Question-and-Answer Resource for the Building Energy Modeling Community
Get started with the Help page
Ask Your Question
0

Autosized FCU not Cooling the Space

asked 2025-05-29 16:13:39 -0500

updated 2025-05-30 08:12:42 -0500

I'm running simulation in EnergyPlus (Design Builder) The cooling coil & fan are operating during designated hours, and the coil is set to autosize so theoretically it should be sized however big it needs to be to cool the space to setpoint? However the result shows ridiculously high operative temperature, as shown in the attached graph.

  • Cooling setpoint: 22 Degrees
  • Cooling setback: 23 Degrees
  • Coil & Chiller are autosizing
  • Fan is operating normally
  • Temperature control is set to Operative Temperature
  • The output shows an operative temperature at 30 Degrees and mean air temperature at 25 Degrees
  • Radiant Load 2.6kW
  • Cooling rate 2.3kW (This is why it's not cooling, but why doesn't the system autosize the cooling rate higher?)

Any ideas how I can troubleshoot this?

edit retag flag offensive close merge delete

Comments

@y.li@22degrees.co.nz what simulation tool are you using? Please mention it in the title or body of your post, as well as add a tag so that others can provide better help.

Aaron Boranian's avatar Aaron Boranian  ( 2025-05-29 16:43:16 -0500 )edit

1 Answer

Sort by ยป oldest newest most voted
2

answered 2025-05-30 08:27:52 -0500

updated 2025-05-30 08:28:58 -0500

EnergyPlus sizes coils to meet zone sensible loads. You might try increasing the Sizing:Zone Zone Cooling Design Supply Air Temperature (e.g., from 12.7 C to 14 C). This will increase the zone design cooling air flow rate and potentially provide more cooling capacity.

Sizing:Zone,
  Offices,                   !- Zone or ZoneList Name
  SupplyAirTemperature,      !- Zone Cooling Design Supply Air Temperature Input Method
  12.7777777777778,          !- Zone Cooling Design Supply Air Temperature {C}

Look in the eio file after the simulation to see the impact of design changes. Specifically, look at these results:

! <Zone Sizing Information>, Zone Name, Load Type, Calc Des Load {W}, User Des Load {W}, Calc Des Air Flow Rate {m3/s}, User Des Air Flow Rate {m3/s}
 Zone Sizing Information, ZONE_22, Cooling, 8246.43576, 8246.43576, 0.72219, 0.72219
 Zone Sizing Information, ZONE_22, Heating, 2446.81161, 2446.81161, 0.14788, 0.14788

! <Water Cooling Coil Capacity Information>,Component Type,Name,Nominal Total Capacity {W},Nominal Sensible Capacity {W},Nominal Latent Capacity {W},Nominal Sensible Heat Ratio, Nominal Coil UA Value {W/C}, Nominal Coil Surface Area {m2}
Water Cooling Coil Capacity Information,Coil:Cooling:Water,ZONE_22_ZFPFC-22_COOLING COIL,15200.58,11056.89,4143.69,0.73,1565.52,15.88
edit flag offensive delete link more

Your Answer

Please start posting anonymously - your entry will be published after you log in or create a new account.

Add Answer

Training Workshops

Question Tools

1 follower

Stats

Asked: 2025-05-29 16:13:39 -0500

Seen: 189 times

Last updated: May 30