PPD wont come down

[Dathai]

I am running the thermal analysis on a new building which has a very high level of dissatisfied people. I can understand the reason for these results on Sunday (when the heating and cooling profiles are off) however, I am getting this problem during the week also. 20.7% of the time more than 10% of the people are dissatisfied within the main room of the building during working hours. As I am new to IES I would have assumed that you simply:
Set up APLocate
Assign Constructions
Set the heating and cooling profile
Enter your Set point temperatures
Define your Apache systems (Split system Electric Air con unit)

Then Retrieve your results for the Heating and cooling loads that are required to maintain a temperature between your set point temperatures.

I can't understand why Apache does not ramp up the cooling load in the summer months in order to overcome the solar gains. The cooling load does increase but the air temperature can be very high 32 deg C in some cases.
(by the way, the solar gains are higher in May than in June and the cooling load is able to control the temperature better in May)

There has got to be something I'm missing here I've modeled local shading for the Curtain wall to no avail (we don't have the sun cast licence though). The curtain wall is solar neutral too. Here are some of the graphs and figures for the results [img=http://www.fotoshack.us/images/37600Thermal calculations for 426.jpg]

Basically I need to know if I'm missing something here that will bring my room temperatures down. If you need me to be more specific let me know.

Thanks in advance.

[Complex Potential]

Hello Dathai

I would hazard a guess that the temperature spikes you are seeing are happening when the cooling is actually going off but the annual view of the graph is misleading. The cooling profile you have applied may be switching off too early each day resulting in a rapid temperature spike. This can happen if your cooling profile is not covering the occupied period correctly or if the space has a large window or rooflight for example and the cooling goes off at 5pm because the solar gains can actually still be pretty intense until about 8pm in the summer. Go into the first graph again and examine a single day. Are the temperatures being held in check when the cooling is active?

If this doesn't help go into the system tab within the room information (the one over from room conditions) and ensure that the cooling unit capacity is set to unlimited by checking the box. However, from looking at your graph it already appears as though this is set correctly.

Also, the PPD graph will not filter out unoccupied hours and so you may actually find that the % dissatisfied figure is actually fine whenever people are in and the cooling is on. Another tip is to use the "Comfort Settings" dialogue box (a button near the top with a question mark and a tick on it) when inside Vista to select clothing level, activity level and air speed which will all have a direct impact on the PPD. Note that these settings are lost as soon as you exit Vista and will need to be re-input.

Report back and let us know how you get on.

CP

[Dathai]

CP,

Thanks for the response. The problem has corrected itself as far the PPD goes. The fix seemed to be to click the "rezero auto sized parameters" button about 10 times under the cibse loads . I'm not sure if this was really what fixed it because it was the Apache sim I was using for my results. (I had changed the constructions for my curtain wall you see, making it more solar neutral however it made very little difference until the re-zero button was clicked a few times)

The problem was actually that the rooms weren't being cooled during the occupied times even though the cooling profile was active. I could understand that the Gains were making the room uncomfortable after 6 pm however my AC profile was on until 5 pm so it was very strange for it not to have just increased the cooling load to maintain my temperatures between 7 and 5pm.

Yea I had the cooling unit capacity on unlimited (thanks for the tip though, Ill keep an eye on that next time).
I was going of the 'range test' button to determine the PPD as I had a funny feeling the occupancy profile for plotting the graphs wasn't the same as the occupancy profile for my building (that would be a handy tool though, to be able to filter the input data for graphs). I had the comfort settings customized alright, however I didn't know that they reset after leaving vista, thanks for the tip!!
My new problem is that my cooling loads and heating loads are coming in a bit low, So if I don't get this sorted out tomorrow you may be hearing back from me soon enough.

All the best and thanks again for the response.