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Heating Units and Controls
There are four common types of heating units:
- A furnace provides heat through a forced air distribution system.
- A boiler provides heat through a hydronic distribution system. (Hydronic systems are also referred to as hot water systems.)
- A space heater supplies heat directly to the room where it is located.
- A heat pump extracts heat from the air, ground or water outside the house and usually delivers it through a forced air distribution system.
Most heating systems need air for combustion. Furnaces, boilers and space heaters that burn fuels need a supply of air to be able to burn properly, and a vent to the outdoors so that combustion gases can escape from the house. Electric heaters do not need to be vented. Combustion is a two-step process: air in, and gases out.
In the past, there was usually plenty of air leaking into a house to keep the furnace, boiler or stove burning well. Modern homes, however, are better sealed and use controlled ventilation, rather than uncontrolled leakage, to provide greater comfort and energy efficiency. Vents that supply air for heating units should never be blocked. It is important to ensure that there is an adequate supply of combustion air available, even when other air exhausting equipment is in use.
Venting used to be done through a chimney. Today, however, many models of natural gas, oil and propane equipment can be vented by pipe directly through the wall, which greatly simplifies
installation. Remember that combustion gases cannot escape from your home unless you provide air to replace them. That’s why venting problems can often be traced to air supply problems.
The indoor temperature is automatically controlled by a thermostat. Two important considerations are location and type. Central systems are normally controlled by a single thermostat. To achieve proper temperature control, the thermostat must be located in an area where it will sense the “average” indoor temperature. Locations exposed to localized temperature extremes (outside walls, drafts, sunlight, hot ducts or pipes, etc.) should be avoided.
Different types of thermostats are available. Basic types maintain a fixed indoor temperature. However, you can reduce your heating costs by installing a set-back thermostat which can be programmed to automatically lower the temperature when no one is home or everyone is in bed, and then warm up the house before you get home or wake up. Savings will vary, but a set-back of 3ºC for eight hours daily could reduce your heating costs by about 5%.
Where space heaters are used, each unit will likely be individually controlled by its own thermostat – which is usually the basic type. This allows you to keep unused areas at a lower temperature than those areas you do use.
There are three types of distribution systems.
- A forced air system circulates warmed or cooled air around the house through a network of ducts. It also provides a means of distributing ventilation air.
- A hot water (hydronic) system distributes heat through hot water pipes and radiators.
- Space heaters, though not technically a distribution system, provide direct heat to the room in which they are located.
It is important that a distribution system is properly designed, installed and operated to ensure maximum energy efficiency and comfort levels. Try to avoid placing any part of your distribution system outside of your home’s insulation. This is sometimes done as a simple remedy to a routing problem, but there is always some heat loss through the wall of any distribution system. It is better that any losses heat (or cool) you rather than your attic.
Registers in each room can be adjusted to control the air flow. Return registers draw air from the rooms through separate ducts back to the furnace to complete the cycle of air flow through the
house. Leaks in forced air distribution systems are often ignored because they normally do not cause any obvious damage, but it is important to avoid/eliminate such leaks. Leaks will affect a distribution system’s ability to provide comfort in all areas of the house, and leaks in some parts of the system can result in significant energy loss and/or condensation-related damage which may be hidden from sight.
Hot water (Hydronic) Heating
Distributes hot water from a boiler to radiators, convectors or under-floor heating systems in each room. In older homes, large cast-iron radiators are common. Modern systems feature smaller boilers, narrow piping and compact radiators that can be regulated to provide temperature control in each room. Under-the-floor heating systems can be built into the floors of new and existing homes.
These have no central heating unit or distribution system. Instead, individual space heaters – such as a wood stove, electric baseboards, radiant heaters or heaters fueled with oil, natural gas or propane – supply heat directly to the room. For safety, all space heaters except electric ones need to be vented to the outside. An appropriately sized space heater can supply some heat to all parts of a home if the design of the home allows for natural distribution of heat from the heater location. In most cases, more than one unit is required to comply with building code requirements, but multiple units allow you to vary the temperature around the house.