What is "dry burning" of explosion-proof electric heaters?
 
  What is "dry burning" of explosion-proof electric heaters?
For the safety device of explosion-proof electric heaters, its characteristics are quite obvious. Let's take a detailed look at the situation. First, its equipment is relatively reasonable, and the overall technology is very mature. This means that during operation, abnormal situations are rare, thus reducing usage costs. Moreover, during installation, the overall installation period is relatively short, which better ensures safe completion of operation. Second, its technology is very reliable, adopting an internal thermal cycle heating method, which improves its utilization rate and ensures energy-saving effects. During operation, its cost is very low. The planetary reducer indicates that an important point is that this safety device is very reliable and can be used in many different industries, with more pronounced effects. For example, it is used in processes such as hot pressing, calendering, and extrusion.
Currently, explosion-proof electric heaters on the market are generally equipped with various temperature controllers or thermal protectors. These components can disconnect the circuit and stop heating when the temperature of the heated water reaches the set value at the test point; when the water temperature at the test point drops to the lower limit, the device will automatically close. Many explosion-proof electric heater manufacturers demonstrate products with such temperature controllers under long-term power-on in air to prove their products can "prevent dry burning." In fact, this so-called dry-burning prevention promotion, if not intentionally misleading by the manufacturer, is a misconception by the product maker. Indeed, this demonstration itself not only fails to prove that the product can "prevent dry burning"! On the contrary, it proves that without water, the product repeatedly dry-burns time and again.
Electric heater "dry burning": The deadly "killer" of solar water heaters
"Dry burning" refers to the heating state when there is no water or water below a certain level in the tank during electric heater operation. Dry burning is not a set working state but an accident during system operation, i.e., a fault state. Continuation of this state will lead to more serious consequences. When the electric heater "dry burns" in the tank, the high temperature generated by the heater is conducted to the tank connection parts, repeatedly heating and damaging the sealing ring (gasket), insulation layer, and tank. Compared with most "quick heating" electric heaters, a fully cast aluminum electric heater with the heating element and sealing surface cast as one unit heats up faster and higher at the tank junction during dry burning, accelerating the aging of the sealing ring more quickly, causing greater harm.
In a single solar water heating system, the "dry burning prevention" of the auxiliary electric heater may only need to achieve "prevent continuous dry burning." That is, when power is supplied in a water-deficient or waterless state, the system should terminate operation within a limited time before consequences occur, cutting off power for treatment. Before the waterless or water-deficient state is eliminated, regardless of how the temperature controller acts, whether the system power is cut off or not, it should not be powered again. Of course, if it can be achieved that power is not supplied once there is no water or insufficient water, or dry burning does not occur, it is actually a more thorough "dry burning prevention." Although many control instruments on the market have the function of power-off when water is insufficient (or absent), sometimes due to sensor instability, the signal of no water (or insufficient water) is uncertain.
In fact, once an electric heater is inserted into the tank of a solar water heater, it becomes a storage-type electric water heater. Storage-type electric water heaters have formed a complete production technology management system and implementation standards through long-term application. According to (GB4706.1—12) requirements, such storage-type electric water heaters should be equipped not only with an auto-reset temperature controller but also with a non-auto-reset device specifically for dry burning prevention. When the water being heated in the heater is less than a certain amount, this non-auto-reset device will forcibly disconnect the circuit, stopping heating. Only after relevant personnel confirm that the fault state has been eliminated and manually reset the device can the system be put into operation again. This prevents the serious consequences of dry burning accidents.