Designing a General Purpose Heat Pump Controller

[buffalobillpatrick]

Whew! took hours, lots of stuff don't work in a ISR (Interrupt Service Routine)
delay(x) , lcd.print, &
biggest pain was
Compiler was optimizing out various "delay for loops" that I tried, even with index declaired volatile.
I wanted about 30 sec. delay between Compressor off & water pumps off.
analogRead didn't optimize out!

This WORKS!

//done in setup:   attachInterrupt(1, Stop_Compressor_ISR, RISING);// Attach Interrupt 

    // (IRQ1 is on Digital Pin 3) Pin 3 going high (+) sets Interrupt 1
    // This is Master signal to STOP HP Compressor, by denergizing R3
    // with a short power cycle to Solar pump, which picks a relay
    // N/O point connects Arduino +5v to Digital Pin 3
    // Digital Pin 3 has a 10K pulldown resistor to Gnd.
    // This allows the water pumps to continue after Compressor is off	     
    // After a delay the master will power off this Slave Arduino
    //	This would be a normal ending sequence for HP satisfying Load 
   	     
void Stop_Compressor_ISR()	     
{			
//#define Max_Long_int_number   2147483647 
#define Big_number               250000

  long Z;
  int Y;
  
  detachInterrupt(1);   
  
  digitalWrite (HP_RLY_R3,                  HIGH); //Compressor OFF
  
  for (Z = 0; Z < Big_number; Z++) {analogRead(1);}  //delay about 30 sec.  
  
  digitalWrite (HP_RLY_R2,                  HIGH); //Pumps OFF  
  digitalWrite (ALIVE_RLY_R1,               HIGH); //Alive OFF

  do{Y = Y;} while (Y == Y);  //hang forever
}

[buffalobillpatrick]

Question:

If a water pump does stop working while HP is running, what is best sequence for shutting down?

Turn off Compressor & pumps together OR Compressor 1st & then delay before turning off pumps?

[jeff5may]

Oh no. What? Whoa...

This is why I am trying to stay away from interrupt and library calls. God save your soul.

[buffalobillpatrick]

Hard to figure out when code looks correct & compiles, but just acts like No-ops.

From Nick Gammon, an Oz Arduino expert:
"The compiler optimizes, that is well-known. Variables shared between an ISR and "main" code should be declared volatile.

Attempts to make loops by doing something with non-volatile variables are frequently optimized away."

[AC_Hacker]

Originally Posted by buffalobillpatrick

Question:

If a water pump does stop working while HP is running, what is best sequence for shutting down?

Turn off Compressor & pumps together OR Compressor 1st & then delay before turning off pumps?

The reason to delay pump shutdown is to get the last few BTUs from each system heating cycle.

In my opinion, having a water pump fail is an emergency condition. Of course shut down the compressor first, then whether you allow the pumps to run on a bit longer or not is of little consequence, because your heating system will be going down until the failed pump is remedied or replaced.

-AC

[AC_Hacker]

Originally Posted by buffalobillpatrick

Whew! took hours, lots of stuff don't work in a ISR (Interrupt Service Routine)
delay(x) , lcd.print, &
biggest pain was...

Do you have any kind of physical simulator test fixture?

-AC

[buffalobillpatrick]

A/C Thanks, No on physical simulator test fixture.

In example, this compiles but don't work (no delay) even though Z & Y are not sharred outside this ISR

#define Big_number               500000

  long Z;
  long Y;

  for (Z = 0; Z < Big_number; Z++)
  {
    for (Y = 0; Y < 10000; Y++) {Z = Z;}
  }

Compiler must think "that don't make no kinda sense" why would anyone want to do this.

This however works (delays) volatile is key here, even though Z & Y are not sharred outside this ISR

#define Big_number               500000

volatile long Z;
volatile long Y;

  for (Z = 0; Z < Big_number; Z++)
  {
    for (Y = 0; Y < 10000; Y++) {Z = Z;}
  }

[jeff5may]

Originally Posted by buffalobillpatrick

Question:

If a water pump does stop working while HP is running, what is best sequence for shutting down?

