iWorx® SMZ1
18
505-048-2, Effective: March 10, 2015
© 2015 Taco Electronic Solutions, Inc.
Zone Sense with Idle
This mode operates similar to the Zone Sense mode except it also activates when the zone slab temperature drops
below the idle temperature setpoint regardless of the state of the Local Snow Sensor.
Zone Output Operation
The four zone outputs may be used for zone valves or other 24 VAC-actuated heat sources. If not disabled by the out-
door limits, the outputs for each zone are operated to maintain the zone setpoints established above. The outputs are
hysteretically controlled by comparing each zone temperature (Zone 1/2/3/4 Temperature) with the respective setpoints
(Zone 1/2/3/4 Setpoint), or by a PI loop modulated output.
The status of each output is displayed on the LCI (Zone 1/2/3/4 Output).
Primary and Group Circulators
The primary circulator output is an on/off output that energizes whenever any of the four zone outputs are turned on.
Group Circulator outputs turn on whenever their associated zones are active. See
Zone X Configuration
for more info.
Gain Control
The analog outputs are modulated by a Propor Integral (P+I) control loop based on the heating loop setpoint
and the space temperature. The P+I control loop modulates the valve to maintain a constant slab temperature. As the
temperature decreases below the heating loop setpoint, the heating valve is modulated open. The heating valve is
modulated closed as the temperature increases above the heating loop setpoint.
To prevent the integral component from becoming too large, there is anti-wind up reset protection. This protection
clamps the integral value when all of the components add up to more than 100% or less than 0%.
Demand Outputs & BLM Communication
When any of the zone outputs are turned on, the
Primary
output is turned on. This may be used to operate a supply
pump for the zone circuits or to signal a heat demand to a non-networked boiler control or other heat source. If the
SMZ1
Heat Demand
setting is on, then the status of this output is communicated to the BLM as a primary loop
demand.
The greatest of the four zone demands is displayed as the
Maximum Zone Demand
. If the SMZ1
Zone Demand
setting
is on, this maximum value is communicated to the BLM as a sub-zone demand for the secondary loop. If the outdoor
temperature is below the OAT heating cutoff of the BLM, the BLM zone pump is operated and the injection output is
controlled to provide the appropriate outdoor reset temperature in the secondary loop. The boilers and primary pump
are operated as needed to meet the injection demand.
If the SMZ1 zones are on the secondary loop of the BLM, only the SMZ1
Zone Demand
setting needs to be on, since
the demand for the boiler is dictated by the injection requirements. This method fires the boiler only as needed. How-
ever, both BLM settings, the
Heat Demand
and the
Zone Demand
may be turned on. The effect of this is to create a
demand for the boiler whenever a SMZ1 zone is calling. This serves to keep the boiler in a standby mode that could
reduce cycling as the demand from the secondary loop varies.
Additional Features
Commissioning Switch
In addition to the individual zone commissioning switches, a single switch setting can be adjusted at the LCI. By setting
Commissioning
to "On,” all eight digital outputs are turned on simultaneously.
Alarm Monitoring
The controller detects certain conditions and sends them to the LCI as alarms. These alarms are displayed and
recorded for later access, but do not alter the system operation.
Temperature Sensor Alarm
If the analog input from a thermistor is outside of the expected range of the thermistor (-60 °F to 230 °F [-51 °C to 110
°C]), this alarm is sent to the LCI. An alarm of this type is most likely due to a wiring fault causing the input to be shorted
or open. An open sensor results in a reading of -60 °F (-51 °C), while a short appears as 230 °F (110 °C).
