Running a simple 30’x30’ OpenOffice roombox model to understand peak loads. The room is west/southwest facing in Gainesville FL. I am using the DDY file directly downloaded from the EWP Map (TMYx). The PeakLoads component is showing the cooling period is 2/21 - I expect July/August.
The roombox is conditioned but we have not specified detailed HVAC info.
Interestingly…when I run the same model but simply use the EPWtoDDY component instead of the downloaded .ddy file, the cooling period is 7/21 (as expected).
Best practice would be to use DDY not the EPW estimate but why may this be happening?
I am getting something different when I use that DDY file because my model has windows facing a different orientation than yours (my peak is occurring when the noon sun is low in November). But it’s clear that both of our models have their peaks being driven by solar load and not outdoor air temperature. Hence why it happens in February for you when the sun is low.
I can see that there are 114 different design days in this file, which tells me that OneBuilding DDYs are kinda getting out of hand.
If you are going to put 114 different options into a DDY file why are we even bothering with the design day methodology anymore? We might as well just run an annual simulation.
In any event, your peak is technically in February for your model because that is the time of year that you get the most stun through your windows. So I guess best practice would be to size the system for this load rather than the load in July when the sun is higher and not getting through your windows as easily.
