subject: Installing A Duct Fan Will Lower Your Heating And Air Conditioning Bills [print this page] What's a channel fanWhat's a channel fan. It's a fan that's placed in the ductwork in your house to move air from one part of the house to another. Why did we add a channel fan within the ductwork in our home? It's usually because we have got a 2nd floor that includes an office, a loo and what we call the craft room. Our air conditioner unit just couldn't get sufficient air to the upstairs. In the summer months, it was always too hot and in the winter months it was always too cold.
The new HVAC system we had installed in our home last year was meant to be sufficiently big to heat and chill the complete house. The issue turned out that when the house was built, the primary contractor made some obvious mistakes.
We had channels that didn't go anywhere and / or weren't sized properly for the air flow needed. When the new air conditioner was put in, that was all fixed apart from the channel going to the second floor.
We weighed our options and decided to put in a duct fan and here is how I installed it.
I cut open the supply channel before it went into a supply distribution box. The distribution box supplied our upstairs registers. Our channel was twelve inches, so inserting a 12 in. fan wasn't a gigantic deal.
I then cut into the flex channel and pulled the Mylar and fiberglass material back.
I checked for the air flow direction arrow on the side of the fan to make certain I didn't have the fan facing the incorrect direction. Then I inserted the it.
The duct fan itself is just a hard galvanized metal tube with the fan mounted in it and two wires hanging out through a plastic grommet. I mounted a standard metal electrical box to the side of the fan housing that will allow me to connect all wiring in a protected enclosure. I really hate to see wires loose and just connected together. Also, the National Electrical Code requires it.
The next step is to reattach the supply duct to the fan. Once again slide the Mylar liner over the outside of the fan housing and tape it using Foil Sealant tape, mastic tape or butyl tape. All these tapes are a metal faced tape with a soft foam lining to seal the tape to the duct. It is really sticky stuff and it works great! Make sure you seal everything as you do not want any air leaks.
Then cover the entire assembly with more duct insulation to keep all air passing through the ducts and not leaking out. If any air leaks out, you can have condensation on the outside of the fan housing. This water can drip down and ruin your ceiling. I use foil tape with a fiberglass reinforced lining. I also use a foil tape for sealing joints and seams against moisture and vapor on foil jacket insulation.
Never use the grey material tape as it is not rated for this kind of use.
After the electric work is finished, the last remaining piece of insulation will be sealed round the fan.
As a temporary measure to see if everything worked, I wired the fan motor to an extension cord and plugged it in. Immediately, there was cool air in the office area. Within the hour, the temperature was the same on both floors.
Now, to make it permanent, I installed a 4x4 electric box. It was supplied with a vehicle / manual override switch and a variable speed motor control.
An air pressure switch was installed in the riser duct to automatically turn the fan on or off when the air conditioning unit turns on and off downstairs. The objective is to have fully automatic action with minimal electrical usage.
The total cost to install the duct fan and the controls were less than $200.
by: Alf Rainer
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