Hi, Richard
I have a look at your IDF.
It is well organized and is running with no fatal errors. However, there are still lots of warnings.
I do not know whay you have chosen to use VAV and 16 AHU for such a large building. If the equipment are already there, then you have no choice.
If it is a new installation, you may reconsider.
========================
Basically, the traditional HVAC uses the thermostat to control temperature directly. Turn off the heating or cooling when the set point is reached.
With VAV, the zone temperature is controlled by changing the damper position. The input air temperature is always lower than set point value for cooling. When the damper is at the minimum value, and it is still too cold, the reheat heater is turned on. The minimum setting is to let in the fresh air. You can shut the damper to zero and without using any reheat.
==========================
HeatPump is generally used when you want to switch heating to cooling or vice versa, in the change over season. HeatPump is not efficient in Winter, therefore you all the supplementally heaters.
Cooling towers cannot be left open in Winter, therefore, it must be seasonal.
If individual temperature is needed for ev ery zone, the split fan coil unit and water fan coil units can be used.
==============================
VAV requires extra sensors and controllers, such as variable fan speed controller, damper controller. These are simulated in EPlus but not obvious as additional equipment. Computer control is generally required for over all control.
VAV does not always save energy, and is definitely more costly to install. The running cost may be lower, it it is a large installation with maximum demand penalty charges.
==============================
A few points that you need to change in your IDF.
The season year schedule was there, but not used for the cooling tower.
The dead band for type 4 thermostat may not have been defined.
Most input field are with values and not autosized. This may force the system into non operating mode.
Maximum or nominal values may not be correct. For example, reheat heater has a rating of more than 50kw. This is very large. The reason is because the reference temperature for cooling is set too low.(13°C)
Depends on the internal load, the reference cooling temperature should just below the cooling set point. (18 to 22°C) Similarly the heating reference temperature should be just above the heating set point and must be lower than the cooling setpoint.
If the heating set point is 20°C, the cooling set point must be higher than 20°C, say 20.1°C.
If you have the seasonal control with type 1 and 2 theremostat control, the range may overlap.
You can change some of these values for one floor and observe the result.
You can also run a 3 or 5 zone example to find out more. It is too slow to run your actual building simulation.
==========================
I will suggest to identify the set point values first and change them, and made some values autosize.
Turn on more dianostics objects.
!- =========== ALL OBJECTS IN CLASS: OUTPUT:DIAGNOSTICS ===========
Output:Diagnostics,
DisplayAllWarnings, !- Key 1
DisplayExtraWarnings; !- Key 2
Output:Diagnostics,
DisplayUnusedSchedules, !- Key 1
DisplayUnusedObjects; !- Key 2
Output:Diagnostics,
DisplayAdvancedReportVariables; !- Key 1
!- ======================
You will see many warnings, but don't be affraid, because each warning is multiplied by the number of zones in your building.
If the set point values are properly chosen, the supplementally and reheat heater will not be turned on.
If you use HP with DX cooling coil , and electric or boiler for heating, the condenser loop and tower may not be needed. The HP condenser coil can be air cooled. There are moduilar HP compressors in the market.
Dr. Li
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: richardluo88@xxxxxxxxxxxxxx
Date: Sun, 23 Oct 2011 15:12:43 -0400
Subject: Re: [EnergyPlus_Support] How to control the system with UnitaryHeatPump:WaterToAir
__._,_.___
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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__,_._,___
I have a look at your IDF.
It is well organized and is running with no fatal errors. However, there are still lots of warnings.
I do not know whay you have chosen to use VAV and 16 AHU for such a large building. If the equipment are already there, then you have no choice.
If it is a new installation, you may reconsider.
========================
Basically, the traditional HVAC uses the thermostat to control temperature directly. Turn off the heating or cooling when the set point is reached.
With VAV, the zone temperature is controlled by changing the damper position. The input air temperature is always lower than set point value for cooling. When the damper is at the minimum value, and it is still too cold, the reheat heater is turned on. The minimum setting is to let in the fresh air. You can shut the damper to zero and without using any reheat.
==========================
HeatPump is generally used when you want to switch heating to cooling or vice versa, in the change over season. HeatPump is not efficient in Winter, therefore you all the supplementally heaters.
