RT-SVD03L-EN
151
Low Ambient Mechanical Cooling Operation (3 to 25
Ton Units)
Evaporator Defrost Control
(EDC) Function
The Evaporator Defrost Control (EDC) function
provides low ambient cooling, standard, down to 0º F.
At this temperature, equipment can provide
approximately 60% of the mechanical cooling capacity.
During low ambient operation compressor run time is
counted and accumulated by the RTRM.
Low ambient operation is defined as 55º F for single
compressor units, and 40º F for dual compressor units.
Dual condenser fan units provide condenser cycling.
N
No
otte
e:: If the outside air sensor fails, the EDC logic is
disabled and the #2 condenser fan will run
continuously.
Compressor
OFF
ON (10 min. accumulated compressor run time)
OFF
ON
Indoor Fan
OFF
ON (Continues to run during 3 min. defrost time)
Minutes
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
When accumulated compressor run time reaches
approximately 10 minutes, an evaporator defrost cycle
is initiated. An evaporator defrost cycle lasts for 3
minutes; this matches the compressor 3 minutes
minimum OFF time.
When an evaporator defrost cycle occurs, the
compressors are turned off and the indoor fan motor
continues to run. After completing an evaporator
defrost cycle, the unit returns to normal operation, and
the compressor run time counter is reset to zero.
N
No
otte
e:: Economizer operation is not affected by an
evaporator defrost cycle.
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