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Installing My Solar 
Domestic Hot Water Heating System

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HOME Receiving

Live statistics

Sensor location Gauges update every 10 seconds Readings for the last 48 hours update every 10 minutes
hover your mouse over the charts to see specific readings. 
Re-load the page to update the charts after 10 minutes
Collectors showing sensor location with red dot

Collector (40 sq. ft.)

DC Differential Temperature Controller

circulation pump
Collector circulation
pump is:
top of storage tank showing sensor location with red dot
Top of storage tank

40 gallon storage tank top

bottom of storage tank showing sensor location with red dot
Bottom of storage tank

Storage tank bottom

view of house showing sensor location under porch with red dot
Outside temperature

Outside temperature

Click for Woolwich, Maine Forecast

Things to notice:

If the weather report above shows overcast or precipitation during daylight hours that explains why there has been no heat gain in the storage tank.  Solar heating requires sunlight!  You can mouse-over the charts above to see specific time stamped readings, or click+drag to expand a section of the chart.  On a partially sunny day you might see the collector temperature jump around a lot as clouds pass over.  Whereas on a completely sunny day there should be a very clean curve representing the collector temperature. 

The 2 circulation pumps are activated by a differential temperature controller.  They are only activated if the collector temperature is more than 12F above the storage tank temperature to account for the temperature drop in the 25 ft. plumbing run from the collector to the tank.  It turns off when the difference drops below 10F difference.  This prevents the system from losing heat when the collectors become cooler than the storage tank late in the day.

The heat builds up in the tank as a stratified layer with the hottest water rising to the top that then fills downward.  If you look at the tank top and bottom temperatures during the time that the tank is gaining heat you will see that they are very similar because the pump is mixing the water in the tank.  A few hours after sundown the tank temperatures begin to stratify so that the top will be 10-30F hotter than the bottom.

Rinnai R75LSi tankless water heaterIn the evening and overnight the tank temperature begins a slow decline of about 1F/3hours.  This is the heat loss through the walls of the tank. This loss is why I replaced the tank style water heater with a tankless on-demand unit. 
See this blog I did about that.  Most of the homes in Europe and Asia use demand water heaters -- America is way behind the curve on this energy efficiency strategy.

A sudden dip in the storage tank temperature represents hot water usage such as a shower, dishwasher or clothes washer.  The dip will be more pronounced at the bottom of the tank as this is where the cold 50F well water enters.   These dips become more noticeable at the top of the tank as the overall heat in the tank reduces.

If there was no solar gain, the tank temperature falls to the incoming well temperature of about 50F.  But the tank temperature will rise slowly because the pressure tank and storage tanks are in a heated part of the basement at around 70F, this was an unexpected bonus that I had not considered until I installed the monitoring system.

Annual propane usage, total $/year and average $/gallon Propane use and cost annually
Propane used for building heating, cooking, clothes drying AND water heating

July 2006: Solar collectors installed
August 2008: Added heat exchanger + pump
June 2010: Installed tankless on-demand water heater
2016: First year living alone after my divorce in 2015
2019: Installed Nest thermostats and used more electric heating
2021: Installed heat pump in ground floor
+ rented out a room heated 24/7 in winter

I also monitor the solar heating system on my workshop, and the solar electric power generated by my solar array.  If you are an electronics geek like me, then you need to know about the technology behind this web page.  It is a device called an ioBridge that is designed to monitor and control things through the internet.  It is affordable and relatively easy to set up.  In order to monitor the AC and DC pumps on this page, I built my own interfaces to the ioBridge.  Here are the schematics for them.

If you found the information presented on my web site to be helpful you can send me a donation to show your appreciation for the many hours I have invested in presenting my knowledge and experience.  This is NOT tax deductible and will show as a consulting fee on your receipt.