Rheem 266A Pool Heater - Rapid rise in temp reading, then shutoff... but no error message

DaveG3030

New member
Jun 30, 2020
3
53144
I have a Rheem 266A and it has been functioning great for about four years. Recently, the temperature display on startup quickly - within minutes - climbs to the set temperature. 78 to 90 in less than two minutes. Unfortunately, the pool temperature is no where near what the reading says, and then the heater shuts off. The heater then will then start up again and go through the same cycle continuously. Water outputting to the pool is hot and there is no error on the display. The PSI from the multi-valve says 20. That has been the normal reading, however it feels like the water pressure outputting into the pool is less, but enough to keep the heater on. I have backwashed the filter several times. So, I heard that it is either a faulty sensor, dirty sensor or still a dirty sand filter. Please help... thanks!
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
18,959
Northern NJ
Welcome to TFP.

Sounds like a low flow problem causing the heater high limit switch to shut it down. Once it cools down the heater works again. Problem could be in your filter, or a miss set valve, or a clogged heat exchanger.

Or it could be a bad Unitherm Governor or Bypass Valve. See page 19 in http://cdn.globalimageserver.com/FetchDocument.aspx?ID=c404f1c5-ac50-4209-9457-56246d010b20

Do you have a heater bypass valve?

Check the Service Menu and Fault History
To access the Service Menu and fault history, press the MODE and UP buttons simultaneously for 3 to 5 seconds. The heater will continue to operate normally while in the Service Menu. The first screen displayed is the Flame Strength indicator, which indicates the pilot flame current using a bar graph and numerical display. A signal of less than 4 indicates a weak flame signal and may require service. Refer to Section 5 Troubleshooting for possible causes and corrections.

Press the DOWN button. The Supply Voltage screen indicates the voltage supplied to the control board. Normal readings range from 24 to 29 volts.

Press the DOWN button. The Run Time indicates the total hours of operation for the pool heater, as measured by the amount of time that the main gas valve has been powered. The Cycle count indicates the number of on/off cycles of the heater, as measured by the number of times the pilot valve has been powered.

Press the DOWN button. The Fault History can display up to ten faults in memory. The order of the faults begins with “Fault Last,” which is the most recent fault, and proceeds through ten most recent messages in chronological order. The second line of the display shows the fault message. If there are no faults in the history buffer, the second line reads “All Faults Clear.”

@ps0303 @Pool Clown @swamprat69 ideas?
 

DaveG3030

New member
Jun 30, 2020
3
53144
Welcome to TFP.

Sounds like a low flow problem causing the heater high limit switch to shut it down. Once it cools down the heater works again. Problem could be in your filter, or a miss set valve, or a clogged heat exchanger.

Or it could be a bad Unitherm Governor or Bypass Valve. See page 19 in http://cdn.globalimageserver.com/FetchDocument.aspx?ID=c404f1c5-ac50-4209-9457-56246d010b20

Do you have a heater bypass valve?

Check the Service Menu and Fault History
To access the Service Menu and fault history, press the MODE and UP buttons simultaneously for 3 to 5 seconds. The heater will continue to operate normally while in the Service Menu. The first screen displayed is the Flame Strength indicator, which indicates the pilot flame current using a bar graph and numerical display. A signal of less than 4 indicates a weak flame signal and may require service. Refer to Section 5 Troubleshooting for possible causes and corrections.

Press the DOWN button. The Supply Voltage screen indicates the voltage supplied to the control board. Normal readings range from 24 to 29 volts.

Press the DOWN button. The Run Time indicates the total hours of operation for the pool heater, as measured by the amount of time that the main gas valve has been powered. The Cycle count indicates the number of on/off cycles of the heater, as measured by the number of times the pilot valve has been powered.

Press the DOWN button. The Fault History can display up to ten faults in memory. The order of the faults begins with “Fault Last,” which is the most recent fault, and proceeds through ten most recent messages in chronological order. The second line of the display shows the fault message. If there are no faults in the history buffer, the second line reads “All Faults Clear.”

@ps0303 @Pool Clown @swamprat69 ideas?
I appreciate the info and will try these steps. There is no heater bypass.