The Lennox T834C1475 themostat has four wires but the Honeywell TH4110D seems to require five wires - what do I need to do to fit the Honeywell

If the honeywell thermostat is a battery operated thermostat you should be able to make it work with only four wires.

The gerenaly accepted wiring at the thermostat is:

Red wire on the Rh terminal

White wire on the W terminal

Green wire on the G terminal

Yellow on the Y terminal.

The Rc terminal should have jumper already installed to the Rh terminal.

Now your colors may not match the colors I gave you, if they don't you neet to go to your furnace or air handler and look at the low voltage area of the circuit board and see how the colors are matched there and then do the same at the thermostat.