Does a surge protector have to be on the top breaker spaces?

No code requires it, but landing near the main with the shortest possible leads minimizes let-through voltage, which is why top of bus is standard practice.

Are surge protectors required by code now?

Yes for dwellings. NEC 230.67 requires a Type 1 or Type 2 SPD at dwelling unit services, including service equipment replacements.

What size breaker feeds a Type 2 SPD?

Whatever the manufacturer instructions specify, commonly a 2-pole 15 to 30 amp breaker. Instructions are enforceable under NEC 110.3(B).

Does it matter where a panel surge protector is landed?

For code, barely. For performance, enormously. A Type 2 surge protective device can land on any properly sized 2-pole breaker in the panel, and the NEC does not dictate which slot. But every inch of lead between the busbar and the SPD adds inductance, and during a fast surge each foot of lead can add hundreds of volts to the let-through voltage your equipment actually sees. The manufacturer instructions, enforceable under 110.3(B), all say the same thing: shortest, straightest leads possible, which in practice means a breaker position as close to the SPD knockout as you can get.

The rules that do apply

Surge protection stopped being optional for homes: NEC 2023 230.67 requires an SPD, Type 1 or Type 2, for dwelling unit services, and it applies to service replacements too. Article 242 governs the devices themselves, Type 1 can go on the line side of the main, Type 2 installs on the load side. The SPD breaker size follows the unit instructions, commonly a 2-pole 15, 20, or 30, and whole-panel SPD breakers combining both functions exist for most residential lines and eliminate the lead question entirely.

How to land it right

Punch the knockout adjacent to the chosen breaker, keep the leads untrimmed only if the instructions say length matters less than routing, otherwise cut them short, avoid loops and sharp bends, and twist the hot leads together where the manufacturer recommends it. Top of the bus next to the main is the classic location. Landing the SPD across the bottom two spaces with leads snaked around the entire gutter throws away most of what the customer paid for.

Top of the bus or anywhere

Some argue the SPD should be electrically first so surges meet it before other breakers. The bus is effectively a single node at surge timescales for a residential panel, so slot order matters far less than lead length. Pick the slot that minimizes wire, not the slot with the lowest number.

Field notes

Check the SPD status indicators face where the homeowner can see them, note the install date, and remember the SPD protects against surges, not sustained overvoltage from a lost utility neutral. On services with frequent lightning exposure, layering a Type 1 at the service with Type 3 point-of-use protectors at the electronics is the arrangement the SPD makers themselves run at home.