Student questions asked in live office hours about this problem
OH 33: HVAC: HVAC-23
Q: In HVAC-23, once I have the latent and sensible loads, why can't I find the coil CFM and bypass using a mixing problem — does this fail because I'm assuming 100% coil efficiency?
A: We might be arriving at the same conclusion from two different directions — let me re-read the problem and think through whether the approaches are truly different. The coil bypass factor is central to this problem, and if you're assuming 100% coil efficiency, that's a different physical assumption than what the problem intends.
OH 44: HVAC: HVAC-23
Q: For HVAC-23, what's the most accurate way to draw the SHR slope on the psychrometric chart using the protractor in the reference handbook?
A: On the psychrometric chart, the SHR protractor is in the upper-left corner — align a line from the pivot through your calculated SHR value, then draw a parallel process line from the room condition on the main chart. I'll walk through exactly how to do this step by step.
OH 49: HVAC: HVAC-23
Q: In HVAC-23, I got SHR = 0.73 correctly but my ADP reads as 46-47°F while yours is 44°F — where does the line diverge?
A: I don't actually demonstrate the SHR protractor drawing in the video — I do it in cartoon form — so I can't pinpoint exactly where your line diverges from mine. My standard answer on the protractor is to do your best with the line tool and accept a degree or two of uncertainty in the ADP read.