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hinge brackets.
3. Close panel as describe above.
BALANCING (TF-C, TF-CW AND TF-HC)
THERMA-FUSER
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 maxi-
ADJUSTING TEMPERATURE
mum air flow by fully opening them, the system is really a con-
stant 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.
Room temperature set points are adjusted by screwing
1. Prepare system for balancing. (Make necessary checks for
the thermostats in or out – in for cooler or out for warmer.
diversity, fan capacities, fan rotation, miminum outside air
Determine the set point by aligning the white indicator with the
requirements, duct leaks and static pressure controller design
setting. Set outside air control damper for minimum air and
°F or °C numbers on the temperature scale. (See Fig. 4)
return air control damper for maximum air.)
2. Open Therma-Fuser diffusers.
a. Open appearance panel.
b. Unhook tension spring from bracket adjacent to cooling
thermostat. See Fig. 2.
c. If perimeter blades do not immediately drop to open posi-
tion, turn the control plate slightly until they open.
d. Close appearance panel.
Note: If the Therma-Fuser diffuser is equipped with a R-Ring
(Ceiling plenum relief ring) do not disconnect the spring.
Use temporary balancing stops made of wood supplied with
the diffuser to hold the blades open the proper distance for
balancing. Thickness of the stop will depend on the size of
the R-Ring used.
Recommended Adjustments for Various Conditions
3. Start fans, adjust system for 100% air flow and make system
checks. (Measure static pressure across filters and coils and at
Cooling
sensor for static pressure controller. Measure supply, return
and branch duct air flow.)
Mode
4. Place a direct reading diffuser balancing hood over the face of
STR-C
each Therma-Fuser diffuser and adjust damper at duct takeoff
to obtain maximum design air volume.
STR-HC
5. Return Therma-Fuser diffusers to operating condition.
a. Open appearance panel.
b. Attach tension spring to bracket (removed in step 2b).
c. Close appearance panel.
Fig. 3 Measuring blade opening
Foam
Heating
Mode
ST-HC
Blade
Too
Noisy
ST-C
ST-HC
The thermostats may be slightly harder to screw in or out when warm because the shaft is extended putting more pressure on the
thermostat. If you are unable to turn the thermostat in this situation, cool the thermostat by holding an ice cube to the large end.
The shaft will then contract and the thermostat will turn easily for adjustment.
For proper operation make sure that the extension shaft on the cooling thermostat is in the actuator arm dimple. Check by sighting
through the control plate viewport. (See Fig. 4) If the shaft is not in the dimple, cool the thermostat by holding ice to the large end
until the shafts retracts and move the shaft into the dimple.
Fig. 2 Remove spring to drop
blades open for balancing
Remove spring to drop blades open
ACH
SF
open
Too Cold
closed
open
Too Warm
closed
open
Too Cold
closed
Housing
open
Too Warm
Small Steel Rule
closed
Any
Any
2. Adjust for proper air volume with the balancing damper at the
duct takeoff. Each blade on the diffuser can also be separately
adjusted. Recommended discharge velocity is 1200 fpm –
6m/sec.
ADJUSTING TEMPERATURE
Room temperature set points are adjusted by screwing the ther-
mostats in or out – in for cooler or out for warmer. Determine the
set point by aligning the white indicator with the °F or °C num-
bers on the temperature scale. (See Fig. 4)
FIG. 4 ROOM TEMPERATURE SET POINT ADJUSTMENT
Fig. 4 Room temperature set point adjustment
Temperature
set point
indicator
(white)
Screw
RECOMMENDED ADJUSTMENTS FOR
VARIOUS CONDITIONS
Room
Blade
Temp.
Position
Adjust cooling for higher room temperature set point.
Cooling
Too
Open
Mode
Cold
(Turn cooling thumbwheel out.)
Closed
Therma-Fuser diffuser is correct.
TF-C
Too
Open
Check if cooling is still required, and if not, turn cooling unit off.
TF-CW
Warm
TF-HC
Therma-Fuser diffuser is correct.
Closed
Check for lack of air or for too warm air temperature.
Heating
Too
Open
Mode
Cold
Adjust cooling for lower room temperature set point.
Closed
(Turn cooling thumbwheel in.)
TF-HC
Too
Open
Therma-Fuser diffuser is correct.
Warm
Check for lack of air or too low air temperature.
Closed
Adjust heating for higher room temperature set point.
Too
Any
Any
(Turn heating thumbwheel out.)
Noisy
Adjust heating for lower room temperature set point.
TF-C
TF-CW
(Turn heating thumbwheel in.)
TF-HC
TF-D
Therma-Fuser diffuser is correct.
Check if heating is still required, and if not, turn it off.
Reduce static pressure. Recommended static pressure is .05 to .25
wg / 10 to 62 Pa at the inlet of the diffuser. If lower noise level does
not result from lower static pressure, check for and correct noise
generating restrictions in the duct up stream such as large pressure
drops over dampers, heaters, etc.
acutherm.com | THERMA-FUSER - Manual
Continued on next page
Control Plate
Cooling
Thermostat
Shaft
Recommended
CFM
Action
Adjust cooling for higher room temperature set point.
(Screw cooling thermostat out.)
Therma-Fuser diffuser is correct. Check if cooling is
still required, and if not, turn cooling unit off.
Therma-Fuser diffuser is correct. Check for lack of
air or for too warm air temperature.
Adjust cooling thermostat for lower room tempera-
ture set point. (Screw cooling thermostat in.)
Therma-Fuser diffuser is correct. Check for lack of
air or too low air temperature.
Adjust heating thermostat for higher room tempera-
ture set point. (Screw heating thermostat out.)
Adjust heating thermostat for lower room tempera-
ture set point. (Screw heating thermostat in.)
Therma-Fuser diffuser is correct. Check if heating is
still required, and if not, turn it off.
Reduce static pressure. Recommended static pres-
sure is .05 to .25 wg / 10 to 60 Pa at the inlet of the
diffuser. If lower noise level does not result from
lower static pressure, check for and correct noise
generating restrictions in the duct up stream such as
large pressure drops over dampers, heaters, etc.
View Port
Actuator
Arm
5
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