Price VKD Series User manual

v001 –Issue Date: 08/04/23
© 2023 Price Industries Limited. All rights reserved.
MANUAL – INSTALLATION + OPERATIONS
Small Square VAV Diffuser
with Blade Damper
VKD - Varitherm Series

priceindustries.com/vavdiffusers | VARITHERM SMALL SQUARE VAV DIFFUSER - Manual
VARITHERM SMALL SQUARE VAV DIFFUSER
VARITHERM SMALL SQUARE VAV DIFFUSER - Manual | priceindustries.com/vavdiffusers
TABLE OF CONTENTS
Installation Instructions.................................................. 1
System Balancing (VKD-HC, VKD-C) ............................ 3
Adjusting Miminum Flow & Temperature Setpoints........ 4
Blow Patterns (VKD-HC, VKD-C, VKD-D) ..................... 6
Maintenance & Controlling The System......................... 7
Trouble Shooting (VKD-HC, VKD-C).............................. 8
Ten Year Warranty....................................................... 10

1
priceindustries.com/vavdiffusers | VARITHERM SMALL SQUARE VAV DIFFUSER - Manual
VARITHERM SMALL SQUARE VAV DIFFUSER
INSTALLATION INSTRUCTIONS
Damaged Freight Claim Procedure
When the diffusers are received, inspect for damage which
may have occured during shipment. If damage is evident, it
should be noted on the carrier’s freight bill. A written request
for inspection by the carrier’s agent should be made at once.
Storage
Cartons should always be stacked on end. Do not stack
cartons flat on their sides. Excessive weight may cause
damage to the diffusers. Do not store at temperatures
exceeding 130°F/56°C.
Identification
The model designation is on the diffuser and on the carton.
Installation Precautions
FIG. 1 DIMENSIONS
When installing diffusers, make sure construction debris does not enter the diffuser or duct system. Because the model VKD-HC
controls room temperature by sensing the room air induced up the center of the room, care should be taken not to disturb room
air induction and entrainment. For example, location next to walls or dropped lights results in the reflection of primary air back at
the Varitherm Small Square VAV diffuser and should be avoided. A three-way blow Varitherm Small Square VAV diffuser should be
used in this instance if either the light or the Varitherm Small Square VAV diffuser cannot be relocated.
Installation Instructions
1. Inspect the carton for damage before opening. Notify carrier if external damage exists. Submit all claims for shipping damage
to the carrier.
2. Move diffusers (in cartons) to installation area. Note unit identification.
3. Remove cardboard box and other packaging. Discard packing material.
4. If other than 4 way blow pattern is factory installed, note the “AIRFLOW” markings on the top of the diffuser and locate those
sides in the proper direction.
5. Install in ceiling grid. Install T-bar support wire close to each corner of diffuser. Make sure that only wire suspended T-bars are
used to support diffuser weight. (Adaptor frames are available for other ceilings.)
6. Connect and secure the supply duct to the collar. Flexible duct should NOT be formed in a centerline radius of less than 1½
times the duct diameter (9in/230mm radius).
7. Do NOT reset the temperature set point on the VKD-HC model until the space is occupied. It is factory preset for average
conditions (74°F/23°C).
8. Balance the system. See System Balancing.
9. After the air conditioning system is started and after the space is occupied, where necessary adjust the temperature set point
on VKD-HC models to suit the occupant. See Adjusting Temperature.
Operating Instructions
Operating instructions for model VKD-HC are located on the back of the appearance panel.
DAMAGED FREIGHT CLAIM PROCEDURE
When the diffusers are received, inspect for damage which
may have occured during shipment. If damage is evident, it
should be noted on the carrier’s freight bill. A written request
for inspection by the carrier’s agent should be made at once.
STORAGE
Cartons should always be stacked on end. Do not stack
cartons flat on their sides. Excessive weight may cause
damage to the diffusers.
Do not store at temperatures exceeding 130°F/56°C.
IDENTIFICATION
The model designation is on the diffuser and on the carton.
INSTALLATION PRECAUTIONS
When installing diffusers, make sure construction debris
does not enter the diffuser or duct system.
Because the model TK-HC controls room temperature by
sensing the room air induced up the center of the room,
care should be taken not to disturb room air induction and
entrainment. For example, location next to walls or dropped
lights results in the reflection of primary air back at the
Therma-Fuser diffuser and should be avoided. A three-way
blow Therma-Fuser diffuser should be used in this instance
if either the light or the Therma-Fuser diffuser cannot be
relocated.
INSTALLATION INSTRUCTIONS
1. Inspect the carton for damage before opening. Notify
carrier if external damage exists. Submit all claims for
shipping damage to the carrier.
2. Move diffusers (in cartons) to installation area. Note unit
identification.
3. Remove cardboard box and other packaging. Discard
packing material.
TK-HC VAV cooling and VAV heating
TK-C VAV cooling only
TK-D Manually adjustable blades
TK-RA Return air
Models:
TABLE OF CONTENTS
Installation Instructions ......................................... 1
System Balancing .................................................. 2
Adjusting Miminum Flow ..................................... 2
Adjusting Temperature Setpoints ..................... 3
Blow Patterns ........................................................ 3
Maintenance .......................................................... 4
Controlling the System ......................................... 4
Troubleshooting .................................................... 5
Ten Year Warranty ............................................... 6
4. If other than 4 way blow pattern is factory installed, note
the “AIRFLOW” markings on the top of the diffuser and
locate those sides in the proper direction.
5. Install in ceiling grid. Install T-bar support wire close
to each corner of diffuser. Make sure that only wire
suspended T-bars are used to support diffuser weight.
(Adaptor frames are available for other ceilings.)
6. Connect and secure the supply duct to the collar.
Flexible duct should NOT be formed in a centerline
radius of less than 1½ times the duct diameter (9
in/230mm radius).
7. Do NOT reset the temperature set point on the TK-HC
model until the space is occupied. It is factory preset for
average conditions (74°F/23°C).
8. Balance the system. See System Balancing.
9. After the air conditioning system is started and after
the space is occupied, where necessary adjust the
temperature set point on TK-HC models to suit the
occupant. See Adjusting Temperature.
OPERATING INSTRUCTIONS
Operating instructions for model TK-HC are located on the
back of the appearance panel.
OPENING THE APPEARANCE PANEL
(TK-HC, TK-C, TK-D)
The appearance panel is attached with a latch clip 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 to the right
(clockwise) from the thermostats.
2. Using two hands, one on each side of the latch clip
bracket, place your fingers above the appearance
panel and firmly pull down to disengage the clip. The
appearance panel will rotate and hang down vertically
on the hinges.
To close the appearance panel:
1. Rotate the panel upward.
2. Latch the panel by pushing the clip into the small square
hole in the bracket.
Figure 1. Dimensions
12" Square/305mm
125/8" Square/320mm
515/16" OD
150mm
1
1
/
2
"
38mm
23/8"
60mm
200% of actual size
FORM 051.201 REV 1704
THERMA-FUSER™ SYSTEMS
SQUARE 1’ x 1’ / 300mm - THERMALLY POWERED VAV DIFFUSER
INSTALLATION & OPERATIONS MANUAL

