Because the diagram only showed part of the system, therefore, I can make comment only on what is on it.
As regards to the use of HE, I did mentioned that if the mixer is the OA mixer, it would not work in most cases. Otherwise, it is not really a mixer. Part of the returned air is split to feed the HE, and the flow volume is controlled by the exhaust fan.
Dehumidification of air to prevent condensation on the exposed cold surfaces in a super market, is a special requirement.
If the Mixer shown OA is not an OA mixer, the set point manager:MixedAir may not function.
Dr. Li.
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: jim@xxxxxxxxxxxxxxxxxxxxxxxxxxx
Date: Mon, 21 May 2012 18:56:35 -0400
Subject: RE: [EnergyPlus_Support] Setpoint Managers are driving me crazy!
Dear Forum,
I think I figured it out. Dehumidification is working! Edits are shown below in the original (just in case anyone cares other than I J)
I ended up not using the :OutdoorAirPretreat manager; it seemed like a good idea, but the :SingleZone:Humidity:Maximum seems do all that is needed.
Dr. Li,
Thank you for your detailed comments! Here are some responses:
1. I am modeling a system designed for a supermarket, so whether or not it is a ?good idea?, my purpose is to simulate the actual design.
a. Thus the locations for pre-cooling coil, heat exchanger
b. The heat exchanger is used for sensible energy only
2. The pre-cooling coil is intended to dehumidify the retail area so that load is removed from refrigerated casework. (principally less defrost energy)
a. I think the economizer is not used in this design because they are problematic when humidity control is important
3. SetpointManager:Warmest is used to monitor each of the zones and adjust the AHU discharge temperature to whatever is needed for the warmest zone. This minimizes reheat energy.
a. You are correct that reheating is often wasteful. In this case, all lighting energy is added to the zone because the lights are installed on pendants (no suspended ceiling or return plenum)
4. The SetpointManager:MixedAir is only used for adjusting control nodes to account for fan heat; it does not actually control anything.
The Building Performance Team
James V. Dirkes II, P.E., BEMP , LEED AP
1631 Acacia Drive NW
Grand Rapids, MI 49504
616 450 8653
On 5/21/2012 11:55 AM, Jim Dirkes wrote:
Dear forum,
Apologies in advance for a messy question?..
Below is a schematic of an air loop.
· Note that there is a pre-cooling coil upstream of the Mixing Box.
· Also note that all of the numbers (e.g., 1200, 1204, etc.) are ?shorthand? for a node name.
I want the pre-cooling coil to operate solely as a dehumidification device to maintain a specific humidity ratio. Everything else should operate in a fairly typical fashion for heating and cooling control, except that there is no economizer.
I show below the SetPointManagers and related mixed air NodeList that I am using with no success for dehumidification. Can you offer a suggestions to make this work?
Thanks!
SetpointManager:MixedAir
Name
SPMgr_MixAir_AHU-1
Control variable:
Temperature
reference set point node name
1210 (Node name equivalent)
fan inlet node name
1208
fan outlet node name
1210
Name of the set point Node or Node List
MANodeLIST_AHU-1
SetPointManager:Warmest
Name
SPMgr_DischAir_AHU-1-warmest
Control Variable
Temperature
HVAC Air Loop Name
AirLoop_AHU-1
Minimum Setpoint Temperature
12.8
Maximum Setpoint Temperature
26.7
Strategy
MaximumTemperature
Setpoint Node or NodeList Name
1210
SetpointManager:SingleZone:Humidity:Maximum
Name
SPMgr_ZoneRH_AHU-1
Control Variable
MT
Schedule Name
MT
Setpoint Node or NodeList Name
1204.5
Control Zone Air Node Name
Node_MainStore
SetPointManager:Scheduled
Name
SPMgr_Sched_AHU-1
Control Variable
Temperature
Schedule Name
SchCpct_Always70F
Setpoint Node or NodeList Name
1204.5
SetPointManager:OutdoorAirPretreatName
SPMgr_OAdehum_AHU-1Control Variable
MaximumHumidityRatioMinimum Setpoint Temperature
10Maximum Setpoint Temperature
30Minimum Setpoint Humidity Ratio
0.0008Maximum Setpoint Humidity Ratio
0.0091Reference Setpoint Node Name
1205Mixed Air Stream Node Name
1205Outdoor Air Stream Node Name
1204.5Return Air Stream Node Name
1200Setpoint Node or NodeList Name
1204.5
NodeList
Name
MANodeLIST_AHU-1
Node Name1
1205
1207
1208
1204.5
Making me think?.
"He who is kind is free, even if he is a slave. He who is evil is a slave, even if he is king."
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