The EPlus is not a simple program to use. I read the Ver3 I/O Ref. manual a few years ago almost from cover to cover, in order to get a complete picture of the capability of the EPlus program. Since then many new features have been added. That is why I have to look up the new references in the manuals on the objects to make sure.
I do not usually answer question without the IDF posted, because there are so many details to be verified. I use the error file to guide me to fine the problems.
This is not possible for a new user, because you have not seen the error message before, and do not where to get additional information from the output files.
==============================
Templates are there to help user to select a system together without having to know how to arrange the class object names. When you have more experience, meaning to run a few different combination of the templates, you will see how the zone, system and plants are put together.
There are complete examples, using different components which are not derived from templates.
========================
If a set of templates do not give you what you want, you should try another set or by changing the conditions in the same set. By saying no to some fields, the templates may give you a different object in the expanded version.
============================
If you now go back to the original version using the VAV:reheat, your simulation would probably be running correctly. However, you wanted to stop the reheat heater from comming on.
If VAV:No-reheat is available in the template, you should change to that at this level. Removing the reheat coil in the expanded IDF is not a simple task. You need to replace the object and adjust the node names. As you did not which object to use, the result did not work.
===========================
If you read the I/O manual on the VAV:reheat, you will know that the reheat will come on only the damper is at the minimum and when it is cooling. This condition can happen ony when the mail coil temperature is set much lower than the zone thermostat value. When the damper is at the minimum, the air is still too cold. Therefore, the reheat heater is turn on to warm up the zone to the required temperature.
To stop the reheat heater from coming on, simply increase the main AHU temperature to just below the required zone thermostat value. The damper will remain open and the reheat will not come on.
When the damper is fully open and the zone is still not cold enough, the main fan speed will increase and thus increasing the zone air flow rate and deliver more cooling capacity to the zone.
==========================
Similarly, if the heating coil capacity is sufficient and set to priority one and re-heat coil set for heating priority two, the re-heat coil will not be used. Set the re-heat maximum value to a lower value will also keep it from turning on.
====================
The setpoint manager:Mixed Air is also a new feature. (page 1639 of the IO manual) The purpose is to set the air loop temperature without using one of the zone thermostat.
I do not know whether you added this one yourself or was in the templates.
The control has be be tied to the zone thermostat schedule values.
SetpointManager:SingleZone:Reheat Set the temperature range and the zone nodes.
and many others.
SetpointManager:MixedAir specify the OA mixer node is to be controlled. When the weather is cold, the OA inlet is reduced and the return air is increased.
This are more advanced applications and I have not used them before.
===============
If your thesis requirement is to simulate one building using certain HVAC, you should start with the building requirement. Draw a flow diagram showing the zones and special requirements.
Do the following first to verify the building and the schedules.
HVACTemplate:Thermostat
HVACTemplate:Zone:IdealLoadsAirSystem
This will also give you the building heating and cooling demand and annual energy usage. Any real HVAC system component added in your simulation will use more energy. Equipment efficiency is always less than 100%.
=======================
Are you a system designer, a building designer, or just an building energy usage report writer or appraiser? If you have less than six month to learn the EPlus, you may need to discuss the program again with your supervisor.
If you can understand the result presented by the IdealLoadsAirSystem, then you can use them directly applied to your thesis need in building design, within a shorter time.
==============================
Variable speed fan, variable speed pumps are not commonly used because the cost of making these components and the controls required to make them work.
Fans with 1,2,3 step control are not variable speed fans. A DX coil with two compressors is also not a VRV system.
There are VAV diffusers with electronic control, and computor controlled sensers for constant duct temperature, fan supply with VSD control, etc. These are for special building for research purposes.
=====================
I will try my best to help. I am learning also on these advanced features of EPlus.
Dr. Li
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:
>
>
>
> 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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>
>
>
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>
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>
>
>
>
> Hi Jean,
>
> 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!
>
__._,_.___
Primary EnergyPlus support is found at:
http://energyplus.helpserve.com or send a message to energyplus-support@xxxxxxxx
The primary EnergyPlus web site is found at:
http://www.energyplus.gov
The group web site is:
http://groups.yahoo.com/group/EnergyPlus_Support/
Attachments are currently allowed but be mindful that not everyone has a high speed connection. Limit attachments to small files.