2priceindustries.com/vavdiffusers | VARITHERM SMALL SQUARE VAV DIFFUSER - Manual
VARITHERM SMALL SQUARE VAV DIFFUSER
INSTALLATION INSTRUCTIONS
VARITHERM SMALL SQUARE VAV DIFFUSER - Manual | priceindustries.com/vavdiffusers
Opening the Appearance Panel
The appearance panel is attached with a latch clip on one side and hinges on the opposite side.
To open the appearance panel (on a Varitherm Small Square VAV diffuser installed in the ceiling):
1. Locate the side of the Varitherm Small Square VAV diffuser to the right (clockwise) from the thermostats.
2. Using two hands, one on each side of the latch clip bracket, place your fingers above the appearance panel and firmly pull
down to disengage the clip. The appearance panel will rotate and hang down vertically on the hinges.
To close the appearance panel:
1. Rotate the panel upward.
2. Latch the panel by pushing the clip into the small square hole in the bracket.
To remove the appearance panel:
1. Open appearance panel as described above.
2. Rotate the appearance panel away from the latch clipbracket 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 closearound the hinge brackets.
3. Close panel as described above.

3
priceindustries.com/vavdiffusers | VARITHERM SMALL SQUARE VAV DIFFUSER - Manual
VARITHERM SMALL SQUARE VAV DIFFUSER
VAV systems are balanced for design air volume at maximum air flow and systems using Varitherm Small Square VAV VAV diffusers
are no exception. When all the Varitherm Small Square VAV 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 Varitherm Small Square VAV diffuser.
1. Prepare the system for balancing. (Make necessarychecks
for diversity, fan capacities, fan rotation,miminum outside
air requirements, duct leaks andstatic pressure controller
design settings. Set outsideair control damper for mini-
mum air and return aircontrol damper for maximum air.)
2. Open Varitherm Small Square VAV diffusers.
a. Open appearance panel.
b. Using a flat blade screwdriver or coin, turn thedamper
opening cam clockwise until the damperblades are
fully open and the blade tips toucheach other.
See Fig. 3.
c. Close appearance panel.
3. Start fans, adjust system for 100% air flow and
makesystem checks. (Measure static pressure across
filtersand coils and at sensor for static pressure controller.
Measure supply, return and branch duct air flow.)
4. Place a direct reading diffuser balancing hood over theface
of each Varitherm Small Square VAV diffuser and adjust
damperat duct takeoff to obtain maximum design air
volume.If a velocity meter is used, measure discharge
velocityat the housing (See Fig. 3). Multiply the velocity in
fpmtimes Akof .12 ft2to get air flow in cfm.
5. Return Varitherm Small Square VAV diffusers to operating
condition.
a. Open appearance panel.
b. Turn damper opening cam to allow damper blades
to close.
c. Close appearance panel.
Balancing (VKD-D)
1. The damper blade opening is factory set at ¾inch/19mm
(See Fig. 4). Readjust where necessary byturning the
damper opening cam (See Fig. 2).
2. Place a direct reading diffuser balancing hood over theface
of each VKD-D diffuser and adjust damper at ducttakeoff
to obtain design air volume. If a velocity meteris used,
measure discharge velocity at the housing (See Fig. 3).
Multiply the velocity in fpm times Akof .12 ft2toget air flow
in cfm.
SYSTEM BALANCING (VKD-HC, VKD-C)
FIG. 2 TURN DAMPER OPENING CAM TO OPEN FOR BALANCING
FIG. 3 MEASURING DISCHARGE VELOCITY
FIG. 4 MEASURING DAMPER BLADE OPENING
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 described above.
SYSTEM BALANCING (TK-HC, TK-C)
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 the system for balancing. (Make necessary
checks for diversity, fan capacities, fan rotation,
miminum outside air requirements, duct leaks and
static pressure controller design settings. Set outside
air control damper for minimum air and return air
control damper for maximum air.)
2. Open Therma-Fuser diffusers.
a. Open appearance panel.
b. Using a flat blade screwdriver or coin, turn the
damper opening cam clockwise until the damper
blades are fully open and the blade tips touch
each other. See Fig. 2.
c. Close appearance panel.
Fig 2. Turn damper opening cam to open for balancing
Damper Opening Cam
3. Start fans, adjust system for 100% air flow and make
system checks. (Measure static pressure across filters
and coils and at sensor for static pressure controller.
Measure supply, return and branch duct air flow.)
4. Place a direct reading diffuser balancing hood over the
face of each Therma-Fuser diffuser and adjust damper
at duct takeoff to obtain maximum design air volume.
If a velocity meter is used, measure discharge velocity
at the housing (See Fig. 3). Multiply the velocity in fpm
times Akof .12 ft2to get air flow in cfm.
5. Return Therma-Fuser diffusers to operating condition.
a. Open appearance panel.
b. Turn damper opening cam to allow damper blades to close.
c. Close appearance panel.
Fig 3. Measuring Discharge Velocity
Diffusion
Damper
Housing
Probe
Appearance
Panel
Gauge
1250 to 
2300 fpm
Figure 7 @ 200%
Figure 3 @200%
BALANCING (TK-D)
1. The damper blade opening is factory set at 3/4
inch/19mm (See Fig. 4). Readjust where necessary by
turning the damper opening cam (See Fig. 2).
2. Place a direct reading diffuser balancing hood over the
face of each TK-D diffuser and adjust damper at duct
takeoff to obtain design air volume. If a velocity meter
is used, measure discharge velocity at the housing (See
Fig. 3). Multiply the velocity in fpm times Akof .12 ft2to
get air flow in cfm.
Foam
Housing
Blade
Small Steel Rule
Fig 4. Measuring damper blade opening
Fig 5. Percent Minimum Flow vs. Blade Opening
ADJUSTING MINIMUM FLOW (TK-HC, TK-C)
Minimum flow is adjusted by turning the damper opening
cam until the damper blades are open the correct amount.
Determine the correct blade opening for the required percent
minimum flow from the graph in Fig. 5. Measure the blade
opening as shown in Fig. 3 and adjust the damper opening cam.
PERCENT of AIR FLOW CAPACITY vs. BLADE OPENING
PERCENT AIR FLOW CAPACITY
100
80
60
40
20
0
0 .10 .20 .30 .40 .50 .60 .70 .80
(0) (2.5) (5.1) (7.6) (10.2) (12.7) (15.2) (17.8) (20.3)
BLADE OPENING — INCHES
(MM)
Page 2 of 6
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 described above.
SYSTEM BALANCING (TK-HC, TK-C)
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 the system for balancing. (Make necessary
checks for diversity, fan capacities, fan rotation,
miminum outside air requirements, duct leaks and
static pressure controller design settings. Set outside
air control damper for minimum air and return air
control damper for maximum air.)
2. Open Therma-Fuser diffusers.
a. Open appearance panel.
b. Using a flat blade screwdriver or coin, turn the
damper opening cam clockwise until the damper
blades are fully open and the blade tips touch
each other. See Fig. 2.
c. Close appearance panel.
Fig 2. Turn damper opening cam to open for balancing
Damper Opening Cam
3. Start fans, adjust system for 100% air flow and make
system checks. (Measure static pressure across filters
and coils and at sensor for static pressure controller.
Measure supply, return and branch duct air flow.)
4. Place a direct reading diffuser balancing hood over the
face of each Therma-Fuser diffuser and adjust damper
at duct takeoff to obtain maximum design air volume.
If a velocity meter is used, measure discharge velocity
at the housing (See Fig. 3). Multiply the velocity in fpm
times Akof .12 ft2to get air flow in cfm.
5. Return Therma-Fuser diffusers to operating condition.
a. Open appearance panel.
b. Turn damper opening cam to allow damper blades to close.
c. Close appearance panel.
Fig 3. Measuring Discharge Velocity
Diffusion
Damper
Housing
Probe
Appearance
Panel
Gauge
1250 to 
2300 fpm
Figure 7 @ 200%
Figure 3 @200%
BALANCING (TK-D)
1. The damper blade opening is factory set at 3/4
inch/19mm (See Fig. 4). Readjust where necessary by
turning the damper opening cam (See Fig. 2).
2. Place a direct reading diffuser balancing hood over the
face of each TK-D diffuser and adjust damper at duct
takeoff to obtain design air volume. If a velocity meter
is used, measure discharge velocity at the housing (See
Fig. 3). Multiply the velocity in fpm times Akof .12 ft2to
get air flow in cfm.
Foam
Housing
Blade
Small Steel Rule
Fig 4. Measuring damper blade opening
Fig 5. Percent Minimum Flow vs. Blade Opening
ADJUSTING MINIMUM FLOW (TK-HC, TK-C)
Minimum flow is adjusted by turning the damper opening
cam until the damper blades are open the correct amount.
Determine the correct blade opening for the required percent
minimum flow from the graph in Fig. 5. Measure the blade
opening as shown in Fig. 3 and adjust the damper opening cam.
PERCENT of AIR FLOW CAPACITY vs. BLADE OPENING
PERCENT AIR FLOW CAPACITY
100
80
60
40
20
0
0 .10 .20 .30 .40 .50 .60 .70 .80
(0) (2.5) (5.1) (7.6) (10.2) (12.7) (15.2) (17.8) (20.3)
BLADE OPENING — INCHES
(MM)
Page 2 of 6
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 described above.
SYSTEM BALANCING (TK-HC, TK-C)
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 the system for balancing. (Make necessary
checks for diversity, fan capacities, fan rotation,
miminum outside air requirements, duct leaks and
static pressure controller design settings. Set outside
air control damper for minimum air and return air
control damper for maximum air.)
2. Open Therma-Fuser diffusers.
a. Open appearance panel.
b. Using a flat blade screwdriver or coin, turn the
damper opening cam clockwise until the damper
blades are fully open and the blade tips touch
each other. See Fig. 2.
c. Close appearance panel.
Fig 2. Turn damper opening cam to open for balancing
Damper Opening Cam
3. Start fans, adjust system for 100% air flow and make
system checks. (Measure static pressure across filters
and coils and at sensor for static pressure controller.
Measure supply, return and branch duct air flow.)
4. Place a direct reading diffuser balancing hood over the
face of each Therma-Fuser diffuser and adjust damper
at duct takeoff to obtain maximum design air volume.
If a velocity meter is used, measure discharge velocity
at the housing (See Fig. 3). Multiply the velocity in fpm
times Akof .12 ft2to get air flow in cfm.
5. Return Therma-Fuser diffusers to operating condition.
a. Open appearance panel.
b. Turn damper opening cam to allow damper blades to close.
c. Close appearance panel.
Fig 3. Measuring Discharge Velocity
Diffusion
Damper
Housing
Probe
Appearance
Panel
Gauge
1250 to 
2300 fpm
Figure 7 @ 200%
Figure 3 @200%
BALANCING (TK-D)
1. The damper blade opening is factory set at 3/4
inch/19mm (See Fig. 4). Readjust where necessary by
turning the damper opening cam (See Fig. 2).
2. Place a direct reading diffuser balancing hood over the
face of each TK-D diffuser and adjust damper at duct
takeoff to obtain design air volume. If a velocity meter
is used, measure discharge velocity at the housing (See
Fig. 3). Multiply the velocity in fpm times Akof .12 ft2to
get air flow in cfm.
Foam
Housing
Blade
Small Steel Rule
Fig 4. Measuring damper blade opening
Fig 5. Percent Minimum Flow vs. Blade Opening
ADJUSTING MINIMUM FLOW (TK-HC, TK-C)
Minimum flow is adjusted by turning the damper opening
cam until the damper blades are open the correct amount.
Determine the correct blade opening for the required percent
minimum flow from the graph in Fig. 5. Measure the blade
opening as shown in Fig. 3 and adjust the damper opening cam.
PERCENT of AIR FLOW CAPACITY vs. BLADE OPENING
PERCENT AIR FLOW CAPACITY
100
80
60
40
20
0
0 .10 .20 .30 .40 .50 .60 .70 .80
(0) (2.5) (5.1) (7.6) (10.2) (12.7) (15.2) (17.8) (20.3)
BLADE OPENING — INCHES
(MM)
Page 2 of 6

