Abstract: A preheater unit magnetically attachable to the surface of the oil pan of an automobile engine includes an electric heating unit and a magnetic device situated within a rectilinear shell having an open side closed by a non-magnetic heat transfer plate. The heating unit is encased in the plate and surrounds the magnetic device. The magnetic device includes a permanent magnet disposed between two magnetic end portions situated to be operative in the same plane as the outer planar surface of the plate through parallel spaced apart openings in the plate for magnetically attaching the preheater unit to the surface of the oil pan. A temperature control switch within the shell maintains the heat transfer plate within predetermined temperature limits.

Abstract: A solar heater includes an elongated solar collector having two fixedly connected solar panels of highly heat conductive material supported by a roof clamp on a shingled roof. The bottom edges of each of the solar panels include upturned gutter portions. One form of roof clamp for shingled roofs includes a J-shape shingle clamp member having a clamp bolt extending therethrough, and a solar collector clamp member assembled on the bolt and clamped to the bottom gutter portions of the solar panels. A bottom plate of the J-shape clamp member is slid under a shingle of a first shingle course and under a shingle of a second upper shingle course to carry the bolt into the top of the gap between adjacent shingle portions of the first course and to position a top plate of the shingle clamp member over parts of the shank portions of the first course and over a part of the one shingle of the second course. A clamp nut clamps the collector clamp member and the shinlge clamp member firmly to the contacted shingles.

Abstract: A preheater unit magnetically attachable to the surface of the oil pan of an automobile engine includes an electric heating unit and a magnetic device situated within a rectilinear shell having an open side closed by a non-magnetic heat transfer plate. The heating unit is encased in the plate and surrounds the magnetic device. The magnetic device includes a permanent magnet disposed between two magnetic end portions situated to be operative in the same plane as the outer planar surface of the plate through parallel spaced apart openings in the plate for magnetically attaching the preheater unit to the surface of the oil pan. A temperature control switch within the shell maintains the heat transfer plate within predetermined temperature limits.