Response to Hello, Aaron. I was unable to locate a definition for Limit#1. If the board is reading HL1 that means, The high-limit has exceeded 135F. The possible solutions are. 1. Possible excessive water temperature in the tube bundle. Once heater cools, high limits resets automatically.2. Check for blockage in tubes.3. Check for low water flow.4. Check Unitherm governor- replace if necessary 5. check bypass assembly- replace spring or bypass if necessary. If that is not correct for you, you may contact Raypak directly at  805-278-5300. (Raypak Heater Fault Code Guide)

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