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RE: [EnergyPlus_Support] Setpoint Managers are driving me crazy!





Thank you, Jim, for the detailed explanation of your design requirement.
 
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:OutdoorAirPretreat

Name

SPMgr_OAdehum_AHU-1

Control Variable

MaximumHumidityRatio

Minimum Setpoint Temperature

10

Maximum Setpoint Temperature

30

Minimum Setpoint Humidity Ratio

0.0008

Maximum Setpoint Humidity Ratio

0.0091

Reference Setpoint Node Name

1205

Mixed Air Stream Node Name

1205

Outdoor Air Stream Node Name

1204.5

Return Air Stream Node Name

1200

Setpoint Node or NodeList Name

1204.5

 

 

NodeList

Name

MANodeLIST_AHU-1

Node Name1

1205

 

1207

 

1208

 

1204.5

 

 

 

 

 

 

Description: BPT BizCard JVDII Updated

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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