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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 6022
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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I have a Rheem (Raypak) 400,000 BTU pool heater the " Limit

Customer Question

I have a Rheem (Raypak) 400,000 BTU pool heater
the "Hi Limit 2 Fault" limit switch trips after about 10 min
checked gas flow under 14 inches by gas comp
Tank 40% full propane
it has worked well for the past two summer
Hasn't work this year since we opened the pool
Removed top to make sure no mice made a nest anywhere inside
looked at stack through to the top is OK
I have a positive vent squirrel cage on the top seems to be working well
The flow of water through the furnace is good on HIGH
Submitted: 1 year ago.
Category: HVAC
Expert:  Phil replied 1 year ago.

Hello, its either a low water flow condition but you have verified its on high, we may need to verify the flow rate by mechanical means. The water filters or line strainers might be clogged.

Thats first.

Secondly there might be air inside the heat exchanger, reducing water flow (a vapor lock sort of condition)

Lastly the high limit sensor might be bad, we will need to verify the temperature at the probe insertion point.

Let me know a lot about your skill sets in these regards ***** ***** I can coach you most effectively.. we can go from there.