EcoRenovator - Radiant Ceiling Cooling

EcoRenovator (https://ecorenovator.org/forum/index.php)

- Renovations & New Construction (https://ecorenovator.org/forum/forumdisplay.php?f=28)

- - Radiant Ceiling Cooling (https://ecorenovator.org/forum/showthread.php?t=4311)

Radiant Ceiling Cooling

http://www.oorja.in/wp-content/uploa...antcooling.pdf

"Unlike most cooling systems in California, which circulate cold
air to maintain comfort, most radiant cooling systems circulate
cool water through ceiling, wall, or floor panels. “Coolth” from
that water is then absorbed by occupants and interior spaces
according to the dynamics of thermal radiation. These radiant
cooling systems, which are popular in Europe, are rarely found
in California buildings, however. That’s bad news for building
owners and occupants, because radiant cooling systems are
more efficient, more comfortable, more attractive, and more
healthful than systems that circulate air. Over their lifetimes, they
are also less expensive to own and operate.
Given these advantages, radiant cooling is poised to make a big
splash in California markets in all climate zones. Currently, there
are two important barriers to its entry into these markets: a lack
of familiarity with radiant cooling technology and lingering
memories of moisture control problems experienced by a few
pioneering systems installed decades ago. The latter barrier
should be mitigated by recent advancements in sensor and con-
trol technology. The first barrier, local industry unfamiliarity, will
probably diminish as information becomes more widely avail-
able about successful applications in Europe, North America,
and California. Healthcare facilities, which especially benefit
from the way radiant cooling systems separate comfort cooling
from ventilation functions, may lead the way."

Seems like a good match for a Water-to-water Heat Pump.
I know that ceiling would have to kept above the Dew point.
Would need dehumidifiers.

I got the Dew Point Arduino sketch working that A/C linked to in another similar thread.

I modified sketch to be able to use multiple AM2301 sensors & to take 25 samples & average them before each Serial Print, this is done to smooth out a little bouncing around that I was seeing.

BTW, the 2 AM2301 sensors that I have on hand consistantly read RH about 2.7% apart from each other. I have ordered 3 more from China, I will probably have to correct for their offsets with code.

It would be easy to modify some more & have sketch energize a relay to run dehumidifier automaticaly and to stop cooling ceiling until humidity drops enough.

Code:

// Example testing sketch for various DHT humidity/temperature sensors

// Written by ladyada, public domain

// Modified by BBP

// Sensors are wired to pins D2, D3, etc





#include <DHT.h>



#define NUM_SENSORS           2

#define SENSOR_STARTING_PIN   2    //D2



#define Sample_cnt 25





#define DHTPIN 2     // what pin we're connected  D2

//#define DHTPIN 3     // what pin we're connected  D3



// Uncomment whatever type you're using!

//#define DHTTYPE DHT11   // DHT 11

//#define DHTTYPE DHT22   // DHT 22  (AM2302)

#define DHTTYPE DHT21   // DHT 21 (AM2301)



// Connect pin 1 (on the left) of the sensor to +5V

// Connect pin 2 of the sensor to whatever your DHTPIN is

// Connect pin 4 (on the right) of the sensor to GROUND

// Connect a 10K resistor from pin 2 (data) to pin 1 (power) of the sensor



//DHT dht(DHTPIN, DHTTYPE);



float tF;

float dP;

float dPF;

float h;

float t;

   

float alpha =   0.9;     // factor to tune

float average;

  

int i;

 

int I;



void setup() {

  Serial.begin(9600);

  Serial.println("DHTxx test!");



//  dht.begin();

}



void loop() {



  for ( I = SENSOR_STARTING_PIN; I < (SENSOR_STARTING_PIN + NUM_SENSORS); I++ )

  {

  

  DHT dht(I, DHTTYPE);

  dht.begin();

   

  // Reading temperature or humidity takes about 250 milliseconds!

