Raypak 600892B AGS 135°F High Limit (Auto Gas Shut-Off), Red Epoxy, for 206A-406A, 207A-407A (prior to 12/2019), RP2100 and Versa Pool Heaters

This is the 135°F automatic-reset high limit that screws into the heater's water header. If the water gets too hot it opens and shuts the burners down, then resets by itself once the water cools. The older Versa, Gemini and Spa-Pak lists simply call it High Limit 135°F.

Older models it also fits:

• RP2100 R185, R265, R335, R405 (1993 to 1998)
• Versa 185A to 405A (1986 to 1988), Versa 185B to 405B and 185C to 405C (1988 to 1993)
• Versa 155A (1987 to 1991), Versa 155B/C (1991 to 2006), Versa 105A (1991 to 1999) and the brass version of the Versa 105B (1999 to 2006)
• Gemini and Spa-Pak 183A, 263A, 333A, 403A (1984 to 1986), 153A (1984 to 1987) and 153 (1981 to 1984); Gemini 181, 261, 331, 401 (1974 to 1982); Spa-Pak and California III 151 (1974 to 1981)
• Raytherm commercial pool heaters 334, 404, 514, 624, 724 and 824 (1982 to 2021; sizes 334 and 404 to 1986), and Raytherm P commercial pool heaters 926/962, 1083/1125 and 1178/1223 that have the header made for a screw-in high limit

The 140°F limit used alongside it (600893B) has black epoxy. Raypak's parts-library photo shows a brass threaded switch with two spade terminals, supplied with a wire lead.

This is not the surface-mount 135°F limit: Raypak shows 006725F for polymer-header and bronze-header 206A to 406A heaters and for the cast-iron Versa 105B. Versa 055A, 055B and Spa-Pak 053A, 053B use a different 135°F limit, 600889B.

Raypak's manuals note that an erratic high limit is often a sign of a heat exchanger problem such as scale build-up or a defective bypass. Safety controls should be replaced by a qualified service technician.