Mars 70803 User manual

INSTALLATION AND OPERATING INSTRUCTIONS
Non-Programmable Electronic
Thermostat Heat/Cool
®
Model 70803
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Compatible with low voltage single stage gas, oil or electric heating or cooling systems and single stage heat
pumps. For use on 24VAC systems (not to exceed 30VAC) and 250mv to 750mv millivolt heating only systems.
WARNING!
• To prevent electrical shock and/or equipment damage, disconnect electric power to system at main fuse or cir-
cuit breaker box until installation is complete.
• This thermostat requires 2 AA Alkaline batteries for power.
• Do not use this thermostat on applications with voltages above 30VAC.
• Wiring must conform to all local and national building/electrical codes and ordinances.
• Do not short (jumper) across terminals on the gas valve or at the system control to test the installation. This
will damage the thermostat and void the warranty.
•This thermostat is equipped with automatic compressor protection to prevent damage due to short cycling.
The short cycle protection provides a 5-minute delay between heating (heat pump models) or cooling cycles to
prevent the compressor from being damaged.
• Do not switch the system to cool if the outdoor temperature is below 50 F (10 C). This may damage the cool-
ing system and may cause personal injury.
• This thermostat should be used only as described in this manual.
SPECIFICATIONS
Electrical Rating: 24 Volt AC (18-30 VAC)
1 Amp Maximum per Terminal
3 Amps Total Load
Control: 1 Heat / 1Cool Non-Heat Pump
Set Point Range: 45 F – 90 F (7.0 C – 32.0 C)
Accuracy: +/- 1 F (.5 C)
Terminations: RC, RH, G, Y, W, B, O
Power: 3 VDC (2 AA Alkaline batteries)
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Removing The Existing Thermostat
1) CAUTION: Make certain the power to the system has been disconnected.
2) Remove the cover of the old thermostat and locate the wires that are connected to the terminal board.
IMPORTANT: Before removing these wires, NOTE (ON A PIECE OF PAPER) THE COLOR OF EACH WIRE
AND THE CORRESPONDING TERMINAL MARKING ON THE OLD THERMOSTAT.
3) Remove the wires from the terminals. Remove the old thermostat and mounting base from the wall.
Installing The New Thermostat
1) CAUTION: Make certain the power to the system has been disconnected.
2) If this is a new installation, locate the thermostat 4 to 5 feet above the floor in accordance with applicable
codes. Select a location that provides good airflow. Avoid locations in direct sunlight, near sources of heat,
or near air vents. NOTE: The display is designed to be best viewed from a front downward angle.
3) Remove the back plate of the thermostat by gently depressing the bottom locking tab and swinging the back
plate up and away.
4) Place the back plate against the wall in the desired mounting location with the thermostat wires protruding
from the wall through the large rectangular whole in the back plate.
5) Mark placement of the (2) mounting holes (oval shaped holes in back plate) on the wall, remove the back
plate, and drill (2) 3/16” holes.
6) Tap supplied plastic anchors into the holes.
7) Secure the back plate to the wall with the supplied screws making certain the thermostat wires have been
inserted through the large rectangular hole in the back plate.
8) Carefully attach the thermostat wires to the appropriate connections on the terminal board on the back plate.
Use the notes taken from step 2 of Removing The Existing Thermostat to determine their location on the new
thermostat. Reference wiring diagrams are available in the back of this manual.
9) Carefully place the thermostat body face down on a soft surface to expose the main circuit board. Gently set
the following switches in the correct position for the application.
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•GAS / ELECTRIC: Configures the thermostat to either gas/oil or electric heating systems.
•C / F: Sets the display in either Celsius or Fahrenheit.
•NORM / HP: Configures the thermostat for normal heating/cooling systems or heat pump systems (sin-
gle stage).
10) Attach the thermostat body to the back plate by resting the top of the thermostat body on the two clips on
the upper portion of the back plate. Then gently press the front body into place until the bottom locking
tab snaps into place. NOTE: The terminal board pins must be properly aligned with the sockets on the
terminal board (on the back plate) in order for the front body to properly snap into place.
11) Set the system switch to the OFF position.
12) Set the fan switch to the AUTO position.
13) Open the front thermostat door and open the battery compartment door; install 2 AA Alkaline batteries
(included).
14) Remove the clear plastic film from the display.
