Bob said:

> I have been unable to find a thermostat for a furnace  which goes
> from 40 F. to 100 F.

Take one of the old-style round Honeywell thermostats, remove the
cover, and look at the base of the shaft that turns when you turn the
knob.

You will notice that a "wing" extends from the shaft, and stops the
knob from being turned lower than about 42 F or higher than about
88 F.

DO NOT DISASSEMBLE THE DEVICE!!!!  You are sure to break it.
Simply use an X-Acto knife, and shave off the edge(s) of this wing.

The mercury-filled bulb and bimetallic spring will still function as
expected, and you can clearly expect operational accuracy
beyond 88 F, but you will have to use a thermometer to find the
exact 100 F setting.

This is not the best thermostat in the world, and a programmable
unit would be much nicer, but to get 100 F, you will likely have
to go to a supplier of "industrial controls", and pay a fortune.

As for keeping the pipes from freezing, I'd apply the electrical
"heater tape" to the pipes, and insulate the heck out of them
rather than try to heat the whole area.  Insulation is cheaper
than any fuel, and you do not need much heat to keep pipes
from freezing.  Another approach would be to install cut-offs
and drain the pipes in winter.

        jim