any help as always greatly appreciated.

I am fairly new to Open Studio but know EnergyPlus pretty well. I have built a basic PTAC (system 1 LEED) in Open studio with hot water coils. What I don't understand is that when I run the simulation in Open Studio, my boiler plant loop won't turn on. When I export it to EnergyPlus I noticed that the operation scheme was set to PlantEquipmentOperation:ComponentSetpoint. I ran this and the plant loop wouldn't turn on, there was no flow through the boiler and consequently no heating in the entire model. I changed the operation scheme to PlantEquipmentOperation:HeatingLoad and the boiler and plant loop turned on and worked perfectly. My questions are a) is there a way to change the plant equipment operation in Open Studio? b) Is there a way I can make PlantEquipmentOperation:ComponentSetpoint work so that flow goes through the boiler?

Have you tried going down the passive route...

Lots of exterior insulation around the building, triple glazing (this should reduce heating to near zero), natural ventilation during swing seasons and rather than VRF a radiant system. I understand that humidity might be an issue, less so for residential so perhaps a mechanical ventilation system in the summer with heat exchanger (more important really for the winter) and some dehumidification. This is what I see for extremely well performing buildings in Germany (building built today climate zone 5a). They tend to hook up to the district heating system so have the advantage of thermal hot water delivered to the building but maybe a really good heat pump will do the job instead if you have to all electric. Also have you tried solar thermal?

Those would be my first thoughts, something to ponder if you haven't already.

Annie

@dradair our next task here is to work out how to automatically get all these inputs into the idf file without copy paste. I am looking forward to looking at @Julien Marrec answer on this.

@dradair ok...

1) this is just excel and is separate from the idf file (i like the link to Julien marrec info on this) 2) I have 4 excel sheets to write the whole file + one input summary excel sheet so yes it only writes part of the file at a time 3) When making changes the bits that are changed are deleted from the original file and the new pieces pasted in 4) Yes there is sometimes some swearing when new versions are released. overall however the objects don't tend to change, when they do we update the excel files sometimes we skip a version release though if the changes are very dramatic

Excel has great functionality and most engineers already know how to use it. That is why we have stuck with it. Also I agree with you @mdahlhausen if we can write it in excel we aren't going to learn programming because we have already solved the problem sufficient to our needs. Not great I grant you, but unfortunately how we are right now.