Types of Water Heaters

A water heater uses a heating source to raise the temperature of incoming cold water from a municipal main or well. The heated water is stored in a tank and distributed on demand to showers, bathtubs, sinks and other water-using equipment in the home. Several types of water heaters are available:

• Storage tank water heaters
• Tankless water heaters
• Integrated space/sater heating systems
• Solar water heaters

Storage Tank Water Heaters

List of models: Electric Water Heaters
List of models: Gas Water Heaters
List of models: Oil Water Heaters

Storage tank water heaters are by far the most common type used in Canada. These systems heat and store water in a tank so that hot water is available to the home at any time. As hot water is drawn from the top of the tank, cold water enters the bottom of the tank and is heated. The heating source can be electricity, gas or oil.

More efficient storage tank water heaters can perform as much as 40 percent better than conventional models. An energy-efficient model will typically have one or more of the following features:

• extra tank insulation for better heat retention and less standby loss (loss of heat through the walls of the tank)
• a better heat exchanger to transfer more heat from the energy source to the water
• factory-installed heat traps, which allow water to flow into the tank but prevent unwanted flow of hot water out of the tank

Energy-efficient gas-fired storage tank water heaters may include additional design features, such as:

• electronic ignition, which saves energy by eliminating the need for a continuous pilot light
• powered exhaust
• improved control of flue baffle and flue damper, which reduces heat loss through the flue vent
• condensing heat exchangers, which greatly improve the overall efficiency
• oil-fired water heaters with state-of-the-art burners, which offer high-efficiency performance and minimal stack losses.

Tankless Water Heaters

List of models: Tankless Water Heaters

These systems (also known as demand or instantaneous water heaters) do not have a storage tank. They heat water only when it is needed, thus avoiding standby heat loss through tank walls and water pipes. The most basic units consist of either an electric element or a gas burner surrounded by flowing water.

Tankless water heaters are usually installed to serve a specific need near the point of use, such as under a kitchen sink. Depending on overall water usage, they may not have the capacity to supply an entire home with hot water. For this reason, they are often used as booster heaters to supplement another water heating system.

A relatively new tankless technology – the low-mass water heater – is capable of supplying much more hot water to the home. These systems are typically gas-fired with electronic ignition and power exhaust. This makes them more efficient than conventional tankless heaters. They can be connected to an external storage tank if necessary.

Integrated Space/Water Heating Systems

Integrated space/water heating systems combine the household heating requirement with the household hot water needs, saving money on total system installation. A single boiler is used, requiring only one combustion burner and one vent. Often these systems employ an insulated external storage tank with a high-efficiency low-mass boiler to heat the water, which then passes through a fan coil (as in a car radiator). The system then blows the heat around the house in a warm air distribution system, like a conventional furnace.

For integrated systems that do not use high efficiency boilers, the initial cost saving is soon eliminated by very low seasonal efficiency. The heater is sized to produce enough heat to warm a house on the coldest winter day. However, in the spring, summer and fall, when no heating is required, the same heater heats domestic hot water only. The effect is an oversized water heater that operates for several months of the year with a low heating demand – and low efficiency, as a result.

One type of integrated system that has been around for many years, particularly in the Maritime provinces, is a fuel-fired hot water boiler with a tankless coil water heater that uses a heat exchanger in the boiler to heat tap water but without a separate storage tank. The water flows through a coil inside the boiler whenever a hot water faucet is turned on. The drawback is that this system is dramatically less efficient in warmer months, when space heating is not required, as the boiler water must be kept hot all the time.

Solar Water Heaters

Solar water heaters use the sun’s energy to heat water. Active solar systems, on the other hand, use pumps and controls to move the heated water from the collector to the storage tank. In areas where the temperature drops below freezing, the fluid in the collectors is usually antifreeze, which is then run through a heat exchanger to heat the household water.

Solar systems can supply up to 50 percent of the energy needed to heat water for an average household (depending on climate conditions and water use). Since energy from the sun is free, solar water heaters can significantly reduce a household’s water heating costs – savings that in turn can offset the higher purchase and installation costs of a solar system.

Thermostats for Heat Pumps

• Electronic
• Conventional

Thermostats for Heating Systems

• Programmable Thermostats
• Zone control thermostats for hydronic systems

Thermostats for Heat Pumps

Electronic Thermostats

Programmable heat pump thermostats are available today from most heat pump manufacturers and their representatives. Unlike conventional thermostats, these thermostats achieve savings from temperature setback during unoccupied periods, or overnight. Although this is accomplished in different ways by different manufacturers, the heat pump brings the house back to the desired temperature level with or without minimal supplementary heating. For those accustomed to thermostat setback and programmable thermostats, this may be a worthwhile investment. Other features available with some of these electronic thermostats include the following:

• Programmable control to allow for user selection of automatic heat pump or fan-only operation, by time of day and day of the week.
• Improved temperature control, as compared to conventional thermostats.
• No need for outdoor thermostats, as the electronic thermostat calls for supplementary heat only when needed.
• No need for an outdoor thermostat control on add-on heat pumps.

Setback savings of 10 percent are possible, with one setback period of eight hours each day in most Canadian locations. Two such periods per day can result in savings of 15 to 20 percent.

Conventional Thermostats

Most residential heat pump systems are installed with a “two-stage heat/one-stage cool” indoor thermostat. Stage one calls for heat from the heat pump if the temperature falls below the preset level. Stage two calls for heat from the supplementary heating system if the indoor temperature continues to fall below the desired temperature.

