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Listed below are links to installation/operating instructions for 90 Series Digital thermostats.
For Single Stage models there are 3 possibilities to consider (excluding tampering):
Loss of power from the system and back-up batteries not functioning.You may want to see if the thermostat maintains the display when removed from the subbase to determine if the batteries are functioning on power loss. You may want to check the fuses or breakers, the on/off switch on the furnace and the door to the blower compartment. If the blower compartment door is loose there may be a switch inside the door that disconnects power to your system. Also consult the furnace manufacturer to see if they have any other ideas on what could drop out the system power.
Static electricity or a voltage spike from the heating equipment might be resetting the thermostat. Static electricity can be eliminated by touching something before touching the thermostat to dissipate the static charge. A voltage spike from the equipment can be eliminated using an isolation relay as described in this instruction sheet 0037-5426.
You can also check the wire routing to verify the thermostat or remote wires are not running parallel to high voltage lines with high inductive loads that could (in extreme cases) create a voltage spike at the thermostat.
For Multi-Stage or Heat Pump staging models there are other possibilities to consider and they are as follows:Loss of power from the system. You may want to check the fuses or breakers, the on/off switch on the furnace and the door to the blower compartment. If the blower compartment door is loose there may be a switch inside the door that disconnects power to your system. Also consult the furnace manufacturer to see if they have any other ideas on what could drop out the system power. Static electricity. Static electricity can be eliminated by touching something before touching the thermostat to dissipate the static charge.
A voltage spike from the heating equipment might be resetting the thermostat and if you have a system that generates a high voltage spark (D.S.I.) you may want to contact the Equipment manufacturer for information on how to eliminate that condition. You can check the wire routing to verify the thermostat or remote wires are not running parallel to high voltage lines with high inductive loads that could (in extreme cases) create a voltage spike at the thermostat.
On the 1F92-371, 1F93-380, 1F94-371, 1F95-371 and 1F95-377 the E2/P switch controls how the E2/P terminal of the thermostat will be energized. When the switch is in the E2 position (down), the E2/P terminal will be energized only when in emergency heat. When the switch is in the P position (up), the E2/P terminal will always be energized except when in emergency heat. Consult the equipment manufacturer or a qualified heating/cooling service person if your system requires an E2 or P terminal output before setting this switch. If your system has no connection to E2/P, no change in the switch setting is required.
On the 1F95-391 the E2/P Switch is located on the back of the thermostat body. This switch controls how the DHM terminal will be energized. 1. In the P position (up) the DHM terminal will be energized on a call for dehumidification. 2. In the E2 position (down) the DHM terminal will always be energized except on a call for dehumidification. The switch must be in the E2 position on some electronically controlled variable speed blower systems.
The most common reasons why a thermostat does not follow your program are:
1. AM or PM set incorrectly in program 2. AM or PM set incorrectly on clock 3. Voltage spike or static discharge
Check current clock and program settings including the AM or PM designations for each time period. If a voltage spike or static discharge occurs use the RESET operation by pressing PROGRAM RUN once and release, and then press FAN, TIME BACK and TEMPERATURE DOWN arrow at the same time and hold until your display goes blank then release. Models with EMR (Energy Management Recovery) start early to make the temperature they are programmed for by the time specified in the program. See the Configuration Menu of your thermostat Operating Instructions for information on how to disable EMR if you do not want the thermostat to start early.
Adjustable Heating and Cooling Cycle Times (also called Anticipation ).
90 Series Premium thermostats have a feature that allows you to increase or decrease the cycle times in heating and cooling. This is useful if you think your cycle times are too long or too short. 90 SeriesPremiums are adjusted by going into the Installer/Configuration Menu; see your Installation/ OperatingInstructions for adjustment.The higher the number you select, the longer the cycle. The lower the number you select, the shorter the cycle. The range of adjustment for HEATING is from 2 to 40. The factory Preset is 5. The range of adjustment for COOLING is from 9 to 40. The factory Preset is 14. The cooling will not go below 9 because compressors require a longer cycle. The Heat-Pump models also have an AUXILIARY CYCLE rate adjustment that can be adjusted in the Installation Instructions Installer table. The adjustment range for Auxiliary (heat pump only) is from 1 to 40. The factory default for models 1F92-371, 1F93-380, 1F94-371 and 1F95-377 is (6). The factory default for model 1F95-391 is (8).The chart below shows how this adjustment range affects thermostat performance.
† These numbers are approximate and represent operation with a typical system. Actual temperature differentials and run times will vary based on your building and equipment, as well as outdoor temperature conditions.
Your thermostat is designed to cycle on and off in heating or cooling, keeping your building in an accurate temperature range. This maximizes your comfort by keeping the room temperature very close to the temperature you set. It is not unusual for your thermostat to be set for 70 and cycle on and off at 70 keeping you right on target.
A note on older style thermostats; Anticipation on older style thermostats (mercury bulb or mechanical) used the current draw of the equipment to set the anticipation. Some heating and cooling equipment manufacturers still refer to setting the anticipator to the current draw of the equipment. This does not apply to your new digital thermostat. Right from the box your new thermostat will do an excellent job of keeping your building at an accurate temperature. The information above allows you to customize the performance of your digital thermostat to your requirements.