Perfect for medium to heavy seasonal or light residential use, the Centrex 2000 A/F AC/DC allows for both a longer composting cycle, and larger waste volumes. The increased surface area in the evaporating chamber coupled with the larger heating element also provides better evaporation when the unit is on AC power. When used seasonally by up to 7-9 adults, compost will normally only need removing annually each spring. In residential use compost will have to be extracted more frequently. The Centrex 2000 A/F AC/DC combines the features of the non-electric and electric units to produce a hybrid unit that will be ideal for those anticipating 110 volt power in the future, those who are in an area that sees frequent power outages, or those who would like to take advantage of the evaporative capacity of the heater when 110V electricity is available to them. Even with the evaporation capacity, the overflow drain should be installed with this unit as there will be overflow when the unit is being used in DC mode, and when it is used to maximum capacity in AC mode. The Centrex 2000 A/F AC/DC is designed for use with a Sun-Mar Dry Toilet (purchased separately). This unit is ideal for those who do not have water, but still want the composting action to take place outside of the bathroom area. The Centrex 2000 A/F AC/DC is supplied with a 29½" pipe piece (10" diameter). This is long enough if the floor of the bathroom is up to 38" above the surface that the composter is placed on. The pipe piece can be cut to size and additional pieces ordered if necessary. The Centrex 2000 A/F AC/DC requires that 2 vent stacks be installed to handle the separate venting functions. The 2" vent is in use when the AC fan is in operation, and the 4" vent is venting the unit passively when there is no power available. As an extra option, we include a 12 Volt 1.4 Watt fan with the Centrex 2000 A/F AC/DC. You may want to install this fan if the unit is to see maximum capacity use, and you should install the 12 Volt fan if you have to put any bends in the 4" vent stack, as you will then lose the "chimney effect" advantage of a vertical stack, and will need to provide air movement with the fan. While in AC operation, the unit should not require that an overflow drain be connected, unless it is being used heavily. While in DC operation, the overflow drain should be connected. Click here for more information on handling excess liquid.