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# How are ASHRAE design mean coincident variables calculated?

I’m having some trouble finding documentation on how this is done. I’ve gone through the HoF but I couldn’t find much on specific methods.

For example what I’m trying to get at: let’s say that the 0.4% condition temperature somewhere is 90F. In the ordered distribution of temperatures there are sure to be more than one hour in the measurement period that is 90, so which coincident WB, for example, is chosen? I assume it must be the max, or an average or something.

Thanks

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I see this from HOF chapter 14:

Simple design conditions were obtained by binning hourly data into frequency tables, then deriving from the binned data the design condition having the probability of being exceeded a certain percentage of the time. Mean coincident values were obtained by double-binning the hourly data into joint frequency matrices, then calculating the mean coincident value corresponding to the simple design condition.


Seems like it's just the mean of all the coincident values?

( 2023-01-10 12:06:57 -0500 )edit

Thanks I had missed that paragraph. It still doesn't really explains what it's doing though. I guess from the word 'mean' in MCWB for example, we can infer that they are just averaging all the coincident values, but all that jargon about double binning into joint frequency matrices isn't super helpful (and I don't think even neccesary if they are just taking a simple average).

( 2023-01-10 16:29:01 -0500 )edit

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Here is some information from ASHRAE HOF:

Simple design conditions were obtained by binning hourly data into frequency tables, then deriving from the binned data the design condition having the probability of being exceeded a certain percentage of the time. Mean coincident values were obtained by double-binning the hourly data into joint frequency matrices, then calculating the mean coincident value corresponding to the simple design condition.

The use of the word "mean" is to imply that a mathematical mean, or average, is used.

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Yes thank you, I think you are right, as was Eric's comment above. It's just not a very clear way to word it in my opinion, but I think that's the answer

( 2023-01-10 16:30:08 -0500 )edit