Rheem Tankless water heater manual if this is allowed RTEX-13

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Manufacturer: Rheem

Type of Appliance: Water Heater (tankless)

Model Number: RTEX-13

Have you validated the model number at an online parts site like Repair Clinic? (yes or no): YES

Have you watched the video on how to search for manuals and have you searched the Downloads section prior to posting this request? (yes or no): YES

Wondering if we have manuals for Rheem tankless water heaters wanted to take a look for a lady I'm going to help on her refrigerator but her tankless went down... looked at it doesn't look super complicated inside but I think it has a thermal fuse or cut off or something like that...

Thank you, David