Subzero SZ-7575 User manual
PACKAGE A/C CONTROLLER SZ-7575 :
No. of switches:
1. OFF - To switch off blower
2. FAN - To start the system in fan mode where only blower will be on.
3. COOL - To start the system in cool mode where act ally controller will work depending on
set point setting.
4. ALARM ACK- To m te the b zzer.
5. Up/Dn – These allows to adj st the set point to desired val e.
At power on, the controller will start in the last mode it was set in before being powered off. There
are 3 states in which the controller can be at power on.
State 1
Controller is in the OFF mode. In this state, all devices are OFF and the system is in Stand By
mode and controller will display the temperat re.
State 2
Controller is in FAN mode. In this state, only Blower will activate and controller will display the
temperat re.
State 3
Controller is in COOL mode. In t is state, system will start activating all devices as required.
To start the system, press the COOL key. Controller starts the BLOWER and COND FAN 1 & 2
enter time delay mode. COND FAN1 activates after 60 seconds and COND FAN2 after 90 seconds.
After COND FAN 1 activates, COMP 1 energises ten seconds later to avoid a s rge.
After COND FAN 2 activates, COMP 2 energises fifteen seconds later to avoid a s rge.
Once setpoint has been achieved, all devices except blower go off.
For example SP is 23, once this is achieved, all devices will go off. Then at 23(SP) + 1 = 24C, the
time delay starts and cycle contin es in a similar manner
To change the Set Point, press the p / dn key. The 7-segment LED will display the c rrent set
point and flash. Whilst the display is flashing, se the Up/Dn key to achieve the desired Set Point.
Once the req ired Set Point is achieved, the display will confirm that the new Set Point has been
saved into memory by displaying “--“ and will ret rn to normal mode.
If setpoint is not changed, controller will ret rn to normal condition after 15 seconds.
At power on, if in cool mode , always cond fan 1 & comp1 will come on thereafter both nits will
cycle amongst themselves .
Both the cooling nit (comp. + cond . fan) are switched off at Set Point.
As temperat re + differential are achieved, both nits will come on after a set time delay.
At power on, the controller will check for Blower O/L error. If the stat s is OK,. the controller will
activate the Blower.
After activating the blower, if the temperat re is eq al to or above Set Point + Differential, both fan
time delays will activate together.
System always checks for COND FAN and COMP O/L and HP/LP fa lts.
On power off , system saves the last mode, so that on power on it will come on in the same mode .
Incase of any fa lt, corresponding cooling nit (compr+ cond fan) will switch off. While other nit
contin es to work normally.
HP/LP fa lt has a man al reset . To reset the fa lt press cool b tton . It will restart that nit with
time delay.
Display will indicate corresponding fault.
For eg incase of COND FAN O/L error, display will show “OL” and COND FAN 1 red led will
blink .
Green led indicates active stat s ( blinks while in time delay and lights p for on condition)
Red led indicates inactive stat s (blinks for errors and light p for off condition)
LED Indication :
Red led on- off stat s
Red led blink- fa lt condition
Green led on- on stat s
Green led blink- delay stat s
Yellow led on- CCH on stat s
Fan led on –Fan mode active
Cool led on – Cool mode active
Off led on- System in Standby mode (Blower + cond fan+ comp =off)
D ring Fa lt condition display will also show fa lt msg.
For overload – “OL”
For hp/lp- “HP “ “LP”
For probe fail- “PP”
Also , fa lt led will blink.
C [11]
C [18]
NEUTRAL
PHASE
COMMON
C [10]
C [15] C [16] C [17]
C [13] C [14]
A / 250Vac
COND1
COND2
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