Four Main Sources of Hydonric Heating
Heat Pumps for Radiant Heating
A heat pump extracts energy from a low temperature source and elevates it to meet a high temperature demand. A ground source heat pump extracts energy from ground water or ground loop sources, such as extracting the heat rejected from a refrigerator’s inner cooling and freezing compartments.
Ground water source for heat pumps consists of two wells, one for supply and one for rejection. Energy is extracted from the water as it flows through the heat pump. This is referred to as an open loop system.
The ground loop source consists of a series of horizontal or vertical pipe loops, called heat exchangers, in lengths of 60 to 300 meters buried approximately two meters below ground surface. This is referred to as a closed loop system.
Heat pumps are rated by the Coefficient of Performance (C.O.P.). C.O.P. is the ratio of energy output versus input. A good ground source heat pump system provides a C.O.P. of four or five. For every kilowatt of electrical energy input, you will get 4 or 5 kW of heat energy output. The optimum output temperature is approximately 37°C, the ideal temperature for radiant floor heating systems.
Btu output and cost typically determines the purchase of a boiler. Inexpensive boilers are inefficient as their minimum operating temperature of 60°C is 45°C higher than the ideal source temperature for most radiant floor heating systems. Chose a low temperature condensing boiler if energy savings is the main consideration. A lifelong low temperature condensing boiler is low-maintenance, cost effective, and energy efficient.
A low mass boiler has very little energy storage capacity, using thin wall metal heat exchangers and a small volume of water. This results in a short cycle boiler operation. A high mass boiler, on the other hand, has high energy storage factors which result in a longer cycle boiler process.
The most common service problem on any combustion appliance is the ignition cycle and a shorter cycle means less service.
Electric boilers are the simplest and lowest cost installation of all boiler options. Operating costs are also reasonable. Using supply temperature controls, an electric boiler can be operated at the exact temperature required by a radiant floor heating system (RFH). Stand-by costs are subsequently eliminated. For every 1.5°C the operating temperature is lowered, there will be a 1% reduction of energy input. Therefore, in combination with the efficiencies of RFH, an operating cost can be achieved that is quite competitive with a convection Natural Gas system.