4.11 - Air Cooled Condensing Pressure Control
Head pressure differential value and head pressure differential timer can be adjusted in the Service menu.
Decreasing these values will increase fan cycling. This differential value and timer can be reduced since the unit is
fitted with an important number of fan stages, as to increase the condensing control accuracy. But in certain cases,
notably on units with few fan stages, at too small value can causes superheat hunting problems.
Varifan PID gains can be modified in the Service menu (not recommended). See section 4.2.3.
SCT control point without varifan
To avoid fan cycles and also to ensure a minimum expected SCT for oil pressure, SCT control shall be
adjusted based on OAT, the same for SCT differential as
55°C (13°F1)
OAT
20°c
0°c
68°F
32°F
+ 1 fan
- 1 fan
SCT cont
rol point
35°C (95°F)
40°C (104°F)
35°C (95°F)
SCT Diff
4.12.1 - Air Cooled Condensing Pressure Control - Fan staging with Aux board
Each DO shall support only one fan.
The first DO is not used if varifan is present to standardize the way
of making connection and to avoid wiring mistake
.
4.12.2 - Air Cooled Condensing Pressure Control - Fan staging
The combination described here below is for 4 fans configured maximum, each DO commands 1 fan
4
fan_1 + fan_2 + fan_3 + fan_4
on
on
on
on
4
3
fan_1 + fan_2+ fan_3
off
on
on
on
3
2
fan_1 + fan_2
off
off
on
on
2
1
fan_1
off
off
off
on
1
0
0
off
off
off
off
0
total
fans
fans controlled
DO_4
DO_3
DO_2
DO_1
stage
CARRIER SA
USER'S GUIDE FOR
30GX&HX PRO_DIALOG 4 V.2
ECG-UG-02-002
Rev: Original
Page: 46/98
©
C
ARRIER
S
.
A
NOT
TO
BE
DISCLOSED
TO
PERSONS
OUTSIDE
CARRIER
ORGANIZATION
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