Airwell /yaz218, Service Manual

Page: 51 / 84

CONTROL SYSTEM
11-12
SM YAZ218 1-A.2 GB
11.5.2.5 Speed Step Limitations
11.5.2.5.1 Step 1 and step 2
The compressor speed cannot go below
Step1Freq
or above
Step2Freq
during 3 continuous
minutes once after the compressor starts up when the ODU unit changes from STBY
11.5.2.5.2 Step 3 limit
The speed cannot go higher than
Step3Freq
unless it was operating for more than 1
continuous minute between
Step3Freq
– 5 and
Step3Freq
.
11.5.3 EEV Control
11.5.3.1 Operation Range
The EEV operation range is defined according to the operation mode as following
ODU Mode Normal operation IDU inactive Compressor off
SB
400
COOL
50
to
480
0
HEAT
50
to
480 50
to
120
400
11.5.3.2 Reaching target value rules
For all cases except at EEV initialization procedure, each EEV can move no more than
20
steps at a time.
When required the EEV’s move, one by one in sequence, until the target position is achieved
for every EEV.
The following diagram presents the EEV steps until the target position is set.
EEV1 EEV2 EEV3 EEV4 EEV1 EEV3 EEV4 EEV3 EEV4 EEV3 EEV3
EEV2
set EEV1
set EEV4
set EEV3
set
11.5.3.3 EEV homing
When compressor stops or unit is power on, the following is performed immediately:
-
All EEV’s are set to
400 .
-
They remain in this position for
80
Sec.
-
Then, close to 60 steps below 0 to ensure full closure, then proceed to normal operation
11.5.3.4 EEV Opening Determination
The target EEV value is the sum of open loop value (OL) and a result of the accumulative
correction values (CV).
∑
+ =
CVi OLi i
EEV EEV EEV
EEVi
is the EEV opening for each ‘i’ IDU.
11.5.3.5 EEV initial value determination
The EEV initial value (open loop) is determined according to the number of the active indoor
units, mode, and the capacity code of the unit.