Testing The New Thermostat
WARNING!
•Do not switch the system to cool if the outdoor temperature is below 50 F (10 C). This may damage the
cooling system and may cause personal injury.
• This thermostat is equipped with automatic compressor protection to prevent damage due to short
cycling. The short cycle protection provides a 5-minute delay between heating (heat pump models) or
cooling cycles to prevent the compressor from being damaged.
1) Restore the system power. The LCD (liquid crystal display) will display
the room temperature. The LCD will illuminate at the touch of the red
or blue arrow keys. LCD will return to its normal state after 10 sec-
onds.
2) Set the fan switch to the ON position. The system blower should start.
3) Set the fan switch to the AUTO position. The system blower should stop.
Image shows
room temperature of 78.
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4) Set the system switch to the HEAT position and depress the red
arrow key until the temperature set point is at least 3 degrees
above the room temperature. The LCD will display a flame icon
to indicate heat. The heating system should start within several
seconds (the system blower may not come on immediately).
5) Set the system switch to the OFF position. The system should shut down within several seconds. The LCD
will again display only the room temperature.
6) Set the system switch to the COOL position and depress the
blue arrow key until the temperature set point is at least 3
degrees below the room temperature. The LCD will display a
snowflake icon to indicate A/C. The cooling system should start
within several seconds. WARNING: Do not perform this test if the outdoor temperature is below 50 F.
7) Set the system switch to the OFF position. The system should shut down within several seconds. The LCD
will again display only the room temperature.
Programming The User Settings
Temperature Differential is factory set at .5 F (0.25 C) for both heating and cooling cycles. The room tempera-
ture must change .5 F (0.25 C) from the set point temperature before the thermostat will initiate a call for heat or
A/C. This should be appropriate for most applications. However, if the system is cycling on and off too frequent-
ly, the setting can be adjusted as follows.
1) With the system setting in the OFF position, simultaneously
depress the red and blue arrow keys. The LCD (liquid crystal
display) will display the temperature differential setting. Using
the red and blue arrow keys set the differential to the desired
setting of .5, 1, or 2 degrees. The higher the setting, the less
frequently the system will cycle.
Image shows room temperature
of 70 and HEAT set point of 73.
Image shows room temperature
of 78 and A/C set point of 68.
Image shows temperature
differential setting of 0.5.
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2) When the desired setting is made, release the key and the unit will automatically store the setting after 5
seconds.
Cooling Fan Time Delay is factory set at 60 seconds. When the thermostat is set in the COOL position, the
system blower will continue to circulate air for a period of 60 seconds after the compressor(s) has shut off.
This feature can be adjusted.
1) With the system setting in the OFF position, simultaneously
depress the red and blue arrow keys. The LCD (liquid crystal dis-
play) will display the temperature differential setting. Release the
keys and immediately press them again; the display will now show
the fan delay time in seconds. Use the red and blue arrow keys to set the delay time to the desired set-
ting of 0, 30, or 60 seconds.
2) When the desired setting is made, release the key and the unit will automatically store the setting after 5
seconds.
Operating The New Thermostat
1) Set the System switch to either the HEAT or COOL position and the Fan switch to either the AUTO or ON
position. NOTE: In AUTO, the system blower will run only when the A/C or heat is running. In ON, the
system blower will operate continuously.
2) Use the red and blue arrow keys to select the desired temperature set point.
3) The LCD (liquid crystal display) displays the room tempera-
ture on the left and the set point temperature on the right.
Note: The set point temperature may sometimes differ slight-
ly from the room temperature due to a rapidly changing room
temperature or a differential setting of 1 or 2.
Image shows room temperature
of 78 and A/C set point of 68.
Image shows fan delay
setting at 60 seconds.
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Understanding Additional Features
•High Temperature Protection: While in the HEAT position, if the room temperature reaches 93 F (34 C),
the thermostat will automatically shut off. In the unlikely event the room temperature reaches 99 F (37 c), a
mechanical bimetal switch will shut off the thermostat.
•Low Temperature Protection: While in the HEAT position, if the room temperature drops below 40 F (4
C), the thermostat will automatically initiate a call for heat.
•Compressor Protection: To protect the system compressor(s) from damage, the thermostat features a 5
minute delay. After the cooling system (or heat pump turns off), the thermostat will not allow it to re-start
until the 5 minute delay expires. A blinking snowflake or flame (heat pump) indicates this feature has been
activated. Once the 5 minute delay expires, the snowflake will illuminate continuously and the system will
be able to re-start when called upon.
