Solar Hot Water - Drainback Type

Item Description Number

My Future Plans

I am in the process this summer (I started in March of '08) of installing a Solar Hot Water System (Solar Thermal). I will likely use this design:

hp88-34_peltz_drainback.pdf

(Used with Permission, Jay Peltz)


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Step 1

Obtain used Solar Collectors
 > check!

I bought five used 4'x10' panels in Austin. I am in the process of pressure testing each one (I paid less than the pressure tested price) Thanks www.craigslist.org!

These panels cost at least $1000 each new and can be found for 100-500 used. Read more about buying used panels from www.homepower.com See issue 112 page 68 (no direct free link to that article anymore $$).

After pressure testing, I will sell the 2 or 3 excess panels.


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Step 2

Map out where to put the panels.
A. Using the Solar Pathfinder, I mapped out the southern exposure of my house. Winter time has a little late start for the Sun, but overall a good exposure. The flu for the furnace will cast a shadow after noon, but it does not have the same impact to the performance of a Solar Hot Water Collector as it would for Solar Electric Panel.

> check!

   
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Step 3

Repaired the Header pipe first, since it was bent. Pressure Test the Panels for air tightness by soldering on new fittings (a reducer to the pressure gauge and caps for all other corners...

I recommend MAPP gas since it gets hotter than Propane alone. MAPP = Methane + Acetylene + Propane

     
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Step 4

Hoist the collectors onto the roof of the house.

> check!

There is a little shade. Not bad for just after 5:00pm at the end of December. There is one tree that should be trimmed back just a bit, since it is touching the edge of the roof. I will not trim the trees too much since they provide shade in the hot summer.

Notice the temperature of the inside of the collector after a full winter's day in the sun! 240F!! Need to get some water circulating!

   
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Step 5

Setup the Heat Exchanger.

The got these four heat exchangers at the same time as the collectors. They are single wall copper tube-in-tube design. I rebuilt most of it, by adding all my own connections, with temperature gauges and other fittings. The heat exchanger also came with two pumps:
  1. Grundfos UPS15-42F (similar to the Taco 009F). This pump circulates the distilled water to the collector and back down the inside tube of the heat exchanger.
  Grundfos: www.grundfos.com (click on HVAC Products, then UP series Pumps)
  2. a Taco 006-BT2. This pump circulates the domestic water through the outside of the exchanger through the storage tank.
  Taco: www.taco-hvac.com

Both pumps still work, the Taco 006-BT2 is too noisy...

I tested the flow and checked for leaks. But I am not sure I will use the heat exchanger as build! It seems to work ok, but it is not double-wall and it might be too large for my application. More testing is needed.

> check! (well almost)


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Step 6

Setup the Heat Exchanger (revisited!).

I separated the double loop heat exchanger into two pieces. I moved the fittings around to reduce the tubing from 1.5" to the 3/4" I need for the connections in order to eliminate the PVC fittings you see in the first picture.

I re-plumbed the pumps and inputs to make it simpler. This is a lot of soldering and fittings to move...

In the future, I will find an all-in-one Controller-Pump-Manifold unit to sell. The sweating of pipes and fittings is too painfully time consuming to be DIY.

I will also substitute the Taco 006-BT2 above for an Ivan Labs EL SID SID10B12 or 10PV

> pending


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Step 7

Install the Differential Controller

I will use the the Sunearth Differential Controller. It monitors the temperature of the Collector and the Storage Tank. When the Collector is hot AND  the Storage Tank is not too hot, then it turns on the pump(s). It has an AC outlet for the AC Pump. I will also wire in a AC-DC converter to power the El-sid 12Vdc pump. I will use the user's manual to program the controller, and I may also need the Hidden_Menu guide...

> pending


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Step 8

Install the Drainback Tank

> pending

 
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Step 8

Connect the Collectors to the Drainback Tank

Connect the Drainback Tank to the Heat Exchanger

> pending

 
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Step 9

Test the Solar heat obtained versus the propane used...

> pending

 
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Updated: July 02, 2010