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RT-SVX26K-EN
39
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.
To configure the proper potentiometer setpoints, connect
a multi-meter across the customer connection header (J7)
to the pins listed in
Table 16
below.
Figure 30.
Supply duct static pressure control
Figure 31.
VHR relay output
Table 15. Variable air volume mode operation
System Mode
Fan “Auto”
Fan “On”
Heat
DWU Active
DWU Off
DWU
2
Off
4
DWU
2
VAV Heating
4
Cool
VAV Cooling
1
VAV Cooling
1
Auto
DWU Active
DWU Off
DWU or
Cooling
1,2,3,4
VAV Cooling
1
DWU or
Cooling
1,2,3,4
VAV Cooling or
Heating
1
Off
Off
4
Off
4
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”.
Table 16. VAV setpoints
Supply Air Cooling
Setpoint (J7-3,4)
Resistance (Ohms)
DC volts
Deg F
240
0.97
50.37
280
1.09
52.30
320
1.21
54.24
360
1.32
56.09
410
1.45
58.18
450
1.55
59.80
Supply Air Pressure
Setpoint (J7-1,2)
Resistance (Ohms)
DC volts
“WC
100
0.45
0.30
350
1.30
0.98
540
1.75
1.49
730
2.11
2.00
>900
>2.38
2.5
Note:
To reduce the risk of coil freezing, it is not recommended to set the
supply air temperature setpoint below 50°F.
