RE: Is Manual J worth it?
I have been learning more and more about “proper” system design because the way i was taught was almost all rule of thumb stuff. I do mostly service and haven’t really done any full system designs. I recognize some short comings in some of the things i was shown and started looking into things like manual j and how to properly size a system if/when i need to do that.
The main point i am wondering about is for your average or even above average single family home, how much larger or smaller can you determine is needed from all the load calculations in manual j versus a simple equation or 1 ton of a/c per 500 square feet. If i oversize a unit by half a ton is that really going to make a noticable difference?
Im asking this in hopes that i learn something, not so i can argue that the way i learned is better.
I know the humidity and short cycling stuff.
I guess what i’d like to know is if anyone has gone from a more simple/old school way of sizing units (volume of conditioned space and general “tightness”) to full manual j load calculations and seen a big difference. Im not denying that it would be good to have a very detailed and accurate load calculation, but someone has to pay for it.