This project is continued from Part 1.
Having removed the old bathroom ceiling vent fan, I can now see into the space between the joists for the 1st and 2nd floors to get a look at the ductwork and wiring.
Bathroom Exhaust Fan Electrical Wiring
Since I don’t like working in the dark, I twisted wire nuts on the ends of the black (hot) and white (neutral) NM-B 14/2 electrical wiring to protect myself against electrical shock. Give the wire nuts a tug to verify they’re on securely and won’t fall off! I then turned on the power at the circuit breaker panel.
I pushed the bathroom ceiling fan wiring out of the way and looked into the space between the first and second floors. The 2nd floor is supported by 2 x 10 inch wood joists spaced on 16 inch centers. Comparing the old fan and new Panasonic WhisperCeiling™ FV-11VQ5 wiring hookup, the NM-B 14/2 electrical cable won’t be long enough to reach the junction box on the far side of the Panasonic bathroom fan unless I remove the two wire staples in the red boxes and reposition the electrical cable to the floor joist on the left. I pulled out the cable staples with a pair of pliers being careful not to damage the insulation. It was awkward working through the small hole in the drywall ceiling while standing on a step ladder with just one arm reaching through, but doable.
Bathroom Ceiling Vent Fan Ductwork
Looking the other way between the floor joists, there is an ~8 feet long section of 3 inch galvanized duct pipe connected to 3 inch flexible duct. I didn’t like the fact that the galvanized duct pipe was sitting on the hot and cold copper water pipes because can transmit vent fan vibration and noise.
I moved the 3 inch galvanized duct pipe to the left and zoomed in with the camera to get a better look at the 3 inch flexible ductwork. The 3 inch flex duct is suspended from the plywood subfloor with two nylon hanger straps. I pushed my tape measure along the drywall ceiling to the far wall and found the total length of the rigid and flexible duct to be about 17 feet.
It appears the flexible duct is routed into the garage on the other side of that far wall.
Interior Soffit: Concealed Ductwork
Inside the garage there is an L-shaped interior soffit that was built to conceal the bathroom ceiling fan ductwork. Checking the floor plan and ceiling ductwork, the interior soffit is positioned in the right place for this purpose.
The old 3 inch bathroom ceiling fan vent is located above the garage door in a position aligned with the interior soffit:
An inspection hole will be cut on the interior soffit because the old 3 inch vent duct will be replaced with 4 inch duct as required by the Panasonic WhisperCeiling FV-11VQ5. I located the edge of the soffit framing stud with my Zircon MultiScanner i520 stud finder and electrical scanner. Don’t want to get shocked by accidentally sawing into a live wire hidden behind the drywall! In the next photo, I’ve located edge of the framing stud. I scanned to the left to locate the next stud and while scanning for live electrical wires.
I cut a small inspection port on the drywall of the interior soffit with my RotoZip spiral saw to get a look at where the ductwork enters the soffit from the master bathroom.
Success! The 3 inch flexible duct enters the soffit from the space above the 1st floor ceiling from the master bathroom.
After verifying there were no obstructions, wiring or plumbing inside the soffit, I marked a 14 inch by 15 inch box for a drywall access panel on the interior soffit with a spirit level. The access panel will be large enough to enable me to work inside the soffit to replace the old 3 inch vent duct with new 4 inch duct.
The dimensions of the drywall access panel as marked on the interior soffit in the garage:
Drywall access panel hole cut on the side of the interior soffit. It appears the drywall contractor was lazy and left scraps of drywall inside the soffit.
Looking inside the interior soffit, the 3 inch flexible vent duct runs to the exterior wall above the garage door. This is an example of the architect not taking into account ventilation requirements. The bathroom vent fan is located just 8 feet from the closest exterior wall, because the floor joists run parallel to the bathroom wall the bath fan vent duct had to be run about 25 feet in an ‘L’ shaped route through the garage to get outside. Long duct runs, elbows and other turns increase the ductwork air friction losses thereby reducing the bathroom vent fan efficiency, causing the fan to work harder and move less air.
I sealed the edges of the drywall access panel hole with painters tape to keep the dust from rubbing off on my arms and hands.
This project is continued in Part 3.
Thanks for reading,
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