Designing a General Purpose Heat Pump Controller

[buffalobillpatrick]

A/C what part do you need help with?

[AC_Hacker]

Originally Posted by buffalobillpatrick

From Steve's post #230

"Delay to stop outlet pump to extract as much useful heat as possible from condenser as you have already paid for it. This would be better done with in and out temp sensors."

As Heat Pump will be within the "heated house envelope" and used to heat the house, any generated heat will not be wasted. (until it passes outdoors)

This is good thinking.

In my case, my basement will protect the heat pump from severe cold, but it is not heated and that's where the heat pump will be located.

I suppose that the user can 'comment out' the prolong-run code, or choose a minimum run time or zero-length run time.

-AC

[takyka]

I have two of the mentioned cheap flow sensors installed. One is in operation (mean heavy waterflow) a lot of times a day. The other one stands for half year (in my heatpump) and in operation gets just gentle flow. Both are working without problem. If you take it apart, you can see it's so simple inside, nothing to stuck if the liquid running trough, does not contain bigger particles, which can jam between rotor and housing.

T.

[buffalobillpatrick]

To me, it makes sense to only heat the Buffer Tank to the minimum temp. required, based on ODR Outdoor Reset.

[buffalobillpatrick]

//OutDoor Reset parameters
#define OUTDOOR_hi_control_temp  62.0  //OD Temp. that House don't require heat
#define OUTDOOR_lo_control_temp   0.0  //Minimum expected OD temp, Design Temp
#define BUFFER_tank_hi_limit    110.0  //Maximum BT temp, find through testing
#define BUFFER_tank_lo_limit     85.0  //Minimum BT temp, find through testing

#define BUFFER_tank_delta         5.0  // Determine with testing

float OUTDOOR_range;
float BUFFER_tank_range;
float ODR_ratio;

int OUTDOOR_temp;  
int BUFFER_tank_temp;
int BUFFER_tank_target_temp;  


void setup() {

  OUTDOOR_range = ( OUTDOOR_hi_control_temp - OUTDOOR_lo_control_temp );
  
  BUFFER_tank_range = ( BUFFER_tank_hi_limit - BUFFER_tank_lo_limit );
 
  ODR_ratio = ( BUFFER_tank_range / OUTDOOR_range );

}



void loop() {
  // OUTDOOR_temp = (readSensor_F (OUTDOOR_sensor));

  // Calculate Buffer Tank Target Temp based on ODR parameters
  BUFFER_tank_target_temp = 
  ( BUFFER_tank_lo_limit +
  (( OUTDOOR_hi_control_temp - OUTDOOR_temp ) * ODR_ratio ));
  
 //  BUFFER_tank_temp = (readSensor_F (BUFFER_tank_sensor));
  
  //Test if BT needs to start heating
  if ( BUFFER_tank_temp < ( BUFFER_tank_target_temp - BUFFER_tank_delta )) 
  { 
    
  do 
  {
   // run HP 
   //BUFFER_tank_temp = (readSensor_F (BUFFER_tank_sensor));
  } while ( BUFFER_tank_temp < BUFFER_tank_target_temp ); 

  }
}

[Ormston]

Originally Posted by buffalobillpatrick

As Heat Pump will be within the "heated house envelope" and used to heat the house, any generated heat will not be wasted. (until it passes outdoors)

As this was intended to be a general purpose controller it needs to work with ASHP which will be outside, also for providing hot water in summer months I would prefer the heat in the waster tank not just somewhere within the heated envelope.

If the feature is not needed for an application then set the time to 0.

AC
Did you try the code from a few weeks back, I didn't look at the version with LCD but certainly the code before that worked on in the simulator (using input 8 to disabled the flow meters).

Steve

[jeff5may]

Originally Posted by takyka

I have two of the mentioned cheap flow sensors installed. One is in operation (mean heavy waterflow) a lot of times a day. The other one stands for half year (in my heatpump) and in operation gets just gentle flow. Both are working without problem. If you take it apart, you can see it's so simple inside, nothing to stuck if the liquid running trough, does not contain bigger particles, which can jam between rotor and housing.

