The Best Off Grid Heating System

March 13, 2013 · 5 comments

The greatest advance in home heating in the past few decades has to be the Open Direct System invented by Radiantec.

The Open Direct System uses a highly efficient condensing tank-style water heater that provides both radiant space heating and domestic hot water. There are no heat exchangers, no poisonous antifreeze and no complicated controls. The same water that flows through your floor, comes out of your hot water tap.

The secret weapon of this system is the Polaris PG10 34-100-2 hot water. It truly is amazing with a real efficiency of 96%. It can heat water as fast as you can use it, has a stainless steel storage tank holding 34 gallons and has standby losses of only 1%.

The best heating system

The Polaris truly is our secret weapon for designing a super high efficiency heating system. There is nothing like it! It produces 100,000 BTU, uses very little electricity and is as easy as connecting the gas supply, cold water in and cold water out.

This high efficiency heating system is designed to work in a radiant heat application as the water traveling through your floor needs to be approximately the same temperature as the water going to your hot water tap. Radiant heat applications use warm water (100-140oF) to heat your floor as apposed to baseboard heaters and radiators that use much hotter water (160-190oF).

Here is how it works. When your zones (or a zone) need heat, the circulating pump will make hot water will flow from the hot water heater, through the check valve, through the pump, to the heating zone and back. This will heat your floor effectively and is pretty normal.making heatIf you look at the above drawing, you can follow the hot water from the top of the hot water heater through the check valve, through the circulating pump, through the heating zone (floor) and back to the hot water heater.

The real difference begins now…

When you open a hot water faucet, cold water enters the system from the cold water supply, goes through the heating zones, and enters the hot water tank. This forces hot water out of the top of the hot water heater, into your hot water piping and out the hot water tap.

providing hot water

In the above drawing, you can follow the hot water out the top of the hot water heater to the piping that leads to your hot water fixtures. The water is replaced by going from the cold water piping, through the circulating pump, through the zone and back to the hot water heater.

By the time this cold water reaches the hot water heater, it has already been preheated by the floor. In the heating season, the cold water will be warm by the time it reaches the hot water heater.

Although this system works awesome in the winter, the real energy savings are in the summer as all the water entering your hot water heater has to go through the floor first. The cold water leaves your well goes through all the zones of your heating system and is warmed.

In the summer you can expect an increase of 10-20 degrees as the water flows through your floor. This cold water cools your floor in the summer and provides some free air conditioning. The cold water will always flow through your floor first because of the check valve in the system.

If you are planning on installing a solar water heating system, the open direct is the perfect companion. Look at the photo below. Every BTU collected with solar, will reduce your fuel consumption. It is just a matter of plumbing in a new loop for the solar collectors if you live in a no freeze zone. If you live in the north, simply add a heat exchanger and antifreeze.

solar water heating

As great as the Polaris/open direct system is, is not the best setup for hot water baseboard heating. Hot water baseboard requires higher temperatures. Although the Polaris could handle it, the resulting water temperature would be too high for bathing, showering or washing dishes.

Advantages of Using the Polaris in an Open-Direct-System:

This system eliminates one of the biggest problems with radiant heating systems….air.

In most radiant heating systems, air gets trapped in the piping and pumps making the system operate poorly. In the open-direct-system, air is forced out of the lines every time you open a hot water fixture.

Radiant heating systems work best at temperatures of 100-140 degrees F. The Polaris is designed to work the best at 100-140 degrees F. It is a match made in heaven. If you try to use a standard boiler with radiant heat, you will always be operating your boiler at a lower temperature than it was designed to operate or use a mixing valve. Mixing valves are not efficient as you are paying money to heat your water only to cool it down with a mixing valve.

You only need to purchase one hot water heater instead of a hot water heater and boiler. This saves a lot of money and also saves standby losses. Every hot water heater you have will add another standby loss.

The open-direct-system is incredibly simple and code approved by the International Code Council (ICC). Email us if you would like the documentation supporting the open-direct-system.

You will save on your heating and hot water energy costs. Think about the summer. Your floor is warm and the sun is shining. Every time you open a hot water faucet, cold water is directed through the floor, preheated and sent to the water heater. We see a 20 degree temperature rise in the middle of the summer. That is a free rise in water temperature.

With a little extra plumbing, you can also direct all the cold water through your floor in the summer months. This can make a decent decrease in cooling costs and provide a much cooler home.

To make the open-direct-system work the best, the Polaris is the most reliable, inexpensive and well built heater available today . We installed our first one about 5 years ago.If we find a better unit, we will update this page immediately.

Leave a Comment

{ 5 comments… read them below or add one }

JonFranton May 22, 2013 at 12:38 pm

Do you really think a Polaris is big enough to heat a home and provide hot water? Are there any other brands you recommend? I can’t seem to find a Polaris. Thanks for your help…


Jody Graham February 1, 2014 at 12:23 pm

Hi John,
The Polaris is absolutely big enough to heat the average home. It has an output of 100,000 BTUs which is as much as most wood boilers. The little bit of energy required to heat the hot water of domestic use is insignificant. It can heat about 4 gallons per minute as well as you always have a storage of 34 gallons. It should not be though of as a hot water heater but more like a boiler. We have used one in our home in eastern Canada for years. The temperature here can go down to -30F. Good luck in your heating adventures….Jody


Jody Graham February 1, 2014 at 12:24 pm

I do not know of any other brands that perform like the Polaris with a small electric power consumption. Try as they are a stocking distributor in Vermont.


Luis July 25, 2014 at 3:14 pm

Hi Jody… you said, “This cold water cools your floor in the summer and provides some free air conditioning. The cold water will always flow through your floor first because of the check valve in the system.”

In the summer time, is there any risk of the cold well water running through the heating loop and cooling the tiles above it so much that water starts to collect on top of the tiles (similar to water collecting on the outside of a glass of ice water)?


Jody Graham August 12, 2014 at 10:02 pm

You know I have never had that experience or had anyone else complain of condensation on the floor. It could happen but I think it doesn’t as the temperature change is so gradual and gentle. The only cool water going through the floor is any water that is filling the hot water heater and that usually isn’t enough to cause any type of water condensation buildup. If anyone has experienced this issue please let us know…Jody


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