ECM Overview and Setup
96
UNT-SVX07E-EN
•
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 2-pipe or 4-pipe 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 4-pipe 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:
1.
A unit is factory configured with a changeover coil
(cooling/heating) as the only coil or as the main coil
portion.
2. SW3 on the CSTI adapter board is turned on, and the
parameter set to
or
to use the
changeover functions.
a.
parameter should be chosen if the unit has a
changeover coil without electric heat.
b.
parameter should be chosen if the unit has a
changeover coil with electric heat. Generally, this
will perform the same as the
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.
3. 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. 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.
b. The input impedance of the thermistor circuit must
be set correctly (the
parameter should be set
to
for CSTI units).
c. The temperature sensed is lower than the
parameter.
d. The
parameter is higher than the
parameter.
e. The temperature is not in the dead-band between
the
parameter and the
parameter (in
this case, previous state will be retained).
4. The customer thermostat is properly hooked up the
input strip 1TB3, and is requesting cooling input (V1)
based on the customer cooling setpoint being lower
than the space temperature.
Table 41.
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
