Trane GEH 006 Manual page 20

Microprocessor Design
The 24 volt deluxe design is a
microprocessor-based control board
conveniently located in the control
box. The board is unique to Trane
water-source products and is
designed to control the unit as well as
provide outputs for unit status and
fault detection.
The Trane microprocessor board is
factory wired to a terminal strip to
provide all necessary terminals for
field connections. See Figure 29 for
the deluxe 24V control board.
Figure 29: Deluxe 24V control board
Deluxe 24V features include:
Random Start
The random start relay provides a time
delay start-up of the compressor when
cycling in the occupied mode. A new
start delay time between 3 and 10
seconds is applied each time power is
enabled to the unit.
Anti-short Cycle Timer
The anti-short cycle timer provides a
three minute time delay between
compressor stop and compressor
restart.
Brown-out Protection
The brown-out protection function
measures the input voltage to the
controller and halts the compressor
operation. Once a brown-out situation
has occurred, the anti-short cycle
timer will become energized. The
general fault contact will not be
20
Features and Benefits
Deluxe Controls
affected by this condition. The voltage
will continue to be monitored until the
voltage increases. The compressors
will be enabled at this time if all
start-up time delays have expired, and
all safeties have been satisfied.
Compressor Disable
The compressor disable relay pro-
vides a temporary disable in compres-
sor operation. The signal would be
provided from a water loop controller
in the system. It would disable the
compressor because of low water
flow, peak limiting or if the unit goes
into an unoccupied state. Once the
compressor has been disabled, the an-
ti-short cycle time period will begin.
Once the compressor disable signal is
no longer present, and all safeties are
satisfied, the control will allow the
compressor to restart.
Generic Relay
The generic relay is provided for field
use. Night setback or pump restart are
two options that may be wired to the
available relay. (Note: Night setback is
available as factory wired). An exter-
nal Class II 24VAC signal will energize
the relay coil on terminals R1 and R2.
Terminals C (common), NO (normally
open), and NC (normally closed) will
be provided for the relay contacts.
Safety Control
The deluxe microprocessor receives
separate input signals from the refrig-
erant high pressure switch, low suc-
tion pressure switch and condensate
overflow.
In a high pressure situation, the
compressor contactor is de-energized,
which suspends compressor opera-
tion. The control will go into soft lock-
out mode initializing a three minute
time delay and a random start of 3 to
10 second time delays. Once these de-
lays have expired, the unit will be al-
lowed to run. If a high pressure
situation occurs within one hour of the
first situation, the control will be
placed into a manual lockout mode,
halting compressor operation, and ini-
tiating the general alarm.
In a low temperature situation, the
low pressure switch will transition
open after the compressor starts. If the
switch is open for 45 seconds during
compressor start, the unit will go into
soft lockout mode initializing a three
minute time delay and a random start
of 3 to 10 second time delays. Once
these delays have expired, the unit will
be allowed to run. If the low pressure
situation occurs again within 30 min-
utes, and the device is open for more
than 45 seconds, the control will be
placed into a manual lockout mode,
halting compressor operation, and ini-
tiating the general alarm.
In a condensate overflow
situation, the control will go into
manual lockout mode, halting com-
pressor operation, and initiating the
general alarm.
The general alarm is initiated when
the control goes into a manual lockout
mode for either high pressure, low
pressure or condensate overflow con-
ditions.
Diagnostics
Component device connections to the
microprocessor board are referenced
in Figure 29. Three LEDs (light emitting
diodes) are provided for indicating the
operating mode of the controller. See
the unit IOM for diagnostics or trouble-
shooting through the use of the LEDs.
WSHP-PRC001-EN