The Open/Direct System by Radiantec Company is the first truly new heating system in a generation. The system uses one very efficient water heater to make domestic hot water for the home and warm water for radiant heating. Radiant heating systems warm the building by locating heating tubes within a large surface area of the building (such as the floors or ceiling), and then circulating warm water through the tubes.
The Open/Direct system takes full advantage of the fact that only warm water is needed for both uses instead of the very hot water that is needed by other types of heating systems. There are significant advantages in simplicity, reliability, initial purchase cost, energy efficiency and pollution reduction.
A solar energy assist is available because the system is based upon the domestic water heater. One attractive feature is that the Open/Direct System is one of the simplest heating systems ever to be developed.
In the heating mode:
When heat is wanted, warm water is pumped from the water heater, through the tubing within the floor and back to the water heater. If space heating and domestic hot water consumption occurs at the same time, the domestic hot water always takes precedence.
In the domestic hot water mode:
When domestic hot water is wanted, warm water comes out of the tank and goes to the fixtures. Cold water must replace the hot water that was used. The cold water goes through heating tubes within the floor on its way to the water heater (an important safety detail!). This flow pattern provides limited free cooling and other benefits. Stagnation is prevented and priority is given to the domestic hot water use over the space heating use. A small amount of free cooling is realized in the summer.
Radiantec_Direct_Radiant_Heating_System_Installation_Manual