Re: [EnergyPlus_Support] Example file 5ZoneVAV-Pri-SecLoop.idf

[Fred Buhl <wfbuhl@xxxxxxx>]

The use of supply air setpoints and hot & chilled water coil controllers 
can vary from
quite simple to somewhat complicated. On the airside this is a 
straightforward VAV system.
The simplest way to control this system is to employ one setpoint 
manager and 2 simple controllers.
The setpoint manager would put a single desired temperature on the fan 
outlet node. The cooling and
heating coil controllers would sense the temperature at this node; if 
the node temperature > setpoint,
the cooling coil would control (reduce) the supply air temperature to 
the setpoint. If the node
tmperature < setpoint, the heating coil would heat the supply air 
temperature to the setpoint.
For economizer control, a SET POINT MANAGER:MIXED AIR could be used to 
set a mixed
air setpoint given the fan outlet node setpoint as a reference.

In this case the author of the input file wants to have the heating coil 
and cooling coil controlled
to different setpoints, separated by a deadband. He desires the supply 
air temperature to be heated to
10 C at the fan outlet, cooled to 14 C at the fan outlet, and not heated 
/ cooled if in between.
There's a problem: there can only be one setpoint on a given node. So 
the user puts the cooling setpoint
of 14 C on the fan outlet. A SET POINT MANAGER:MIXED AIR adjusts this 
setpoint for the fan heat
and assigns the resulting setpoint to the mixed air node and the cooling 
coil outlet node. For the heating setpoint,
the fan outlet node can't be reused. So the user assigns the supply air 
heating setpoint to the central system
inlet node, which normally isn't used (for setpoints or by controllers). 
Another SET POINT MANAGER:MIXED AIR
adjusts this temperature for fan heat gain (just as if it were the fan 
outler node) and assigns the resultant setpoint temperature to the 
heating coil
outlet node. This is definately a trick, and it is too bad there isn't a 
more straightforward way of doing this.
The cooling coil controller looks at the setpoint on its air outlet node 
and controls to that temperature; the
heating coil controller looks at the setpoint on its air outlet node and 
controls to that temperature.

All the sepoint mangers are effective during the simulation. The user 
has taken care that they do not conflict.
You should never assign more than 1 setpoint to a node, and you should 
be careful to specify your heating
and cooling coil setpoints and controls so that the coils on't fight 
each other.

fred Buhl

 
zhaicq98 wrote:
> I posted this message a few days ago, and got no response. I am going 
> to ask it again. Please can anybody provide any help on this? Thanks!
>
> ________________________________________________
> In this example file, there is a cooling and a heating supply air 
> temperature set point managers. First, I do not really understand how 
> these two set point managers work. How does the program determine 
> which one to take effect during the simulation? Second, why is the 
> heating supply air temperature 10oC, but the cooling supply air 
> temperature 14oC?
>
> ! NOTE:  Heating supply air setpoint is placed on Supply Path Inlet 
> node to allow separate heating and cooling setpoints.
> ! SET POINT MANAGER:MIXED AIR <system name> Heating Coil Air 
> Temp Manager adjusts this setpoint for fan heat and places it on the 
> Heating Coil Outlet
>  
>   SET POINT MANAGER:SCHEDULED,
>     VAV Sys 1 Heating Supply Air Temp Manager,  !- Name
>     TEMP,                    !- Control variable
>     COMPACT HVAC-ALWAYS 10.0,!- Schedule Name
>     VAV Sys 1 Supply Path Inlet;  !- Name of the set point Node or 
> Node List
>
>   SET POINT MANAGER:SCHEDULED,
>     VAV Sys 1 Cooling Supply Air Temp Manager,  !- Name
>     TEMP,                    !- Control variable
>     COMPACT HVAC-ALWAYS 14,  !- Schedule Name
>     VAV Sys 1 Supply Fan Outlet;  !- Name of the set point Node or 
> Node List
>
>
>
>
>
> The primary EnergyPlus web site is found at:
> http://www.energyplus.gov
>
> The group web site is:
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>
> Attachments are not allowed -- please post any files to the appropriate folder in the Files area of the Support Web Site.
>
> EnergyPlus Documentation is searchable.  Open EPlusMainMenu.pdf under the Documentation link and press the "search" button.
>  
> Yahoo! Groups Links
>
>
>
>   


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