  // float h = dht.readHumidity();

  // float t = dht.readTemperature();

  

  average = 0.0;  

  for (i=0; i< Sample_cnt; i++) 

  {  

  average =  alpha * dht.readHumidity() + (1-alpha) * average;

  delay(10);

  }

  h = average;



  average = 0.0;  

  for (i=0; i< Sample_cnt; i++) 

  {  

  average =  alpha * dht.readTemperature() + (1-alpha) * average;

  delay(10);

  }

  t = average;



 // delay(10000);



  // check if returns are valid, if they are NaN (not a number) then something went wrong!

  if (isnan(t) || isnan(h)) {

    Serial.println("Failed to read from DHT");

  } 

  else {



    Serial.print("Sensor Pin D");

    Serial.print(I);

    Serial.print("  ");

    

    Serial.print("Humidity:");

    Serial.print(h);

    Serial.print("%  ");

    

    Serial.print("Temp:");

    // Serial.print(t);

    // Serial.print(" *C ");

    tF=((t*9)/5)+32;

    Serial.print(tF);

    Serial.print("*F  ");





  Serial.print("Dew Point:");

  // Serial.print(dewPointFast(t, h));

  // Serial.print(" *C ");

  dP=(dewPointFast(t, h));

  dPF=((dP*9)/5)+32;

  Serial.print(dPF);

  Serial.print("*F");

  Serial.print("  ");



  Serial.print("Heat Index:");

  Serial.print(heatIndex(tF,h));

  Serial.println("*F");



  }  //end else

  

  }  //end for loop reading sensors



}    //end void loop



// delta max = 0.6544 wrt dewPoint()

// 6.9 x faster than dewPoint()

// reference: http://en.wikipedia.org/wiki/Dew_point

double dewPointFast(double celsius, double humidity)

{

double a = 17.271;

double b = 237.7;

double temp = (a * celsius) / (b + celsius) + log(humidity*0.01);

double Td = (b * temp) / (a - temp);

return Td;

}



double heatIndex(double tempF, double humidity)  //how hot it feels

{

  double c1 = -42.38, c2 = 2.049, c3 = 10.14, c4 = -0.2248, c5= -6.838e-3, c6=-5.482e-2, c7=1.228e-3, c8=8.528e-4, c9=-1.99e-6  ;

  double T = tempF;

  double R = humidity;



  double A = (( c5 * T) + c2) * T + c1;

  double B = ((c7 * T) + c4) * T + c3;

  double C = ((c9 * T) + c8) * T + c6;



  double rv = (C * R + B) * R + A;

  return rv;

}

DHTxx test!
Sensor Pin D2 Humidity:36.00% Temp:70.16*F Dew Point:41.95*F Heat Index:76.38*F
Sensor Pin D3 Humidity:33.30% Temp:70.52*F Dew Point:40.25*F Heat Index:76.16*F
Sensor Pin D2 Humidity:36.10% Temp:70.16*F Dew Point:42.02*F Heat Index:76.39*F
Sensor Pin D3 Humidity:33.20% Temp:70.52*F Dew Point:40.18*F Heat Index:76.15*F
Sensor Pin D2 Humidity:35.99% Temp:70.16*F Dew Point:41.94*F Heat Index:76.38*F
Sensor Pin D3 Humidity:33.20% Temp:70.70*F Dew Point:40.33*F Heat Index:76.15*F
Sensor Pin D2 Humidity:35.90% Temp:70.16*F Dew Point:41.88*F Heat Index:76.37*F
Sensor Pin D3 Humidity:33.09% Temp:70.70*F Dew Point:40.25*F Heat Index:76.14*F
Sensor Pin D2 Humidity:35.80% Temp:70.16*F Dew Point:41.81*F Heat Index:76.37*F
Sensor Pin D3 Humidity:33.21% Temp:70.52*F Dew Point:40.18*F Heat Index:76.15*F

Quote:

Originally Posted by buffalobillpatrick (Post 43457)

...BTW, the 2 AM2301 sensors that I have on hand consistantly read RH about 2.7% apart from each other. I have ordered 3 more from China, I will probably have to correct for their offsets with code...

