"Dave M." wrote:

I've got the Honeywell CT3200, which matches your pictures but not
your description. My unit has 3 dip switches and a larger fuel
switch.

I obtained the documentation for a MagicStat CT3300 and it shows a
diagram of the back of the unit that is identical to what I have. I
copied that diagram and it can be seen he

http://www.fileden.com/files/2008/7/.../Magicstat.gif

The PDF file itself can be downloaded from he

http://www.fileden.com/files/2008/7/...StatCT3300.PDF

The manual offers no suggestions about altering the duty cycle.

That appears to be the case from what I read as well.

The furnace is expected to cycle about 5 times per hour and
is meant to hold within 1 deg F of the setpoint.

That's a pretty tight temperature range and to be able to hold it within
1 degree F and keep to only 5 cycles per hour really depends on a lot of
factors (how the premesis is constructed, how drafty it is, how cold /
windy is it outside, how many BTU's the furnace puts out, etc).

This thermostat basically has 4 binary-selectable settings:

A-in / B-in Conventional warm-air (nat-gas?) furnace
A-in / B-out Electric furnace (or electric base-board?)
A-out / B-in Hot water boiler (radiant heat?)
A-out / B-out not defined (hmm...)

Just guessing here, but why would a thermostat need to know between
which of the above 3 systems is it controlling?

The speed of response of the system? Nat-gas forced-air can respond
faster than a boiler, for example. To anticpate the call for heat
(reduce the control span?)

The thermostat doesn't want the ambient temp to drop too far below the
setpoint, and it doesn't want to over-shoot the setpoint. It's not
clear which of the above options would give me a wider span (and hence
fewer cycles per unit time). I guess I'll just have to experiment - or
buy a new thermostat with a user-settable span or hysteresis setting.