Solar Water Heaters, Tankless Water Heaters, and Hot Water Demand Systems

I was asked by a potential customer about using a solar water heater in conjunction with a tankless water heater this morning. Using a solar water heater to feed a tankless water heater is a great idea and a green idea too.

Solar water heaters come in several types including active systems including direct, indirect, and passive.

The passive solar systems locate the storage tank above the solar panels, that way the hot water rises into the storage tank, and cooler water from the tank sinks down to the bottom of the collectors. This thermo siphon cycle continues as long as the water in the collectors is being heated.

In active type solar systems a pump circulates the water from the collectors into the storage tank when the temperature in the collectors is sufficiently high and above the temperature in the tank. Some systems use an indirect method of heating the water. These indirect systems circulate a fluid through the solar collectors and then through a heat exchanger in the hot water tank.

Solar hot water tanks are very well insulated, and they do not have a flue through the center, so they have minimal standby losses.

Tankless water heaters modulate the gas burners or electric heating elements to maintain a steady pre-set outlet temperature. If you feed the inlet with the outlet from your solar water heater the tankless unit will not turn on unless the water temperature coming from the solar water hater isn’t hot enough, and if it isn’t, it will burn just enough gas or consume just enough current to keep the outlet temperature at the pre-set temperature.

You end up with a highly efficient hot water plumbing system that uses the minimum amount of energy when solar hot water is available, and you still have unlimited amounts of hot water when you need it. It’s a great way to turn your residential plumbing system green.

Adding a hot water demand system makes the system even greener. By adding the hot water pump you save water as well as energy. A demand pump uses very little energy, typically about $2.00 per year in electricity costs, and saves many thousands of gallons of water per year.

By combining all three items, solar hot water heating, tankless hot water heater, and a hot water demand system you get the greenest possible solution to your hot water problems providing you with water savings, energy savings, and the convenience of fast and endless hot water. You reduce green house gas emissions and reduce your carbon foot print and save money.

More about Solar and Tankless Combined

Hot Water Recirculation System? Replace it with a Demand System!

Many residential single family and multi-family homes built in the past have full time hot water recirculation pumps and systems installed. This no doubt saves a whole lot of water, but it also wastes a tremendous amount of energy.

Hot water recirculation

Recirculating systems were typically used in larger homes, say 3,000 square feet and up. Long pipes mean long waits, and if you could afford a big house you didn’t want to have to wait forever for the hot water to arrive.

Full time recirculation systems slowly circulate the hot water through the hot water piping keeping the water in the pipes hot for instant use. Turn on a faucet and within a second or two you have hot water. It’s a great convenience, but there is a penalty to pay.

Wasting energy

Your hot water plumbing becomes a giant heat exchanger causing your water heater to fire more often and longer. Not only does this waste a huge amount of energy, but it substantially increases the wear and tear on your water heater.

Even if you heavily insulate the pipes and put the recirc pump on a clock timer, you still end up spending a lot of money for that wasted energy. It’s not helping your carbon footprint either.

Hot water demand systems

A demand hot water system on the other hand will still save you thousands of gallons of water each year, and it won’t waste any energy. Demand pumping systems typically use about $1.00 per year in electricity to run the pump. This is because the pump only runs for a few seconds and only when you really want hot water.

With a demand system, you simply push a button when you want hot water, and that starts the pump. The pump sends the water to the fixture at a faster rate than if the faucet was just run. When the hot water reaches the fixture, the pump shuts off, and when you turn on the faucet you have instant hot water. No water was run down the drain.

Installation is easy. Simply remove the old pump and replace it with the demand pump. Buttons can be hard-wired from the points of use, or wireless switches can be used.

You will still save water, and you will save energy and extend the life of your water heater. Best of all you will feel good every time you use your hot water knowing that you are doing your part to reduce global warming!