BBP,

I'm glad you are moving forward on this kind of project.

When I was working with the temp and humidity portion of my CO2 controller, I discovered the Sensirian SHT15, which I have found to be very precise.

It can be fairly expensive, but better deals can be found.

If your part works for you, great. If it doesn't deliver the goods, you'll know where to look.

Best,

-AC

A/C that looks to be a more accurate model, thanks

$3.45
http://www.ebay.com/itm/DHT22-AM2302...item566d189e8d

or spend 5.8x more for the real Swiss part, hehe
"SENSIRION swiss Digital Temperature Sensor Humidity Sensor original" (made in China)

$19.88
http://www.ebay.com/itm/1x-SHT15-SEN...item5412f9c09f

DIY method for wall or ceiling panels that A/C has posted before:

Renewable Hydronic Heating | Home Power Magazine

Click on Radiant Wall System Schematic

Looks like mucho cooling will be needed in my future house.

I'm getting too old (73) to build the planned house up in Teller County Colorado.

That would be a 14hr. drive to get to my daughter's house for medical help in DFW area in Tx.

So I will be moving to Tx. instead. Need to be close to grandkids.

If a person had a well or pond they could easily make a pump driven air conditioner , using ceiling mount radiant cooling. Which might be cheaper then powering a table fan.

BBP,

https://www.heatspring.com is running some free seminars, as a way to encourage people to take their (too expensive) courses. But there is a lot of good info in the courses, and Siegenthaler has given some good ones on low temperature heating and cooling.

From viewing his pre-recorded presentations, I get the feeling that he has read through some of the most progressive entries from EcoRenovator. More likely, we're drinking from the same well... but it took him a long time to come around.

He is all about high efficiency, low-mass, low delta-T, to get the required heating and cooling. And he is pushing ceiling and wall heating and cooling, and saying very little about floors.

Seems a bit odd to me, since a floor is the best place to put a radiant heating panel, even when you are talking about ultra high efficiency, and very low delta-T.

I did a search for Siegenthaler's PDFs and recent presentations on "Low Water Temperature Hydronic Distribution Systems" and this is what I found CHECK_IT_OUT.

But he really knows his stuff, and it's worth seeing.

Quote:

Originally Posted by buffalobillpatrick (Post 43461)

I'm getting too old (73) to build the planned house up in Teller County Colorado... That would be a 14hr. drive to get to my daughter's house for medical help in DFW area in Tx... So I will be moving to Tx. instead. Need to be close to grandkids.

I can certainly understand your decision, and the motivation for it. But still, it makes me a bit sad, since you have done so much of the fundamental design work on you mountain dream.

I hope that others will find the work you have done and recognize the value in it.

It would take a powerful force to move a man from a mountain in Colorado, and make him want to go to Dallas.

Yeah, grandkids would certainly are a power draw!

I wish you the best. I'm sure you will find some 'energy mischief' to get into.

Keep us posted.

With great appreciation,

-AC_Hacker

It seems that a radiant cooling wall/ceiling system would work with best with a thermostat for each area or room, just like a radiant floor system.

Install a large emitter surface in each area for heating & cooling. I like low power use Taco zone valves & Grundfos Alpha ECM pump.

Use my DIY 2.7 Ton water-to-water heat pump.
Rent a large Ditch Witch & install 2 runs of 1" PE pipe about 4' & 6' deep, & long enough to handle 3 tons of heating/cooling in 78*F wet sandy soil.

Quote:

Originally Posted by buffalobillpatrick (Post 43468)

It seems that a radiant cooling wall/ceiling system would work with best with a thermostat for each area or room, just like a radiant floor system...

It all sounds just great!

I don't know if you are 'onto' this source of information yet, but there is an Italian maker of hydronic accessories, named 'Caleffi', that I have no interest in or experience with, who do publish amazingly useful free technical magazines for the industry.

The issue that would be of most use to you would be ISSUE_#13, which focuses directly on hydronic cooling.

The MotherLoad of issues (AKA: "library") is HERE.

Best,

-AC