4priceindustries.com/vavdiffusers | VARITHERM SMALL SQUARE VAV DIFFUSER - Manual
VARITHERM SMALL SQUARE VAV DIFFUSER
VARITHERM SMALL SQUARE VAV DIFFUSER - Manual | priceindustries.com/vavdiffusers
Adjusting Minimum Flow (VKD-HC, VKD-C)
Minimum flow is adjusted by turning the damper opening
cam until the damper blades are open the correct amount.
Determine the correct blade opening for the required percent
minimum flow from the graph in Fig. 5. Measure the blade
opening as shown in Fig. 3 and adjust the damper opening
cam.
Adjusting Temperature Setpoints
The VKD-HC Varitherm Small Square VAV diffuser is factory
set for 74° F/28°C for both heating and cooling. Because heat
loads in various rooms differ and individual occupants prefer
different temperatures, it is recommended that the thermostats
should not be adjusted until after a few days of operation.
Room temperature set points are adjusted by screwing
the thermostats in or out – in for cooler or out for warmer.
Determine the set point by aligning the white indicator with the
°F or °C numbers on the temperature scale (See Fig. 6).
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.
ADJUSTING MIMINUM FLOW & TEMPERATURE SETPOINTS
FIG. 5 PERCENT MINIMUM FLOW VS. BLADE OPENING
FIG. 6 ROOM TEMPERATURE SET POINT ADJUSTMENT
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 described above.
SYSTEM BALANCING (TK-HC, TK-C)
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 the system for balancing. (Make necessary
checks for diversity, fan capacities, fan rotation,
miminum outside air requirements, duct leaks and
static pressure controller design settings. Set outside
air control damper for minimum air and return air
control damper for maximum air.)
2. Open Therma-Fuser diffusers.
a. Open appearance panel.
b. Using a flat blade screwdriver or coin, turn the
damper opening cam clockwise until the damper
blades are fully open and the blade tips touch
each other. See Fig. 2.
c. Close appearance panel.
Fig 2. Turn damper opening cam to open for balancing
Damper Opening Cam
3. Start fans, adjust system for 100% air flow and make
system checks. (Measure static pressure across filters
and coils and at sensor for static pressure controller.
Measure supply, return and branch duct air flow.)
4. Place a direct reading diffuser balancing hood over the
face of each Therma-Fuser diffuser and adjust damper
at duct takeoff to obtain maximum design air volume.
If a velocity meter is used, measure discharge velocity
at the housing (See Fig. 3). Multiply the velocity in fpm
times Akof .12 ft2to get air flow in cfm.
5. Return Therma-Fuser diffusers to operating condition.
a. Open appearance panel.
b. Turn damper opening cam to allow damper blades to close.
c. Close appearance panel.
Fig 3. Measuring Discharge Velocity
Diffusion
Damper
Housing
Probe
Appearance
Panel
Gauge
1250 to 
2300 fpm
Figure 7 @ 200%
Figure 3 @200%
BALANCING (TK-D)
1. The damper blade opening is factory set at 3/4
inch/19mm (See Fig. 4). Readjust where necessary by
turning the damper opening cam (See Fig. 2).
2. Place a direct reading diffuser balancing hood over the
face of each TK-D diffuser and adjust damper at duct
takeoff to obtain design air volume. If a velocity meter
is used, measure discharge velocity at the housing (See
Fig. 3). Multiply the velocity in fpm times Akof .12 ft2to
get air flow in cfm.
Foam
Housing
Blade
Small Steel Rule
Fig 4. Measuring damper blade opening
Fig 5. Percent Minimum Flow vs. Blade Opening
ADJUSTING MINIMUM FLOW (TK-HC, TK-C)
Minimum flow is adjusted by turning the damper opening
cam until the damper blades are open the correct amount.
Determine the correct blade opening for the required percent
minimum flow from the graph in Fig. 5. Measure the blade
opening as shown in Fig. 3 and adjust the damper opening cam.
PERCENT of AIR FLOW CAPACITY vs. BLADE OPENING
PERCENT AIR FLOW CAPACITY
100
80
60
40
20
0
0 .10 .20 .30 .40 .50 .60 .70 .80
(0) (2.5) (5.1) (7.6) (10.2) (12.7) (15.2) (17.8) (20.3)
BLADE OPENING — INCHES
(MM)
Page 2 of 6
ADJUSTING TEMPERATURE
SETPOINTS (TK-HC, TK-C)
The TK-HC Therma-Fuser diffuser is factory set for
74° F/28°C for both heating and cooling. Because heat
loads in various rooms differ and individual occupants
prefer different temperatures, it is recommended that the
thermostats should not be adjusted until after a few days of
operation.
Room temperature set points are adjusted by screwing
the thermostats in or out – in for cooler or out for warmer.
Determine the set point by aligning the white indicator with
the °F or °C numbers on the temperature scale (See Fig. 6).
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.
BLOW PATTERNS (TK-HC, TK-C, TK-D)
A major selling feature of the TK-HC diffusers is the ability
to easily add or remove blow patterns in the field. This is
done by blocking the air off behind the blades on the
appropriate sides.
DO NOT:
— Disconnect the spokes.
— Tape, screw or otherwise lock the blade closed.
This unbalances the loads on the center bearings.
— Block the venturi nozzle.
DO block air flow behind the blades or between the
standoffs. (Standoffs are the supports between the
housing and the diffusion plate.) Ways to do this are:
1. Factory installed directional baffles. These are strips of
metal wrapped around the standoffs to block one, two
or three sides. These can be removed in the field after
first removing the diffusion plate assembly.
2. Field installed directional baffles. These are made of
1-1/8”/ 28.575mm diameter x 5-5/8”/143mm long
insulation (Armaflex) for 3/8”/ 9.525mm refrigeration
lines. Insert between the housing and the diffusion
plate/blade assembly and wedge between the standoffs
(See Fig. 7). Take care to clear the damper hinges so
that the damper operates freely.
The rule for blocking the appropriate side is: Always block
the side adjacent to the thermost. (See Fig. 8 for examples.)
When blocking for direction, reduce maximum air volume
for a given static pressure and throw in the performance
guide by:
Blow Patterns Reduction
3 way (D3) .80
2 way opposite (D2) .64
2 way corner (D2C) .59
1 way (D1) .45
Fig 7. Field installed foam baffle
Page 3 of 6
Fig 6. Room temperature set point adjustment
RECOMMENDED ADJUSTMENTS FOR
VARIOUS CONDITIONS
Thermostats
Read setpoints here
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.
Open
Closed
Open
Closed
Open
Closed
Open
Closed
Any
Too
Cold
Too
Warm
Too
Cold
Too
Warm
Any
Cooling
Mode
TK-HC
Heating
Mode
TK-HC
Too
Noisy
TK-HC
TK-D
Room
Temp.
Blade
Position
Recommended
Action THERMA-FUSER
DIFFUSER
Diffusion
Damper
Housing
Probe
Appearance
Panel
Gauge
1250 to 
2300 fpm
Figure 7 @ 200%
Figure 3 @200%

5
priceindustries.com/vavdiffusers | VARITHERM SMALL SQUARE VAV DIFFUSER - Manual
VARITHERM SMALL SQUARE VAV DIFFUSER
ADJUSTING MIMINUM FLOW & TEMPERATURE SETPOINTS
Recommended Adjustments for Various Conditions
Room Temp. Blade Position Recommended Action
Cooling
Mode
VKD-HC
Too Cold
open Adjust cooling for higher room temperature set point.
(Screw cooling thermostat out.)
closed Varitherm Small Square VAV diffuser is correct.
Check if cooling is still required,and if not,turn cooling unit off.
Too Warm
open Varitherm Small Square VAV diffuser is correct.
Check for lack of air or for too warm air temperature.
closed Adjust cooling thermostat for lower room temperature setpoint.
(Screw cooling thermostat in.)
Heating
Mode
VKD-HC
Too Cold
open Varitherm Small Square VAV diffuser is correct.
Check for lack of air or too low air temperature.
closed Adjust heating thermostat for higher room temperature setpoint.
(Screw heating thermostat out.)
Too Warm
open Adjust heating thermostat for lower room temperature setpoint.
(Screw heating thermostat in.)
closed Varitherm Small Square VAV diffuser is correct.
Check if heating is stillrequired,and if not,turn it off.
Too
Noisy
VKD-HC
VKD-D
Any Any
Reduce static pressure. Recommended static pressure 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 upstream such as
large pressure drops over dampers, heaters, etc.

