Airwell /yaz218, Service Manual

Page: 54 / 84

CONTROL SYSTEM
SM YAZ218 1-A.2 GB 11-15
11.5.10 ODU Protections
There are 3 ODU protections:
•
Compressor overheating
•
Heat sink overheating
•
System over power
Operation logic of all protections is the same. The controlled input (CTT, HST, or PWR) is
controlled by changing the protection level using the fuzzy logic algorithm according the input
level and the change rate.
There are two sets of POWER values, the selection of the values are set according to the state
of the Power-Shed dry contact input.
Power-Shed input open
Æ
Power1
Power-Shed input sort
Æ
Power2
The following table summarizes the basic levels of each protection.
Protection
level
Comp Overheat
(CTT)
Heat Sink
(HST)
Power1 Power2
Stop compressor
105 84 2800 2100
Down 2
100 80 2650 1988
Down 1
95 77 2500 1875
Stop rise
90 74 2350 1763
Normal
85 71 2350 1763
11.5.10.1 Total Protection Level Definition
The total protection level is defined by the higher level of protection received.
11.5.11 Deicing
11.5.11.1 Deicing Starting Conditions
Deicing operation will start when either one of the following conditions exist:
Case 1: OCT < OAT –
DST
AND TLD >
DI
Case 2: OCT < OAT – 12 AND TLD > 30 minutes.
Case 3: OCT is Invalid AND TLD >
DI
Case 4: Unit is just switched to STBY AND OCT < OAT –
DST
Case 5: NLOAD = 0 AND OCT < OAT -
DST
Case 6: OAT is invalid AND OCT<
DST
AND TLD >
DI
AND Compressor ON Time >
CTMR
minutes
OCT – Outdoor Coil Temperature
OAT – Outdoor Air Temperature
TLD – Time from Last Deicing
DI – Deicing Interval (Time Interval between Two Deicing)
DST – Deicing static threshold (Temperature)
Deicing interval time when compressor is first started in heat mode, is 10 minutes if OCT < -2,
and is 40 minutes in other cases.
Deicing interval time is changed (increased/ decreased in 10 minutes steps) as a function of
deicing time. If deicing time is shorter then former deicing time, the deicing interval time will be
increased. If deicing time is longer then former deicing time, the deicing interval time will be
decreased.