Radiant Floor Company pioneered the use of on- demand, tankless water heaters for radiant floor heating more than 20 years ago, when many in the heating industry believed that “on-demand water heaters would never work for radiant heat. We disagreed and have been doing this longer than anyone, with great success!
On-demand water heaters can be configured for OPEN, CLOSED, HEAT EXCHANGER and COMBINATION UNIT systems. The photos and schematics below show how it’s done.
Our OPEN SYSTEM features dual mixing valves — one for the radiant floor, and a second for regulating the domestic hot water. With this approach, the customer has the option to send 140-degree water to the floor while simultaneously providing the domestic hot water fixtures with temperatures as low as 110 degrees.
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- Heat Exchanger system schematic
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- Open system plumbing
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- Fully installed Open system with an on-demand heater
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- 2 Zone Closed system
Our HEAT EXCHANGER systems are pre-assembled, then disassembled for shipping.
Below is a schematic of the system with parts labeled. Components include a temperature gauge, pressure relief valve, check valve, pump and flanges, isolation valves, pressure gauge, and dielectric unions for easy assembly.
Heat Exchanger System Schematic
PRIMARY LOOP
Some Radiant systems require a Primary/Secondary plumbing configuration (illustrated below). For more details on Primary/Secondary plumbing, see this link: Primary/Secondary Plumbing
Primary/Secondary plumbing using the “open” variation. In this configuration, the on- demand unit provides both domestic hot water AND space heating. With the “mixing valve” installed before the domestic hot water supply, the floor and the domestic hot water can run at different temperatures.
This entire array — plumbing fittings, gauges, pressure relief valve, shutoff valves, dielectric unions, check valves is pre-assembled and pressure-tested at our factory. The installer can literally use a crescent wrench to connect it to the on-demand heater in less than three minutes. A photo and labeled plumbing schematic are shipped along with the hardware to eliminate any guesswork.
COMBINATION UNIT SYSTEM
The “COMBI” (OR COMBINATION) system (below) is a closed system that will supply both space heating and domestic hot water. This system utilizes an integrated (i.e., “built-in”) heat exchanger to separate the potable domestic water supply from the floor’s water, and/or anti-freeze mixture. One liquid heats the other, and the two never come in contact. Only one heat source is needed.
