Malfunction detector for an oil-fuel heat exchanger

A detector for detecting the level of oil in an oil reservoir comprising:

• a) electrically actuated level sensing means operatively associated with the reservoir so as to sense the level of oil in the reservoir, the level sensing means having an electrical outlet terminal and means to supply a voltage U to the outlet terminal such that voltage U varies in direct proportion to the level of oil in the reservoir;
• b) first circuit means operatively connected to the outlet terminal and having a first outlet junction at which is applied a voltage U.sub.1 which varies as voltage U varies;
• c) second circuit means operatively connected to the outlet terminal and having a second outlet junction at which is applied a voltage U.sub.2 which decreases as voltage U decreases, but does not increase as voltage U increases;
• d) comparison circuit means operatively connected to the first and second outlet junctions so as to compare the difference between voltages U.sub.1 and U.sub.2 with a predetermined reference voltage U.sub.0 and to supply an output signal when the voltage U.sub.1 -U.sub.2 exceeds the reference voltage U.sub.0 ;
• and,
• e) indicator means operatively connected to the comparison circuit means so as to indicate the presence of the output signal.