Warm Air/ a/c

GMcD

Blasting air around as a combined heating and cooling energy delivery system is a pain and tries to defy the laws of physics. Now, if you talk hydronic radiant - radiant heat exchange happens at the speed of light and in an omnidirectional manner, so you CAN combine radiant heating and cooling in one system AND be energy efficient about it, AND comply with the laws of physics.

KAG

Duct Work

About 10 years ago I went to a class to size warm-air systems. The class start off on sizing, but end up in a debate over proper installation. I asked a question that since properly installed duct work should be in the floor (feed) and ceiling (return) shouldn't you reverse the flow from summer to winter. Warm air rises cool air falls. The instructor said in a perfect world yes. This set off the debate and the question was never really anwsered. I believe the two systems (heating and cooling) should be completely independant to achieve total comfort year round. Am I wrong in this thought process? Would appreciate any responces.

joel_19

yup

You are not wrong they should be completly seperate.

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clammy

heating /cooling ducts

I mainly do heating and a/c res/comm but i do some furnace replacements but it has been many years since i have done new homes with combi furnace and coil systems ,i have always found that seperate supply and returns should be used in each room and using hi low stack heads in either 10 x6 or 12 x 6 work nicely ,returns on outide walls and supplies on inside walls that's if all things where equal but in real life they are not .Doing job this way cost more espically if your doing it all in sheetmetal with no flex and your going to externally wrap it there's alot of labor invoulved .It's hard to complete with the floor or single return guys there prices are way lower due to lack of materal and less time doing the job .There's always a wrong and a right way of doing things and it seem that what you always see is some where in the middle .Some say systems like i have described are over engeenered but i don,t agree it just that some have not been around long enough or have not seen enough to know any better i was very luckly early on in the field that i had worked in older custom homesbuilt in the late 50 and early 60 's where that's how all the hot air system where and these systems worked great most all of the duct work was sized properly and even with a new furnace and a/c coil these homes cooled excellent most did not need additinal returns thay had more then enough just change those older stamp return and supply grills and you where set.Back then all the duct duct was sheetmtal and your main trunk reduced after each take off try to find that these days every body does a extended pleum or just runs all the tin out in one smaller size and uses damper collors to adjust air flow .Now a days on a/c i do not even look at new work or deal with gc's i basically just do older homes retro fits ,overheads and some unicos it a much smaller market more suited for my expereines and my prices as compared to larger companies that do alot more volume .But don,t give up on your thoughts you are on the right track .System with seperate supplies and returns and properly sized duct work sized for the correctcfm and static and fpm for main and branch ducts always are always quiter and offer better comfort then the whistler systems that occur all the time .Keep up on your path be different and offer quiter system your custemers will love you .Peace and good luck clammy