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INSTALLATION/OPERATING INSTRUCTIONS
A Control for Under Slab Heating Systems
The RSM is designed to control under slab heating systems to prevent accumulations of ice or snow. To do this, it
monitors three temperatures, the outside temperature, the temperature of the fluid going to the slab, and the temperature
of the fluid returning from the slab.
The slab must be kept above freezing (32°F) whenever there could be frozen precipitation. Therefore, any ice or snow
which falls on the slab will melt immediately. If precipitation is allowed to accumulate before the slab is heated, 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 be dry, but the remaining accumulation will melt very
slowly. To prevent this, the RSM activates the slab heating system whenever the outside temperature falls below the
adjustable outdoor cutoff temperature or whenever the optional external system starter is activated.
Once the slab heating system is activated, the amount of energy entering the slab is determined by the difference between
the temperature of the fluid going to the slab (the Slab Supply) and the temperature of the fluid returning from the slab
(the Slab Return). The difference between these two is called the
be different for each slab composition. The higher the
large, the slab itself can be damaged. The RSM provides a maximum
The RSM will control a 3-way motorized mixing valve to regulate the amount of heat being supplied to the slab. The
motorized valve will mix the heated fluid from the heat source with the fluid returning from the slab. As the slab or its
components can be damaged by excessive temperatures, the maximum temperature for the slab supply can be adjusted
from 70
F to 180
F. If the Slab Supply temperature reaches this limit, the control will immediately begin to close the valve.
°
°
Due to the twin constraints of maximum
heating systems, a typical slab will take many hours to reach melting temperatures. A 24 hour warm-up period is not
unusual. The RSM is provided with a Tune adjustment to insure the slab temperature will be sufficient to melt frozen
precipitation once the warm-up period has ended. The Tune value compensates for both different slab types and
different outdoor weather conditions. After making a change in the Tune value, it is necessary to wait at least several
hours before accessing what affect it will have on slab temperatures.
WARNING:
This Heat-Timer control is strictly an operating control; it should never be used as
a primary limit or safety control. All equipment must have its own certified limit and safety
controls required by local code. The installer must verify proper operation and correct any
safety problems prior to the installation of this Heat-Timer control.
RSM
Used to Melt Ice or Snow
How the RSM works...
∆
T, the more energy is being input to the slab. If the
∆
T and maximum Slab Supply temperature, as well as the nature of under slab
∆ (Delta)
T or the difference in temperature. The
∆
T adjustment which can be set from 5
1
∆
T will
∆
T is too
F to 50
F
°
°
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Table of Contents
Related Manuals for heat-timer RSM
Summary of Contents for heat-timer RSM
- Page 1 How the RSM works... The RSM is designed to control under slab heating systems to prevent accumulations of ice or snow. To do this, it monitors three temperatures, the outside temperature, the temperature of the fluid going to the slab, and the temperature of the fluid returning from the slab.
-
Page 2: Typical Installation
• Select a location which is indoors, or which is protected from the elements. The control must be protected from extreme heat or cold. • The RSM is designed to mount on a standard 1900 (4" x 4") electrical box or can be flush mounted on a panel with the extension skirt included. -
Page 3: Wiring Diagram
• The N.O. contacts do not output power. They simply switch power through the circuit. • If the heat source will be active whenever the RSM will activate the slab heat (as would be the case if the heat source is also used for space heating), connect the blue wires in series with the power for the slab pump. - Page 4 2. The display will show the version number of the RSM software. 3. Wait approximately 5 seconds and the display will change to read either °F or °C. If the display shows °F the RSM will operate in Fahrenheit degrees. If the display shows °C then the RSM will operate in Celsius degrees.
- Page 5 IMPORTANT: The values for Slab ∆( delta) T, Supply Limit, Outdoor Cutoff, and Tune, can only be changed when they are being displayed. Once the values have been set, they will remain in the RSM memory even if power to the unit is interrupted or lost.
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Page 6: Operation
When the Outdoor Cutoff is set to ON, the slab heating system will be activated and run on its limits regardless of outdoor temperature. The RSM will control the valve to hold either the Supply Limit or Slab ∆ (delta) T whichever results in a lower Slab Supply temperature. -
Page 7: Troubleshooting
If the RSM does not activate the heating system: Remove any connections to the Blue output wires. Then take a wire and short out the two RSM terminals marked EXT and COM (see pg. 3). The red output light should turn on, and the Blue output wires should be continuous. - Page 8 Checking the sensors TEMPERATURE VALUE Each of the three RSM sensors are interchangeable and can be tested in the (in degrees F) (in Ohms) same way. The display (see pg. 7) will indicate which sensor is registering 4 2 6 8 3 open or short, or the temperature reading for that sensor.