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# CFM

kind of instructor. It will always serve the tech well if he knows how to do his calculations the old way. It also helps them to understand how the software works when they finally get to the place that I will let them use it.

• Member Posts: 37
CFM

If I had a house that was 800 squared ft. How much CFM would I need? Is there a section in the text that could help me with this.
• Member Posts: 1,380
CFM Requirement

The cfm requirement for a system (for either heating or cooling) is directly related to the heat gain/loss of the structure. The heat gain/loss for any structure is determined by a number of factors including construction materials used, fenestration types, structure orientation, insulation materials.

When you take your design class, you will be performing Manual J calculations which wil help you evaluate all the gorey details that go into answering your question.

The goos new is that you will be doing this in 2 short semesters!
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Bigb

Grasshopper!Listen very very carefully to the Master,you will learn something from the Professor,I did and do!!From a fellow Grasshopper!38 years and counting that is!
• Member Posts: 2,343
Hey Gene....+

I don't know if your program has the ability to actually move the orientation of the house, but I have R "J" and love it. I can move the house in any direction I wish. I think it would show the importance of proper sizing.

Mike T.
• Member Posts: 1,380
I Prefer...

In the classroom I prefer to NOT use software for heat gain/loss calculations. Instead, my guys do it all by hand. This way they learn the concepts involved and, in the event their computers crash, they can still get the job accomplished.

Once they learn the basics, then they can go ahead and use the software packages.

• Member Posts: 1,380
Thanks Timmie

The same holds true for ductwork.

Many sheet metal contractors use plasma cutters and computer software to layout their duct sections. You just tell the computer that you want an elbow of this or that size and the computer pays it out and cuts the pieces.

What happens when the computer crashes or your plasma cutter is on the fritz?

WHen my guys go into the duct shop its ALL BY HAND. They have to do all of the calculations and cutting.
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