40
Enertech Global IOM, VS/VT Models, Rev A
Section 9: Controls
Over/Under Voltage Protection
The lockout board protects the compressor from
operating when an over/under voltage condition
exists. The control monitors secondary voltage
(24VAC) to determine an over/ under voltage
condition is occurring on the primary side of the
transformer. For example, if the secondary voltage
is 18VAC, the primary voltage for a 240V unit would
be approximately 180V which is below the minimum
voltage (197V) recommended by the compressor
manufacturer. Under voltage (<18VAC) causes the
compressor to disengage and restart when the
voltage returns to >20VAC. Over voltage (>31VAC)
causes the compressor to disengage and restart
when the voltage returns to <29VAC.
When an O/U Voltage condition occurs, the board
will initiate a fault, shut down the compressor, and
start the ve minute ASC period. All four fault LEDs
will ash (HP + LP + FS + CO) and the thermostat
“Call For Service” indicator will be illuminated. This
feature is self- resetting and never retries or locks out.
If voltage returns to normal range normal operation
will resume if/when the ASC period is over. When
normal operation is restored the four fault LED’s will
stop ashing and the “Call For Service” indicator will
turn off.
Lockout with Emergency Heat
While in lockout mode, if the thermostat is calling
for auxiliary heat (W1), emergency heat mode will
energize. W2 is energized two minutes after W1 is
energized.
Diagnostics
The lockout board includes ve LEDs (Green-HP,
Orange-LP, Red-FS, Yellow-CO, Green-Status) for fast
and simple control board diagnosis. Below is a table
showing LED function.
Temperature Sensor Operating Range
SenSorS’ name range (°F)
T1 10 – 220
T2 20 – 257
T3 20 – 220
T4 10 – 220
Temperature vs Resistance Characteristics
Temp. (°F) Rst. (KΩ) Temp. (°F) Rst. (KΩ)
10 46.95 130 3.60
15 41.39 200 1.16
20 36.50 220 0.87
30 28.61 250 0.59
77 10.00 257 0.54
Fault Retry
All faults (except O/U Voltage) are retried twice
before nally locking the unit out. The fault retry
feature is designed to prevent nuisance service
calls. There is an anti-short cycle (ASC) period (5
min.) between fault retries. On the third fault within
30 minutes, the board will go into lockout mode and
the “Call For Service” indicator on the thermostat will
illuminate.
Intelligent Lockout Reset
If the thermostat is powered off for one minute
then back on (soft reset), the board will reset and
the last fault will be stored in memory for ease of
troubleshooting. If power is interrupted to the board,
the fault memory will be cleared.
To Next Page
Loading...
