The boiler can be configured to provide supplemental heat when the heat pump can’t quite keep up with the load. This allows the heat pump to be sized for 50 percent to 75 percent of design load while still providing the majority of the total seasonal heating energy requirement.
While it’s true geothermal heat pumps do offer excellent opportunities in combination with low-temperature hydronic distribution systems, they are not the only viable way to combine the heat-leveraging ability of heat pumps with the unsurpassed comfort offered by modern hydronic distribution systems.
Long before Americans had access to natural gas, propane, fuel oil, or electricity, and long before there were automatically controlled central heating systems, wood was the most commonly used heating fuel.
The combined cost of hydronic radiant panel heating, along with a separate central cooling system, often strains the construction budget to a point where something has to go, and that something is usually the radiant heating option. It gets trumped by a lower-cost forced-air system that delivers both heating and cooling, albeit often at reduced comfort.
Last fall, I taught my first online course dealing with designing hydronic heating systems. The course was titled “Mastering Hydronic System Design.” It was a collaborative effort between HeatSpring Learning Institute, BNP Media’s CE Campus, and myself.
The following formula has been around the North American hydronics industry for a long time: Btuh = 500 x gpm x delta T. It can be used to estimate the rate of heat transfer into or out of a device that has a stream of water flowing through it at a known flow rate, and with a measured temperature change between the inlet and outlet of that water stream.