Additional Function - McQuay MDS Series Service Manual

4.6.3 Additional Function

Unit setting may be modified by clicking Modify Outdoor Unit Parameter under Circuit Monitor screen. It is
advisable not to change any data unless under the instruction from the factory side. The default value set had
been decided after numerous testing conducted by R&D and should be suitable for most condition.
A new window will prompt out when the user click on the Modify Outdoor Unit Parameter button in circuit
monitor page.
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 Defrost curve A, B point: It is used to define defrost area. For the defrost curve A point, the outdoor ambient
is set at 6° C. User is only allowed to change the suction temperature. The allowable range is from -2° C to -
15° C (Default value is -6° C).
 Defrost curve B point: The outdoor ambient is set at -15° C. User is only allowed to change the suction
temperature. The allowable range is from -30° C to -15° C (Default value is -24° C).
Note: If the value is smaller, the defrost area (shaded area I) will become smaller. This means that it is harder for
the system to enter the defrost cycle. After the system had enter the defrost cycle, the system will terminate the
defrost cycle faster.
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TH12 (°C) TH12 (°C)
(Suction) (Suction) -5 -5
-10 -10
-15 -15
-20 -20
B B
(-15,-24) (-15,-24)
-25 -25
-30 -30
-30 -30 -20 -20 -10 -10
Defrost Area Definition
A A
(6,-6) (6,-6)
Ⅰ Ⅰ
Defrost Area Defrost Area
TH8 (°C) TH8 (°C)
(Outdoor (Outdoor
Ambient) Ambient)
0 0 10 10 20 20
Service Manual SM-MDS_(ii)