IOMM ACZ1
ACZ 010A through 039A
25
Overview
The MicroTech II controller's state-of-the-art design will not only permit the unit to run more
efficiently but also simplifies troubleshooting if a system failure occurs. Every MicroTech II
controller is programmed and tested prior to shipment to contribute to a trouble-free start-up.
Operator-friendly
The MicroTech II controller menu structure is separated into three distinct categories, which provide
the operator or service technician with a full description of current unit status, control parameters, and
alarms. Security protection deters unauthorized changing of the setpoints and control parameters.
MicroTech II control continuously performs self-diagnostic checks, monitoring system temperatures,
pressures and protection devices, and will automatically shut down a compressor or the entire unit if a
fault occurs. The cause of the shutdown will be retained in memory and can be easily displayed in
plain English for operator review. The MicroTech II controller will also retain and display the time
the fault occurred. In addition to displaying alarm diagnostics, the MicroTech II controller also
provides the operator with a warning of limit (pre-alarm) conditions.
Staging
The two scroll compressors are staged on and off by contact closure of the field supplied remote two-
stage staging thermostat. Lead/lag is automatic and switched every ten starts.
General Description
NOTE: When the following descriptions refer to "evaporator pressure", the pressure is actually the
suction pressure within the condensing unit itself.
Compressor Motor Protection
ACZ 016 – 039:
The solid-state compressor motor protector module incorporates a 2-minute “time-
off” relay utilizing the bleed-down capacitor principle. Any time the protection system opens or
power to the module is interrupted, the 2-minute “time-off” delay is triggered and the module will not
reset for two minutes. Once the 2-minute period has passed the motor protector contacts M1 and M2
reset, provided the protection system is satisfied and power is applied to the module.
Note:
If the power circuit is broken once the 2-minute period is passed, the pilot circuit will
reset without delay when power is reapplied.
ACZ 010 - 013:
The model ACZ 010 and ACZ 013
compressors have internal line breakage with
automatic reset.
FanTrol Head Pressure Control
FanTrol is the standard method of head pressure control that automatically cycles the condenser fan
motors in response to condenser pressure. This function is controlled by the microprocessor,
maintains head pressure and allows the unit to run at low ambient air temperatures down to 35
°
F
(1.7
°
C). Fans are staged as follows:
Table 8, Fan Staging Pressures
Fan
Two-Fan Unit
Three-Fan Unit
Stage #1
On 150 psig, Off with unit
On 150 psig, Off with unit
Stage #2
On 290 psig, Off 170 psig
On 290 psig, Off 170 psig
Stage #3
On 310 psig, Off 180 psig
Note: Fan #1 is on with first compressor above 75
°
F (24
°
C).