Manual 2100-359
Page 14
PRESSURE SERVICE PORTS
High and low pressure service ports are installed on all
units so that the system operating pressures can be
observed. A pressure table can be found later in the
manual covering all models. It is imperative to match the
correct pressure table to the unit by model number.
Low Pressure Switch, Bypass, and Lockout
Sequence
If the low pressure switch opens for more than 120
seconds, the compressor contactor will de-energize and
go into a soft lockout. Regardless the state of the low
pressure switch, the contactor will reenergize after the
delay on make time delay has expired. If the low
pressure switch remains open, or opens again for longer
than 120 seconds the unit will go into manual lockout
condition and the alarm relay circuit will energize.
Recycling the wall thermostat resets the manual lockout.
Alarm Relay Output
Alarm terminal is output connection for applications
where alarm relay is employed. This terminal is powered
whenever compressor is locked out due to HPC or LPC
sequences as described.
NOTE: Both high and low pressure switch controls are
inherently automatic reset devices. The high
pressure switch and low pressure switch cut out
and cut in settings are fixed by specific air
conditioner or heat pump unit model. The
lockout features, both soft and manual, are a
function of the Compressor Control Module.
PHASE MONITOR
All units with three phase scroll compressors are
equipped with a 3 phase line monitor to prevent
compressor damage due to phase reversal.
The phase monitor in this unit is equipped with two
LEDs. If the Y signal is present at the phase monitor and
phases are correct the green LED will light.
If phases are reversed, the red fault LED will be lit and
compressor operation is inhibited.
If a fault condition occurs, reverse two of the supply
leads to the unit. Do not reverse any of the unit factory
wires as damage may occur.
High Pressure Switch and Lockout Sequence
If the high pressure switch opens, the compressor
contactor will de-energize immediately. The lockout
timer will go into a soft lockout and stay in soft lockout
until the high pressure switch closes and the delay on
break time has expired. If the high pressure switch
opens again in this same operating cycle the unit will
go into manual lockout condition and the alarm relay
circuit will energize. Recycling the wall thermostat
resets the manual lockout.
ADJUSTMENTS
Adjustable Delay on Make and Delay on Break
Timer
The potentiometer is used to select Delay on Break time
from 30 seconds to 5 minutes. Delay on Make (DOM)
timing on power-up and after power interruptions is equal
to 2 minutes plus 10% of Delay on Break (DOB) setting:
0.5 minute (30 seconds)
DOB = 123 second DOM
1.0 minute (60 seconds)
DOB = 126 second DOM
2.0 minute (120 seconds) DOB = 132 second DOM
3.0 minute (180 seconds) DOB = 138 second DOM
4.0 minute (240 seconds) DOB = 144 second DOM
5.0 minute (300 seconds) DOB = 150 second DOM
During routine operation of the unit with no power
interruptions the compressor will operate on demand with
no delay.
Typical Settings for Dual Unit Installation:
Unit No. 1: DOB set at 2 minutes, and DOM is 132
seconds
Unit No. 2: DOB set at 4 minutes, and DOM is 144
seconds
