Look for the part-load ratio variable for your AC system. If your AC system has this report variable, then it will tell you how long the unit runs. A part-load ratio (PLR) of 0.5 means the AC unit is on for 10-min and off for 10-min. Or on for 20-min and off for 20-min. The point is that the AC unit will not run until the set point is met and then turn off. It will always run if there is a load and cycle at a frequency of PLR.
On 6/9/2011 4:23 PM, Aditya wrote:
May be I need to read the input requirements again throughly. By HVAC ON, thought, depending on the requirement, the modes between heating and cooling would change automatically. Guess I was wrong. Like you have suggested I will need to selectively control them.
Also say if I am working only for cooling, i.e. only Summer, what I want to do is, keep the HVAC ON for the entire day and keep different cooling set points for different times of the day, where during the unoccupied period there will be a setback, say I increase it to 40deg C, which I assume means the HVAC will not KICK ON until the zone temperature reaches 40deg C. So now for this configuration what I noticed is, even though the HVAC cools the room to a set point say 22, it continues to consume energy(remains ON) and keeps the room at 22. Why does the HVAC not cut off on reaching a set point. Is it because of the Heat Balance Algorithm used by E+?
Regards,
Aditya
--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, YuanLu Li <yli006@...> wrote:
>
>
> I would suggest that you work through the example in the Getting started first before trying to write the IDF on your one.
>
> A one zone house does not simplify the IDF entry very much.
>
> Run the PTAC example file in the exampleFiles folder. Then change the building geometry to your design, and location to where you are. Yhere is spread sheet index there to help you find what you want.
>
> Computer entries are very exact, and can not be randomly inserted, without following all the necessary linking objects.
>
> For example, is your thermostat declared correctly with control type, zone and shedule names. Is you schedule orrectly spepifyin the uear or season or week or day, and time?
>
> If you have Winter and Sommer, the HVAC has cooling and heating functions. HVAC on constantly does not make sense. The heiting and cooling components must be selectively controlled for the two seasons or for two working temperature bands.
>
> If you do not following what I am describing, you have not read sufficiently into the EPlus input requirements.
>
> Dr. Li
>
>
>
>
>
>
> To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> From: adityaravi87@...
> Date: Wed, 8 Jun 2011 15:24:27 -0700
> Subject: [EnergyPlus_Support] Frist Time User - doubts in scheduling
>
>
>
>
>
>
> Hello,
>
> I am starting to learn this software. I have a few doubts.
>
> Firstly, the SIZING:PERIOD, where we need to define a winter or summer design day. Can anyone explain what this means and how it affects the simulation.
>
> Two: I have created two set point schedules which the HVAC must follow. One is for WINTER and the OTHER for SUMMER. However I am using only a single HVAC(PTAC) and single thermostat. Due to this I have assumed that my model has only ONE ZONE. Despite giving this schedule and running it for a random date in a year, when I see the outputs the cooling schedule does not follow exactly the same as what I had mentioned. For example, I said the HVAC is ON constantly, then I mentioned Until: 09:00 , 22(set point) then Until: 13:00, 40, Until 19:00, 24 and Until 24:00, 22. But when I saw my results they look different.
>
> Please help me in writing a schedule for a one zone residential house model. I am really confused as to how the software works and what are the parameters it is considering while running the idf file.
>
> Regards,
>
> Aditya
>
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