I have a ceiling mounted heater, 5000 watt, 220 volt with a heater mounted thermostat. I am interested in changing to a wall mounted 24 volt programmable thermostat. How do I accomplish this?

You will have to have a 24 volt transformer and a 2 pole 240 relay with a 24 volt coil. Just wire it up for the W terminal to control the coil of the relay. This will be much like The A/C compressor if you have A/C except use the W rather than the Y.

It depends on what kind of gas valve your heater uses. If it is a 24 volt valve with two wires going to it then you can do it . Just take one of the wires off the gas valve and connect it to on wire of a two wire 18 gauge cable going to where ever you want to put the thermostat, connect the wires to the R. and W. connectors on the thermostat and then connect the second wire back to where you took the wire off the gas valve.