T.

I have used these sensors before with hot and cold water and oily stuff, too. They work well in low pressure applications. I wouldn't try to run water close to boiling through them, not freeze them. For the price, they rock.

[AC_Hacker]

Originally Posted by takyka

I have two of the mentioned cheap flow sensors installed. One is in operation ... The other one stands for half year (in my heatpump) ... Both are working without problem.

Originally Posted by jeff5may

I have used these sensors before with hot and cold water and oily stuff, too. They work well in low pressure applications. I wouldn't try to run water close to boiling through them, not freeze them. For the price, they rock.

takyka & jeff5may, thanks for the feedback on the flow sensors. In my opinion, this is sufficient to proceed with them. Ormston's experience with a failed sensor does point out the hardware reality of the need to provide for easy replacement, and the software reality of either being able to easily de-select flow monitoring (toggle switch?) or provide for flow sensor failure as being a "soft failure", where functioning can continue without the sensor(s), but with warning (warning beeper?, failure light?). I can easily imagine an un-attended deep winter, when everything is functioning well and a $14 dollar part no longer sends it's information to the CPU... We don't want to return to cold house and frozen pipes.

Originally Posted by buffalobillpatrick

To me, it makes sense to only heat the Buffer Tank to the minimum temp. required, based on ODR Outdoor Reset.

This make sense to me. Can you go into more detail about the rationale, etc of the ODR Outdoor Reset? I generally know what they do.

Originally Posted by Ormston

As this was intended to be a general purpose controller it needs to work with ASHP which will be outside, also for providing hot water in summer months I would prefer the heat in the waster tank not just somewhere within the heated envelope.

If the feature is not needed for an application then set the time to 0.

Your comment made me realize that in my mind, I was visualizing several dirfferent versions of code that were all based off of a proven core of code. It looks like you are envisioning a single multipurpose piece off code that can be modified to suit more than one hardware setup. Your concept may be better than mine.

But I should explain that in the four or so years of living with the 'Manifesto' thread (686,531 hits), I have come to recognize the very large spread in technical savvy of people who have shown interest.

As this discussion is developing, It seems that the flow of our development is toward a single piece of code that has full functioning features.

So I think it is better to go with the flow, and go full feature.

After that phase approaches a satisfactory point (code is never finished), it would be a good idea to 'prune back' the feature set to a simpler, rudimentary Level Zero Version of the code, that an unsophisticated user could use and understand.

Originally Posted by Ormston

AC
Did you try the code from a few weeks back, I didn't look at the version with LCD but certainly the code before that worked on in the simulator (using input 8 to disabled the flow meters).

I'll try that one again... We have several code versions in this thread, and referring to a post number might make communications clearer.

-AC

[jeff5may]

Thats one reason I have not posted any code yet. I am still working on the menu and options to do lots of different configurations. I am going to be able to set the thing up without any attachments or other computers attached straight from the LCD panel when I get it right.

[buffalobillpatrick]

From Tekmar, a leading controls company:

energy-savings

Outdoor Reset, is a control strategy that continuously adjusts heating system supply water temperatures to compensate, providing more heat when it’s colder and less heat when it’s warmer.


Outdoor Temperature Reset

"Outdoor Temperature Reset

In order to properly control a hot water heating system, the heat supplied to a building must equal the heat loss from the building. The heat loss is dependent on the outdoor temperature. It is therefore necessary to reset the supply water temperature based on the outdoor temperature. The ratio at which the water temperature increases as the outdoor temperature decreases is the Heating Curve. Outdoor Temperature Reset improves comfort by limiting indoor temperature swings, and provides higher energy savings by minimizing distribution and boiler stack losses."

All modern Mod-Con boilers come with ODR.
The 4 parameters that are used to calculate ODR Ratio are entered on control panel.
This is equivalent to the 4X #define at the start of my code in post #245 above, where each user must determine what works best for their climate & house.