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NC-v4 EAp2:Minimum energy performance

Water Coil Sizing, heating and cooling

Hi all! I have a problem with water coil sizing. I set the following parameters for cooling and heating: 

 

Coil:Cooling:Water,

   AHU%A%01 AHU Cooling Coil,        ! - Component name

   Cooling Coil,                                ! - Availability schedule

   0.001700,                                    ! - Design Water Volume Flow Rate of Coil (m3/s)

   6.580000,                                    ! - Design Air Flow Rate of Coil (m3/s)

   18.00,                                          ! - Design Inlet Water Temperature (C)

   28.20,                                          ! - Design Inlet Air Temperature (C)

   24.00,                                          ! - Design Outlet Air Temperature (C)

   0.008,                                          ! - Design Inlet Air Humidity Ratio

   0.008,                                          ! - Design Outlet Air Humidity Ratio

 

Coil:Heating:Water,

   AHU_A_01 AHU Heating Coil 1,                                          ! - Component name

   Heating Coil,                                                                     ! - Availability schedule

   autosize,                                                                           ! - U-factor times area value of coil (W/K)

   autosize,                                                                           ! - Max water flow rate of coil (m3/s)

   AHU_A_01 AHU Heating Coil 1 Water Inlet Node,                ! - Water inlet node name

   AHU_A_01 AHU Heating Coil 1 Water Outlet Node,             ! - Water outlet node name

   AHU_A_01 AHU Steam Humidifier Air Outlet Node,             ! - Air inlet node name

   AHU_A_01 AHU Heating Coil 1 Air Outlet Node,                  ! - Air outlet node name

   NominalCapacity,                                                              ! - Coil performance input method

   59500.00,                                                                          ! - Rated capacity (W)

   45,                                                                                    ! - Rated inlet water temperature (C)

   16.8,                                                                                 ! - Rated inlet air temperature (C)

   40,                                                                                    ! - Rated outlet water temperature (C)

   24,                                                                                    ! - Rated outlet air temperature (C)

   0.50;                                                                                  ! - Rated ratio for air and water convection

 

But in the HTML I find this for Cooling:

AHU%A%01 AHU Cooling Coil: Nominal Total Capacity = 119722.30 [W]

 

And this for Heating:

AHU_A_01 AHU Heating Coil 1: Nominal Total Capacity = 138443.99 [W]

 

How is it possible? Where did I make the mistake?

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Wed, 03/07/2018 - 17:23

This question is related to the specific software.
Profile picture for user sheffer
Marcus Sheffer
LEED Fellow
7group / Energy Opportunities
LEEDuser Expert
4454 thumbs up

Wed, 03/07/2018 - 17:33

Looks like EnergyPlus? You might have better luck here - https://energyplus.net/support 

Thu, 03/08/2018 - 09:33

Thank you Marcus. The software we use is Design Builder. I put correct inputs in Design Builder: the same data reported in technical sheets for coils cooling and coils heating. After annual simulation The Nominal Capacity reported in html outputs in Design Builder is a values greater than value entered in. How it is possible? I have investigated on web, but it seems that it is a problem of software. (We have also called Software house and they told us the same). So I hope that with this explanation USGBC clarifications are ok. But if you have any suggestions please let me know. Thank you so much.
Profile picture for user sheffer
Marcus Sheffer
LEED Fellow
7group / Energy Opportunities
LEEDuser Expert
4454 thumbs up

Thu, 03/08/2018 - 14:50

Design Builder runs on the EnergyPlus engine. I have no idea how this is possible. I would recommend that you ask the Energy Plus help desk. The disparity on the heating capacity could potential be a red flag for the reviewer so I would recommend that you find out what is going on before submitting for LEED.

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