NOTE: For the purpose of unit installation, this delay can be overridden by pressing the RESET button.
This will erase any programmed settings.
•System Reset: The thermostat can be reset to factory software settings. All user entered settings will be
lost. The reset will also override the 5 minute compressor protection feature. To reset the thermostat, gen-
tly press the reset button on the front panel using a paper clip or similar small pointed object.
•Low Battery Detection: Low battery power is displayed by the illumination of a battery icon in the LCD.
The thermostat can operate for a period of 2 months once the warning has been initiated. Two fresh AA
Alkaline batteries should be installed as soon as the warning icon illuminates.
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Troubleshooting
SYMPTOM CORRECTIVE ACTION
Display is blank Install 2 fresh AA Alkaline batteries
No heat Set system switch to HEAT and raise set point above room temperature.
Check thermostat wiring and connections.
Check pilot light or HSI system on furnace.
No cool Set SYSTEM switch to COOL and lower set point below room temperature.
If snowflake is blinking, allow the 5 minute compressor lock-out to expire.
Check thermostat wiring & connections.
Blinking snowflake/flame Allow the 5 minute compressor lock-out to expire.
System turns on/offAdjust the differential setting on the thermostat.
too frequently or Ahigh differential decreases cycle rate and a low differential increases cycle
not enough rate.
Display is not illuminated Touch the up or down arrow key. Display will illuminate for 10 seconds.
Change the batteries (display will not illuminate when batteries are low)
Room temperature and Normal (depending on differential setting).
set point disagree Check for drafts that could quickly change the room temperature before the
system is able to correct it.
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(Troubleshooting cont.)
SYMPTOM CORRECTIVE ACTION
System fan runs continuously Set fan switch to AUTO.
Check thermostat wiring & connections.
HI is displayed Reduce room temperature or allow a newly installed thermostat to
acclimate.
HI indicates a room temperature reading greater than 90 F (32 C).
LO is displayed Increase room temperature or allow a newly installed thermostat to
acclimate.
LO indicates a room temperature reading less than 45 F (7 C).
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Wiring Diagrams
Typical 5-Wire System
RC RH GYWBO
Install Ju
HEAT 24 VAC
TRANSFORMER
COM
HOT
COOL 24 VAC
TRANSFORMER
COM
HOT
FAN
CONTROL
COOL
CONTROL
HEAT
CONTROL
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Wiring Diagrams
Typical Single Stage Heat Pump System
RC RH GYWBO
Install Jumper Install Jumper
COO
TRA
REV. VALVE
COOL ENERGIZED
24 VAC
TRANSFORMER COM
HOT
FAN
CONTROL
COMPRESSOR
CONTROL
REV. VALVE
HEAT ENERGIZED
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Wiring Diagrams
Typical 2-Wire Millivolt System
RC RH GYWBO
Install Ju
COO
TRA
COM
HEAT
CONTROL
24 VAC
TRANSFORMER
HOT
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Wiring Diagrams
Typical 4-Wire System
RC RH GYWBO
Install Jumper
COO
TRA
HEAT
CONTROL
COM
24 VAC
TRANSFORMER
HOT
COOL
CONTROL
FAN
CONTROL
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Warranty
ONE YEAR LIMITED WARRANTY
Motors & Armatures Inc. warrants each new MARS thermostat against any defects due to
non-conforming material or workmanship for a period of one year after the original date of
purchase by a professional service technician and does not include the cost of removal or
re-installation. This warranty extends to the contractor or dealer who purchased the
product from a wholesaler. For warranty claims, consumers should contact the contractor
or dealer who installed the thermostat.
This warranty and Motors & Armatures’ liability does not include damage to merchandise or
thermostat resulting from accident, alteration, neglect, misuse, improper installation, or any
other failure to follow Motors & Armatures’ installation and operating instructions. Contact
Motors & Armatures Inc. for full details on product warranty policy.
Motors & Armatures Inc.
250 Rabro Drive East
Hauppauge, NY 11788
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INSTALLATION AND OPERATING INSTRUCTIONS
Non-Programmable Electronic Thermostat Heat/Cool
®
Model 70803
70803-IM 12/18/06 2:10 PM Page 16