Re: [EnergyPlus_Support] Constant Volume Reheat

[fred buhl <wfbuhl@xxxxxxx>]

Davide,

The system is overcooling and then needs to reheat to reach the 
setpoint. The system controls
do not allow the zone heating coils to reheat above the heating 
setpoint. Another way of putting it
is that this system has no control of cooling output, so the cooling 
setpoint is unused.

Fred Buhl

davidedelloro wrote:

>Dear All,
>   I am modelling a residential building composed by 15 temperature
>controlled zones.
>The HVAC type used is Constant Volume Reheat. The cooling coil is
>COIL:DX:CoolingBypassFactorEmpirical, the fan chosen is
>FAN:SIMPLE:ConstVolume, and for reheating SINGLE DUCT:CONST
>VOLUME:REHEAT with COIL:Gas:Heating. The system is on the whole year,
>and the Zone Control used is DUAL SETPOINT WITH DEADBAND.
>All the systems and plants are autosized.
>What I expected is to have within the zones 15°C (night) - 20°C (day)
>during winter period and 24°C during summer days.
>I obtained those temperatures during winter period, but during summer
>the zone temperatures are like the winter ones, they don't go above 20°C.
>
>Beside, if I try to set up the night summer temperatures close to 30°C
>the simulation gives me the following error:
>
>   ** Severe  ** For object = COIL:DX:COOLINGBYPASSFACTOREMPIRICAL,
>name = "ACDXCOIL 1", the combination of
>   **   ~~~   ** rated air volume flow rate, total cooling capacity
>and sensible heat ratio yields coil exiting
>   **   ~~~   ** air conditions above the saturation curve. Possible
>fixes are to reduce the rated total cooling
>   **   ~~~   ** capacity, increase the rated air volume flow rate, or
>reduce the rated sensible heat ratio for this coil.
>   **   ~~~   ** If autosizing, it is recommended that all three of
>these values be autosized.
>
>Everything is autosized as suggested in the message, and I cannot
>figure out my mistakes.
>
>Besides, if I use heating setpoints for winter and cooling setpoints
>during summer for controlling my zone temperature, the reheat coil
>during summer is not working, and the zone air temperatures are relly
>low (close to 14°C). 
>I checked all the schedules and everything is on.
>
>I checked the SVG file as well and everything appears to be correct.
>Hope you can help me.
>Thanks
>--Davide
>
>
>
>
>
>
>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 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.idf and press the "search" button.
> 
>Yahoo! Groups Links
>
>
>
>  
>


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