Cooling towers cannot be left open in Winter, therefore, it must be seasonal.
If individual temperature is needed for ev ery zone, the split fan coil unit and water fan coil units can be used.
==============================
VAV requires extra sensors and controllers, such as variable fan speed controller, damper controller. These are simulated in EPlus but not obvious as additional equipment. Computer control is generally required for over all control.
VAV does not always save energy, and is definitely more costly to install. The running cost may be lower, it it is a large installation with maximum demand penalty charges.
==============================
A few points that you need to change in your IDF.
The season year schedule was there, but not used for the cooling tower.
The dead band for type 4 thermostat may not have been defined.
Most input field are with values and not autosized. This may force the system into non operating mode.
Maximum or nominal values may not be correct. For example, reheat heater has a rating of more than 50kw. This is very large. The reason is because the reference temperature for cooling is set too low.(13°C)
Depends on the internal load, the reference cooling temperature should just below the cooling set point. (18 to 22°C) Similarly the heating reference temperature should be just above the heating set point and must be lower than the cooling setpoint.
If the heating set point is 20°C, the cooling set point must be higher than 20°C, say 20.1°C.
If you have the seasonal control with type 1 and 2 theremostat control, the range may overlap.
You can change some of these values for one floor and observe the result.
You can also run a 3 or 5 zone example to find out more. It is too slow to run your actual building simulation.
==========================
I will suggest to identify the set point values first and change them, and made some values autosize.
Turn on more dianostics objects.
!- =========== ALL OBJECTS IN CLASS: OUTPUT:DIAGNOSTICS ===========
Output:Diagnostics,
DisplayAllWarnings, !- Key 1
DisplayExtraWarnings; !- Key 2
Output:Diagnostics,
DisplayUnusedSchedules, !- Key 1
DisplayUnusedObjects; !- Key 2
Output:Diagnostics,
DisplayAdvancedReportVariables; !- Key 1
!- ======================
You will see many warnings, but don't be affraid, because each warning is multiplied by the number of zones in your building.
If the set point values are properly chosen, the supplementally and reheat heater will not be turned on.
If you use HP with DX cooling coil , and electric or boiler for heating, the condenser loop and tower may not be needed. The HP condenser coil can be air cooled. There are moduilar HP compressors in the market.
Dr. Li
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: richardluo88@xxxxxxxxxxxxxx
Date: Sun, 23 Oct 2011 15:12:43 -0400
Subject: Re: [EnergyPlus_Support] How to control the system with UnitaryHeatPump:WaterToAir
Attached is the IDF.
On Sun, Oct 23, 2011 at 2:42 PM, YuanLu Li <yli006@xxxxxxxxxxx> wrote:
It is difficult to tell what you have in your system.
If you post or attach your IDF (the template original, if you are using template model.)m I will have a look at it.
The cooling and heating using a HP are simulated separately with two loops.
If you do not enter the heating loop in EPlus, they are not installed. Supplemental coil and/or heater are provided, because HP will not run efficiently when the evaporating coil is at a temperature of lower than 5°C.
The condenser loop is controlled by the temperature of the condensing coil of the HP, when it is in the cooling mode. When the zone cooling is turned off, the compressor pumps stops, condenser coil temperature falls, and the condenser loop pump is turned off. This is the general way a system operates.
Dr. Li
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: richardluo88@xxxxxxxxxxxxxx
Date: Fri, 21 Oct 2011 16:29:04 -0400
Subject: [EnergyPlus_Support] How to control the system with UnitaryHeatPump:WaterToAir
Hello,I am trying to simulate a model with condenser system, which means the dx cooling coil connected with a cooling tower.So I choose UnitaryHeatPump:WaterToAir to realise it. (So I have to turn off the heating coil and supplemental coil)But I find it's hard to give all the parameters for such a component. And I can only use fan:onoff and there is no water coil controller so that I can't control the supply temperatures properly.
Do you have any suggestions for simulating such a model? How can I put in all these parameters in?And most important, how can I get it better controlled?(I already build the model, it run successfully. But the zone temperature changes a lot and I can't get the unmet load hours down to 300 hours.)Looking forward to your reply!Thanks.Chen
__._,_.___
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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