Not familiar with "Optimum" by Raypak. 346 is probably your output BTU/Size in 100,000's, so 346,000 btu
What is model number of your heater? Metallic label on inside of the heater behind the front cover/door. Some Common heater models current & obsolete are as follows:Gemini, Versa, RP2100, Delta, xfyre
Answers & Comments
Not familiar with "Optimum" by Raypak.
346 is probably your output BTU/Size in 100,000's, so 346,000 btu
What is model number of your heater? Metallic label on inside of the heater behind the front cover/door.
Some Common heater models current & obsolete are as follows:Gemini, Versa, RP2100, Delta, xfyre