Start Up
38 RT-SVX25M-EN
temperature is outside the deadband. As long as the
supply air temperature is within the setpoint deadband,
the system is considered to be satisfied and no staging up
or down will occur.
Supply Duct Static Pressure Control
The supply duct static pressure is measured by a
transducer with a 0.25 to 2.125 Vdc proportional output
which corresponds to an adjustable supply duct static
pressure of 0.3" w.c. to 2.5" w.c. respectively with a
deadband adjustment range from 0.2" w.c. to 1.0" w.c. The
setpoint is adjustable on the RTAM Static Pressure
Setpoint potentiometer or through ICS.
Example:
Supply Duct Static Setpoint = 2.0" w.c.
(RTAM) deadband = 0.2" w.c. (RTAM)
Duct Static Control Range = 1.9" w.c. to 2.1" w.c.
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 Tabl e 12 below.
Figure 30. Supply duct static pressure control
Figure 31. VHR relay output
Table 11. 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 12. VAV setpoints
Resistance
(Ohms) DC volts
Supply Air Cooling Setpoint (J7-
3,4)
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
Resistance
(Ohms) DC volts
Supply Air Pressure Setpoint (J7-
1,2)
“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.
To Next Page
Loading...
