2800 LAURA LANE
❘
MIDDLETON, WI 53562
❘
(800) 288-9383
❘
FAX (608) 836-9044
❘
www.tcs-basys.com
14
In programming screen #32b (SZ1041) or #31a (SZ1051), you
are asked to enter a discharge air setpoint. The discharge air
temperature will be controlled to this setting by modulating
the outdoor air dampers, when economizer operation is
enabled. In programming screen #33b (SZ1041) or #32a
(SZ1051), you are asked to enter a discharge air low limit set-
point. If the discharge air falls to this setpoint, the outside air
dampers will close.
A proportional band (throttling range), whether you want the
analog output to modulate from 4 to 20mA or 0 to 20mA, and
direct or reverse action must also be programmed.
DI2 AQUASTAT (SZ1017a, SZ1051)
When DI2 is selected to have an aquastat function, and analog
output one is selected to have an aquastat function, operation
is as follows.
With DI2 "Open", the analog output operates in cooling mode,
and uses selected direct or reverse action. When DI2 is
"Closed", the analog output operates in heating mode, and
uses the opposite of the selected direct or reverse action.
SMART RECOVERY
“Smart Recovery” may be enabled. It ramps the setpoint
4°F/hr. when going from the unoccupied mode to the occu-
pied mode. At the beginning of the occupied mode, the occu-
pied setpoint will be reached, many times without the need for
the second stage to come on. This feature is automatically dis-
abled when DI3 is set to external time clock.
AUXILIARY OUTPUT
An auxiliary relay output is available to output a signal based
on the occupancy status. It is commonly used with an econo-
mizer minimum position control, or to signal an outdoor air
damper to open in occupied times in lieu of an economizer. It
may also be used for lighting or hot water heaters. Keep in
mind that although it is an isolated relay (separate common ter-
minal), it is rated at 24 VAC. For loads that exceed this, use an
external relay. It may be set to be open (NO) or closed (NC)
when the thermostat is operating in the occupied mode, and will
be the opposite during the unoccupied mode.
BUILT-IN DELAYS
The SZ1017a, SZ1041, SZ1051 and SZ1053 have delays built
into the programming sequences to protect equipment. The fan
has a minimum on and off time of 30 seconds. When the fan
is in AUTO or COOL mode, it will come on 30 seconds
before the heating or cooling devices are allowed to sequence
on, and remain on for 2 minutes after the heating or cooling
devices sequence off. Each stage has a minimum on and off
time of two minutes. There is a minimum of 2 minutes
between when one stage turns on until the next stage is
allowed to turn on, as well as when one stage turns off until
the next stage is allowed to turn off.
DIGITAL
APPLICATION
LED
SERVICE SCREEN
CONTROL
SENSOR OR
INPUT
INDICATION?
(DI STATUS SCREEN)
PROVIDED
DEVICE NEEDED
DI1
Fan Proving
YES
CHECK FAN,
YES - turns system mode to "off"
Differential
FAN OK
— requires manual re-start
pressure or
or FAIL
(set system to auto)
current switch
DI1
Equipment
NO
OK
NO
Dry contact, switch. Any type
Monitoring
(DI1 OPEN or CLOSED)
for monitoring and indication
DI2
Service Alert
YES
OK or CHECK DI2
NO
Dry contact, switch. Any type
(DI2 SERVICE OFF or ON)
for monitoring and indication
DI2
Monitor with
NO
OK
YES - shifts setpoint by
Dry contact, switch.
setpoint shift
(DI2 OPEN or CLOSED)
programmed amount
DI2
Cooling Lockout
NO
OK
YES - locks out 2nd
(COOL LOCKOUT ON or OFF)
and 3rd stage cooling
DI3
Filter Service
YES
OK or CHECK FILTER
NO
Differential pressure switch
(FILTER OK or CHECK)
DI3 External Occupancy Override
NO
OK
YES - switches to occupied mode
Dry contact such as twist
(EXT OVER ON or OFF)
as long as contact is made
timer, light switch, etc.
DI3
External Time Clock Input
NO
OK
YES -input overrides thermostat
Dry contact;
YES
(EXT TIMECLOCK ON or OFF)
occupancy program
external time clock
Occupied?
(TCS part SL1001a)
Digital Input Summary Table
