Custom Heating System

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Master of None
I'll add my $0.02 vote for solar as well. There is LOTS of DIY info on solar out there. 2 years ago, I replaced my LP hot water heater with a DIY solar system which also has a small 40 gal electric tank as "standby". I do not have hydronic heat running off the solar, but run the domestic hot water off it. The solar "loop" is a drainback system with 80 sq. ft. of commercial collector on the roof and a 250 gallon storage tank. The circulator is a Grundfos Alpha and is controlled by a differential controller. The tank typically sits at 150 degrees with a 160 degree high limit. Drainback means when the circulator is not running the plain water in the solar loop drains back to the storage tank and the collectors are empty. This is the freeze protection. The domestic cold water runs into a 100' 3/4" copper pipe heat exchanger loop in the storage tank, then feeds into the standby heater. Water delivered to the standby heater is typically in the 130 to 140 degree range, and the standby heater very rarely comes on.

When we first turned the system on, I forgot to turn on the breaker for the standby heater and the system provided all of our hot water needs (family of 4) for nearly 6 months before I realized the standby heater was off!

In the future, we may add some under-floor hydronic loops to the system, the 80 sq ft of collector is way more than we need for DHW. On a typical sunny day the circulator only runs for a couple of hours at most total to "top up" the temp on the storage. In the 18 months since we installed the system, our energy costs have dropped 15% (price adjusted).

Because we all LOVE pictures, here's some...






New User
Hopefully you have included a pop off valve that does not have a cut off valve between the source of heat and the POV. Otherwise you have created a BOMB! I once saw a oil-fired, 60 gal water heater destroy a six story building with a steam explosion. BTU capacity of POV should exceed the total amount of system's heat input. Be careful and read labels. Install drain line of POV so that it can't be capped, plugged, or stopped up by mud dobbers. Leave end of drain line unthreaded. Do not reduce diameter of drain line vs diameter of POV outlet. POV will start to trickle leak at the end of its life. Make it possible to ONLY replace it! Test open the POV at least annually.


Senior User
So my custom heating system has been in operation for a week and I must say--so far so good. Although I haven't had any real cold weather yet to see how it works, it has no problem bringing the temp. of the shop from 40 - 60 in about an hour.
I did have to make a few modifications to the system but nothing major. I filled the WH with antifreeze only to discover that a 40 gal. water heater only holds 38 gal.I set the thermostats at 130 degrees only to find out that the expansion of the antifreeze caused the radiator cap to open at 13 lbs so I had to add an expansion tank to maintain the liquid in the system.
I also had to remove the back flow preventer from the pump and had to switch the location of the pump from the hot water outlet to the cold water inlet to make sure that a good supply pressure was available for the pump to cycle the antifreeze. Another modification I had to do was reduce the speed of the airflow to prevent cooling the liquid too fast. Luckily the fan had a slower speed setting that I could rewire for. Raised the thermostat settings to 135 degrees.So with the modifications done I am getting a discharge temp of 95 degrees which should keep the shop toasty when the cold hits.
My average electric bill at present is about $30 a month so it will be interesting to see what it goes to when I get the next bill.
To be continued
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