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BCX-SVX002A-EN
For CSTI units, the board mounted switches have to be set
appropriately to enable the desired functionality.
Figure 53. CSTI board-mounted switches
Table 22. CSTI adapter board: switch functions
Switch (L-R) SW1 SW2 SW3 SW4
Function Valve one operation logic Valve two operation logic Changeover Function Electric Heat / Fan Proving
Function
UP position (towards
terminal strip)
Normally Open Valve Normally Open Valve Changeover Function ON Electric Heat / Fan Proving
Function
DOWN position (towards
black relays)
Normally Closed Valve Normally Closed Valve Changeover Function OFF Electric Heat / Fan Proving
Function
• All switches are factory-set based on customer
configuration of the unit model number. The unit will
function correctly as shipped; however, the switch
functions and positions are depicted for customer
convenience and for service and troubleshooting aids.
• SW3 and SW4 work in conjunction with settings on the
motor control board controller. Simple activation of
changeover and electric heat lockout function may not
work correctly unless the motor control board is
configured to perform these functions.
• Customers are advised to locate the changeover coil
temperature sensor on the bypass line if possible, to
avoid measuring standing water temperature.
• If a 4-pipe unit with changeover function is selected, the
heating input will drive the main coil if hot water is
detected, but will always drive the auxiliary coil or
electric heat (where available).
• Where electric heat is available with a changeover coil,
the electric heat is factory-configured to be deactivated
if there is hot water available and if there is a fan failure.
The CSTI board comes with courtesy valve inversion relays
that allow both normally open and normally closed two-
position valves to be used with simple thermostats that do
not have the configurability to adapt to the customer choice
of valves. Independent switches, SW1 and SW2, are
provided for 2pipe or 4pipe units, or 2–pipe units with an
optional reheat coil. The functions of SW1 and SW2 is
downstream of the changeover function (SW3 and motor
control board). Decisions made by the changeover circuits
will be flowed to the inversion circuits, if they are selected.
SW3 enables or disables the changeover function for 2–
pipe changeover coil units, or 4pipe units where the coil
has both a heating/cooling circuit and a heating circuit
piped internally. If SW3 is turned off, the changeover
function will be disabled, and the unit will then be
configured as a cooling only coil, a heating only coil, or a
combination of cooling only/heating only coil. Thus,
customer cooling requests will drive the main valve, and
heating requests will drive the auxiliary valve.
The changeover function is designed to work with customer
controllers that request heating or cooling (based on
customer request), but have coil water temperatures that
are “changed over” from heating to cooling (or cooling to
heating) depending on the season and the building
equipment available. Customer thermostats MUST be
hooked to the correct terminal strip locations (V1 and V2)
for the changeover function to work.
Cooling
In general, the (CSTI) changeover function will provide
cooling if:
• A unit is factory configured with a changeover coil
(cooling/heating) as the only coil or as the main coil
portion.
• SW3 on the CSTI adapter board is turned on, and the
FFpprrvv parameter set to EEHHll or EEhhffss to use the
changeover functions.
– EEhhll parameter should be chosen if the unit has a
changeover coil without electric heat.
– EEhhFFss parameter should be chosen if the unit has a
changeover coil with electric heat. Generally, this
will perform the same as the EEhhll parameter but will
in addition, disable the heating function on electric
heat and on the changeover coil heat if there are
fan failures. The auxiliary heating coil valve will
continue to respond to customer heating requests.
• The motor control board has sensed that there is cold
water available on the supply/bypass line for the
changeover coil. In this case, “cold” water is inferred by
the motor control board if:
– A 10K NTC thermistor (similar to Trane part number
X13790374010) is wired properly to the motor
control board, through the crossover cables and
CSTI adapter boards.
– The input impedance of the thermistor circuit must
be set correctly (the AAiippuu parameter should be set
to in for CSTI units).
– The temperature sensed is lower than the AAii22MM
parameter.
Installation - Controls
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