On Dec 29, 8:44*pm, HVAC Guy wrote:
" wrote:
I remember that Thermostat . *The *A and B screws act as a heat
anticipator does ; *the more you back out the A *screw with the B
screw turned all the way in....the greater the differential will be
and the greater the room temperature swing will be.

Your explanation indicates that the amount of turns of the screw is
somehow sensed by the thermostat's circuitry.

This assumption is incorrect.

On this thermostat, the screw is not functioning as the core of an
inductor or coil (as per your explanation). *The only function the screw
has is to bridge the wire contacts on the upper surface of a machined
plastic block. *The wires connect to the PC board.

If variable operating was desired, then Honeywell would have used a
potentiometer instead of a significantly more complicated reactance
circuit.

All the printed manuals for these thermostats indicate that the screw
has basically only 2 settings: *Fully turned in (tightened down) or
unscrewed (turned out) by one turn. *The one turn is sufficient to raise
the underside of the screw head enough so that it is not contacting
(bridging) the wires.

Whenever i adjusted the 'A' screw in or out partially...it DID make a
difference on the cycle time (differential) . I wouldnt give
Honneywell too many accolaides as far as engineering goes because this
thermostat of theirs is a poor example of quality..certainly one
Engineers wet dream to flood the market with a most inexpensive
thermostat without much consideration to accuracy. A proper
electronic thermostat that is designed well, is one where the Person
can make a definitive selection between 1,2,or 3 degrees F.
differential for heating AND for cooling....and not a psuedo-
thermostat like a Honneywell Magic Stat. Sadly, these are things the
typical homeowner isnt up to par on.