Does a Type 1 SPD perform better than a Type 2 SPD?

Not necessarily. A Type 1 SPD offers versatility by being able to be connected to either side of service entrance, however UL does not compare the surge clamping performance of a Type 1 SPD versus that of a Type 2 SPD. UL investigates clamping performance of all SPDs equally, without regard for SPD type. UL also evaluates all SPDs for safe operation within their intended installation location. Beginning with UL 1449 3rd Edition, Type 1 approved SPDs will include devices that were formerly known as Secondary Surge Arresters and will also include many devices that were formerly known as TVSS. It is important to understand that many Secondary Arresters type devices were designed with a higher MCOV (Maximum Continuous Operating Voltage) than were TVSS type
devices. And since the MCOV rating of an SPD can have a direct impact on surge clamping performance, the best practice for SPD selection should include careful consideration for ratings such as maximum surge current, IEEE clamping voltage, UL VPR, and surge life ratings.