This electric hot plate is a stationary single-burner heating device for the natural science classrooms — biology, chemistry, physics and astronomy — of general secondary education institutions. It is an electric heater used during demonstration experiments and practical and laboratory work for heating liquids, solutions and bulk substances in vessels with a flat bottom, for bringing them to the boil and for maintaining a temperature over a long period. Connection and work with the plate are provided by the teacher or the laboratory assistant, students work only under supervision, and the recommended age of learners is from 10 years, that is pupils of grade 5 and above.
The plate is powered from a single-phase alternating current mains at a rated voltage of 220 V and a rated frequency of 50 Hz; connection to a mains with other values of voltage or frequency is not allowed. The rated power consumption is 1500 W. The heating element is of closed design, protected by a solid working surface: the plate has no open spiral that could be touched accidentally or have liquid spilled on it. There is one burner of cast iron with a diameter of 155 mm, the heating level is set steplessly by a rotary switch on the body, the working surface temperature ranges from 120 to 320 °C, a built-in thermostat with overheating protection keeps the set temperature and a light indicator on the body signals the operation of the heating element. The body is made of steel with a heat-resistant coating and stands on four heat-resistant non-slip feet. The plate belongs to protection class I against electric shock and is earthed; the power cord is non-detachable, 1.0 m long, with a European plug with an earthing contact. Overall dimensions, width by depth by height, are 235 × 215 × 75 mm and the net weight is 2.4 kg. The plate is installed on a table, on the level stable surface of a laboratory or kitchen table, and is supplied assembled and needing no preliminary adjustment. Operating conditions are the premises of an educational institution at an air temperature from +5 to +40 °C and relative humidity from 40 to 60 % without condensate. Marking and operating documentation are in Ukrainian, the marking carries the trade mark, the model and a place for the inventory number, and the documentation comprises the passport with the warranty coupon and the operating instructions. The service life is 5 years and the warranty period is 12 months.
The set includes the Labotrix Heat P1 electric hot plate — 1 pc; the passport with the warranty coupon — 1 pc; and individual transport packaging — 1 pc, an individual corrugated cardboard box with the contents fixed inside. The power cord with the plug is a non-detachable part of the body of the plate and is not supplied separately, laboratory and kitchen vessels are not part of the set and are obtained separately, and the plate is supplied ready for connection and needs no assembly before the first use.
Before the first work the transport stickers and the protective film are removed, including from the surface of the burner, the burner and the body are wiped with a dry soft cloth and the plate is installed with the switch in the O position. The first heating is then carried out: without a vessel on the burner the switch is turned to the maximum position and the plate is switched on for 3 to 5 minutes so that the factory-applied technological grease burns off — this is the only case foreseen by the passport in which the plate may be switched on without a vessel, and the slight smoke and specific smell that appear are normal and do not recur. In work, vessels with a flat, level and dry bottom of a diameter from 155 to 200 mm are used, filled to two thirds of their volume, placed in the centre of the burner and kept within the outline of the body. The switch positions are O for the plate switched off, the minimum position of about 120 to 150 °C for keeping a dish or a solution warm and for slow evaporation, the middle position of about 200 to 250 °C for even heating of solutions and for work on a water bath, and the maximum position of 320 °C for bringing a liquid quickly to the boil; intermediate positions are also allowed because the regulation is stepless. After switching on the indicator glows steadily and, once the burner reaches the set temperature, it goes out and then switches on and off periodically, which is the normal working mode of the built-in thermostat. The plate is not left switched on continuously for more than 4 hours in a row and is then given a break of 30 minutes.
The plate is installed on a level, stable, non-combustible horizontal surface at a distance of 20 cm from walls, furniture, curtains and other combustible materials, with 50 cm of free space above the burner, and the cord is laid so that it does not touch the heated burner, does not hang from the edge of the table and does not cross walkways. The mains socket must have an earthing contact and be rated for a current of 10 A, and the plate is not connected through one extension lead or adapter together with other powerful consumers. During work the body and the burner become very hot, so heat-resistant gloves, holders or laboratory tongs are used, and after switching off the burner stays hot for 30 minutes, so the plate is neither moved nor cleaned until it has cooled completely. Flammable and volatile substances such as alcohol, ether, acetone, petrol and solvents are never heated on the burner or on a water bath, because the burner reaches 320 °C and ignites them; hermetically closed vessels and aerosol cans are not placed on the burner, and the plate is not used for heating a room or drying clothes, footwear or other objects. Cleaning is carried out only after complete cooling and disconnection from the mains: the burner is wiped with a dry or slightly damp soft cloth and burnt-on residues are removed with a wooden or plastic scraper, while the body is wiped with a cloth moistened in a neutral detergent solution and then dried. Abrasive powders and pastes, metal brushes and scrapers, solvents, acetone and agents containing chlorine or acid are not used and the plate is not washed in a dishwasher. At least once a month the integrity of the cord insulation, the condition of the plug and the absence of cracks and chips on the burner are checked, along with the stability of the plate and the condition of the feet; the plate needs no lubrication or calibration by the user and repairs are made only by an authorised service centre.
