What is a duct fan. It is a fan that is settled in the ductwork in your home to move air from one part of the house to another. Why did we add a duct fan inside the ductwork in our home? It is because we have a second floor that includes an office, a bathroom and what we call the craft room. Our air conditioner unit just could not get adequate air to the upstairs. While the summer months, it was always too hot and While the winter months it was always too cold.
The new Hvac law we had installed in our home last year was supposed to be large adequate to heat and cool the entire house. The qoute turned out that when the house was built, the first contractor made some glaring mistakes.
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We had ducts that did not go everywhere and/or were not sized correctly for the air flow required. When the new air conditioner was put in, that was all fixed except for the duct 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 provide duct before it went into a provide distribution box. The distribution box supplied our upstairs registers. Our duct was 12 inches, so inserting a 12 inch fan was not a big deal.
I then cut into the flex duct and pulled the Mylar and fiberglass material back.
I checked for the air flow direction arrow on the side of the fan to make sure I did not have the fan facing the wrong 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 straight through a plastic grommet. I mounted a suitable metal electrical box to the side of the fan housing that will allow me to associate all wiring in a protected enclosure. I well hate to see wires loose and just associated together. Also, the National Electrical Code requires it.
The next step is to reattach the provide duct to the fan. Once again slide the Mylar liner over the face 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 well sticky stuff and it works great! Make sure you seal all things as you do not want any air leaks.
Then cover the entire assembly with more duct insulation to keep all air passing straight through the ducts and not leaking out. If any air leaks out, you can have condensation on the face 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 gray cloth tape as it is not rated for this type of usage.
After the electrical work is completed, the last remaining piece of insulation will be sealed colse to the fan.
As a temporary quantum to see if all things 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 climatic characteristic was the same on both floors.
Now, to make it permanent, I installed a 4x4 electrical box. It was qualified with an auto/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 self-acting operation with minimal electrical usage.
The total cost to install the duct fan and the controls were less than 0.
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