I assume that the IDF you used was HVACTemplate-5ZonePackagedVAV.idf
The following was extract from the expIDF without your editing.
ã??
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ã?? SetpointManager:Scheduled, Because this is low compared with the zone thermostat setting, the reheat coil is uded to heat the zone to the required temperature. Find this compact schedule in your expIDF and change it to 22 or 23°C. and rename it to IDF with a diffeent name. The reheat coil should stop working. You can also change the reheat coil avilability schedule to always OFF. Then the zone will be cold, unless you turn on more lights. This is another way to test the program, with your own added heating. If the reheat power is 1000 watt, add 1100 watt to your lighting would turn off the reheat of that zone. SetpointManager:MixedAir, This manager defines the fan locatin and the mixed air node to be controlled to the temperature in the schedule which was set to 12.8. ================= ! NOTE: Heating supply air setpoint is placed on Supply Path Inlet node to allow separate heating and cooling setpoints. ! SetpointManager:MixedAir <system name> Heating Coil Air Temp Manager adjusts this setpoint for fan heat and places it on the Heating Coil Outlet This note explains why you have two MixedAir managers. Draw a diagram to see where these nodes are in the air loop system. SetpointManager:Scheduled, DXVAV Sys 1 Heating Supply Air Temp Manager, !- Name SetpointManager:MixedAir, Because this is set to 10°C, the reheat heater is used to heat the zone to 20°C. So change this to 19°C may stop the reheat. The temperature are normally set this way so that indivitual zones can have its own make up heating source. ======================== Controller:OutdoorAir, Hope this will help to explain how the setpoint managers work in your IDF.
DXVAV Sys 1 Cooling Supply Air Temp Manager, !- Name
Temperature, ! Control Variable
HVACTemplate-Always 12.8, ! Schedule Name
DXVAV Sys 1 Supply Fan Outlet; ! Setpoint Node or NodeList Name
DXVAV Sys 1 Cooling Coil Air Temp Manager, !- Name
Temperature, ! Control Variable
DXVAV Sys 1 Supply Fan Outlet, ! Reference Setpoint Node Name
DXVAV Sys 1 Heating Coil Outlet, ! Fan Inlet Node Name
DXVAV Sys 1 Supply Fan Outlet, ! Fan Outlet Node Name
DXVAV Sys 1 Mixed Air Nodes; ! Setpoint Node or NodeList Name
Temperature, ! Control Variable
HVACTemplate-Always 10, ! Schedule Name
DXVAV Sys 1 Supply Path Inlet; ! Setpoint Node or NodeList Name
DXVAV Sys 1 Heating Coil Air Temp Manager, !- Name
Temperature, ! Control Variable
DXVAV Sys 1 Supply Path Inlet, ! Reference Setpoint Node Name
DXVAV Sys 1 Heating Coil Outlet, ! Fan Inlet Node Name
DXVAV Sys 1 Supply Fan Outlet, ! Fan Outlet Node Name
DXVAV Sys 1 Heating Coil Outlet; ! Setpoint Node or NodeList Name
DXVAV Sys 1 OA Controller, ! Name
DXVAV Sys 1 Relief Air Outlet, ! Relief Air Outlet Node
DXVAV Sys 1 Air Loop Inlet, ! Return Air Node Name
DXVAV Sys 1 Mixed Air Outlet, ! Sensor Node Name
DXVAV Sys 1 Outside Air Inlet, ! Actuated Node
autosize, ! minimum outside air flow rate {m3/s}
autosize, ! maximum outside air flow rate {m3/s}
DifferentialDryBulb, ! Economizer Control Type
ModulateFlow, ! Economizer Control Action Type
19, ! Fixed Dry Bulb Temperature Limit {C}
, ! Fixed Enthalpy Limit {J/kg}
, ! Fixed Dew Point Temperature Limit (C)
, ! Electronic Enthalpy Limit Curve Name
4, ! Dry Bulb Temperature Lower Limit {C}
NoLockout, ! Lockout Type
ProportionalMinimum, ! Minimum Limit Type
Min OA Sched, ! Minimum Outdoor Air Schedule Name
, ! Minimum Fraction of Outdoor Air Schedule Name
, ! Maximum Fraction of Outdoor Air Schedule Name
; ! Mechanical Ventilation Controller Name
This controller has economizer action. When the outdoor air is between 3 to 19°C, the outdoor air can be used for air temperature adjustment.
======================
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: n_junk@xxxxxxxxxxxxxx
Date: Sun, 17 Jul 2011 01:23:15 +0000
Subject: [EnergyPlus_Support] Re: Problem with removing reheat coils in VAV
Hi Dr. Li,
Many thanks for your assistance!
I'm trying to analyze what you've said and see what I can change in my file.
Since it's my first simulation in energyplus, I'm still trying to learn the basics.
One thing that it's very odd to me and I can't understand at all it's the behavior of the heating coils of the system. I really don't know what is controlling them, in the program. Everytime I deactivate (not remove, just shut them off) the reheat coils in the zones, the heating coil of the main system seems to just turn off, even if I put setpoints in the heating coil outlet temperature or rise the design temperature. It's like the program quits to care about controlling the setpoint temperatures I inserted everytime I shut off the reheat coils.
I was expecting something far more easy and simple, that when I removed the reheat coils the program would 'think': «ok, since I can't rely anymore on the reheat coils, I need to heat more the air in the system's heating coil, so I will rise the heating coil's capacity». If I'm just shutting off the reheat coils, and not removing anything, and even rising the "heating coil design setpoint" in the HVACTemplate:System:PackagedVAV, what is going so wrong that shuts off or undersizes the heating coil's capacity, makes the setpoint temperatures not being met and doesn't heat the zones as expected?
Please note again that I'm still learning the basics of EnergyPlus and I'm using the HVACTemplates as a starting point, and then editing the expidf file, because it would be impossible to me to design all the air, system and plant loops, with my current knowledge, in time to deliver my thesis.
Once again, thanks in advance!
--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, YuanLu Li <yli006@...> wrote:
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> Hi, Lixeira I think you are trying to replace the usual air loop with one master zone thermostat control with one which uses the set point manager to control the air loop temperature and variable damper at the zone without reheat coil. In this way all thermostat are available in each zone. Because you are using setpoint manager for the air loop, the temperature should not be a range, but one temperature slightly below the wanted zone temperature. This difference is normally compensated by reheat. The heating should also be slightly lower. The type 4 dead band should also be maintained at the zone, with modified schedules. When the OA is cool in Summer, your system is turning on the heater to keep the temperature at the zone thermostat setting.
> There is no severe error. Just need some tuning on the available schedules and set point values or managers. AirTerminal:SingleDuct:VAV:NoReheat, should not be running at constant mode. I do not know how to change this yet. What I did of my own project was to use the one with reheat and disable the coil, not removing it, so that the damper will still have control of the air flow. Because the zone demand loads are not the same and dampers are not controlled, therefore the temperatures are all different. Dr. Li
> To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> From: n_junk@...
> Date: Sat, 16 Jul 2011 09:39:20 -0700
> Subject: [EnergyPlus_Support] Re: Problem with removing reheat coils in VAV
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> Hi Jean,
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> I'm sending the file that I'm testing as an e-mail attachment. I hope that the attachment will be send and received without errors.
> Note that the "plenum" temperatures are not controlled, but all the "spaces" temperatures should be controlled (always above 20ºC).
> Could the problem be in the VAV terminal damper position?
>
> Thanks in advance!
>
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