Mike,
Thank you for your reply. The Lennox dealer installed the same size airhandler, but it has a variable speed motor. I was told that this also make a difference with regards to air flow.
We'll see what happens when they finish today with the duct work. I was told by the General Manager that they use a "ductalator"(spelling) to determine the amount of duct work. They told me that we have a 5 ton unit which requires 2000 cfm's.
Thanks,
Doug
Hey Doug,
The ductalator (in my opinion) is a fine tool in starting the calculations for duct work. Along with the ductalator, I thing some good old faction common sense, and experience is what makes a well balanced system. Like I said before, I’ve seen a lot of systems that have been installed by well known HVAC contractors here in Phoenix, and my faith of knowing what they really know what they are doing is diminished. The water column test, after and before work is done, (I think) tells almost the entire story of weather everything is working in harmony or not. I think it should be mandatory, for all systems to me tested after installation, or after improvements are made to an existing system. There is not a factory hook up, on the air handlers to perform this test so, I had to drill my own hole to do the test, (and that I also think is wrong).
Another test I think that should be performed is a leak test, to all new installations, and all improved systems. It would probably be mind boggling on how much power savings this would be state wide if these two tests were mandatory. Not only that, but if these two tests were mandatory, it would force the contractors to do a lot better job, (again in my opinion) then what they are doing now. I did I leak test in my friends house using smoke bombs, and it looked like his attic was on fire, with all of the duct work leaks that were up there.
Here is a chart, (from Carrier) that I found that is based on performance of using that Water Column tester. Notice that anything more then a 0.5 is off of the chart. On the unit that I just added that 14" air return to, her's was up to 0.80 and now is down around a 0.25, (and still has room for improvement at that 0.25).
Blower Performance Chart
Air Handler CFM @ ESP. – in. W. C.
Model Blower Speed
in W.C. .10 .20 .30 .40 .50
18 Low (Red) 754 716 674 626 569
High* (Black) 1020 958 886 800 689
24 Low (Red) 998 938 868 786 681
High* (Black) 1042 978 905 817 704
30 Low (Red) 1146 1091 1029 959 877
High* (Black) 1349 1289 1224 1150 1066
36 Low (Red) 1407 1341 1268 1186 1090
High* (Black) 1561 1481 1392 1290 1169
42 Low (Red) 1785 1705 1616 1516 1402
High* (Black) 1938 1846 1744 1629 1495
48 Low (Red) 1870 1789 1699 1599 1484
High* (Black) 1943 1858 1765 1660 1540
60 Low (Red) 2077 1986 1886 1774 1646
High* (Black) 2161 2066 1962 1845 1710
Good luck, for sure,
Mike