INSTRUCTIONS
Fig. 3. Open for Balancing
To open, push the lever to the right and
up. To close, pull lever down.
Balancing Lever
Minimum
Flow Dial
Minimum
Flow Scale
PERCENT FL
OW
10" INLET
3. Start fans, adjust system for 100% air flow and make sys-
tem checks. (Measure static pressure across filters and
coils and at sensor for static pressure controller. Measure
supply, return and branch duct air flow.)
4. Measure air flow from each Therma-Fuser diffuser and
adjust the damper at the duct takeoff to obtain maximum
design air flow. Air flow measurement may be with a direct
reading diffuser balancing hood or air velocity meter.
In
either case, measurements are made with all appear-
ance panels in place.
This is because the appearance
panel affects pressure drop through the diffuser. When a
velocity meter is used to measure the discharge velocity,
the velocity is measured at the top edge of the housing.
See
Fig. 4
.
Ak factors when the Therma-Fuser diffuser is fully open
are as follows:
Inlet Description
Ak Factor
6
0.13 ft
2
8
0.18 ft
2
10
0.24 ft
2
12
0.33 ft
2
5. Return Therma-Fuser diffusers to operating condition by
pushing the balancing lever down until it latches.
Fig. 4 Measuring Velocity
ADJUSTING MINIMUM FLOW
Turn dial until desired minimum flow on the scale intersects
with the lower metal piece. See
Fig. 5
.
Fig. 5 Adjusting Miminum Flow
OPENING THE APPEARANCE PANEL
The appearance panel is attached with two latch clips on one
side and hinges on the opposite side.
To open the appearance panel (on a Therma-Fuser diffuser
installed in the ceiling):
1. Locate the side of the Therma-Fuser diffuser with the ther-
mostat. Using two hands, one on each side of the channel,
place your fingers above the appearance panel and firmly
pull down to disengage the clips. The appearance panel
will rotate and hang down vertically on the hinges.
See
Fig. 2.
Fig. 2. Open Appearance Panel
To close the appearance panel:
1. Rotate the panel upward.
2. Latch the panel by pushing the clips into the small square
holes in the channel.
To remove the appearance panel:
1. Open appearance panel as described above.
2. Rotate the appearance panel away from the latch clip
bracket to force the hinge hooks open on the panel.
3. Slightly lift the panel to remove from the hinges.
To reattach the appearance panel:
1. Hang the appearance panel on the hinges.
2. Press the hinge hooks against the panel to close around
the hinge brackets.
3. Close panel as describe above.
SYSTEM BALANCING
VAV systems are balanced for design air volume at maximum
air flow and systems using Therma-Fuser VAV diffusers are
no exception.When all the Therma-Fuser diffusers are set for
maximum air flow by fully opening them, the system is really
a constant air volume system and is balanced as a constant
volume system. Balancing dampers are best located at the
takeoff before the runout to the Therma-Fuser diffuser.
1. Prepare system for balancing. (Make necessary checks for
diversity, fan capacities, fan rotation, miminum outside air
requirements, duct leaks and static pressure controller
design setting. Set outside air control damper for minimum
air and return air control damper for maximum air.)
2. Open Therma-Fuser diffusers. ST-C and ST-HC.
a. Locate the side of the ST diffuser with the thermostat
and the balancing lever.
b. Push the balancing lever to the right and up. See
Fig. 3
.
Page 2
Probe for
Velocity Meter
Appearance
Panel
Damper Disc
