I haven’t given up on concealed duct option
When last we visited our intrepid fool, he had just about given up on the potential installation of a concealed duct unit for his Seattle home.
The task at hand is finding a unit to serve the first floor which consists primarily of an open plan Living, Dining, Kitchen, two bedrooms and bath. The basement furnace that used to serve the house is gone. Heating loads for the first floor rooms are 6862 LV/DN/KT, 1852 in BR1, 2111 in BR 2.
A 9RLFCD would do nicely for the load — the question comes back to duct and static. Based on a few found tools and the five part duct design article from Energy Vanguard, I’ve come up with what I think (operative word) might be a reasonable size and layout. One run however, extends 22 ft and most folks don’t think the low static concealed duct can handle the distance.
The layout image attached, includes what I believe are reasonable calculations. They start with a available static pressure of .36. I reduced that by about .10 to address filters and grills to start at .26.
The attached illustration shows the general layout (These runs are under and between the joists in the basement and leading to floor/lower wall vents in the upstairs area. There’s a first floor image to show the room layout.
I applied 30′ per 90 degree bend as part of the effective length calculations. The Friction Rate reductions per 100 ft were drawn from the Super Cool calculator app in the Apple store as well as from the calculations used in the HVAC Calc Residential software I downloaded. I’ve assumed 300 CFM which is the mid point on the 9rlfcd flow rate.
I know this is a lot to ask — but can anyone take a look at this and comment if I’m way off on these numbers — It seems to me that the 9rlfcd is a viable unit taking into consideration the static pressure.
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