Online Journal

Solar Hot Water

Tracker 1&2

Array 3

Control Center

Wind Turbine






Solar Hydronic domestic hot water system. 

It seems the original tank sensor may have been faulty. I replace it 2/2009 and all problems highlighted below, before this date, have disappeared. UPDATE 5/4/2009, I replaced the entire controller with a MADE IN USA "Eagle 2" and now the solar hydronic system works much better. The Thermomax SMT100 finally failed completely on 4/25/09. The Eagle's operation is much better than the Thermomax, for us. Thanks to G2power in St. Louis for turning us on to the Eagle 2!

This is the second system I have used. Back in the late "70"s, I had an Earth Enterprise system installed. The collector enclosures failed after many years of service. The new collectors look like they are superior.

4/6/08 We installed the 100+ gallon stainless steel tank and unpacked all the hardware but the two solar collectors.

4/9 installed the controller and expansion tank on the wall next to the storage tank. Making a list of hardware to buy the next time we leave our valley. Begin the preparations for installing the panels on our roof.

4/12 Pretty much have the routing of pipes figured out. Not an easy task with 12" to 36" thick concrete and masonry walls, floors and ceilings everywhere. Also need to coordinate wood heat liquid tie in.

5/5 Mounted wooden rib to concrete wall to strap tank for earth quake survivability.

5/9 Ready to install spar extensions to beams for mounting panels.


 5/21 Put up the solar hydronic panels today.

 5/28 Have a week of meetings to coordinate. Just need the pipe to plumb system together.

6/9 Some of the fittings, 1" to 3/4" connectors, are special ordered and will take several days to arrive.

6/11 The hot water storage tank is connected, full of water and pressurized. Still missing two fittings for the panels, but I should be able to completely plumb the PEX and insulation tomorrow. I need one 1" fitting for a air bleeder and one 1" fitting for a cap and pressure relief valve. Have everything else ready to install tomorrow.

6/12 Finished plumbing and insulating system. Just waiting on two special fittings due in Monday Morning.



6/14 Put temporary plugs on two fittings and flooded panels, bled air and turned on system for first time. Had to work out a few changes to thermometers for proper metering but now heating water properly. Took my first shower with solar hydronic hot water in 27 years. Well that's not true, many hot baths in China using solar hot water. It looks like it is imperative to install a pressure relief valve...the water was boiling in the panels today before I could turn on the circulator pump. We will debug the system and operate for a while before adding auto engine antifreeze to system.

6/21 Solar hydronic system is now fully installed with check valve, pressure relief valve, thermostat sensor properly placed and pressurized. It is automatic and fully functional. It uses 60 watts for a circulation pump from 10:30 to 18:00 on a partly cloudy to sunny day.


1/7/09 There seems to be a bad habit with this controller to fault the tank temp and shut off the pump, then the panels boil and release fluid onto our south porch. I believe the problem is within the connection between the PLC and the back board. If I wiggle the tank sensor connection no difference but if I wiggle the PLC the tank temp changes. A persistent problem since installing and not going away. Right now I feel when the wood boiler is installed the solar hydronic system is coming out! The solar hydronics don't work well in winter anyway. They heat water if the sun is out and not hazy. But that doesn't happen but about one day a week, not enough to maintain hot water. We will see what is decided soon.

1/15/09 A third collector would not go to waste in this system for winter time. Still having trouble with the controller internal connection block.

1/19/09 Made a major change. Connected the demand of the solar heater tank to the supply of the electric heater tank. I have to heat most of my water with electric anyway this winter so at least the solar hydronic will act as a pre heater for the supply to the electric heater.

1/30/09 I replaced the tank sensor and the system now works perfectly. That has been the problem for the last 7 months.

5/4/09 The SMT failed completely a week ago and I ordered an Eagle Sun Control and installed it yesterday.


5/5/09 I like the Eagle 2's operation much better! Just ordered a third sensor to put on the electric heating tank to monitor temperature of it too. COOL!

11/8/2010 I completed the hydrothermal loop between our Central Boiler outdoor water jacket wood furnace and the hot water storage tank. Now our water is heated by free waste wood from our sawmill and solar. I turned off the electric water heater and hooked the storage tank directly to the domestic hot water through a tempering valve.

11/9/2010 This morning the hot water is 148 degrees, up from 106 yesterday morning.

11/15/2010 I took off the water pipes from the solar hydronics and replaced them with the pipes from the Central Boiler wood furnace, for the water to go directly through the internal heat exchanger loop in the water storage tank last night and now I have 176 degree water in the storage tank, and 300 gallons total in the furnace and tank ready to give BTU to the house heating system when needed. Reason being;

1.) The configuration of the hydronic collectors is wrong and they boiled over before they circulated with the new furnace also heating water in the storage tank.

2.) Using the internal loop inside the storage tank for the water furnace boiler makes the water hotter than the outer exchanger and now I can use the extra BTU for house heat, ie, heat can now go both ways efficiently and I can use it for house heating or domestic hot water.

3.) If all I need is one stick of wood per day through the summer to keep unlimited 176 degree hot water, then that is what I want to do. I'd need to rebuild the hydronic array to work better anyway, so I am taking it down. Remember, I get literally tons of wood waste to use every week from the sawmill. It is rare when I don't need the electric water heater on to maintain hot water constantly, that being off now saves between 6 to 20 KWh per day with just one 3 speed circulator pump running at 60 watts on low.

4.) I only need a wheel barrow to move a little wood from the sawmill to the wood furnace now. They are 350 feet apart.

11/26/2010 Our Central Boiler is proving to be an important part of electric conservation. The reduction of electric consumption during cloudy conditions has had dramatic results to our overall use of power. On top of that, It's now 17 degrees F. and I can run everyone out of the house from heat if I leave the heaters on. Hot water storage tank is running at 176 F. It is a good thing there are tempering valves.

This Central Boiler outdoor wood furnace may be the best thing since solar panels! My electric consumption has drastically dropped with unlimited hot water and house heating with no extra electricity needed. I dropped 6 to 22 KWh per day. 6 less than a previously sunny day making solar hydronic hot water and 22 less on the frequent winter cloudy days when the electric water heater had all the work to do.


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