Manual 2100-508A
Page
17 of 25
SEQUENCE OF OPERATION
COOLING
– Circuit R-Y makes at thermostat pulling
in compressor contactor, starting the compressor and
outdoor motor. The G (indoor motor) circuit is
automatically completed on any call for cooling
operation or can be energized by manual fan switch on
subbase for constant air circulation. On a call for
heating, circuit R-W1 make at the thermostat pulling in
heat contact for the strip heat and blower operation. On
a call for second stage heat, R-W2 makes bringing on
second heat contactor, if so equipped.
COMPRESSOR CONTROL MODULE
The compressor control module is standard on all
models covered by this manual. The compressor control
module is an anti-short cycle/lockout timer with high
and low pressure switch monitoring and alarm relay
output.
Adjustable Delay On Make And Break Timer
On initial power up or anytime power is interrupted to
the unit, the
delay on make
period begins, which will be
2 minutes plus 10% of the
delay on break
setting. When
the delay on make is complete and the high pressure
switch and low pressure switch is closed, the compressor
contactor is energized. Upon shutdown, the delay on
break timer starts and prevents restart until the delay on
break and delay on make periods have expired.
During routine operation of the unit with no power
interruptions, the compressor will operate on demand
with no delay.
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.
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 the 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 unit model. The lockout features,
both soft and manual, are a function of the
Compressor Control Module.
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 1: DOB set at 2 minutes, and DOM is 132 seconds
Unit 2: DOB set at 4 minutes, and DOM is 144 seconds
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.
See Table 3.