EnergyPlus Documentation is searchable. Open EPlusMainMenu.pdf under the Documentation link and press the "search" button.
![]()
__,_._,___
I do not usually answer question without the IDF posted, because there are so many details to be verified. I use the error file to guide me to fine the problems.
This is not possible for a new user, because you have not seen the error message before, and do not where to get additional information from the output files.
==============================
Templates are there to help user to select a system together without having to know how to arrange the class object names. When you have more experience, meaning to run a few different combination of the templates, you will see how the zone, system and plants are put together.
There are complete examples, using different components which are not derived from templates.
========================
If a set of templates do not give you what you want, you should try another set or by changing the conditions in the same set. By saying no to some fields, the templates may give you a different object in the expanded version.
============================
If you now go back to the original version using the VAV:reheat, your simulation would probably be running correctly. However, you wanted to stop the reheat heater from comming on.
If VAV:No-reheat is available in the template, you should change to that at this level. Removing the reheat coil in the expanded IDF is not a simple task. You need to replace the object and adjust the node names. As you did not which object to use, the result did not work.
===========================
If you read the I/O manual on the VAV:reheat, you will know that the reheat will come on only the damper is at the minimum and when it is cooling. This condition can happen ony when the mail coil temperature is set much lower than the zone thermostat value. When the damper is at the minimum, the air is still too cold. Therefore, the reheat heater is turn on to warm up the zone to the required temperature.
To stop the reheat heater from coming on, simply increase the main AHU temperature to just below the required zone thermostat value. The damper will remain open and the reheat will not come on.
When the damper is fully open and the zone is still not cold enough, the main fan speed will increase and thus increasing the zone air flow rate and deliver more cooling capacity to the zone.
==========================
Similarly, if the heating coil capacity is sufficient and set to priority one and re-heat coil set for heating priority two, the re-heat coil will not be used. Set the re-heat maximum value to a lower value will also keep it from turning on.
====================
The setpoint manager:Mixed Air is also a new feature. (page 1639 of the IO manual) The purpose is to set the air loop temperature without using one of the zone thermostat.
I do not know whether you added this one yourself or was in the templates.
The control has be be tied to the zone thermostat schedule values.
SetpointManager:SingleZone:Reheat Set the temperature range and the zone nodes.
and many others.
SetpointManager:MixedAir specify the OA mixer node is to be controlled. When the weather is cold, the OA inlet is reduced and the return air is increased.
This are more advanced applications and I have not used them before.
===============
If your thesis requirement is to simulate one building using certain HVAC, you should start with the building requirement. Draw a flow diagram showing the zones and special requirements.
Do the following first to verify the building and the schedules.
HVACTemplate:Thermostat
HVACTemplate:Zone:IdealLoadsAirSystem
This will also give you the building heating and cooling demand and annual energy usage. Any real HVAC system component added in your simulation will use more energy. Equipment efficiency is always less than 100%.
=======================
Are you a system designer, a building designer, or just an building energy usage report writer or appraiser? If you have less than six month to learn the EPlus, you may need to discuss the program again with your supervisor.
If you can understand the result presented by the IdealLoadsAirSystem, then you can use them directly applied to your thesis need in building design, within a shorter time.
==============================
Variable speed fan, variable speed pumps are not commonly used because the cost of making these components and the controls required to make them work.
Fans with 1,2,3 step control are not variable speed fans. A DX coil with two compressors is also not a VRV system.
There are VAV diffusers with electronic control, and computor controlled sensers for constant duct temperature, fan supply with VSD control, etc. These are for special building for research purposes.
=====================
I will try my best to help. I am learning also on these advanced features of EPlus.
Dr. Li
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:
>
>
>
> 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
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
> Hi Jean,
>
> 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!
>
__._,_.___
Primary EnergyPlus support is found at:
http://energyplus.helpserve.com or send a message to energyplus-support@xxxxxxxx
The primary EnergyPlus web site is found at:
http://www.energyplus.gov
The group web site is:
http://groups.yahoo.com/group/EnergyPlus_Support/
Attachments are currently allowed but be mindful that not everyone has a high speed connection. Limit attachments to small files.
EnergyPlus Documentation is searchable. Open EPlusMainMenu.pdf under the Documentation link and press the "search" button.
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