My gas heater has no electrical connection either. It uses a thermocouple to open and close the gas valve. A thermocouple generates minute voltages based on temperature differences. The heater requires no timer because it senses demand for heat from the water flowing through it. I think they also have flow sensors in them too. All you should need in an Intermatic (or another brand) time switch, I replaced mine with one from Home Depot. I also have another timer for my booster pump which is wired to only function if the main pump switch is on.