Illustration A Horizontal One-Tank System

Above If you have (or plan to add) a sunspace or greenhouse to your home, a horizontal one-tank batch heater can be ideal. Mounted high on the sun-space's rear wall, it takes up very little room, and the sunspace's inherently mild interior climate means that the batch heater's enclosure can be as simple as the hinged boards of rigid insulation shown here. The insulation is closed manually at night to help keep the water warm.

Above Because they lie on their sides, horizontal tanks have difficulty taking  advantage of warm water's natural tendency to rise. For maximum efficiency, the inlet and outlet tubes must be very carefully designed and installed (as shown) to minimize unwanted mixing of the tank's thin layers of hot and cold water.

Illustration C Vertical Two-Tank System

Below Two-tank systems work even better in a vertical orientation because the warmest water is allowed to rise to the top of the upper tank, where it easily can be drawn off without mixing with the incoming cold water. In addition, this freestanding ground-mount avoids any structural problems posed by the wall mounts of the first two systems we've seen. The pipes connecting this batch heater to the home's existing water heater are in an underground trench for heat retention and aesthetics. (In cold climates, the relatively long pipe run means that electric heat-tapes are mandatory to prevent freezing of the underground pipes during sudden, unexpected cold snaps.) This particular design uses double glazing and a cusp-shaped reflector to increase the collection efficiency. A cutaway view of a cusp is on page 26.

it belongs.) Together, triple glazing plus a selective surface work virtually as well as movable insulation, but without the bother.
There's another heat-loss problem that affects batch heaters in the snow belt: freezing. Because water expands as it freezes, burst tanks and pipes are a very real danger. Good bye, hundreds of bucks.
There are two basic approaches to solving the problems of freezing. One is to mount the batch heater in a sheltered location such as a sunspace or a green- house. (See Illustration A.) Because the sunspace or greenhouse provides both temperature moderation and weather-proofing, this type of batch heater can
be simpler and less expensive than designs that must face the elements alone.
The second method of freezeproofing is for batch heaters in their own enclosures, whether freestanding or built as part of a home's exterior wall: You simply drain the tank in early winter, and let it stand idle during the coldest months. (A rule of thumb: Hatch heaters should be shut down during any month that racks up more than 1,000 degree-




Above Vertical two-tank systems are plumbed much like their horizontal cousins. Drain valves must be located at the lowest point of the system's plumbing, and all pipes should maintain a steady downward slope to that point.