Advanced Spa/LA Spas Flo-Thru 5.5kw Heater Assembly 240v This Advanced/LA Spas heater assembly is stainless steel and measures 2" x 15" with a 1/8" npt pressure tap & external thermowells. It is 5.5kW/240v, two 2" solid nut tailpieces, two 1 -32 x 3/8" mounting studs and single groove thermal well cover & gasket.