Fault codes / Aqua-Hot / OVERLOAD (red)
Aqua-Hot: Overload (red)
What it means: 12V short or controller overheated.
What to check
Short in the main 12V supply, or high 12V load plus a hot controller. Auto restarts when corrected.
Learn the system
Practice it on a service call
Guided diagnosis
Other Aqua-Hot codes
- Aqua-Hot: Low tank-level cutoff (red) Boiler fluid low
- Aqua-Hot: Low battery voltage (red) 12V too low
- Aqua-Hot: Zone light red Short in that zone
- Aqua-Hot: Pump #1/#2/#3 red Short in that pump circuit
- Aqua-Hot: Engine preheat red Short in the preheat pump circuit
- Aqua-Hot: Electric element red Short in the element's 12V control circuit
Full field guide: Aqua-Hot 450 hydronic heater
Codes come from the maker manuals and public service sheets. Your model's own chart always wins, and LP and 120 volt work belongs to a qualified technician.