Re: [EnergyPlus_Support] heating/cooling at same time

["Michael J. Witte" <mjwitte@xxxxxxxx>]

Reporting every 10 minutes is at the zone time step level.  There can 
be multiple HVAC time steps within a zone time step.  Change your 
reporting from "timestep" to "detailed" to see every HVAC time step, 
which can be as short as 1 minute under rapidly changing conditions.  

What variables are you looking at to determine if there is heating or 
cooling occuring?  What types of HVAC system are you modeling?

If you are reporting Zone/Sys Sensible Heating and Zone/Sys Sensible 
Cooling, these report how the system acted on the zone.  These 
variables look at the difference between the supply air temperature 
and the zone air temperature and in systems with a constant fan will 
often report heating and cooling even if the thermostat does not 
request it.  For example, if it is cool outside and the fan is 
bringing in ventilation air, the cool air will show as Zone/Sys 
Sensible Cooling even if the zone if below the cooling setpoint.

Mike


On 30 May 2003, at 18:11, idoebber wrote:

> Thank you for those that replied to my email.  Unfortunately, my
> reporting frequency of my data is every time step (10 minutes since I
> am modeling an HVAC system).  Therefore, on some time steps, the
> system is heated and cooled at the same time and I don't think it is
> due to reheat.  For instance, in January my cooling coil will turn on
> for approximately 20 minutes even though my conditioned space
> temperature is exactly at my heating point temperature (21 degrees C),
> which is less then my cooling setpoint temperature (23 degrees C). 
> Therefore, cooling is turned on even when the zone air temperature is
> below the temperature when the cooling system should turn on.  Either
> my HVAC system is possessed or I am plugging something very
> fundamentally wrong in.
> 
> Thanks
> Ian
> 
> 
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