A heating apparatus comprises an exposed tube formed into an outer coil and an inner coil. The outer coil is formed around the inner coil with a gap separating the outer coil and the inner coil. The tube is supported by a support frame. The heating apparatus also comprises a spacer frame that extends from the top portion of the support frame to the base portion of the support frame. The spacer frame has a plurality of apertures formed therein, each aperture operable to support a corresponding ring of the outer coil. The apparatus also comprises a spacer rod having a first end that couples to the top portion of the support frame and a second end that couples to the base portion of the support frame, wherein the spacer rod is threaded through the spacer frame between the outer coil and the vertex of the spacer frame.