My 44 year old home has oil fired hot water heat, with four zones, each controlled by its own circulator and LINE VOLTAGE thermostat. I want to replace one thermostat with a programmable type, but these are all low voltage (24 volts). Exactly what do I need–I assume a step down transformer, and some type of relay? Ive done extensive home wiring so the connections are no problem–I just need to know the actual parts. Thanks for the help!Ken Harris