Hello All,
Has anyone ever tried to use eQuest for sizing equipment? I know about
the design day input, but it only allows for a single design day, which
doesn't necessarily cover all of the bases for solar angles. Based on
the standard TMY2 weather files, I know that shouldn't be done, but has
anyone ever created some design day weather files? I'm especially
suspicious of the equipment sizing due to the sunlight clarity factors.
It would save a lot of time if eQuest could do design day and simulation
calculations that could be trusted, but I'm not sure if there is a time
effective way to do it. Any input would be greatly appreciated.
Thanks,
Todd Lagus, EIT
Todd,
I have been told in the past that it is best to use the TMY weather file
rather than the Design Day input. If you use the TMY3 file you should
have all the latest weather/solar info. Just do as you would with DD
calcs: revise you schedules for summer hottest day with everything on
and winter coldest day dead of night with everything off, set your
sizing factors to what you want and hit enter. This should give you good
output. Be sure to have all the wall/glass info in that you want and be
sure you have the right thermostat type and throttling range for it
based on your HVAC system type.
Carol
Thanks for your input Carol.
I think my main concern is that the sizing peaks aren't necessarily going to occur in the summer. Say you have a building with a lot of south facing glass. This space may peak in October. I did a quick validation model in eQuest and another peak sizing program to see how different the loads would be for such a case. The eQuest model solar gains were only about 35% of what the sizing program calculated. I believe this is because the sizing program always assumes a clear day to size equipment for peaks, while the eQuest weather files use average data. Each kind of calculation serves a purpose, one for sizing and one for simulation, but relying on the simulation weather file to size equipment seems risky. Everything may turn out ok in these cases because the temperature is less in October than in the summer, but I'm not to a point where I'd trust it yet.
Thanks,
Todd
Todd,
If you put in any data at all in the DD screens and run eQUEST it will
do the DD sizing off that information. If you delete the data on those
screens, however, and let the model run using the TMY data you should
get output that looks more like what you want. The TMY data extremes are
frequently higher than the DD input from ASHRAE and do include all the
solar info. Try it out and see what you think.
Carol