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Open Direct System

The Open Direct System is one single system that operates in three different and distinct ways. Yet, this ingenious system is entirely automatic. It needs no separate actions or adjustments by the homeowner at all.

Heating Mode Operation

Domestic Hot Water Mode Operation

Summertime Cooling Mode Operation (optional)

Diagram of an Open Direct Heating System

Photograph of an Open Direct Heating System

Open Direct System Diagram

We believe this system is the best alternative. It is simple in design, efficient in operation, has modest initial costs and can make use of environmentally friendly solar technology. When and where local codes permit the delivery of space heating and domestic hot water through a single system, we recommend the Open Direct System. Here's why:


The Open Direct System uses a single domestic water heater for space heating and domestic hot water, eliminating the need for a boiler. The low operating temperatures of radiant heating allow the use of state-of-the-art "condensing" domestic water heaters which are 95 percent efficient. The summertime cooling feature is free and actually lower the costs of heating domestic hot water (see diagram).

Initial cost

The Open Direct System is extremely simple and simplicity costs less. Consider, for example, a 2,500 sq. ft. house with two zones. The cost for underfloor materials, pumps and controls is approximately $4,300. Add to this the price of high-efficiency Polaris water heater (no boiler is needed) and the cost totals $7,500, an unbeatable price for a high-quality system.


Besides keeping initial costs low, this translates into greater reliability.


Major components are all made of stainless steel or polyethylene plastic and should last a lifetime. And our components are backed by exceptionally strong warranties.

Environmentally Friendly

This type of system can be designed to use solar energy initially or can be converted to solar at any time. Click here to see how the open direct system can make use of solar energy.

The Open Direct System is our customer's preferred system.
Click here to find out why.

Questions and answers about the Open Direct System.

Please visit our pages on Building Code Compliance here!!



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Open Direct System
Installing the Closed System
Installing the Indirect System
Installing tubing for a concrete slab
Installing tubing between floor joists
Installing tubing in the ceiling
Installing tubing in the walls
Installing a heated towel rack
Installing Radiantec Controls
Doing your own tubing layout.
Radiantec Basic Solar Domestic
   Water Heater Installation Manual.

Radiantec Basic Solar Domestic
   Water Heater Owners Manual.

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