If panel requirements are 24 amps, which transformer should be used?

• A. A 20 amp transformer
• B. A 30 amp transformer
• C. A 40 amp transformer
• D. A 50 amp transformer

Answer: (B)

The key idea is to match the transformer's output to what the panel needs, without undersizing. The transformer's amp rating is the maximum current it can safely supply, so using a transformer smaller than the panel's demand risks overloading or triggering voltage issues. The safest, most economical choice is the smallest standard size that is at least equal to the panel’s requirement. Larger ratings are technically fine but wasteful and add cost and bulk. So you pick the standard size just above the 24-amp need, ensuring the panel has enough current without paying for unnecessary extra capacity.