Turn off Compressor & pumps together OR Compressor 1st & then delay before turning off pumps?

Always try to run the evaporator side pump for a minute or two after the compressor stops. This way you will have eliminated any chance of the residual refrigerant freezing the hx as it peters out. A lot can happen in a few minutes.

The condenser hx is not as important. However, having the pump run as well will reduce the high side pressure and pinch off the residual flow faster.

[buffalobillpatrick]

Rewrite of estimate_COP to make it easier to understand & relate to Climatemaster graph

I would rather try to closely estimate COP, than to use trouble prone flow sensors.

  // COP estimation
  // http://www.climatemaster.com/downloads/RP881.pdf
  // p19 graph for model TMW036 W/W

float estimate_COP (void) 
{   
  int   cop;
  int   ESWT;
  int   ELWT;
  int   DELTA_T;
  float COP;
 
  
  ESWT       =  (Read_10K_NTC (SOURCE_IN_sensor));
  lcd.clear();
  lcd.home (); // go home
  lcd.print(F("ESWT="));
  lcd.print(ESWT);
  custom_delay();     //Delay 5 sec. & Checks Water SRC OUT 
  
  ELWT       =  (Read_10K_NTC (LOAD_IN_sensor));
  lcd.clear();
  lcd.home (); // go home
  lcd.print(F("ELWT="));
  lcd.print(ELWT);
  custom_delay();     //Delay 5 sec. & Checks Water SRC OUT 
 
  if (ESWT > ELWT)  //if source is hotter than load
  {
  cop = 80;    //force high COP
  }
  else
  { 
  DELTA_T = ELWT - ESWT;
 
  lcd.clear();
  lcd.home (); // go home
  lcd.print(F("DELTA_T="));
  lcd.print(DELTA_T);
  custom_delay();     //Delay 5 sec. & Checks Water SRC OUT   
    
  if (ELWT <= 70)    //don't use constrain so graph lines on
                     //Climatemaster graph in Fig 2-11 p19
                     //can be interpolated past ends 
                     //by map function, which only works on whole ints, not floats
  {
  cop  =  map(DELTA_T, 10, 50, 73, 44);
  }  
  else if (ELWT <= 75)
  {
  cop  =  map(DELTA_T, 15, 55, 69, 41);
  }  
  else if (ELWT <= 80)
  {
  cop  =  map(DELTA_T, 20, 60, 65, 38);  //this maps the top blue line 
                                             // on graph
  }
  else if (ELWT <= 85)
  {
  cop  =  map(DELTA_T, 25, 65, 61, 36);
  }  
  else if (ELWT <= 90)
  {
  cop  =  map(DELTA_T, 30, 70, 57, 33);
  }
  else if (ELWT <= 95)
  {
  cop  =  map(DELTA_T, 35, 75, 53, 30);
  }  
  else if (ELWT <= 100) 
  {
  cop  =  map(DELTA_T, 40, 80, 49, 28);  //this maps the middle red line
                                             //on graph
  }    
  else if (ELWT <= 105) 
  {
  cop  =  map(DELTA_T, 45, 85, 46, 26);
  }      
  else if (ELWT <= 110) 
  {
  cop  =  map(DELTA_T, 50, 90, 43, 25);
  }
  else if (ELWT <= 115) 
  {
  cop  =  map(DELTA_T, 55, 95, 40, 23);
  }   
  else if (ELWT <= 120) 
  {
  cop  =  map(DELTA_T, 60, 100, 37, 22);  //this maps the bottom green line
                                              //on graph
  }    
  else if (ELWT <= 125) 
  {
  cop  =  map(DELTA_T, 65, 105, 34, 21);
  }   
  else {STOP();}
  
  }
  
  COP = cop / 10.0;

  return (COP);
  }

[buffalobillpatrick]

I'm doing this "esoteric" master quick pulse of Solar tank pump to cause Int 1
because I'm out of pins on Master Arduino, and the AC power line for Solar pump will run between house & shop where this Slave Adruino will reside.

In any case I think that using Int 1 as a quick way to Shut Down of HP from
remote Master on "Normal HP satisfying Load" OR "Downshifting to boiler" is the best way.