The air heating capability of an indoor heat exchanger is limited to set the temperature of the indoor heat exchanger to a first predetermined temperature Tel or lower during heating. The cover plate includes a plate element that attaches to and at least partially covers a side of the electrical box. A plate is formed in the silicon wafer which can be pivoted about a rotational axis lying in the wafer plane. Discs of non-uniform flexibility also may be employed, and blocking tabs or gripping material may be used to inhibit undesired backward movement of a cleaner when its operation commences.