36
RT-SVX51H-EN
Table 17. Enthalpy operation with DCV (CO
2
sensor) - 2 speed fan
DCV
OA Good to
economize?
Y1-I Y2-I FAN SPD Y1-O Y2-O
Occupied Unoccupied
Below set
No
Off Off Low
0-v/Off 0-v/Off
VENTMIN L Closed
On Off Low
24-v/On 0-v/Off
VENTMIN L Closed
On On
High
24-v/On 24-v/On
VENTMIN H Closed
Yes
Off Off Low
0-v/Off 0-v/Off
VENTMIN L Closed
On Off Low
0-v/Off 0-v/Off
VENTMIN L to Full-Open Closed to Full-Open
On On
High
24-v/On 0-v/Off
(a)
VENTMIN H to Full-Open Closed to Full-Open
Above set
No
Off Off Low
0-v/Off 0-v/Off
VENTMIN L to VENTMAX Closed
On Off Low
24-v/On 0-v/Off
VENTMIN L to VENTMAX Closed
On On
High
24-v/On 24-v/On
VENTMIN H to VENTMAX Closed
Yes
Off Off Low
0-v/Off 0-v/Off
VENTMIN L to VENTMAX Closed
On Off Low
0-v/Off 0-v/Off
VENTMIN L to Full-Open Closed to Full-Open
On On
High
DELAY 24-v/On
(b)
0-v/Off
(a)
VENTMIN H to Full-Open Closed to Full-Open
(a)
With stage 3 delay (STG3 DLY) in Advanced setup menu can turn on 2nd stage of mechanical cooling Y2-O after the delay if the call for Y1-I and Y2-I have
not been satisfied.
(b)
With 2SP FAN DELAY (Advanced Setup Menu) when in the economizing mode there is a delay for the high speed fan to try to satisfy the call for second
stage cooling by turning on the fan to high and opening the OA damper 100% before the first stage mechanical cooling is enabled.
Economizer Set-Up
Adjusting the minimum position (MIN POS/VENTMAX
on the SETPOINTS menu) sets the required amount of
ventilation air.
Ambient temperature controls the economizing cycle
by sensing the outside air dry bulb temperature. Table
18, p. 36 lists the five selectable dry bulb values (ENTH
CURVE) on the SETPOINTS menu.
Table 18. Single enthalpy and dual enthalpy boundaries (parameters ES1 through ES5)
Enth.
Curve
Temp. dry-Bulb
(ºF)
Temp.
dewpoint (ºF)
Enthalpy (btu/
lb/ da)
Point P1 Point P2
Temp. ºF
Humid.% RH
Temp. ºF
Humid.% RH
ES1 80.0 60.0 28.0 80.0 36.8 66.3 80.1
ES2 75.0 57.0 26.0 75.0 39.6 63.3 80.0
ES3 70.0 54.0 24.0 70.0 42.3 59.7 81.4
ES4 65.0 51.0 22.0 65.0 44.8 55.7 84.2
ES5 60.0 48.0 20.0 60.0 46.9 51.3 88.5
HL 86.0 66.0 32.4 86.0 38.9 72.4 80.3
Note: For differential enthalpy there is a high limit boundary. The high limit boundary is ES1 when there are no stages of mechanical cooling
energized and HL when a compressor stage is energized.
NNoottee:: To disable the economizer to do functional
testing, use a 10 mm wrench to completely
unsecure the shaft coupling. After testing,
tighten shaft coupling securely onto damper
shaft using minimum 120 lb-in. (13.6 Nm) to
maximum 180 lb-in. (20.3 Nm) torque.
Drain Pan Condensate Overflow Switch
(Optional)
The Condensate Overflow Switch (COF) is utilized to
prevent water overflow from the drain pan. The float
switch is installed on the corner lip of the drain pan.
When the condensate level reaches the trip point, the
COF relay energizes and opens the 24 Vac control
circuit which disables the unit. Once the 24 Vac control
circuit is opened, a delay timer will prevent unit start-
up for three minutes.
Low Ambient Operation (Optional)
During low ambient operation, outside air temperature
below 50°F, the Low Ambient Controller will cycle the
outdoor fan motor "Off" and "On" based on discharge
pressure. The indoor fan motor (IDM) will continue to
operate and the outdoor fan will return to normal
operation once the ambient temperature is above 50°F.
10 Horsepower Motor Overload
10HP indoor fan motors are not internally protected.
For proper protection, ensure the adjustable dial on the
front of the overload (located in the control box) is set
to the nameplate FLA value of the indoor motor.
SSttaarrtt UUpp
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