Typical Slab Sensor Mode Installation Steps - heat-timer SMC Installation & Operation Manuals

The slab must be kept above freezing whenever there could be frozen precipitation. As a result, any ice or
snow that falls on the slab will melt immediately. If precipitation is allowed to accumulate before heating the
slab, an effect called bridging can occur. The snow or ice directly in contact with the slab will melt. But, the
snow above will act as an insulator, reflecting the heat back into the slab. The slab itself will have no ice
touching its surface, but the remaining accumulation will melt very slowly. To prevent this, the SMC activates
the slab heating system whenever the slab temperature falls below the adjustable WWC setting.
On a further drop in slab temperature below the CWC, the control is said to be in CWC Mode. In this mode
the SMC stops its heating process. It does this by de-energizing the boiler and System Pump and closing
the motorized valve. In addition, it pulses the Slab Pump to prevent the slab and its radiant solution from
freezing. See "Antifreeze" on page 30.
The SMC includes several additional features that can be used to protect the plant and slab. The SMC
can be used with a Boiler Return Sensor to help reduce boiler thermal shock possibility. Additionally, it is
equipped with an Alarm output. This alarm is activated when any sensor fails to read correctly or if the slab
was not receiving sufficient heat.
Moisture
Not Detected
Slab Target = Off
Boiler = Off
Valve = Close
Slab Pump = Off
System Pump = Off
38°F
Slab Target = Off
Boiler = Off
Valve = Close
Slab Pump = Pulse to even slab temp.
System Pump = Off
34°F
Slab Target = ISP
Boiler = On
Valve = Modulating
Slab Pump = On
System Pump = On
10°F
Slab Target = Off
Boiler = Off
Valve = Close
Slab Pump = Pulse to eliminate freezing
System Pump = Off

TyPICAL SLAB SENSOR MODE INSTALLATION STEPS

To install and set the control to operate based on the Slab Sensor follow these steps:
• Install the Slab Sensor Base, Dummy Plastic Plug, and conduit before the slab concrete pour. See "Slab
Sensor Installation" on page 10.
• Install the SMC control indoors. See "Mounting the Enclosure" on page 9.
• Install and wire the Slab Supply, Slab Return, and the optional Boiler Return Sensor in their wells. See
"Water Temperature Sensor Installation" on page 11.
• After the concrete pour and slab installation, replace the Dummy Plastic Plug with the Slab Sensor, making
sure to run the cable through the conduit.
• Wire the power to the SMC. But do not power it. See "Wiring the Power" on page 12.
• Wire the SMC outputs to the System and Slab Pumps, Motorized Valve, and Boiler. See "Output Wiring" on
page 12.
• Power the SMC.
SMC Installation and Operation Manual
Warm Weather
Cutoff (WWC)
Idle Set Point (ISP)
Cold Weather
Cutoff (CWC)
Moisture
Detected
Slab Target = WWC
Boiler = On
Until Precipitation
Valve = Modulating
is dry
Slab Pump = On
System Pump = On
38°F
Slab Target = WWC
Idle Set
Boiler = On
Point (ISP)
Valve = Modulating
34°F
Slab Pump = On
System Pump = On
10°F Cold Weather
Cutoff (CWC)
Slab Target = Off
Boiler = Off
Valve = Close
Slab Pump = Pulse to eliminate freezing
System Pump = Off
Warm Weather
Cutoff (WWC)
5