kiva autocalculated deep ground depth (-0.919 m)???

asked 2019-03-05 10:09:11 -0600

mldichter
2575 ●2 ●11

updated 2019-03-05 10:12:55 -0600

I took the example files for the kiva objects, ZoneCoupledKivaSlab.idf and ZoneCoupledKivaBasement.idf, and changed the Site:Location, SizingPeriod:DesignDay objects, and weather file for each of the CA climate zones. There are some strange errors for the "autocalculated deep ground depth" in some of the simulations. Obviously, something is wrong. Here is a google drive link to the files.

I'll report this as a bug on github, but my question right now is: Is there a field in Energyplus I can use to override the faulty behavior?

ZoneCoupledKivaSlab.idf

Foundation:Kiva="SLAB FOUNDATION", the autocalculated deep ground depth (1.328 m) is shallower than foundation construction elements (1.500 m)

Foundation:Kiva="SLAB FOUNDATION", the autocalculated deep ground depth (-0.919 m) is shallower than foundation construction elements (1.500 m)

ZoneCoupledKivaBasement.idf

Foundation:Kiva="BASEMENT FOUNDATION", the autocalculated deep ground depth (1.328 m) is shallower than foundation construction elements (3.425 m)

Foundation:Kiva="BASEMENT FOUNDATION", the autocalculated deep ground depth (3.883 m) is shallower than foundation construction elements (3.425 m)

Foundation:Kiva="BASEMENT FOUNDATION", the autocalculated deep ground depth (-0.919 m) is shallower than foundation construction elements (3.425 m)

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answered 2019-03-05 10:19:29 -0600

Neal Kruis

4745 ●10 ●17 http://bigladdersoftware.com/

updated 2019-03-05 10:24:33 -0600

This is not a bug. It is intended behavior. The autocalculate option attempts to calculate the depth of the water table based on the elevation of your location to determine the depth of the deep ground boundary condition. If the predicted water table is higher than the deepest element of your foundation, EnergyPlus will modify the depth to be one meter below your foundation. You will see this warning (it isn't an error) just to let you know that the water table is really close to your building and EnergyPlus is making an exception to allow Kiva to work properly.

Some of your locations are below sea level resulting in an initial estimate of the water table being above grade (e.g., -0.919 m).

Here is the full warning:

** Warning ** Foundation:Kiva="SLAB FOUNDATION", the autocalculated deep ground depth (-0.919 m) is shallower than foundation construction elements (1.500 m)

**   ~~~   ** The deep ground depth will be set one meter below the lowest element (2.500 m)

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@Neal Kruis Okay. That handles the negative values. What about the second warning in the basement simulation about 3.883 < 3.425? At the very least, the warnings are poorly worded.

mldichter ( 2019-03-05 10:25:25 -0600 )edit

That's a fair point. The actual calculation is making sure that the water table isn't within one meter of the lowest point of the foundation. How about this:

"Foundation:Kiva="SLAB FOUNDATION", the autocalculated water table depth (-0.919 m) is higher than one meter below the deepest foundation construction elements (1.500 m). The water table depth will be set to one meter below the deepest foundation elements (2.500 m)."

Neal Kruis ( 2019-03-05 10:44:30 -0600 )edit

@Neal Kruis Okay. That handles that. I was poking around a bit to see if I could get rid of the warning though, found the Deep-Ground Depth field of the Foundation:Kiva:Settings object, and reran with 2.5 instead of its former empty field. Changing the field didn't seem to override the autocalculate as the warning still appeared in the very first file. Does the Deep-Ground Depth field specify what the warnings are referring to, or is this field referring to something else?

mldichter ( 2019-03-05 10:58:10 -0600 )edit

You need to change the Deep-Ground Boundary Condition to something other than autocalculate. We should also add a warning if you specify both autocalculate a deep ground depth to notify the user that the deep ground depth will be overwritten.

Neal Kruis ( 2019-03-05 11:08:22 -0600 )edit

@Neal Kruis Thanks! That worked.

One more thing, it's autoselect not autocalculate in the idf editor.

mldichter ( 2019-03-05 11:15:13 -0600 )edit

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