The thermostat’s display has four distinct fields. These fields are the Menu field, the Item
field, the Number field and the Status field. The four buttons on the face of the thermostat are
used to navigate through the menus and items to view and / or adjust the desired settings.
The thermostat operation is based on cycles per hour. The number of cycles per hour is adjustable
through the HEAT CYC setting in the Adjust menu. During each cycle that heating is required,
the thermostat turns on the Heat relay for a calculated amount of time. This amount of time is
the “ON time”. The ON time is calculated based on the requirements of the zone. If the zone
requires more heating, the ON time is increased. If the zone requires less heating, the ON time
is reduced.
In order to prevent short cycling of the heating relay, the
thermostat ensures that the relay remains on or off for
a minimum amount of time.
An AUTO CYC setting is available for the heating cycle.
This setting allows the thermostat to determine the
best number of cycles per hour that balances both
temperature swings and equipment cycles.
Cycles Per Hour
ononon
offoff
⇐ Cycle Length ⇒
Time
off
AUXILIARY SENSOR
The thermostat has a single built-in sensor to measure air temperature at the
thermostat. In addition to the built-in sensor, the thermostat has terminals to connect
one auxiliary sensor. This sensor can be either an indoor sensor, a slab sensor, or
an outdoor sensor.
Indoor Sensor
An indoor sensor is used to measure the air temperature in the zone that the thermostat
is controlling. The temperature being read by the indoor sensor is used in the calculations
of the ON time for the relay in the thermostat. This setting is made through the Adjust
menu of the thermostat. If the built-in sensor is set to ON and the auxiliary sensor is set
to Indoor, the temperatures of the sensors are averaged and used to calculate the ON
time of the relay.
Slab Sensor
A slab sensor is used to measure the slab temperature in the zone that the thermostat
is controlling. The temperature being read by the slab sensor is used in the calculations
of the ON time for the Heat relay and allows the thermostat to operate the slab between
the slab minimum and slab maximum settings.
An outdoor sensor can be connected to the thermostat. The temperature measured by
an outdoor sensor does not affect the ON time of the relay and is only used for display
purposes.
ACCESS LEVELS
The 508 thermostat has two access levels.
These access levels restrict the number of items
available in the menus of the thermostat. The
two access levels are User and Installer. This
selection is made using the DIP switch located
on the circuit board inside the thermostat.
Installer access level - allows the installer
to adjust all of the settings in the thermostat
including those required to match the thermostat
to the mechanical system and the devices
used.
24 V
4653
For 3 wires,
install jumper
R to Rh
POWER
Thermostat 508
One Stage Heat
Power:
Relay:
NO
2
1
Sensor
24 V ±10% 50/60 Hz 1.5 VA.
24 V (ac) 2 A Class 2
RhRCW
Made in
Canada
Meets Class B:
Canadian ICES
FCC Part 15
Installer
Not used
Access level
1
2
ON
508
944-02
Apr 2010
Lot 1234
User
User access level - allows the end user
to adjust the temperatures used by the
thermostat.
Dip Switch
Set to User access level once installation and settings have been completed.
Note: DIP switch 2 is not used.
Sequence of Operation
AIR SENSOR(S) ONLY OPERATION
When operating with only an air sensor, the ON time for the Heat relay is calculated to
satisfy the requirements of the air sensor.
SLAB SENSOR ONLY OPERATION
When operating with only a slab sensor, the ON time for the Heat 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: 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 relay to satisfy the slab sensor’s requirements and an ON time to satisfy the air sensor’s
requirements. The Heat relay operates for the longer of these two ON times.
During light heating loads, overheating can occur due to the minimum slab temperature
requirements.
During heavy heating loads, the maximum slab temperature setting limits the ON time of
the Heat relay. In this situation, underheating can occur.
Heat In the heat mode, the Heat relay is operated to satisfy the temperature requirement of the zone.
Off In the OFF mode, the Heat relay is not operated.
NOTE: If an air or slab sensor is active in the OFF mode, a freeze protection is enabled
that allows the Heat relay to be operated to keep the zone above 35°F (2°C).
GETTING READY
Check the contents of this package. If any of the contents are missing or damaged, please
contact your wholesaler or tekmar sales representative for assistance.
