Pool heater throws code h5? smoked - Hayward H Series Pool & Spa Heater Electronic Dual Ignition 400,000 Btu Natural Gas H400ed2

HS = High Limit Sensor
Heaters Maximum Water Temperature has been Exceeded.
A few reasons this occurs...

• Low water flow thru heater, check :
  • Dirty Filter
  • Opened By Pass Valves
  • Plugged pump impeller
  • Dirty/Full baskets at skimmer or pump
  • Anything that may reduce water flow
• Sensor could actually be doing its job, in a different aspect, Thermostat failure, and water is overheating in spa or pool?

HS
Water Temperature Sensing Error

A) Inlet water temperature sensor is reporting a temperature in excess of 104 degrees.
Normal operation resumes 2 minutes after inlet water temperature sensor reports temperatures of 104 degrees or less. This error functions in both normal and remote thermostat modes.
or
B) Inlet water temperature sensor is reporting a temperature change at a rate faster than 6 degrees in 60 seconds, indicating a potentially damaging low water flow conditon. Normal operation resumes when temperatures stabilize. If this condition is detected 3 times, the heater will lock-out until the electrical power is cycled off and back on.