6priceindustries.com/vavdiffusers | VARITHERM SMALL SQUARE VAV DIFFUSER - Manual
VARITHERM SMALL SQUARE VAV DIFFUSER
VARITHERM SMALL SQUARE VAV DIFFUSER - Manual | priceindustries.com/vavdiffusers
BLOW PATTERNS (VKD-HC, VKD-C, VKD-D)
A major selling feature of the VKD-HC diffusers is the ability to
easily add or remove blow patterns in the field. This is done by
blocking the air off behind the blades on the appropriate sides.
DO NOT:
• Disconnect the spokes.
• Tape, screw or otherwise lock the blade closed. This
unbalances the loads on the center bearings.
• Block the venturi nozzle.
DO block air flow behind the blades or between the standoffs.
(Standoffs are the supports between the housing and the
diffusion plate.) Ways to do this are:
1. Factory installed directional baffles. These are strips of
metal wrapped around the standoffs to block one, two or
three sides. These can be removed in the field after first
removing the diffusion plate assembly.
2. Field installed directional baffles. These are made of
1-1
/8"/ 28.575mm diameter x 5-5/8"/143mm longinsulation
(Armaflex) for 3/8"/ 9.525mm refrigerationlines. Insert
between the housing and the diffusionplate/blade
assembly and wedge between the standoffs (See Fig. 7).
Take care to clear the damper hinges sothat the damper
operates freely.
The rule for blocking the appropriate side is: Always block the
thermostat side. (See Fig. 7 for examples.)
NOTE: Some earlier VBD-C and VBD-CW models have one
induction slot by the thermostat instead of four venturi nozzles.
The rule for blocking the appropriate side for this version is:
Never block the thermostat side.
When blocking for direction, the air volume for a given
static pressure is reduced from max. air volume listed in the
performance guide by:
Blow Patterns
3 way (D3)
2 way opposite (D2)
2 way corner (D2C)
1 way (D1)
Blade Opening
0.80
0.64
0.59
0.45
ADJUSTING TEMPERATURE
SETPOINTS (TK-HC, TK-C)
The TK-HC Therma-Fuser diffuser is factory set for
74° F/28°C for both heating and cooling. Because heat
loads in various rooms differ and individual occupants
prefer different temperatures, it is recommended that the
thermostats should not be adjusted until after a few days of
operation.
Room temperature set points are adjusted by screwing
the thermostats in or out – in for cooler or out for warmer.
Determine the set point by aligning the white indicator with
the °F or °C numbers on the temperature scale (See Fig. 6).
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.
BLOW PATTERNS (TK-HC, TK-C, TK-D)
A major selling feature of the TK-HC diffusers is the ability
to easily add or remove blow patterns in the field. This is
done by blocking the air off behind the blades on the
appropriate sides.
DO NOT:
— Disconnect the spokes.
— Tape, screw or otherwise lock the blade closed.
This unbalances the loads on the center bearings.
— Block the venturi nozzle.
DO block air flow behind the blades or between the
standoffs. (Standoffs are the supports between the
housing and the diffusion plate.) Ways to do this are:
1. Factory installed directional baffles. These are strips of
metal wrapped around the standoffs to block one, two
or three sides. These can be removed in the field after
first removing the diffusion plate assembly.
2. Field installed directional baffles. These are made of
1-1/8”/ 28.575mm diameter x 5-5/8”/143mm long
insulation (Armaflex) for 3/8”/ 9.525mm refrigeration
lines. Insert between the housing and the diffusion
plate/blade assembly and wedge between the standoffs
(See Fig. 7). Take care to clear the damper hinges so
that the damper operates freely.
The rule for blocking the appropriate side is: Always block
the side adjacent to the thermost. (See Fig. 8 for examples.)
When blocking for direction, reduce maximum air volume
for a given static pressure and throw in the performance
guide by:
Blow Patterns Reduction
3 way (D3) .80
2 way opposite (D2) .64
2 way corner (D2C) .59
1 way (D1) .45
Fig 7. Field installed foam baffle
Page 3 of 6
Fig 6. Room temperature set point adjustment
RECOMMENDED ADJUSTMENTS FOR
VARIOUS CONDITIONS
Thermostats
Read setpoints here
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.
Open
Closed
Open
Closed
Open
Closed
Open
Closed
Any
Too
Cold
Too
Warm
Too
Cold
Too
Warm
Any
Cooling
Mode
TK-HC
Heating
Mode
TK-HC
Too
Noisy
TK-HC
TK-D
Room
Temp.
Blade
Position
Recommended
Action THERMA-FUSER
DIFFUSER
Diffusion
Damper
Housing
Probe
Appearance
Panel
Gauge
1250 to 
2300 fpm
Figure 7 @ 200%
Figure 3 @200%
FIG. 7 FIELD INSTALLED FOAM BAFFLE

