Emerson 850 Thermostat User Manual


 
Symptom Possible Cause Corrective Action
No Heat (continued) 5. Heating system requires service or Diagonistic: Set SYSTEM Switch to HEAT and
thermostat requires replacement. raise the setpoint above room temperature. Within
a few seconds the thermostat should make a soft
click sound. This sound usually indicates the
thermostat is operating properly. If the thermostat
does not click, try the reset operation listed below.
If the thermostat does not click after being reset
contact your heating and cooling service person
or place of purchase for a replacement. If the
thermostat clicks, contact the furnace manufacturer
or a service person to verify the heating is operating
correctly.
No Cool 1. SYSTEM Switch not set to COOL. Set SYSTEM Switch to COOL and lower temperature
below room temperature.
2. Loose connection to thermostat or system. Verify thermostat and system wires are securely
attached.
3. Cooling system requires service or Same procedure as diagnostic for No Heat
thermostat requires replacement. condition except set the thermostat to COOL and
lower the setpoint below the room temperature.
There may be up to a five minute delay before the
thermostat clicks in Cooling.
Heat, Cool or Fan Runs Constantly. 1. FAN Switch set to Fan ON. Check each wire connection to verify they are not
2. Possible short in wiring. shorted or touching together. No bare wire should
3. Possible short in thermostat. stick out from under terminal screws. Try resetting
4. Possible short in heat/cool/fan system. the thermostat as described below. If the condition
persists the manufacturer of your system or
service person can instruct you on how to test the
Heat/Cool system for correct operation. If the
system operates correctly, replace the thermostat.
Furnace Cycles Too Fast or Too Slow 1. The location of the thermostat and/or the Digital thermostats normally provide precise
(narrow or wide temperature swing) size of the Heating System may be temperature control and may cycle faster than
influencing the cycle rate. some older mechanical models. A faster cycle
rate means the unit turns on and off more
frequently but runs for a shorter time so there is
no increase in energy use. If you would like to
increase the cycle time, clip Jumper W-905 as
mentioned in the instructions for Hydronic Heating
Systems. It is not possible to shorten the cycle
time. If an acceptable cycle rate is not achieved as
received or by clipping W-905 contact a local
service person for additional suggestions.
Cooling Cycles Too Fast or Too Slow 1. The location of the thermostat and the size The cycle rate for cooling is fixed and can not be
(narrow or wide temperature swing) of the Cooling System can influence the adjusted. Contact a local service person for
cycle rate. suggestions.
Thermostat Setting and Thermostat 1. Thermostat thermometer setting requires The thermometer can be adjusted +/- 3 degrees.
Thermometer Disagree adjustment. See Temperature Display Adjustment in the
Operation section.
Thermostat Does Not Follow Program 1. AM or PM set incorrectly in program. Check current clock and program settings
2. AM or PM set incorrectly on the clock. including the AM or PM designations for each
3. Voltage spike or static discharge. time period. If a voltage spike or a static discharge
occurs use the Reset Operation listed below.
Blank Display and/or Keypad 1. Voltage spike or static discharge. Replace batteries and check heat/cool system
Not Responding 2. Battery change required. for proper operation. If a voltage spike occurs use
the Reset Operation listed below.
TROUBLESHOOTING
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