Pentair Mastertemp 400 already replaced SFS and still getting E05

emilyutexas

New member
Apr 5, 2020
4
Houston TX
We are having the same problem many have posted about - start up heater, once the ignition kicks in, it blows hot for 10 -20 seconds, then turns off and displays E05. On the control board, the SFS light is lit along with LED11 (service heater). We replaced the SFS yesterday and still get this error code. Interestingly, this happens about 90% of the time, but 10% of the time, it runs without an error code (earlier today, in fact, we had it running for a couple hours then turned it off and now only getting E05 again). We had the pool service company here about 2 weeks ago, and during that time, the error code never showed up (annoying), so they couldn't diagnose. I am thinking the next step is replacing the control board ($300), but wanted to see if anyone else has other thoughts on what could be causing this?
 

JamesW

TFP Expert
Mar 2, 2011
23,916
E05 is usually overheating or open SFS (Stack Flue Sensor).

If you're getting E05 before the heater starts, the stack flue sensor is probably bad or the wiring is compromised.

If you're getting E05 after the heater starts, it might be overheating or a bad stack flue sensor.

When the heater starts, press and hold the On button to make the exhaust temperature display.

Here is what the normal exhaust temperature should be:

Below 250 degrees...very low
250 to 290 ..................low
290 to 350.................acceptable
350 to 480 ..................high
Above 480...................error/shutdown.

Note: HD models can be up to 75 degrees higher. HD models use a cupro nickel exchanger and the efficiency is slightly lower resulting in less heat transfer and more waste heat.

Is your model number 400 hd?
 
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emilyutexas

New member
Apr 5, 2020
4
Houston TX
E05 comes on after the heater starts (about 10-20 seconds after the hot exhaust kicks on) and when I hold down the "pool on" button, it stays on 80, then flashes to 40, then back to 80. We just replaced the stack flue sensor yesterday.
 

JamesW

TFP Expert
Mar 2, 2011
23,916
The 80/40 reading and E05 indicate that the board is not getting a reading from the sensor.

It's usually a bad sensor or damaged wires.

Make sure that the wires are good and not damaged. Mice sometimes get in the heater and chew on the wires.

If the sensor and wires are good, then the main board is the next thing to replace.
 
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