120
RT-SVX072A-EN
Table 53. Minimum starting temperatures for air-
cooled units
Unit
Size
Minimum Starting Ambient
Low Ambient
Standard
(a)
with HGBP without HGBP
20 & 40 55° 10° 0°
25 & 30 50° 10° 0°
50, 55
35° 10° 0°
60 30° 10° 0°
70-130 45° 10° 0°
Note: Min. starting ambients in °F and is based on unit operating
at min. step of unloading and 5 mph wind across condenser.
(a)
With or without HGBP
Standard Ambient Condenser Fans
Standard ambient units stage condenser fans down to
a minimum of one fan per circuit. All standard ambient
units ship with the Symbio™ controller set to allow
mechanical cooling down to 50°F outdoor temperature.
This setting is adjustable. Below table lists the
minimum recommended mechanical cooling setting
for standard ambient units by application and unit type.
Table 54. Minimum outside air temperature
Standard Unit Minimum
Outside Air Temperature for
Mechanical Cooling
Std &
High Cap
units
eFlex™™ units
20, 60,
70, 75
ton
25, 30,
40, 50,
55 ton
Economizer - A/C Applications
45°F 45°F 50°F
No Economizer - 80/67F design
return air 45°F 45°F 55°F
No Economizer - 90/78F design
return air 50°F 50°F 70°F
Low Ambient Condenser Fans
When a unit is ordered with the low ambient option (i.
e., Digit 19 is a “1” in the model number), it can affect
the selection of condenser fan motors. Please see the
table below and “Compressor Blink Codes,” p. 115 to
see which fan motors will be variable speed.
Low Ambient Variable Speed
Condenser Fans
Ton-
nage
Efficiency
Tier
Circuit 1 Circuit 2
20
Std. & High
2M6 -
eFlex All -
25
Std. 2M6 -
High & eFlex
All -
Low Ambient Variable Speed
Condenser Fans
Ton-
nage
Efficiency
Tier
Circuit 1 Circuit 2
30
Std. & High
2M6 -
eFlex All -
40
Std. 2M6 2M9
High & eFlex
All All
50
Std. 2M6 2M9
High & eFlex
All All
55
Std. 2M6 2M9
High & eFlex
All All
60
Std. & High
2M6 2M9
eFlex All All
70
Std. & High
2M6 2M9
eFlex All All
75
Std. & High
2M6 2M9
eFlex All All
90
Any
2M6 2M9
105
Any
2M6 2M9
115
Any
2M6 2M9
130
Any
2M6 2M9
Electric, Steam and Hot Water
Start-Up
(Variable Air Volume Systems)
1. Ensure that the “System” selection switch at the
remote panel is in the Off position.
2. Close the disconnect switch or circuit protector
switch that provides the supply power to the unit
terminal block (1TB1) or the unit-mounted
disconnect switch (1S14).
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