I have a SECO TB1540E-G that has a brown wire connected to Terminal E. The thermostat controls an electric A/C unit and a gas furnace. Does someone know what function Terminal E controls? I need to know so I can properly connect a new programmable thermostat.
E is usually for Emergency heat...back-up heat source, for example in a heat pump system to bring on the electric strip heat if the compressor heat can not keep up with demand. W is usually primary heat.
Can you follow the wire to the furnace and see what it is currently attached to on the furnace control board?