Carrier's HAP 4.22-Weather data

[SLBforever]

I decided to start a new post for this question, with a title more adequate about what we are discussing.

Hope is OK for you.

As far as I understand, this “hourly detail view” is only to calculate the peak coolling loads(am I wrong?), because to do a simulation for the 8760 hours of the year HAP uses another file (the HW1 file), witch is supposed to use a typical meteorogical year, I think.

But if it was only that, a single design value would be enough.

I still don´t understand if this “hourly detail view” data are supposed to represent the average day for that month, or the worst day we can expect for that month.

In my opinion it as to be the “worst case cenario”(for cooling mode, of course).


For instance, for Lisbon, Portugal as far as I remember, we never had a max temperature of 28ºC in January. Although, the numbers in HAP state 28ºC at 3 in the afternoon.
I’ve viewed the “Simulation data Report”, and the values seems much more adequate: they state a 19ºC value for the absolute max temperature, witch is much more in line with the reality.

From your perception, do the values that HAP give for where you live seems correct?

This is very puzzling to me…

The way I see things, one can never be a good user of a software if he doesn’t understand how it works. I ‘m not saying that Carrier or ASHRAE are not right, however something seems to me that it doesn´t match.
As far as I know the weather data are of paramount importance when performing load calculations, so that’s why I’m insisting in this question.

Thank you for your patience…and sorry about my English!

SLB

 

[HVAC68]

There are many methods by which the heat load or cooling load is calculated.

1. Instantaneous load. This is the traditional manual way of calculation using a E20-II form where one calculates the cooling load at 3 pm or 4 pm on a hot summer day.

2. ASHRAE Transfer function method - This is used in HAP. I suggest that you use the F1 or help function in the program to understand more about this. It would be too long and descriptive to explain here.

3. There are other methods which are more complex in nature.

As regards hourly calculation - The program calculates 24 hours a day and for 365 days a year - which would mean 8760 hours. However, as said earlier, if you think that the data contained in the program is not close to reality, maybe you should take it up with ASHRAE and/or Carrier to update their data. Probably, the data changes over a period of time - due to greenhouse effect ???

HVAC68

 

[SLBforever]

I've read the explanatio about the way HAP "do the numbers".
It´s now clear to me,why a daily profile of temperatures is necessary.
However for my climate, perhaps the best ideia is to select only Jun, Jul and Aug months, in the first tab of the "Design parameters" tab. I'm sure the cooling peak point will occur this range.
The "Design solar" is another issue: we can't the correct the values directly, only using a multiplier.
Any one knows why is that so?
Are the values for the several facade orientations obtained from the "Horizintal" values, through mathematical relations?
We can see hourly the values in the "design solar profile",part of the Weather Report.

Thanks

SLB

 

[HVAC68]

Why would you want to select any month ? Allow the program to do it. It will automatically select the peak load.

HVAC68

 

[SLBforever]

The reason is that HAP, for the non-summer-months has values hell above the reality.By excluding those months for the cooling calculation, we are setting aside the possibility that the peak condition will occur(wrongly)in a non summer month.

Here´s what HAp online says:

Design Cooling Calculation Months
This item defines the range of months considered when performing cooling design calculations for systems and plants. Once you choose start and end months, your specification will be used for all subsequent system and plant design calculations in the current project.
To be absolutely sure maximum space loads, zone loads, system loads and plant loads are identified during sizing calculations, January thru December should be selected. However, based on prior experience, you may be able to select a smaller range of months and still be confident that peak loads will fall within this period. For example, for a certain building type and building location choosing summer and fall months might ensure that all possible peak load times are considered in the analysis. The benefit of choosing fewer months is that system and plant sizing calculations will run faster. The risk is that peak load times might be excluded from the analysis resulting in unreliable sizing data. When in doubt, choose January thru December to ensure all peak load conditions are included in your analysis.
Note: Your choice of design cooling calculation months has no effect on design heating calculations. Design heating calculations will always be performed for the winter design condition no matter what design cooling months are selected. For example, in the northern hemisphere it is not necessary to include January in your range of months just to ensure heating calculations are properly performed. In the southern hemisphere, it is not necessary to include July in your range of months to ensure heating calculations are properly performed.

SLB

 

[HVAC68]

Fair enough. It again boils down to the same old question - The correctness of the ASHRAE data vis-a-vis what you perceive is the right data. As I said earlier, take up the issue with ASHRAE with facts and figures.


HVAC68

 

[ub313]

Hi,
To answer to your question on
a)Design Solar. These values are not editable by user and are system calculated based on the latitude and longitude of location.
b) The data used for calculation in Carrier software do not use actual measured weather parameters for the specific location. Thes are based on some empirical distribution of Design Summer DB, Daily Range and Winter design DB. These are not accurate in representing monthly design data correctly. More appropriate way would be to use the ASHRAE2005 design weather data (now available for 4422 cities of the world). Carrier software may not incorporate this data now. So you may have to enter each month's design data manually to get monthly design loads and eventually a more correct annual peak design Load.

A new software is expected to be released in the market soo, which will use the measured weather for many cities to calculate Design Load more closely.