Mitsubishi Ecodan for New Hampshire Homes
Mitsubishi Ecodan is an air-to-water heat pump for hot-water heating systems. It uses electricity to transfer heat from outdoor air into water that circulates through the home. In a house heated by a boiler, that water may supply baseboard heat, radiators or radiant floors.
How is an air-to-water heat pump different from a boiler?
A hot-water heating system, also called a hydronic system, uses water to carry heat through the house. The boiler heats the water, and pumps circulate it through baseboards, radiators or tubing beneath the floor. After releasing heat into the rooms, the water returns to the boiler to be heated again.
An oil, propane or natural-gas boiler produces heat by burning fuel. Ecodan uses an electric compressor and refrigerant to collect heat from outdoor air and transfer it to the heating water. The term air-to-water describes where the heat comes from and where it goes. There is still heat available in cold outdoor air, although the heat pump's output and efficiency change with the conditions.
Both systems supply heated water. The difference is how they heat it. An air-to-water heat pump can replace the boiler as the heat source in a properly designed system, or work alongside a boiler that supplies additional heat when needed.
What equipment does Ecodan use?
The outdoor unit collects heat from the air. Refrigerant piping connects it to an indoor unit called the Hydrobox. Inside the Hydrobox, a heat exchanger transfers heat from the refrigerant to the water in your heating system. A circulator pump moves the heated water through your baseboards, radiators or radiant-floor tubing.
This differs from a ductless mini-split, which delivers heat directly to room air through an indoor unit. Ecodan delivers heat through water piping and the heating equipment connected to it.
We photographed this Ecodan display at the Mitsubishi Diamond Dealer Meeting and Granite Group Trade Show.
Can existing baseboards and radiators be used?
In some homes, the existing piping and heating equipment can remain. The deciding factor is whether the baseboards or radiators can deliver enough heat at the water temperature supplied by the heat pump.
Lowering the water temperature reduces the amount of heat a baseboard or radiator gives off. Equipment that heats a room adequately with hotter boiler water may not provide enough heat at a lower temperature. A room-by-room heat-loss calculation establishes how much heat each room needs. That load must be compared with the output of the existing baseboards or radiators at the proposed water temperature.
This is why replacing a boiler with an air-to-water heat pump requires more than matching the equipment size. Depending on the house, the work may include changes to the baseboards or radiators, piping and controls, or a plan for supplemental heat.
Ecodan operation in New Hampshire winters
Mitsubishi's published specifications for the U.S. single-phase Ecodan line list heating operation down to -22°F, 100% heating capacity at 5°F, and a maximum supply-water temperature of 158°F.
Those ratings describe different operating conditions. They do not mean that the unit delivers full capacity at -22°F or supplies 158°F water in every condition. Equipment selection must account for the home's heating load, the required water temperature and the selected model's output at the winter outdoor design temperature.
Ecodan includes controls for working with a boiler and auxiliary heat. Where a boiler is retained, the system design determines when it operates and how the two heat sources are controlled.
Domestic hot water and cooling
Ecodan can also heat domestic hot water with an indirect storage tank. This is the water used at sinks, showers and other fixtures, kept separate from the water circulating through the heating system.
Cooling requires equipment designed for chilled water, such as hydronic fan coils. Existing hot-water baseboards do not provide air conditioning. Cooling and domestic hot water need to be included in the system design if those functions are planned.
Evaluating an existing heating system
For an existing home, the starting point is the heating load and the equipment already installed. The review should establish the required water temperature, the heat available in each room, the electrical requirements and whether supplemental heat is needed. Those details determine whether Ecodan can serve the house and what changes the installation would require.
For questions about your existing heating system or a proposed replacement, contact A.J. LeBlanc Heating.