Problem: Thermostat works, but
turns furnace on and off rapidly, causes major swings in
temperature, or shows readings other than the setting.
Background: Normally, properly in stalled
thermostats require little or no attention. However, some
common problems can often be remedied by the homeowner,
thereby saving the expense of a service call. If the
thermostat has been recently installed, consult the
instructions that came with the unit. For other thermostat
Doesn't Work and
What to do: If the thermostat turns the furnace on
and off relatively often, the problem is likely that the
burner-on period is too short. Inside the thermostat is a
heat anticipator lever which can be set to a range of
scale markings. Adjust the lever one scale mark higher.
Wait at least several hours for the thermostat to
stabilize. If the thermostat allows major swings in
temperature, the problem likely is a “burner-on” period
that is too long. In this case, adjust the heat
anticipator lever one scale mark lower. Again, wait
several hours for the system to stabilize.
Special advice: If the thermostat set ting and the
thermometer reading disagree, the thermostat may not be
level, it may be affected by drafts or radiant heat, or it
may be out of calibration. To check whether it is level,
place a bubble level or a plumb line against the unit. If
the thermostat is being affected by drafts and heat, it
may need to be relocated. If it is out of calibration,
read the unit’s instructions to find out how to adjust it,
or call a technician.
Helpful hint: Normally
a thermo stat should be placed at least 5 feet off of the
floor, away from sources of heat (including sunlight), and
on an interior wall. It should also be positioned away
from corners and dead spots behind doors and in closets.
It should not be located on walls that have ducts or pipes
inside them, and should be protected from air flow within
the wall. Plug any holes cut into the attic or crawl space
for plumbing and wiring, and plug the hole behind the
thermostat where the low voltage wires emerge.