Arduino thermostat

Earlier I finished the piping for the the two additional zones.  A quick recap, one zone will allow  a boiler to heat the tank that is normally heated by solar.  The second zone is really not a zone but the piping and circulator pump that will add heated water from the chip boiler.

The solar water tank, or solar thermal store has two coils in it, the first coil is heated by the solar loop on the roof.  This coil is physically lower in the tank so that the heated water will rise and the sensor controlling this coil is lower as well.  This allows the maximum storage from the tank from solar at all times.  The second coil and sensor that is intended to be heated from the boiler is mounted higher.  The water at the top is  hottest and therefore the  least amount of energy will be needed and the maximum amount of free energy is used first.  Of course solar is not free, it still requires a circulator pump but I assume it to be negligible and therefore in this context free.

Knowing this and assuming that I am going to use an Arduino microcomputer in the process anyway, I am intending to implement the solution in two steps.  The first step to wire and shrink wrap a thermistor  and run the thermistor back to a breadboard, and display the temperature on an LCD.  If the temperature is below a certain value, digital write to a relay to turn on the circulator pump.  If the temperature is good, do nothing.

In the second iteration of the solution my plan is to add a time chip to the system and make the process more efficient.    The logic is this:

8am, no real need for hot water, and there is a good chance the solar will heat the water.

4pm, heat water and maintain until 8pm if needed.

8pm-8am maintain a minimum, lukewarm temp.  We’re not a shower in the morning family.  Of course on the weekend the program will have to be different.

To implement this 2nd iteration a real time chip will be required.  I have found a few, one at sparkfun.com

http://www.sparkfun.com/products/10160, $19.95

 

and a second one at

http://macetech.com/store/index.php?main_page=product_info&cPath=5&products_id=8

I am inclined to the second link, the board is cheaper with a built in battery holder and battery shipped with the product for $14.99

And the yourduino option for $9.00

http://arduino-direct.com/sunshop/index.php?l=product_detail&p=48

http://adafruit.com/products/264

 

Also $9.00

Any opinions?


Progress-Goal for the week

Potato Harvest drying on floor

I harvested potatoes last weekend with the girls and the floor was covered.  I had to clean up so I could work without stepping on vegetables.  So that was job one on Sat morning, get more liquor boxes and get things cleaned.  Finally finished that with help from the girls on Sunday morning.  It snowed over the weekend so Sunday was spent plowing and going to a party at a friend’s house.  On Saturday,  with help from my 11 year old helper,I did get one half of the circulation loop for the heating of the solar tank installed.

Clean floor after Potato

Today’s goal is to finish installing the loop and run stub piping through the wall to where the chip boiler will be installed.  I want to install the loop in the solar water tank to allow for more energy storage.  This will allow more  flexibility when the microcomputer is deciding where to put the heat from the chip boiler.  Finishing the loop will also allow the Arduino Uno to be the thermostat controller hooked to the Boiler Boss. With a thermistor and LCD added to a relay board the Arduino can be the thermostat to run the zone.  It seems to me this would be a great way to test the Arduino since all that can happen if the thermostat fails to work is a cold shower.  Of course this assumes that the solar loop didn’t heat the water sufficiently and the solar can still heat the water hot enough for a shower on a good sunny day.

Return manifold with piping from heating coil in Solar tank and stub from chip boiler

The boiler boss is one central control unit that contains all the relays for the zones.   This box controls all the circulator pumps and the new circulator pump needs to be wired into this and the Arduino wired in as a thermostat.

Boiler boss with Cover removed

So this weeks goals are simple: 1)  Finish the solar hot water tank loop, wire it in and test with an Arduino controlling the zone, acting as the thermostat. 2)  Apply the sealant to the chip boiler and test for leaks.  3)  Work on the Chimney penetration through the rear wall of the shop for the chip boiler.  This will be a straight 4″ pipe out since there is forced draft.

I got some good comments from a friend concerned with the temperature of the return water so I got a fresh battery for my non contact thermometer and took some temperature measurements  of the zone water at the point  leaving the circulator and just above the return manifold  so here they are:  113 out and 98/99 back, not a lot of difference.  The outside temp is approx. 30 (all temps F).

I am having a difficult time removing the end plug for the upper manifold, this is a 3/4″ black iron plug, I am thinking of using heat, any other suggestions,  I am trying this plug with a 24″ pipe wrench, I am afraid if I try to use a cheater I will break something.