Does a CSP transformer need to be de-energized to replace a fuse?

• A. Yes
• B. No
• C. Sometimes
• D. Depends on model

Answer: (A)

Safety and proper maintenance require de-energizing before replacing protective devices like fuses. A fuse protects the circuit by interrupting current during a fault, but it only does its job safely if there is no voltage present while you service it. Replacing a fuse while the transformer is energized can cause an arc flash, electric shock, or sudden re-energization due to stored energy in the windings. To replace the fuse, power must be shut off, lockout/tagout applied, and the absence of voltage verified before you access and replace the fuse. This approach applies regardless of model, so de-energizing is the correct practice.