possible issues with my heater

[wyattroa]

I have two heaters in the tank. Both are programed with the following


Fallback OFF
Set OFF
If Temp < 77.0 Then ON
If Temp > 78.5 Then OFF
Defer 002:00 Then ON
Defer 001:30 Then OFF
If Temp < 70.0 Then OFF

My temps seem to be off a bit. They seem to be dropping to just under 77 and then turning on as it should.

But the water is only warming to 77 on the head and then shutting off every time. It reaches a max of 77.3 once in the data log in the last 7 days. What could be causing this? It should be shutting off at 78.5.

Here is a picture of my graph. Any help would be great.

 

[Deleted member 143833]

remove the "set off". In short what is happening is that as soon as the "If Temp < 77.0 Then ON" becomes false the heater turns off because you have the SET OFF. Set Off is like an initializer and for each run through the program you start fresh with the heater OFF and once the temp is 77.1 the 1st statement, being false is ignored, leaving the heater as the initialized (SET OFF) state.

 

[wyattroa]

Thank you