7
priceindustries.com/vavdiffusers | VARITHERM SMALL SQUARE VAV DIFFUSER - Manual
VARITHERM SMALL SQUARE VAV DIFFUSER
MAINTENANCE & CONTROLLING THE SYSTEM
Maintenance
The moving parts of the VKD Varitherm Small Square VAV diffuser have no maintenance or lubrication requirements. We are often
asked to recommend periodic maintenance procedures and a spare parts stock. Recommended maintenance is to clean the
outer surfaces of the Varitherm Small Square VAV diffuser—nothing else. We do not recommend stocking any spare parts. Our
customers also confirm that stocking is unnecessary.
Controlling the System
References:
• System Design, p 3, VKD brochure, Form 051.101.
• Chapters 2.2, 3.1 and 3.2, pp 6, 7 and 8,
DesigningModular VAV Systems, Form 5.2.
• Air Handling and Fan Coil Units Subzoned with Varitherm
Small Square VAV VAV modules, Form 6.7.
• DX Equipment Zoned with Varitherm Small Square VAV
VAV Modules,Form 6.5.
Supply Air Temperature
The sources of cooling and heating are controlled from supply air temperature. As with all VAV systems, the goals are to achieve a
constant supply air temperature (may be reset to another constant supply air temperature) and to limit the supply air temperature.
Limits for supply air temperature should be between 50°F/10°C and 68°F/20°C when cooling and between 80°F/26.5°C and
120°F/49°C when heating. The heating temperature limit should be as low as possible. These objectives are best achieved by
modulating chilled water valves, hot water valves and other variable equipment from supply air temperature. On/off equipment
such as DX compressors and electric heat are cycled from supply air temperature. Use a discharge air sensor for the supply air
temperature signal.
Mode change between heating, recirculation and cooling is controlled from room temperature. Signals from one or more room
temperature sensors may be used for mode change. When using more than one sensor, either a “majority rules” or a “cooling
dominant” approach is recommended.
Static Air Pressure
As with all VAV systems, the fan must run continuously during occupied times. Goals of static pressure control are to provide
enough static pressure to obtain the required air volume especially at the diffuser farthest from the fan, to avoid diffuser noise by
limiting static pressure at both full flow and turndown and to provide pressure independence or consistent operation as the system
flow changes.
These objectives can be achieved with the usual methods of automatic static pressure control: bypass dampers, discharge
dampers, zone dampers, and fan control (variable speed drives, inlet dampers, etc.). Locate the static pressure sensor as far down
the duct as possible—at least 2/3 down the duct from the first takeoff.
FIG. 8 BLOW PATTERNS
Page 4 of 6
Fig 8. Blow patterns
TK-HC THERMA-FUSER diffuser
APPEARANCE PANEL REMOVED
MAINTENANCE
The moving parts of the TK Therma-Fuser diffuser have
no maintenance or lubrication requirements. We are often
asked to recommend periodic maintenance procedures and
a spare parts stock. Recommended maintenance is to clean
the outer surfaces of the Therma-Fuser diffuser—nothing
else. We do not recommend stocking any spare parts. Our
customers also confirm that stocking is unnecessary.
CONTROLLING THE SYSTEM
References:
•System Design, p 3, TK brochure, Form 051.101.
•Chapters 2.2, 3.1 and 3.2, pp 6, 7 and 8, Designing
Modular VAV Systems, Form 5.2.
•Air Handling and Fan Coil Units Subzoned with Therma-
Fuser VAV modules, Form 6.7.
•DX Equipment Zoned with Therma-Fuser VAV Modules,
Form 6.5.
SUPPLY AIR TEMPERATURE
The sources of cooling and heating are controlled from
supply air temperature. As with all VAV systems, the goals
are to achieve a constant supply air temperature (may
be reset to another constant supply air temperature) and
to limit the supply air temperature. Limits for supply air
temperature should be between 50°F/10°C and 68°F/20°C
when cooling and between 80°F/26.5°C and 120°F/49°C
when heating. The heating temperature limit should be
as low as possible. These objectives are best achieved by
modulating chilled water valves, hot water valves and other
variable equipment from supply air temperature. On/off
equipment such as DX compressors and electric heat are
cycled from supply air temperature. Use a discharge air
sensor for the supply air temperature signal.
Mode change between heating, recirculation and cooling
is controlled from room temperature. Signals from one
or more room temperature sensors may be used for
mode change. When using more than one sensor, either
a “majority rules” or a “cooling dominant” approach is
recommended.
STATIC PRESSURE
As with all VAV systems, the fan must run continuously
during occupied times. Goals of static pressure control are
to provide enough static pressure to obtain the required air
volume especially at the diffuser farthest from the fan, to
avoid diffuser noise by limiting static pressure at both full
flow and turndown and to provide pressure independence or
consistent operation as the system flow changes.
These objectives can be achieved with the usual methods
of automatic static pressure control: bypass dampers,
discharge dampers, zone dampers, and fan control (variable
speed drives, inlet dampers, etc.). Locate the static pressure
sensor as far down the duct as possible—at least 2/3 down
the duct from the first takeoff.
3-Way D3
2-Way Opposite D2
2-Way Corner D2C
1-Way D1
Page 4 of 6
Fig 8. Blow patterns
TK-HC THERMA-FUSER diffuser
APPEARANCE PANEL REMOVED
MAINTENANCE
The moving parts of the TK Therma-Fuser diffuser have
no maintenance or lubrication requirements. We are often
asked to recommend periodic maintenance procedures and
a spare parts stock. Recommended maintenance is to clean
the outer surfaces of the Therma-Fuser diffuser—nothing
else. We do not recommend stocking any spare parts. Our
customers also confirm that stocking is unnecessary.
CONTROLLING THE SYSTEM
References:
•System Design, p 3, TK brochure, Form 051.101.
•Chapters 2.2, 3.1 and 3.2, pp 6, 7 and 8, Designing
Modular VAV Systems, Form 5.2.
•Air Handling and Fan Coil Units Subzoned with Therma-
Fuser VAV modules, Form 6.7.
•DX Equipment Zoned with Therma-Fuser VAV Modules,
Form 6.5.
SUPPLY AIR TEMPERATURE
The sources of cooling and heating are controlled from
supply air temperature. As with all VAV systems, the goals
are to achieve a constant supply air temperature (may
be reset to another constant supply air temperature) and
to limit the supply air temperature. Limits for supply air
temperature should be between 50°F/10°C and 68°F/20°C
when cooling and between 80°F/26.5°C and 120°F/49°C
when heating. The heating temperature limit should be
as low as possible. These objectives are best achieved by
