Combination boilers, also known as combi boilers are an integrated system that both heats and dispenses hot water, and also provides central heating to a residence. As opposed to systems which require a separate water tank and boiler, a combi boiler has a direct connection to the domestic hot water, or DHW circuit. The combination boiler can therefore provide hot water as long as the boiler is functioning.
When to Use Them: A combination boiler is extremely efficient for residences with one bathroom, or where the demand for water does not exceed more than 2 or 3 showers a day. While some combination boilers can handle multiple demands simultaneously, prolonged use of a combination boiler in a high-use setting is not recommended. Studio and one bedroom apartments in urban areas benefit from having a combination boiler. Because the unit also provides central heat, small spaces benefit enormously from having a combi boiler.
Insulation: Combi boilers benefit in environments that are properly insulated, and can be turned off during long stretches of the day when they are not needed. By adding insulation to doors, windows, and other openings in the house or apartment, a combi boiler can provide ample heat to a room.
Energy Efficiency: A condensing combi boiler is more energy efficient for smaller homes or apartments with low to medium water usage than conventional full size tanks and boilers. Whenever the combi boiler is engaged, that heat is used to also warm the house, making it extremely efficient at reducing duplicate heating bills. However, combination boilers are not as energy efficient as condensing boilers by roughly 30%. This figure can vary depending on the energy efficiency of the overall environment. As has been noted elsewhere, insulation and intelligent use of flow restrictors or other flow-saving devices can drastically improve the performance of a combi boiler. It is also important to note that combination boilers are easy to install and take up far less space than conventional systems.
DHW Flow Rate: A typically sized combi boiler can provide between roughly 2 and half to a little over 6 gallons of water per minute. The DHW flow rate is based on how many kilowatts are provided to the combi boiler. Usually, an average unit has a rating of between 24 and 54 kilowatts. If a shower is properly outfitted with water saving devices, such as restrictive shower heads, the usage of a combi boiler can yield extremely low water usage rates.
Pricing: Because combination boilers provide both central heating and hot water, they are always far more affordable to purchase than the joint cost of each of these units sold separately. They are often on par with condensing boilers, although the smaller the size, the more affordable.
