Step 3. Installing Grommet and Tubing
Note: Grommet should be mounted no more than 30 inches from the
pressure switch in order to allow the tubing to reach from the switch
to the duct.
First, drill a 1/4 inch to 5/16 inch diameter hole in the duct wall.
Carefully insert the grommet into the hole. (Drilling a metal duct
may produce burrs. Be careful not to be cut or pricked by the burrs
or the duct.) Next, force one end of the tubing over the nipple on the
switch. It may be necessary to use a lubricant in order to slide the
tubing over the entire nipple. Make a mark a distance of 1/2 inch
from the other end of the tubing. Slide this end of the tubing through
the center of the grommet up to the mark as illustrated. Do not use a
lubricant on this end of the tubing.
For some installations, it may be necessary to insert the grommet
and tubing, or duct “pressure tap”, in the upstream side (side the air
enters) of an elbow. Applications which may require that the tap be
located upstream of an elbow include installations with an RVF fan
mounted at the end of a long straight duct run (15’ or more) or regions
in higher elevations.
Horizontal Mounting
Switch Above Framing
Switch Below Framing
Switch Above Framing
Switch Below Framing
Angled Mounting
Vertical Mounting
Switch Parallel to Framing
Correct Switch Positioning - Diaphragm Positioned Vertically
Incorrect Switch Positioning
Horizontal Framing
Angled Framing
Pressure Switch Diaphragm Positioning
Step 2. Mount Switch
Note: Switch diaphragm must be mounted vertically
for optimum sensitivity. Refer to illustrations below.
When mounting the switch to a stud, joist, rafter, etc.,
in order to prevent the tubing from being crimped,
locate the nipple so that it clears the edge of the beam.
(Refer to illustration at left.) Using the wood screws
provided, secure the switch to the beam. When
mounting the switch to a wall, mount the 1/2” spacers
provided between the switch mounting bracket and
the wall to prevent the tube from being crimped. When
mounting the switch to drywall, concrete, etc., it is
recommended that the anchors provided be used to
securely hold the screws.
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