There are a few different hydronic heating systems available on the market today. While each system is
unique, the concept is generally the same and pretty simple.

For example, during a thawing application, the unit’s boiler heats a propylene glycol mixture and pump the
warm fluid through the long loops of the heater hose, which are generally laid out 12 to 24 inches apart on
the area to be heated.

Propylene glycol is like a food-grade anti-freeze that effectively conducts heat. The hoses are then covered
with a vapor barrier, which helps prevent water vapor from escaping the thaw area.

On top of the vapor barrier, insulation blankets are placed. The combination of these two is to keep the energy
in the ground, changing the ice to water and further accelerate thawing. As opposed to 15 percent of heat
directed into the ground using air heaters, 93 percent of the heat is conducted into the ground using hydronic
heaters. (This percentage can vary depending on the use of a vapor barrier and number of blankets.)

The goal of each heater during the concrete curing process is as simple as the technology that runs it: to keep
the pour at an ideal, constant temperature so the concrete can cure properly. In the case of a slab, the heater
can also be used initially to heat the ground to give the concrete pour a warm base to start.

The setup of a heater system varies depending on the type of pour your customer would be doing.
For example, when pouring a slab, the ground needs to be preheated first. Fluid in the system in preheated to about 180 degrees, which helps the ground reach a temperature of about 85 to 90 degrees. Then the hoses are placed at 24-inch centers, insulating blankets are placed and the ground is warmed. After removing the heating system and blankets, the concrete is poured.

When the concrete is set, the vapor barrier, hydronic hose (with 24-inch spacing) and insulation blanket are
placed. The heating system temperature should be reduced to 120 degrees F and controlled, so the outgoing
temperature of the glycol mixture stays in a 65- to 75-degree range. The heat will need to be maintained until
the concrete has reached its desired strength. This usually takes three to seven days, depending on the
ambient temperature.

Portable hydronic heaters can be used on various types of concrete placements, including tilt-up concrete
construction, slab-on grade, poured walls, columns and elevated placements, such as bridge decks and
multi-story buildings. They can also use hydronic heaters to heat rebar before pouring.

And these units can be used for more than just concrete applications. As Chuck Porter with Thawzall says,
“The more people use this technology, the more ideas they come up with to use it in other ways.”

Other applications include ground thawing, pipeline maintenance, temporary structure heating and
environmental applications, such as removing hydrocarbons from soil. For more unique applications see the
box, “What will they think of next?”