What the 1500 W rating means in a real circuit
The 1.5KE220: In a 24 VAC or 185 VDC rail, the 185 V reverse standoff means it sits transparently below the clamping threshold, only conducting when the line sees a surge. The 344.4 V maximum clamping voltage at 4.6 A peak pulse current is the ceiling the downstream components see — keep that below the absolute max of whatever you are protecting.
Breakdown, standoff, and the field-swap reality
Breakdown voltage starts at 198 V, so a 185 V nominal rail has about 13 V of headroom before the diode starts to avalanche — enough to ride through normal ripple without clipping. The DO-201AA axial package is a through-hole part, which means it can be swapped on site with a soldering iron and a desoldering pump. No hot-air station needed; the banded cathode marking is clear enough to get orientation right the first time. The 1500 W rating holds across that range, though derating curves apply above 25°C ambient.
Obsolete — sourcing through independent channels
Littelfuse lists the 1.5KE220 as obsolete. If you are filling a BOM line or repairing a legacy board, this is a part you source per order, not from factory stock.