CFMs from Load Calc Program
CFMs from Load Calc Program
(OP)
I'm hoping someone can direct me to the right answer. I've checked the users manual and there are no other ME's in the office to ask. I am using Trane Trace 700 and the outputs for airflow cfm's per room are always some odd number 93, 243, 432, etc. Is there a way for the program to round to the nearest 10, like 90 or 250 cfm since it is unlikely that the cfms will get balanced to 93 cfm? If not, how do I account for this, do I have to go back into every room tab and over-ride the program with the rounded number? With a large building, I would think the rounding could add up significantly (in the 100's of cfms) which would eventually affect the coil loads???





RE: CFMs from Load Calc Program
Your room load isn't changing, your temperature set points aren't changing and the only other component is outdoor air load. I guess there could be a minuscule load from extra fan heat.
As far as keeping track of it, I've printed off the system components selection page and wrote down my rounded numbers next to the rooms on there. We use a 3rd party duct design program that keeps track of our totals for us so I haven't had to manually add them recently but I could.
RE: CFMs from Load Calc Program
RE: CFMs from Load Calc Program
RE: CFMs from Load Calc Program
swoosh172: If you look at that equation, your mixed air DT required across the coil will decrease by the same proportion that your return CFM increases, or visa versa.
RE: CFMs from Load Calc Program
I suggest rounding up for >= 5 and down for <= 4.
You've got enough safety factor in your inputs that it won't matter, and nobody can balance air to a high degree of accuracy.
You won't have a big effect on total airflow that way.
Just my experience!
Good on ya,
Goober Dave
RE: CFMs from Load Calc Program