PLR = Load/Capacity.
RTF tells you how long the system has to operate to overcome cycling losses. When an AC system starts, it takes a few minutes for the capacity to get up to full output. This is the "losses" I describe, the system started but the capacity wasn't fully there for a few minutes. The RTF is usually a few percent larger than PLR because the system has to operate a little longer to get the capacity to the zone. RTF is only used to calculate energy use.
For example PLR=0.43 and RTF = 0.48. The load is 43% of the capacity, or the system ran 43% of the time. To calculate power we look at RTF and it says the system needed to operate 48% of the time (the system had to run 5% longer because the system did not provide full capacity when it started).
Your input file is fine unless you want to change schedules or lighting/equipment loads or something like that.
On 7/11/2011 2:33 PM, Aditya Ravi wrote:
What does the DX cooling coil runtime fraction indicate?
From: Richard Raustad <RRaustad@xxxxxxxxxxxx>
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Sent: Monday, July 11, 2011 1:57 PM
Subject: Re: [EnergyPlus_Support] need help E+ in verify and modifying IDF
The first part-load ratio I see is 0.43. This means that the AC ran 43% of the time. Or the load is 43% of the AC system capacity. So the unit is cycling on (43% of the time) and off (57% of the time). When the building loads get smaller, the PLR will be smaller. In summer, the PLR should approach 1 if you have the correct size system. Anything around 0.9 is about right.
Also change your reporting frequency to match the other report variables. Use Timestep instead of Hourly.
On 7/11/2011 1:50 PM, Aditya Ravi wrote:Hello Mr.Richard,
I have attached the output excel file. Can you explain it to me. As in how this part load ratio is affecting the results and what is its significance.
From: Richard Raustad <RRaustad@xxxxxxxxxxxx>
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Sent: Monday, July 11, 2011 1:37 PM
Subject: Re: [EnergyPlus_Support] need help E+ in verify and modifying IDF
Add these report variables to your file. You should see them in the rdd file after a simulation. The PLR is the cycling that occurs when a cycling fan system operates to meet a load. The RTF is slightly greater than PLR and includes losses due to cycling (i.e., the system has to run a little longer to overcome cycling losses). the PLR is used when calculating loads and how long the system needs to operate to meet the load. The RTF is used to calculate power use.
Output:Variable,*,Packaged Terminal Air Conditioner Part-Load Ratio,Hourly;
Output:Variable,*,DX Cooling Coil Runtime Fraction,timestep;
On 7/11/2011 1:26 PM, Aditya Ravi wrote:Hello,
I have attached an IDF,which I created few days back. I am a beginner with E+. I wanted to check if I have done it properly or not. There are no errors on running the simulation. There are a few warnings which come up since I have not used all day types, I think. However I assume that this does not affect my simulation results. Please go through and let me know if its correct.
Coming to what I want: I need to run a simulation for a 3 bedroom house. I assumed it to be under a single zone, since only one thermostat is to be used to regulate the temperature throughout the house. Firstly is this assumption correct?
Next, I have PTAC with electric heating coil. Is this enough for performing both heating and cooling? Also please look into the output. I find that during winter, at certain time of the day, cooling occurs which sounds not correct. Can you kindly explain why? Am I making a mistake in the scheduling?
Please verify my file and if changes are to be made, please help me out with it.
I had emailed earlier inquiring about this and got few replies. However I did not understand them very clearly. So here it is again: I need the HVAC to cut off on reaching the cooling or heating set point. In other words, I do not want the HVAC to be running continuously and trying to maintain the set point. Zone/room temp = set point, HVAC should turn off. Then once the room/zone temperature rises or falls by 1 deg C, I want the HVAC to once again kick ON to cool or heat the room. And I want the heating and cooling to be electric. This is what we normally observe in our houses. So basically, it will be a cycle of cooling in case of summer and a cycle of heating in winter. Can this be done in E+, if so, can you explain in detail how to do this. It will be really helpful, since I am working on my thesis based on this. In of the replies which i had got earlier, I was asked to look into the part load ratio and I was told that the HVAC operation is
dependent on the load and is not about reaching the set point. It makes sense and I agree speaking technically, but with this software, how do I get to the part load ratio?
Once again I request you to go through the IDF and verify if its correct and suggest modifications to improve it or in case its wrong help me correct it. Also please explain in detail on how to go about to achieve the HVAC operation like I have mentioned.
Sincerely,
Aditya
-- Richard A. Raustad Senior Research Engineer Florida Solar Energy Center University of Central Florida 1679 Clearlake Road Cocoa, FL 32922-5703 Phone: (321) 638-1454 Fax: (321) 638-1439 or 1010 Visit our web site at: http://www.fsec.ucf.edu UCF - From Promise to Prominence: Celebrating 40 Years
-- Richard A. Raustad Senior Research Engineer Florida Solar Energy Center University of Central Florida 1679 Clearlake Road Cocoa, FL 32922-5703 Phone: (321) 638-1454 Fax: (321) 638-1439 or 1010 Visit our web site at: http://www.fsec.ucf.edu UCF - From Promise to Prominence: Celebrating 40 Years
-- Richard A. Raustad Senior Research Engineer Florida Solar Energy Center University of Central Florida 1679 Clearlake Road Cocoa, FL 32922-5703 Phone: (321) 638-1454 Fax: (321) 638-1439 or 1010 Visit our web site at: http://www.fsec.ucf.edu UCF - From Promise to Prominence: Celebrating 40 Years
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