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Personal: Residential

Hydronic systems – Oil and Gas

Integrated systems now being developed offer promise for improved efficiency. If you are considering upgrading or replacing your heating system, you may want to think about installing an integrated space- and water-heating furnace or boiler. Your energy consumption for space and water heating may be higher if these services are provided by two separate units than if provided by a single integrated unit. In other words, integrated units may offer energy savings while still providing the same space heat and hot water.

Hydronic Oil Systems

The efficient integrated oil system couples a mid-efficiency boiler fired with a high-static burner to a well-insulated water storage tank, using an efficient water-to-water heat exchanger. When the house thermostat calls for heat, the boiler supplies heat to the house, either directly into a hydronic system or through a fancoil into a forced-air distribution system. When the house thermostat demand is satisfied, the boiler continues to run instead of shutting off, but it dumps the heat across the heat exchanger into the tap water storage tank.

Some oil-fired boilers provide a continuous supply of domestic hot water by circulating cold water through a finned copper coil immersed directly in the boiler water. This system is known as a tankless coil. The boiler must be kept hot even during the summer to give an adequate supply of tap water.

In the past, these systems were extremely inefficient and were usually grossly oversized for the house heat demands. Today, the efficiencies of some new tankless coil boilers have been improved by using a low-mass boiler with the coil and a well-insulated external storage tank, coming closer to the tankless coil system.

Another arrangement uses a conventional oil-fired hot water heater as the basic energy generator, with heated water being supplied to the house through a fan coil. Although this system has some advantages in terms of lower initial capital costs, its efficiency may not be as high as in other systems.

Integrated hydronic gas systems

An integrated, high-efficiency space and water condensing gas-fired heating system, using water from municipal mains as the driving mechanism to condense the flue gas, can have efficiencies of over 90 percent for both space and water heating. In practice, however, this is rarely the case.

Schematic of an efficient oil-fired integrated space-water heating system

Schematic of an efficient oil-fired integrated space-water heating system

There are also standard-efficiency gas-fired combined systems, but their overall efficiency potential is lower than that of condensing units. It may be more efficient to install a standard-efficiency boiler with an external storage tank. Early combined systems used a conventional natural draft water heater and a fan coil to supply heat to the distribution air. These units suffer from low efficiency and limited life