Proper cable selection for electric water heaters is particularly critical to ensuring stable operation.
Incorrect cable choices often lead to fire hazards. Internally, water heaters may use either single-strand or multi-strand copper cables.
Currently, I opt for single-strand copper cables due to their reliable quality and consistent cross-sectional area, which mitigates risks of overheating and potential fires caused by oxidation or other issues. The downside, however, lies in more challenging installation—requiring pre-cutting and bending by trained personnel.
Multi-strand cables are also used by some manufacturers but demand close attention to variations in cross-sectional area. While easier to install, they pose long-term risks: oxidation can cause strand breakage, reducing effective cross-sectional area and leading to overheating. Moreover, accurately verifying the cross-sectional area of multi-strand cables is difficult. Substandard multi-strand wiring introduces fire risks, especially if terminal crimping is improperly executed—either failing to secure all strands or damaging them—both of which reduce effective conductivity and elevate fire hazards.
Regarding cable gauge, for 4500W or 5000W units, a 12 AWG (American Wire Gauge) copper cable is suitable for connections between heating elements and thermostats. Alternatively, a 4 mm² single-strand copper cable may be used.