Air loop cooling energy is much bigger than plant loop cooling energy

asked 2017-10-23 20:06:26 -0500

katsuya.obara gravatar image

I am studying several energy conservation measures to the model PAU+FCU with chilled water loop.
When I change the plant loop configuration from PrimaryConstantSecondaryVariable to PrimaryVariableNoSecondary, I found that there are big difference between plant loop cooling energy and air loop cooling energy as shown below.
plant loop cooling energy:14999.5MWh
Air loop cooling energy:18102.3MWh
Can anyone tell me what could cause this situation?

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Comments

Do your zone terminals have reheat?

ljbrackney gravatar image ljbrackney  ( 2017-10-23 22:13:53 -0500 )edit

Please be more specific about the exact output variables or table values you mean by "plant loop cooling energy" and "air loop cooling energy".

MJWitte gravatar image MJWitte  ( 2017-10-26 10:27:27 -0500 )edit

Terminal Unit doesn't have. Just PAU unit has reheat to treat OA humidity

katsuya.obara gravatar image katsuya.obara  ( 2017-10-26 22:25:03 -0500 )edit

Plant loop cooling energy = Chiller Evaporator Cooling Energy
Air loop cooling energy = Fan Coil Total Cooling Energy + Air System Total Cooling Energy

katsuya.obara gravatar image katsuya.obara  ( 2017-10-26 22:27:23 -0500 )edit

Fan Coil total Cooling Energy is cooling delivered to the zone. If the fan coil has outdoor air, then this will be quite different from the coil load on the plant loop. Air System Total Cooling Energy is the total heat removal from the air loop so this will be the same as the coil load on the plant loop. Chiller Evaporator Cooling Energy will equal the total coil load plus the chilled water loop pump heat. If you want to compare air side and water side, then start with the chilled water coil outputs plus the pump heat.

MJWitte gravatar image MJWitte  ( 2017-11-30 23:37:03 -0500 )edit