apetersen's profile - activity

Thank you everyone for your help. I determined the issue with my model. The walk-in cooler and freezers had incorrect inputs for the U value of the walls and doors of the walk-in. I believe this incorrect U value carried through from my OpenStudio model. Essentially the U value was very high (~400) instead of 0.04 like it should have been, so it was causing an almost infinite cooling load. This was tricky to see because the input comes in as 4+02, but should have been 4+-02 which is difficult to realize right away. I do think there is an error in how OpenStudio translates this input, so I will be aware of this in the future. Thanks again for everyone's feedback!

Thank you. I submitted the input file and will let Unmet Hours know if the answer is helpful to the community

I do have a lot of refrigerated cases in my model, but a lot of the rooftop units that have 0 cooling load do not have any refrigerated case loads, so I don't think that is the issue. Do the SummerDesignDay and WinterDesignDay key words somehow get recognized by EnergyPlus? The lighting for sure has a summer design day schedule of 1 at all time and winter design day has a design day schedule of 0 at all times, which I think makes sense.

Hello,

I am working on a model that has a fatal error that I am having trouble getting rid of. The error looks like this: PsyRhoAirFnPbTdbW: RhoAir (Density of Air) is calculated <= 0 [-2.17716]

Essentially I think the program is doing a psychometric analysis and calculating a negative air density, which is obviously wrong. Someone using designbuilder had this error and the suggested solution was that the air temperature distribution needed to be changed from "Dynamic Gradient" to "Mixed". Since I searched my IDF for "dynamic" and it was not in my project, I don't believe this is my issue. To give a little more background this error occurs after the model has completed zone sizing, but before the model completes system sizing. This error occurred after I added a unit heater into the model.

Any help would be appreciated!

Alisa

Hello,

I saw someone else asked this question, but they didn't have a thermostat in their zones and that isn't my issue. I have a supermarket with 13 RTUs. One has a design heating load of 0 and 8 have a design cooling load of 0. This surprises me because there is lighting, people, and equipment load in all 9 RTUs that are specifying no load. EnergyPlus still allows me to run the model, so I am able to see that there actually is no heating or cooling energy showing up annually for any of those systems. I tried manually inputting the supply CFM and cooling capacity, but the warning still shows up that there is no cooling load for those rooftop units. Has anyone run into this before?

Thank You, Alisa