Tekmar D 512, Data Brochure

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5 of 20 © 2009 D 512 - 09/09
HEAT / COOL
The Heat / Cool mode of operation is selected using the DIP switch located on the circuit
board inside the thermostat
.
Air Sensor(s) Only Operation
When operating with only an air sensor, the on times of the Heat 1 relay and the Cool
relay are calculated to satisfy the requirements of the air sensor
.
Slab Sensor Only Operation
When operating with only a slab sensor, the on time of the Heat 1 relay is calculated to
satisfy the requirements of the slab sensor. The thermostat operates to maintain the slab
at the minimum slab temperature setting
.
NOTE: When operating with only a slab sensor, the Cool relay does not operate.
Operating with only a slab sensor can lead to either overheating or underheating of the
space
.
Air and Slab Sensor Operation
When operating with both air and slab sensors, the thermostat calculates an on time
for the Heat 1 relay to satisfy the slab sensor’s requirements and an on time to satisfy
the air sensor’s requirements. The Heat 1 relay operates for the longer of these two
on times. The thermostat also calculates an on time for the Cool relay to satisfy the air
sensor’s requirements. In this situation, heating and cooling can happen at the same
time to prevent the space from overheating. This is most likely to occur when the slab is
operating at the slab minimum temperature
.
While the minimum slab temperature is satisfied, the Heat 1 relay on time is calculated
to satisfy the air temperature setting
.
However, the maximum slab temperature setting
limits the Heat 1 relay on time when the slab temperature becomes too warm. In this
situation, underheating can occur in the space
.
Mode
Auto In the Auto mode, the thermostat automatically switches between heating and
cooling the space. However, the heating operation has priority over the cooling
operation. In this mode, the minimum slab temperature is maintained even when
the thermostat is cooling the air
.
Heat In the Heat mode, the Heat 1 relay is operated to satisfy the heating
temperature requirement of the zone and cooling is disabled
.
Cool In the Cool mode, the Cool relay is operated to satisfy the cooling temperature
requirement of the zone and heating is disabled. If a slab sensor is used, the slab
minimum is ignored
.
Off In the Off mode, the Heat 1 and Cool relays are not operated
.
NOTE: If an air or slab sensor is active in the Off mode, a freeze protection is enabled that
allows the Heat 1 relay to be operated to keep the zone above 35°F (2°C)
.