Heat Profile Summary 

RAMP -> Increase measured temperature towards the SETPOINT value at a rate of 1C / hour 

SOAK -> After measured temperature attains the SETPOINT value, maintain measured temperature at SETPOINT value for time (hours) value entered as "HOLD" 

RAMP -> Decrease measured temperature towards value at a rate of 1C / hour to that seen at the start of the initial RAMP segment. 


We increased the SETPOINT value to 115C before leaving the site tonight.  Once home, I logged on and noticed that all four of the displayed (camera looking at controller display) temperatures had risen significantly from the values I had noted when leaving the site, i.e. had ramped up at a rate much faster than the program limit of 1C / hour should have allowed it to.  In spite of this, the heater output was showing 100%, i.e. was fully on (20 kW)!  The output should have responded and been 0% to prevent such a rapid temperature increase.  I also noticed that the "HOLD" lamp was on.  Thus, the heating profile had somehow advanced to the SOAK segment of the profile and was trying to get the measured temperature to match the SETPOINT value of 115C.  

I phoned Sheila D. in the control room and she agreed to go out the Y-mid station and help us remotely.  Unfortunately, she couldn't get into the building as the mid-stations require a unique key.  When I arrived, I lowered the SETPOINT value to slightly less than that of TC1 (T/C used by control loop) which should have caused the heater output to respond by decreasing down from 100%.  I waited several minutes, but the heater output never changed and the HOLD lamp stayed on.  I ended up power cycling the control unit and restarting the program.  I also lowered the SETPOINT value.  It seems to be working now.

NOTE 
TC3's bimetal junction must be sampling the air even though it is intended to be clamped to the SST of CP4.  I believe this because it changes much too rapidly as should be physically possible while in contact with a large mass and it behaves much like TC1 and TC2 which are intended to be sampling air.  TC4 is confirmed anchored to the lift eye on the side of GV11 and is the only T/C which behaves as if in good thermal contact with a large mass of SST.  I will re-examine TC3 tomorrow.