modulating chilled water valves, hot water valves and other
variable equipment from supply air temperature. On/off
equipment such as DX compressors and electric heat are
cycled from supply air temperature. Use a discharge air
sensor for the supply air temperature signal.
Mode change between heating, recirculation and cooling
is controlled from room temperature. Signals from one
or more room temperature sensors may be used for
mode change. When using more than one sensor, either
a “majority rules” or a “cooling dominant” approach is
recommended.
STATIC PRESSURE
As with all VAV systems, the fan must run continuously
during occupied times. Goals of static pressure control are
to provide enough static pressure to obtain the required air
volume especially at the diffuser farthest from the fan, to
avoid diffuser noise by limiting static pressure at both full
flow and turndown and to provide pressure independence or
consistent operation as the system flow changes.
These objectives can be achieved with the usual methods
of automatic static pressure control: bypass dampers,
discharge dampers, zone dampers, and fan control (variable
speed drives, inlet dampers, etc.). Locate the static pressure
sensor as far down the duct as possible—at least 2/3 down
the duct from the first takeoff.
3-Way D3
2-Way Opposite D2
2-Way Corner D2C
1-Way D1
Page 4 of 6
Fig 8. Blow patterns
TK-HC THERMA-FUSER diffuser
APPEARANCE PANEL REMOVED
MAINTENANCE
The moving parts of the TK Therma-Fuser diffuser have
no maintenance or lubrication requirements. We are often
asked to recommend periodic maintenance procedures and
a spare parts stock. Recommended maintenance is to clean
the outer surfaces of the Therma-Fuser diffuser—nothing
else. We do not recommend stocking any spare parts. Our
customers also confirm that stocking is unnecessary.
CONTROLLING THE SYSTEM
References:
•System Design, p 3, TK brochure, Form 051.101.
•Chapters 2.2, 3.1 and 3.2, pp 6, 7 and 8, Designing
Modular VAV Systems, Form 5.2.
•Air Handling and Fan Coil Units Subzoned with Therma-
Fuser VAV modules, Form 6.7.
•DX Equipment Zoned with Therma-Fuser VAV Modules,
Form 6.5.
SUPPLY AIR TEMPERATURE
The sources of cooling and heating are controlled from
supply air temperature. As with all VAV systems, the goals
are to achieve a constant supply air temperature (may
be reset to another constant supply air temperature) and
to limit the supply air temperature. Limits for supply air
temperature should be between 50°F/10°C and 68°F/20°C
when cooling and between 80°F/26.5°C and 120°F/49°C
when heating. The heating temperature limit should be
as low as possible. These objectives are best achieved by
modulating chilled water valves, hot water valves and other
variable equipment from supply air temperature. On/off
equipment such as DX compressors and electric heat are
cycled from supply air temperature. Use a discharge air
sensor for the supply air temperature signal.
Mode change between heating, recirculation and cooling
is controlled from room temperature. Signals from one
or more room temperature sensors may be used for
mode change. When using more than one sensor, either
a “majority rules” or a “cooling dominant” approach is
recommended.
STATIC PRESSURE
As with all VAV systems, the fan must run continuously
during occupied times. Goals of static pressure control are
to provide enough static pressure to obtain the required air
volume especially at the diffuser farthest from the fan, to
avoid diffuser noise by limiting static pressure at both full
flow and turndown and to provide pressure independence or
consistent operation as the system flow changes.
These objectives can be achieved with the usual methods
of automatic static pressure control: bypass dampers,
discharge dampers, zone dampers, and fan control (variable
speed drives, inlet dampers, etc.). Locate the static pressure
sensor as far down the duct as possible—at least 2/3 down
the duct from the first takeoff.
3-Way D3
2-Way Opposite D2
2-Way Corner D2C
1-Way D1
Page 4 of 6
Fig 8. Blow patterns
TK-HC THERMA-FUSER diffuser
APPEARANCE PANEL REMOVED
MAINTENANCE
The moving parts of the TK Therma-Fuser diffuser have
no maintenance or lubrication requirements. We are often
asked to recommend periodic maintenance procedures and
a spare parts stock. Recommended maintenance is to clean
the outer surfaces of the Therma-Fuser diffuser—nothing
else. We do not recommend stocking any spare parts. Our
customers also confirm that stocking is unnecessary.
CONTROLLING THE SYSTEM
References:
•System Design, p 3, TK brochure, Form 051.101.
•Chapters 2.2, 3.1 and 3.2, pp 6, 7 and 8, Designing
Modular VAV Systems, Form 5.2.
•Air Handling and Fan Coil Units Subzoned with Therma-
Fuser VAV modules, Form 6.7.
•DX Equipment Zoned with Therma-Fuser VAV Modules,
Form 6.5.
SUPPLY AIR TEMPERATURE
The sources of cooling and heating are controlled from
supply air temperature. As with all VAV systems, the goals
are to achieve a constant supply air temperature (may
be reset to another constant supply air temperature) and
to limit the supply air temperature. Limits for supply air
temperature should be between 50°F/10°C and 68°F/20°C
when cooling and between 80°F/26.5°C and 120°F/49°C
when heating. The heating temperature limit should be
as low as possible. These objectives are best achieved by
modulating chilled water valves, hot water valves and other
variable equipment from supply air temperature. On/off
equipment such as DX compressors and electric heat are
cycled from supply air temperature. Use a discharge air
sensor for the supply air temperature signal.
Mode change between heating, recirculation and cooling
is controlled from room temperature. Signals from one
or more room temperature sensors may be used for
mode change. When using more than one sensor, either
a “majority rules” or a “cooling dominant” approach is
recommended.
STATIC PRESSURE
As with all VAV systems, the fan must run continuously
during occupied times. Goals of static pressure control are
to provide enough static pressure to obtain the required air
volume especially at the diffuser farthest from the fan, to
avoid diffuser noise by limiting static pressure at both full
flow and turndown and to provide pressure independence or
consistent operation as the system flow changes.
These objectives can be achieved with the usual methods
of automatic static pressure control: bypass dampers,
discharge dampers, zone dampers, and fan control (variable
speed drives, inlet dampers, etc.). Locate the static pressure
sensor as far down the duct as possible—at least 2/3 down
the duct from the first takeoff.
3-Way D3
2-Way Opposite D2
2-Way Corner D2C
1-Way D1
3-WAY D3 2-WAY OPPOSITE D2 2-WAY CORNER D2C 1-WAY D1

