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Frequently Asked Questions
The following
are estimated settings of the heat anticipator for specified heating
systems. Since these are estimated settings, further adjustment may be
needed if the system is running too long or too short. If the system is
running too long, adjust the heat anticipator to the next smallest number.
If the system is running too short, adjust the heat anticipator to the next
largest number. Try a setting for a few hours before making an adjustment.
Don’t set the heat anticipator to small of a number because it can be
damaged and the thermostat will have to be replaced.
The CT87 is
accurately calibrated at the factory under controlled conditions and no re
calibration should be necessary. Verify against another thermometer that the
room temperature reading is accurate and that the set point is not being
maintained. If the room temperature is inaccurate then check to make sure
the thermostat is not subjected to radiant heat from the sun or appliances.
If the set point is not being maintained by the thermostat, such as
overheating or underheating, then check to make sure the thermostat is level
and the heating anticipator is set properly. If those two things check out
then test to see if re calibration is necessary. Remove the cover ring so
you can observe the mercury switch. After a 5 to 10 minute off period (with
thermostat set point below room temperature) slowly raise the setting until
the mercury falls. If the room temperature indicator and setting indicator
read the same temperature when the mercury falls then no re calibration is
necessary.
If re calibration is necessary, proceed as follows.
1. Turn the setting dial a few degrees above room temperature and remove
cover.
2. Slip the 104994 Calibration Wrench onto the hex under the bimetal coil
and holding the dial firmly, turn the hex counterclockwise for Group 1
models and clockwise for Group II models, until the mercury breaks contact.
FOR CALIBRATION ID ONLY -- IF THE THERMOSTAT SCALE PLATE MOVES (POINTER IS
STATIONARY) WHEN SETTING TEMPERATURE, THE THERMOSTAT IS A GROUP I MODEL. IF
THE SCALE PLATE IF STATIONARY AND POINTER MOVES, THE THERMOSTAT IS A GROUP
II MODEL.
3. Turn the dial to a low setting so that the state loses the heat it has
gained from your hands and its own operation. Wait at least 5 minutes.
4. Slowly turn the dial until the pointers read the same.
5. Firmly holding the dial from turning, carefully turn the hex clockwise
for Group I models and counterclockwise for Group II models, until the
mercury switch slips to the heating contact end of the tube.
6. Recheck calibration, select the desired temperature, and replace cover
It is
important to determine where the blue wire was attached on the old
thermostat and what the function of the wire is. The blue wire is used for
different things depending on the electrician. It could be the common wire,
the power to the cooling transformer (in five wire system),or the ac
compressor.
Possible
solutions:
1. Transformer. Disconnect all leads connected to the "R" terminal
of the low voltage control circuit transformer. Measure across the
transformer R-C terminals, checking to see if the output exceeds 28vac. If
so, most likely the transformer is the problem. Replace the transformer with
a NEMA-rated Honeywell AT72 (at least 40VA).
2. Base plate. Oxidation of the silvex ball and/or parts of the metal
circuit grid in the thermostat. Either could cause the circuit resistance to
increase which results in longer cooling on cycles. Replace subbase.
3. Wire. Should use 18 gauge wire. Check the gauge of the wire that runs to
the thermostat. Smaller diameter wire (20, 22 or smaller) combined with long
thermostat wire run, can cause high circuit resistance (with a drop of as
much as 3-4 volts) and poor thermostat performance.
Level the
subbase. This can be done by using a plumb line or a spirit level. --drop a
plumb line and align the marking on the base to the plumb line on the wall.
The plumb line on the wall should fall over the plumb line marking on the
base. On the 104456B the marking is a line and on the Q539 the marking is a
set of diamonds. Spirit Level -- lay spirit level at the top of the 104456B
base or across the leveling posts on the Q539. (switching subbase.)
The mercury
is contaminated. If mercury is contaminated (not bright and shiny)or bulb is
broken, replace thermostat.
The smoke is
caused by the heat anticipator burning out. If the heating anticipator is
set too low then the resistor is producing more fake heat then necessary and
it could damage the heat anticipator. It is always best to match heat
anticipator setting to the current draw of the heating circuit. If the
heating anticipator is damaged then the customer must replace the thermostat
at their own expense, WARRANTY IS VOID.
Make certain that the wires are connected to the "R" and "W" terminals for heating only and "R" and "Y" for cooling only. If they are then replace the thermostat at the store.
If you are
removing an old thermostat that contains mercury in a sealed tube, do not
place the old thermostat in the trash. Contact you local waste management
authority for instructions regarding recycling and the proper disposal of
the old thermostat.
Most of Honeywell's programmable thermostats require 24 volts coming from your heating or cooling system. Fortunately, a vast majority of thermostats that are already installed in homes are powered by 24 volts.
One way to verify that you are currently using 24 volts is to look at your old thermostat. If it is a mechanical thermostat, meaning non-digital display, simply remove the cover and look for 30 V stamped on it. If you see this, you have a low voltage system that will be compatible with a 24 volt thermostat. If you see 120 or 240 vac on your thermostat, a low voltage thermostat will not work with your system.
Regardless of the voltage, Honeywell strongly suggests that you turn off the power to the system at the furnace or at the fuse or circuit breaker panel before installing your thermostat.
If you are unsure about your voltage, please contact a local heating and cooling contractor in your area for assistance.
When removing your old thermostat from the wall, it is important that you label the wires. With the power to your furnace turned OFF, disconnect each wire from the sub base Take the disconnected wire and simply use a piece of masking tape to label it with the old terminal designation. For example, if you removed a wire that went to a screw with the label "G", write the letter "G" on a piece of tape and attach it to that wire. After you have labeled all the wires, you can wrap them around a pencil to keep them from falling back into the wall. It is important to note that if you find an extra wire that is NOT connected to your old thermostat, you will NOT be connecting it to your new one. Simply use some electrical tape to tape it off and put it back in your wall.
Once you have done this, you are ready to install the new thermostat. Simply connect the labeled wires with their corresponding terminal designations on your new thermostat.
The following
is a general list of Honeywell thermostat terminals and their functions:
R - Power
Rh - Heating transformer power
Rc - Cooling transformer power
W - Heating load
Y - Compressor
G - Fan
W2 - 2nd stage of heating
Y2 - 2nd stage of cooling
C - Common
Please note: if your old thermostat had a wire on a C terminal and your new
thermostat model number begins with the letters CT, with the exception of
the CT3611 and CT70, label the wire and tape it off. This wire will not be
used.
Copyright © 1999 Honeywell Inc. All rights reserved