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2800 LAURA LANE • MIDDLETON, WI 53562 • (800) 288-9383 • FAX (608) 836-9044 • www.tcsbasys.com
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STAGE OUTPUT PARAMETERS
The SZ1022N will control up to two stages each of heating
and cooling, with a fifth stage that may be assigned as a third
stage for either. The SZ1024N will control up to two
compressor stages, and up to two stages of auxiliary heat. It is
recommended that all unused stages be disabled.
For each stage, you may specify an offset and a differential
value. This allows you to adjust the operation of the
thermostat to fit your equipment to the building load. The
offset value is the amount away from the setpoint a stage will
turn off. By assigning a stage a value other than zero, you
“anticipate” that the residual heat or cooling in the duct or the
other stages will bring the temperature back to setpoint. In
most cases, the first stage is set to zero. The differential value
is the difference between the on and off points. This value
depends on the load and on the equipment size. If the
equipment is large for the load, you may want to make this
value as high as 5 to prevent equipment cycling. If the
equipment is small compared to the load, or if tight control is
desired, you may want to make this value as low as 1.
The fact that the stages are configurable allows unused stages
to be set to activate physical alarms if desired.
The SZ1022N and SZ1024N also have a P+I option. Without
enabling this option, stages turn on and off based on
temperature vs. setpoint alone, as described above. By
enabling this option, you allow a time factor to be added. This
is useful when you are forced to have a large differential due
to equipment size. At times when the building load is low, the
temperature could potentially sit a few degrees off setpoint
for some time. With the time factor added, the thermostat
would compensate for this, turning on the equipment even
though the temperature had not reached the limits described
above.
DI2 COOL LOCKOUT
DI2 may be set as cool lockout for operation with
economizers. An outdoor temperature switch may be wired in
such that when DI2 is closed, the second and third stages of
cooling are disabled.
SMART RECOVERY
“Smart Recovery” may be enabled to insure occupant comfort
while saving money. It takes the building load into
Heat
Setpoint
Cool
Setpoint
ON
ON
ON
OFF
OFF
OFF
OFF
Differential
Differential
Offset
Offset
Differential
Differential
consideration and ramps the setpoint when going from the
unoccupied mode to the occupied mode. At the beginning of
the occupied mode, the occupied setpoint will be reached,
many times without the need for the second stage to come on.
This feature is automatically disabled 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
economizer 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
terminal), it is rated at 2A@24 VAC. For loads that exceed this,
use an external relay. It may be set to be open (N.O.) or closed
(N.C.) when the thermostat is operating in the occupied mode,
and will be the opposite during the unoccupied mode.
BUILT-IN DELAYS
The SZ1022N and SZ1024N 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 stages are allowed to sequence on, and
remain on for 30 seconds after the heating or cooling stages
sequence off. Each stage has a minimum on and off time of
two minutes. There is a minimum of two 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.
DELAY ON POWERUP
The SZ1022N and SZ1024N have an adjustable delay on
powerup. When several thermostats are used at one location,
and the power goes out, most thermostats turn all of the units
back on at the same time on regain of power, creating a peak.
The thermostat allows you to set a value, in seconds, where
no outputs are allowed to turn on for that length of time on
powerup. Setting each unit to a different delay allows you to
soft start your system, and thus prevent this peak.
Checkout & Troubleshooting
CHECKOUT
Note:
The fan has a minimum on and off time of 30 seconds.
The heating and cooling stages have a minimum on and off
time of 2 minutes.
You may verify the status of heating and cooling stages and
fan in monitoring screens 5, 6, and 7, which are accessed by
pressing the SERVICE STATUS button.
1. Verify all wiring prior to powering the thermostat.
2. Turn power on. The thermostat will display a momentary
screen with the model number , and then the main
monitoring screen with the time, day, and current
temperature.