Type 508 Includes:
Type 509 Includes:
• One Thermostat 508 • Data Brochure D 508 • • User Brochure U 508
• One Thermostat 508 • One 079 Slab Sensor • • Data Brochure D 508
User Brochure U 508
SLAB SENSOR 079
The tekmar Slab Sensor 079 has a stainless steel sleeve which is designed for use in
concrete, thin-set or grout. The 079 is supplied with 10’ (3 m) of 2 conductor zipcord.
Installation - Slab Sensor 079
STEP ONE
INSTALLING THE SENSOR
New Installations
Thin-Set or Thin-Pour Applications
If the floor covering is to be installed over either
a thin-set or thin-pour material of sufficient
depth, the 079 slab sensor can be placed
Electric
Cables
Thin-set
Tiles
directly into either the thin-set material or the
thin-pour material and covered over. Ensure
that the sensor is located in such a position that
the attached wire is able to reach to a suitable
junction location. Splices within the thin-set or
thin-pour should be avoided to ensure trouble free operation. The sensor should be located
mid way between the heating elements to ensure a proper temperature reading.
Thin Floor Coverings (less than 3/8” (10 mm))
If a thin floor covering is to be installed directly
to the subfloor, a groove 1/8” (4 mm) wide by
Hardwood
1/16” (2 mm) deep can be cut into the surface of
the subfloor to accommodate the wire for the
Subfloor
sensor. Ensure that the sensor is located in
such a position that the attached wire is able
to reach to a suitable junction location. Splices
under the floor covering should be avoided to
ensure trouble free operation. A groove 3/16”
(5 mm) wide by 3/16” (5 mm) deep by 1-3/4”
(45 mm) long should be cut to accommodate the sensor. The sensor should be located
mid way between the heating elements to ensure a proper temperature reading.
If a thick floor covering is to be installed directly to the subfloor, a groove 1/8” (4 mm) wide
by 1/16” (2 mm) deep can be cut into the back of the flooring material to accommodate
the wire for the sensor. Ensure that the sensor is located in such a position that the
attached wire is able to reach to a suitable junction location.
Splices under the floor covering should be
avoided to ensure trouble free operation. A
groove 3/16” (5 mm) wide by 3/16” (5 mm)
Hardwood
Subfloor
deep by 1-3/4” (45 mm) long should be cut to
accommodate the sensor. The sensor should be
located mid way between the heating elements
to ensure a proper temperature reading.
NOTE: If it is not practical to cut a groove in the surface covering, follow the installation
method used for thin floor coverings.
Retrofit Installations
Tile Floor Coverings
If a Slab Sensor 079 is to be installed into an existing tile floor with sufficiently large grout
lines, the sensor and wire can be installed in one of the grout lines between the tiles.
Select a low traffic area of the floor that is mid way between the heating elements for
the sensor location. Ensure that the sensor is
located in such a position that the attached wire
is able to reach to a suitable junction location.
Splices within the grout should be avoided to
Subfloor
Tiles
Thin-set
ensure trouble free operation. Remove the
appropriate grout line and place the sensor and
wire in the floor. Re-grout the area.
Installing the Sensor to the Bottom of a Subfloor
If the sensor is to be installed to the bottom of a subfloor, cut a piece of 1” (25 mm)
thick rigid insulation into a 6” (150 mm) by 6” (150 mm) square. A groove 3/16” (5
mm) wide by 3/16” (5 mm) deep by 1-3/4”
(45 mm) long should be cut into the insulation
Subfloor
to accommodate the sensor. Place the sensor
in the groove and sandwich the sensor between
the insulation and the subfloor. Use a suitable
fastening method to affix the insulation to the
subfloor.
STEP TWO
WIRING AND TESTING THE SENSOR
Caution: Do not run sensor wires parallel to telephone or power cables. If the sensor wires
are located in an area with strong sources of electromagnetic interference, shielded cable
or twisted pair should be used or the wires can be run in a grounded metal conduit.
The Slab Sensor 079 is supplied with 10’ (3 m) of cable. If a longer length is required, 24
AWG or larger wire can be spliced onto the two wires from the sensor. The splices should
be properly soldered and protected in an accessible junction box. Follow the sensor testing
instructions given in this brochure and then connect the wires to the control.