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EnergyPlus DOAS Water Cooling Coil Sizing Error

asked 2022-03-15 00:45:15 -0600

Murcielago's avatar

updated 2022-03-15 11:55:06 -0600

I'm having an issue with EnergyPlus 9.6. I added 2 DOAS units to my model, but my model fails to complete the sizing of the cooling coil of the second DOAS unit. The sequence of my setup for the DOAS is (OA - heating coil - cooling coil - fan).

For some reason the [Coil inlet air temperature used for sizing = -997.59 [C]], and I tried everything I can to fix it.

I tried to change (Design Inlet/Outlet Air Temperature) from (autosize) to fixed temperatures, but for some reason I still see the same error.

Here is the full list of errors I'm seeing:


   ** Warning ** SizeWaterCoil: Potential issue with equipment sizing for Coil:Cooling:Water B1 DOAS CC
   **   ~~~   ** ...Rated Total Cooling Capacity = -112120230.17 [W]
   **   ~~~   ** ...Air flow rate used for sizing = 90.45075 [m3/s]
   **   ~~~   ** ...Outdoor air fraction used for sizing = 0.00
   **   ~~~   ** ...Coil inlet air temperature used for sizing = -997.59 [C]
   **   ~~~   ** ...Coil outlet air temperature used for sizing = 17.50 [C]
   ** Severe  ** SizeWaterCoil Coil:Cooling:Water B1 DOAS CC, Developer Error: Component sizing incomplete.
   **   ~~~   ** SizingString = Design Inlet Air Humidity Ratio [kgWater/kgDryAir], SizingResult = -99998.9
   ** Severe  ** Developer Error: sizing of Design Inlet Air Humidity Ratio [kgWater/kgDryAir] failed.
   **   ~~~   ** Occurs in Coil:Cooling:Water B1 DOAS CC
   ** Warning ** SizeWaterCoil: Coil="B1 DOAS CC", Cooling Coil has leaving humidity ratio > entering humidity ratio.
   **   ~~~   **     Wair,in =  -999.000000 [kgWater/kgDryAir]
   **   ~~~   **     Wair,out = 1.200000E-002 [kgWater/kgDryAir]
   **   ~~~   ** ....coil leaving humidity ratio will be reset to:
   **   ~~~   **     Wair,out = -999.000000 [kgWater/kgDryAir]
   ** Severe  ** SizeWaterCoil Coil:Cooling:Water B1 DOAS CC, Developer Error: Component sizing incomplete.
   **   ~~~   ** SizingString = Design Outlet Air Humidity Ratio [kgWater/kgDryAir], SizingResult = -99998.9
   ** Severe  ** Developer Error: sizing of Design Outlet Air Humidity Ratio [kgWater/kgDryAir] failed.
   **   ~~~   ** Occurs in Coil:Cooling:Water B1 DOAS CC
   ** Warning ** SizeWaterCoil: Potential issue with equipment sizing for Coil:Cooling:Water B1 DOAS CC
   **   ~~~   ** ...Rated Total Cooling Capacity = -112120230.17 [W]
   **   ~~~   ** ...Air flow rate used for sizing = 90.45075 [m3/s]
   **   ~~~   ** ...Outdoor air fraction used for sizing = 0.00
   **   ~~~   ** ...Coil inlet air temperature used for sizing = -997.59 [C]
   **   ~~~   ** ...Coil outlet air temperature used for sizing = 17.50 [C]
   ** Severe  ** SizeWaterCoil Coil:Cooling:Water B1 DOAS CC, Developer Error: Component sizing incomplete.
   **   ~~~   ** SizingString = Design Coil Load [W], SizingResult = -99998.9
   ** Severe  ** Developer Error: sizing of Design Coil Load [W] failed.
   **   ~~~   ** Occurs in Coil:Cooling:Water B1 DOAS CC
   **  Fatal  ** Preceding water coil sizing errors cause program termination

Update: To clarify, this is my second DOAS unit in this model, which is identical to my first DOAS unit, but I'm only getting this error after adding the second one.

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answered 2022-03-15 11:11:33 -0600

updated 2022-03-15 11:31:39 -0600

I just fixed this problem from another user post where there was more than 1 AirloopHVAC:DedicatedOutdoorAir object in the simulation. Only the first sized correctly. See GitHub issue. The only thing I can think of to get you running again is to hard size the coils for the first DOAS and then run again. Then hard size the next DOAS coils and run again, etc. Sorry for the head ache.

Update: you said you added a DOAS so there is only 1 DOAS. To size properly the simulation also needs SizingPeriod:DesignDay to find the outdoor conditions used for DOAS sizing. Maybe all you need to do is add summer and winter SizingPeriod:DesignDay objects.

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@Murcielago can you tell me what sizing objects you are using? SizingPeriod:DesignDay, SizingPeriod:WeatherFileDays or SizingPeriod:WeatherFileConditionType?

rraustad's avatar rraustad  ( 2022-03-15 11:36:43 -0600 )edit

@rraustad Thank you so much! Your initial answer is spot on, as this is the exact case of my model; I have 2 identical DOAS units, but I'm only having this issue after adding the second one. I spent the past week double- and triple-checking my model because of this issue. I even suspected an issue with 9.6, and added both DOAS units to an older version of my model to test it in 9.5, but got the same error. Hence I ended up posting this post.

I'm using (SizingPeriod:DesignDay), and it works perfectly when I only have one DOAS.

I'll follow your suggestion to hard size each DOAS. Thanks again

Murcielago's avatar Murcielago  ( 2022-03-15 11:43:26 -0600 )edit

I was thinking about this again. If you hard size the first DOAS and still cannot size the 2nd, then move the 2nd DOAS object in the idf to be the first, and then run again so that the 1st DOAS object in the idf file is the one that is autosized.

rraustad's avatar rraustad  ( 2022-03-15 12:03:46 -0600 )edit

Thanks for the proactive thought, I did actually go through this issue, it wouldn't let me auto-size the 2nd DOAS no matter what I did, I tried moving every object related to the first DOAS to be listed in the idf as the second one (after hard sizing it), but for some reason it was still not going through and not auto-sizing the other DOAS. I ended up creating separate models for each DOAS, and using the auto-sizing values to hard-size them in a combined model. And finally my model is working properly now. Thanks again @rraustad

Murcielago's avatar Murcielago  ( 2022-03-16 00:29:01 -0600 )edit

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Asked: 2022-03-15 00:37:58 -0600

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Last updated: Mar 15 '22