8priceindustries.com/vavdiffusers | VARITHERM SMALL SQUARE VAV DIFFUSER - Manual
VARITHERM SMALL SQUARE VAV DIFFUSER
VARITHERM SMALL SQUARE VAV DIFFUSER - Manual | priceindustries.com/vavdiffusers
Trouble shooting Varitherm Small Square VAV diffusers requires looking at the system as a whole. Before examining the Varitherm
Small Square VAV diffuser for failure it is worth the time to be sure the system is functioning properly and that something has not
been overlooked.
System Check List
The system should be:
1. Delivering 50°- 68°F/10° - 20°C supply air when in
thecooling mode.
2. Delivering 80°-120°F/26.5° – 49°C supply air when inthe
heating mode.
3. Maintaining static pressure at the inlet to each Varitherm
Small Square VAV diffuser between .05"and .25"wg/12 Pa
and 62 Pa.
4. Maintaining continuous fan operation during occupied
hours.
Varitherm Small Square VAV Diffuser Check List
Once the above checks have been completed, examine and record the following (temperature may vary over time; several
measurements at different times may be required):
1. Room temperature 4 feet above the floor directly underthe
Varitherm Small Square VAV diffuser.
2. Supply air temperature at the Varitherm Small Square VAV
diffuser.
3. Static pressure at the inlet of the Varitherm Small Square
VAV diffuser.
4. Blade opening from the edge of the blade,
measuredperpendicular to the housing.
5. Thermostat slider position.
6. Cooling and heating setpoints.
7. Damper opening cam—positioned for blades fullyclosed,
partially open or fully open.
8. Is the Varitherm Small Square VAV diffuser located
within2ft/600mm of a vertical protrusion such as a wallor
dropped beam which could disturb induction airflow?
9. Is the Varitherm Small Square VAV diffuser located within
2ft / 600mm of a vertical protrusion such as a wall or
dropped beam which could disturb induction air flow?
POINT 4
POINT 5
TROUBLE SHOOTING (VKD-HC, VKD-C)
Page 5 of 6
TROUBLE SHOOTING (TK-HC, TK-C)
Trouble shooting Therma-Fuser diffusers requires looking at
the system as a whole. Before examining the Therma-Fuser
diffuser for failure it is worth the time to be sure the system
is functioning properly and that something has not been
overlooked. Before calling Acutherm, please complete the
data log for all Therma-Fuser diffusers to be evaluated.
SYSTEM CHECK LIST
The system should be:
1. Delivering 50°- 68°F/10° - 20°C supply air when in the
cooling mode.
2. Delivering 80°-120°F/26.5° – 49°C supply air when in
the heating mode.
3. Maintaining static pressure at the inlet to each Therma-
Fuser diffuser between .05” and .25”wg/12 Pa and 62 Pa.
4. Maintaining continuous fan operation during occupied
hours.
THERMA-FUSER DIFFUSER CHECK LIST
Once the above checks have been completed, examine
and record the following (temperature may vary over time;
several measurements at different times may be required):
1. Room temperature 4 feet above the floor directly under
the Therma-Fuser diffuser.
2. Supply air temperature at the Therma-Fuser diffuser.
3. Static pressure at the inlet of the Therma-Fuser diffuser.
Thermostats
Read setpoints here
Measure from induction housing
to edge of slider.
Cooling mode < 7/8 in / 22 mm
Heating mode > 1 in / 25 mm
TROUBLE SHOOTING DATA LOG
TimeDateLocation Set Points
Heating Cooling
Damper
Opening
Cam
Position
Room
Temp
S.A.
Temp
Duct
S.P.
Blade
Opening
T-stat
Slider
4. Blade opening from the edge of the blade, measured
perpendicular to the housing.
5. Thermostat slider position.
6. Cooling and heating setpoints.
7. Damper opening cam—positioned for blades fully
closed, partially open or fully open.
8. Is the Therma-Fuser diffuser located within
2ft/600mm of a vertical protrusion such as a wall
or dropped beam which could disturb induction air
flow?
Foam
Housing
Blade
Small Steel Rule
TK-HC THERMA-FUSER diffuser
APPEARANCE PANEL REMOVED
Page 5 of 6
TROUBLE SHOOTING (TK-HC, TK-C)
Trouble shooting Therma-Fuser diffusers requires looking at
the system as a whole. Before examining the Therma-Fuser
diffuser for failure it is worth the time to be sure the system
is functioning properly and that something has not been
overlooked. Before calling Acutherm, please complete the
data log for all Therma-Fuser diffusers to be evaluated.
SYSTEM CHECK LIST
The system should be:
1. Delivering 50°- 68°F/10° - 20°C supply air when in the
cooling mode.
2. Delivering 80°-120°F/26.5° – 49°C supply air when in
the heating mode.
3. Maintaining static pressure at the inlet to each Therma-
Fuser diffuser between .05” and .25”wg/12 Pa and 62 Pa.
4. Maintaining continuous fan operation during occupied
hours.
THERMA-FUSER DIFFUSER CHECK LIST
Once the above checks have been completed, examine
and record the following (temperature may vary over time;
several measurements at different times may be required):
1. Room temperature 4 feet above the floor directly under
the Therma-Fuser diffuser.
2. Supply air temperature at the Therma-Fuser diffuser.
3. Static pressure at the inlet of the Therma-Fuser diffuser.
Thermostats
Read setpoints here
Measure from induction housing
to edge of slider.
Cooling mode < 7/8 in / 22 mm
Heating mode > 1 in / 25 mm
TROUBLE SHOOTING DATA LOG
TimeDateLocation Set Points
Heating Cooling
Damper
Opening
Cam
Position
Room
Temp
S.A.
Temp
Duct
S.P.
Blade
Opening
T-stat
Slider
4. Blade opening from the edge of the blade, measured
perpendicular to the housing.
5. Thermostat slider position.
6. Cooling and heating setpoints.
7. Damper opening cam—positioned for blades fully
closed, partially open or fully open.
8. Is the Therma-Fuser diffuser located within
2ft/600mm of a vertical protrusion such as a wall
or dropped beam which could disturb induction air
flow?
Foam
Housing
Blade
Small Steel Rule
TK-HC THERMA-FUSER diffuser
APPEARANCE PANEL REMOVED
VKD-HC DIFFUSER APPEARANCE PANEL REMOVED

