Types A and B heaters are intended for the following applications:

(a) Type A heaters. Type A heaters are intended for installation in machinery lubricating oil sump tanks to maintain the proper temperature and viscosity of the oil where little circulation or heat is provided (for example, reduction gear sumps).

(b) Type B heaters. Type B heaters are intended for use in lubricating oil and fuel systems where heat is required in purifying or to raise the temperature to operating limits required for the applicable machinery.