That s because when the heater turns off residual heat from the heater will escape and influence the temperature the thermostat senses.
Mounting thermostat exterior wall.
It s fine but not great to install a thermostat above the heater placing a wall thermostat directly above a wall heater is not ideal.
Fiberglass insulation is great for preventing drafts from affecting thermostat operation.
The thermostat will think that this unusually cold or hot area represents the rest of the home and will.
It was really hard to keep up with manually adjusting the thermostat offset.
Our thermostat is mounted on a wall that is opposite our garage.
One other thing to consider.
If a thermostat has to be placed on an exterior wall make sure the back is well insulated to prevent false readings.
During the winter this caused a 5 degree difference when the temperature dropped.
Mount the control unit to the base using the screws included with your thermostat.
Mount the thermostat base by gently pushing the excess wire back into the wall opening and plugging the hole with a fire resistant material.
A good rule of thumb is to mount it 52 to 60 inches off of the floor.
How high you mount your thermostat on the wall matters.
How to choose a thermostat for your home.
What happens in the specific area being considered for thermostat placement has to be thought out.
Putting a thermostat directly above a heater is ok but not ideal.
Since heat rises it can impact your reading.
If the location takes direct sunlight at certain times of the day especially low sun during the winter that can bring the temperature on the thermostat up by 10 to 15 degrees.