Answer some air handler questions & bail out a homeowner??

This sub is probably getting killed with AC questions now that it's getting warm. Sorry... here's one more. Background is I have my AC duct work pretty much disassembled and removed. Our flex ducts weren't insulated properly so in winter time moisture was getting up into the ducts, condensing & freezing. It would then drip down & pool in the troughs or rain from the ceiling registers when it got warm. So I went up into the attic, removed the flex ducts, hung them to dry in the garage and wiped them out with bleach & water. (I took almost 2.5 gallons of water out of the ducts)

Wife says it's now time to put it all back together. We have a Rheem air handler for AC only and hydronic baseboard heat. I kept the air handler together, just removed the duct work. I also air sealed around the ceiling registers.

What I'm wondering is there are places where the duct work is really long --or the ducts could be shortened a bunch. For example, the bathroom register is about 8" from the air handler's supply plenum but the bathroom duct is about 10' long. Can I shorten that or does it need to be that long?

Prior owner had unknown company do the install. I know I'm not a professional --or I know enough to ask and not just F with stuff because air cooling & heat is a very technical and delicate thing I know very little about. But I also know prior owner hired some really terrible people to do much of the other work in the house and seeing the way they installed the AC registers, I'm not sure what was done out of laziness and what was done for a reason.

I understand that duct diameter is important but not sure how much duct length comes into play. I know it must because it's a big factor in sizing woodshop dust removal systems --but I have no idea about HVAC stuff. I do have some tools to measure & tune carburetors (so I can measure in. water, pressure, vacuum, etc.). Do I need to worry about the duct lengths or is it safe to shorten them? I'm trying to avoid troughs in the flex ducts...

Thanks.

submitted by /u/vmuser123
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