9
priceindustries.com/vavdiffusers | VARITHERM SMALL SQUARE VAV DIFFUSER - Manual
VARITHERM SMALL SQUARE VAV DIFFUSER
TROUBLE SHOOTING (VKD-HC, VKD-C)
Trouble Shooting Data Log
Location Date Time Room
Temp
S.A.
Temp
Duct
S.P.
Blade
Opening
T-stat
Slider
Set Points Room Thermostat
Position
Cooling Heating

priceindustries.com/vavdiffusers | VARITHERM SMALL SQUARE VAV DIFFUSER - Manual
10 priceindustries.com/vavdiffusers | VARITHERM SMALL SQUARE VAV DIFFUSER - Manual
VARITHERM SMALL SQUARE VAV DIFFUSER
VARITHERM SMALL SQUARE VAV DIFFUSER - Manual | priceindustries.com/vavdiffusers
Price Industries warrants that its Varitherm Small Square VAV diffusers, exclusive of any options and accessories (whether factory
or field installed) shall be free from defects in material or workmanship for a period of ten (10) years from the date of shipment
and agrees to repair or replace, at its option, any parts that fail during said ten (10) year period due to any such defects which
would not have occured had reasonable care been taken, provided that such parts have been inspected by Price and found
defective and provided the diffusers have been given normal and proper usage and all parts and controls remain unaltered. Price
makes NO WARRANTY OF MERCHANTABILITY OF PRODUCTS OR OF THEIR FITNESS FOR ANY PURPOSE OR ANY
OTHER EXPRESS OR IMPLIED WARRANTY WHICH EXTENDS BEYOND THE LIMITED WARRANTY ABOVE. PRICE’S
LIABILITY FOR ANY AND ALL LOSSES AND DAMAGES RESULTING FROM DEFECTS SHALL IN NO EVENT EXCEED
THE COST OF REPAIR OR REPLACEMENT OF PARTS FOUND DEFECTIVE UPON EXAMINATION BY PRICE. IN NO
EVENT SHALL PRICE BE LIABLE FOR INCIDENTAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR DAMAGES FOR
INJURY TO PERSONS OR PROPERTY. Price shall not be responsible for freight to or from its plant in connection with the
inspection, repair or replacement of parts under the terms of this limited warranty nor for cost of removal or installation.
TEN YEAR WARRANTY

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VARITHERM SMALL SQUARE VAV DIFFUSER
NOTES
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VARITHERM SMALL SQUARE VAV DIFFUSER
NOTES
VARITHERM SMALL SQUARE VAV DIFFUSER - Manual | priceindustries.com/vavdiffusers priceindustries.com/vavdiffusers | VARITHERM SMALL SQUARE VAV DIFFUSER - Manual

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VARITHERM SMALL SQUARE VAV DIFFUSER
NOTES
priceindustries.com/vavdiffusers | VARITHERM SMALL SQUARE VAV DIFFUSER - Manual

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