A refrigerated warehouse uses electric defrost for its evaporators. The defrost termination is achieved via a temperature sensor. The defrost heaters are powered by a 575 V, 3-phase supply. If one phase of the defrost heater circuit fails, resulting in an open circuit, what is the most likely immediate consequence for the remaining working heaters?

Question: A refrigerated warehouse uses electric defrost for its evaporators. The defrost termination is achieved via a temperature sensor. The defrost heaters are powered by a 575 V, 3-phase supply. If one phase of the defrost heater circuit fails, resulting in an open circuit, what is the most likely immediate consequence for the remaining working heaters?

Answer options: ✅ The remaining heaters will operate at reduced power, leading to incomplete defrost.

• The remaining heaters will draw excessive current, potentially tripping a breaker or burning out.
• The system will immediately shut down due to a phase loss monitor.
• The defrost cycle will continue normally, as heaters are single-phase loads.

Correct answer: The remaining heaters will operate at reduced power, leading to incomplete defrost.

Explanation: In a 3-phase heater bank, if one element or phase opens, the remaining elements that are typically wired in a wye or delta configuration will still receive power but may experience a voltage imbalance or operate at a reduced, unbalanced power. This leads to insufficient heating and incomplete defrost, rather than immediate overcurrent for the other elements, assuming they were correctly specified for the 3-phase supply.