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Output Light
The output light has the following three indications:
Light Off
The heating system is not active. This will be the case when the outdoor temperature is above the Outdoor Cutoff
temperature or when the Outdoor Cutoff is set to OFF and the External System Starter is not activated.
Light On
The heating source output is active. The blue output wires are continuous.
Flashing
The heating source output is active and the valve position is being corrected.
Setting the Slab ∆ ∆ ∆ ∆ ∆ T
The Slab ∆ (delta) T is the temperature difference between the Slab Supply and the Slab Return which is necessary to
melt frozen precipitation under extreme conditions. This maximum value is determined by the spacing and number of
loops of tubing, and the slab type. The Slab ∆ (delta) T is actually a measurement of the maximum amount of energy
which can be input to the slab at any time. To prevent slab damage, the Slab ∆ (delta) T must not be set higher than the
design point. Follow the chart on pg. 5 to adjust the Slab ∆ (delta) T.
Setting the Supply Limit
The Supply Limit must be set according to the tubing and the slab manufacturer's specifications. If the Supply Limit is
set too high, the slab could be permanently damaged. For example, if the slab consists of pavers laid in sand, the maxi-
mum slab supply temperature must be set below 140
crystallize. Follow the chart on pg. 5 to adjust the Supply Limit.
Setting the Outdoor Cutoff
The Outdoor Cutoff is the temperature below which the slab heating source will be activated. When the outdoor tempera-
ture rises above this point, the slab heat source relay (blue wires) will be off. The Outdoor Cutoff is adjustable from 20
to 60
F. The Outdoor Cutoff also has two special modes:
°
OFF
When the Outdoor Cutoff is set to OFF, the only way the heat source can be activated is to short out the two input
terminals EXT and COM (see pg. 3). The heat source will stay active until the short is removed. This mode can be
used to start the slab heating system with a switch.
ON
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. This mode is useful for testing the RSM in warm weather.
CAUTION: If the RSM is left in the ON mode, excessive energy bills will result.
Follow the chart on pg. 5 to adjust the Outdoor Cutoff.
Setting the Tune
The Tune value provides an adjustment for the heat losses of a particular slab. Start with the factory default Tune setting
of 0. Use the following steps to adjust the Tune value.
• When precipitation is expected, start the slab heating system and let it run at least 24 hours. This time is needed to
allow the slab temperature to reach the melting point.
• When the precipitation begins, monitor the slab. Check if the precipitation is beginning to accumulate or if it is melted
immediately.
• If there is accumulation, the slab temperature is too low. Increase the Tune value by one number (for example, from 0 to
1).
• If the precipitation is melting immediately, the slab may be using more energy than it needs. Decrease the Tune value
by one number (for example, from 0 to -1).
• After making a change in the Tune value, wait at least four hours to see what affect this change will have on the slab.
• Repeat the above procedure as necessary until the lowest Tune value which still melts precipitation is determined.
Follow the chart on pg. 5 to adjust the Tune.
OPERATION
F, since temperatures in excess of this may cause the sand to
°
6
F
°
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