53
TEMPMASTER
FORM TPM3-EG1 (518)
Single Zone Variable Air Volume (SZVAV) Mode
Units configured for SZVAV operation shall contain a supply fan VFD. The unit shall switch
between cooling mode, heating mode, and standby mode based on zone temperature.
In cooling mode, the supply fan speed shall be varied based on zone temperature. If the
zone temperature gets warmer, the supply fan speed shall increase. Conversely, if the
zone temperature gets cooler, the supply fan speed shall decrease. In heating mode, the
supply fan shall run at full speed. When the zone temperature is satisfied, the unit is nei-
ther in cooling mode nor heating mode, and the supply fan shall run at minimum speed.
Control of cooling and heating stages shall operate as described in the following section.
Unit Mode Determination (Hardwired or Communicated) –
The unit compares the
analog wired zone temperature or communicated zone temperature input to the occupied
zone cooling, occupied zone heating, unoccupied zone cooling, or unoccupied zone heat-
ing setpoints to determine the sub-mode of operation.
Figure 5 on page 53
shows what
the unit mode would be based on the difference between the zone temperature and the
zone temperature setpoints.
The only difference between hardwired and communicated is the method the unit control-
ler uses to determine the zone temperature. In the hardwired mode, the input is an analog
input to the control. In the communicated mode, the input is a serial input from a BAS.
THERE IS NO
DEMAND FOR
HEATING BASED ON
THE ACTIVE ZONE
TEMPERATURE
SETPOINT.
SUPPLY FAN AT
SZVAV MINIMUM
SETPOINT.
ZONE TEMPERATURE
IS MORE THAN 1.5°F
BELOW THE ZONE
TEMPERATURE
SETPOINT.
SUPPLY FAN AT 100%.
Z
O
N
E
S
E
T
P
O
I
N
T
C
O
O
L
I
N
G
L
O
W
OCCUPIED STANDBY
C
O
O
L
I
N
G
H
I
G
H
OCCUPIED COOLING LOW
OCCUPIED COOLING HIGH
OCCUPIED STANDBY
H
E
A
T
I
N
G
L
O
W
H
E
A
T
I
N
G
H
I
G
H
OCCUPIED HEATING LOW
OCCUPIED HEATING HIGH
Single Zone Variable Air Volume (SZVAV)
THERE IS NO
DEMAND FOR
COOLING BASED ON
THE ACTIVE ZONE
TEMPERATURE
SETPOINT.
SUPPLY FAN AT
SZVAV MINIMUM
SETPOINT.
ZONE TEMPERATURE IS
BETWEEN 0.5°F AND 1.5°F
ABOVE THE ZONE
TEMPERATURE SETPOINT.
SUPPLY FAN AT SZVAV
MINIMUM SETPOINT.
ZONE TEMPERATURE IS
MORE THAN 1.5°F ABOVE
THE ZONE
TEMPERATURE SETPOINT.
SUPPLY FAN SPEED
STARTS TO INCREASE.
SUPPLY FAN AT 100%
WHEN THE ZONE TEM-
PERATURE IS MORE THAN
2.5°F ABOVE THE ZONE
TEMPERATURE SETPOINT.
NOTES:
1. WHENEVER THE UNIT ENTERS AN ACTIVE COOLING OR HEATING MODE, THE UNIT CONTROLLER WILL UTILIZE AS MANY OR AS FEW STAGES OF COOLING OR HEATING THAT IT
NEEDS TO ACHIEVE AND MAINTAIN THE ACTIVE SUPPLY AIR TEMPERATURE (SAT) SETPOINT.
2. UNOCCUPIED SEQUENCE WILL BE THE SAME AS ABOVE EXCEPT THE ZONE TEMPERATURE SETPOINTS USED WILL BE THE UNOCCUPIED SETPOINTS’ VALUES.
3. UNIT MODES WILL STAGE DOWN WHEN THE ZONE TEMPERATURE IS 0.5°F UNDER THE SETPOINTS FOR COOLING AND 0.5°F OVER THE SETPOINTS FOR HEATING.
ZONE TEMPERATURE
IS BETWEEN 0.5°F
AND 1.5°F BELOW
THE ZONE
TEMPERATURE
SETPOINT.
SUPPLY FAN AT 100%.
LD19888
FIGURE 5 -
OPERATIONAL MODE: SINGLE ZONE VAV (SZVAV)