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Figure 30. Supply duct static pressure control
VHR Relay Output
For standalone VAV unit operation, the VHR output should
be wired to drive VAV boxes to maximum position during
all heating modes and unoccupied periods. The VHR
contacts are shown in the de-energized position and will
switch (energize) during the above mentioned operating
modes.
Figure 31. VHR relay output
RT-SVX26K-EN
Table 15. Variable air volume mode operation
System Mode
DWU Active
Heat
DWU Off
Cool
DWU Active
Auto
DWU Off
Off
Notes:
1. If Cooling is selected the supply fan will run continuously. If VAV
Heating is activated the supply fan will run continuously.
2. If Daytime Warmup is Activated, the supply fan will run
continuously.
3. Auto changeover between Cooling and Daytime
Warmup depends upon the DWU initiate setpoint.
4. The fan will be Off any time the system selection switch
is "Off".
To configure the proper potentiometer setpoints, connect
a multi-meter across the customer connection header (J7)
to the pins listed in
Table 16
Table 16. VAV setpoints
Resistance (Ohms)
DC volts
240
280
320
360
410
450
Resistance (Ohms)
DC volts
100
350
540
730
>900
>2.38
Note: To reduce the risk of coil freezing, it is not recommended to set the
supply air temperature setpoint below 50°F.
Start Up
Fan "Auto"
Fan "On"
2
2
DWU
DWU
4
Off
VAV Heating
1
VAV Cooling
VAV Cooling
DWU or
DWU or
1,2,3,4
Cooling
1,2,3,4
Cooling
VAV Cooling or
1
VAV Cooling
1
Heating
4
4
Off
Off
below.
Supply Air Cooling
Setpoint (J7-3,4)
Deg F
0.97
50.37
1.09
52.30
1.21
54.24
1.32
56.09
1.45
58.18
1.55
59.80
Supply Air Pressure
Setpoint (J7-1,2)
"WC
0.45
0.30
1.30
0.98
1.75
1.49
2.11
2.00
2.5
4
1
39
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