The most common type of thermostat used is the “set and forget” type. The installer consults with you prior to setting the desired temperature. Once this is done, you can forget about the thermostat; it will automatically switch the system from heating to cooling mode or vice versa.

There are two types of outdoor thermostats used with these systems. The first type controls the operation of the electric resistance supplementary heating system. This is the same type of thermostat that is used with an electric furnace. It turns on various stages of heaters as the outdoor temperature drops progressively lower. This ensures that the correct amount of supplementary heat is provided in response to outdoor conditions, which maximizes efficiency and saves you money. The second type simply shuts off the air-source heat pump when the outdoor temperature falls below a specified level.

Thermostat setback may not yield the same kind of benefits with heat pump systems as with more conventional heating systems. Depending upon the amount of the setback and temperature drop, the heat pump may not be able to supply all of the heat required to bring the temperature back up to the desired level on short notice. This may mean that the supplementary heating system operates until the heat pump “catches up.” This will reduce the savings that you might have expected to achieve by installing the heat pump.

Thermostats for Heating Systems

Programmable Thermostats

The easiest way to save heating dollars is to lower the temperature setting on your house thermostat. As a general rule, you will save 2 percent on your heating bill for every 1°C you turn down the thermostat overnight.

A programmable thermostat will adjust your home’s temperature automatically. These thermostats have a mechanical or electronic timer that allows you to preset household temperatures for specific periods of the day and night.

You could program the thermostat to reduce the temperature a short while before you go to bed and to raise it again before you get up in the morning. You could also program it to reduce the temperature for any period during the day when the house is unoccupied and to restore the temperature shortly before you return. A good guide is to have the temperature set at 17°C (63°F) when you are sleeping or not at home and at 20°C (68°F) when you are awake and home.

Experiment with the unit until you find the most comfortable and economical routine for you and your family.

Programmable thermostats offer at least four daily temperature settings (such as wake, day, evening, sleep) for at least two different program periods (for example, weekdays and weekends). A hold feature allows you to temporarily override the program for a period such as a vacation. When used properly, programmable thermostats can save you 10 to 15 percent on your heating bills.

Many thermostats offer additional features that allow you to:

• store and repeat additional daily settings that can be run and changed without affecting the regular settings
• store more than four daily temperature settings
• adjust heating and cooling turn-on times in response to outside temperature changes

More sophisticated electronic and self-tuning thermostats are also being developed. These sensitive devices help reduce temperature swings from an average range of between 1.5°C and 2°C to a range of between 0.5°C and 1°C. As a result, the heating system turns on and off as close to the required temperatures as possible. Energy savings from these mechanisms can vary, but they usually enhance comfort.

Zone control

You can also reduce energy use through zone control. In a forced-air heating system, this involves placing dampers in duct passages and controlling them with separate thermostats in different areas of the house.

Zone control is also available for hydronic (hot water) heating systems. With it, temperatures of individual rooms are regulated by thermostat-controlled valves on each radiator.

A plumbing and heating contractor can provide more information about zone control and can install the required equipment when the heating system is installed.

Choosing an Energy-efficient Heat Pump

It’s easy to choose an energy-efficient heat pump with theEnerGuide Rating System for heating and cooling equipment. For the heating mode, refer to the heating seasonal performance factor (HSPF).The rating for the cooling mode is the seasonal energy efficiency ratio (SEER). These figures, found in manufacturers’ brochures, are designed to help you make an informed choice when buying a heat pump.

ENERGY STAR for Heating and Cooling Equipment

ENERGY STAR is the international symbol that stands for energy efficiency. It is designed to help consumers quickly identify products that save energy.

Heating and cooling account for nearly half the energy you use in your home. When properly designed and installed, ENERGY STAR designated heating and cooling equipment typically saves 15 percent or more on heating and cooling bills each year. How much you save will depend on where you live and how much you pay for your energy source, but in any case energy savings will pay for themselves over the life of the equipment.

Manufacturers or retailers place the ENERGY STAR symbol on models shown to meet or exceed the ENERGY STAR energy-efficiency criteria. Today, most leading manufacturers of home heating and cooling equipment are producing high-efficiency systems that qualify for the ENERGY STAR symbol.

You can usually locate the ENERGY STAR symbol on the back of the manufacturer’s brochures, beside the EnerGuide rating box. Use the EnerGuide rating to determine the SEER and HSPF ratings and locate the ENERGY STAR symbol to find the most efficient product available for you.

ENERGY STAR qualified air-source heat pumps are about 20% more efficient than standard models.

Ground-source heat pumps use the thermal energy of the ground or groundwater to provide a source of heating and/or cooling for a home. There are three basic types: 1) closed loop; 2) open loop; and 3) direct expansion. ENERGY STAR qualified ground-source heat pumps must meet or exceed specified premium EER and COP levels.

Electric Domestic Water Heaters

Electric Water Heater

Electric water heaters supply hot water for household use in many Canadian homes. An electric water heater usually consists of a tank, thermostats, two electric resistance elements (which are submerged inside the tank), and inlet and outlet pipes for cold and hot water. Internal thermostats regulate the temperature of the water.

Tanks are typically covered with foam insulation and lined on the inside with a ceramic glass layer. When cold water replaces the water withdrawn from the tank and the temperature of the water falls below a certain level, the elements are activated, reheating the water to the correct temperature. Essentially, electric hot water heaters are large closed electric kettles.

The submerged electric resistance heating elements in water heaters are very efficient, providing about 99 per cent of the available heat to the surrounding water. Even so, older water heaters lose heat as a result of standby losses.

Reducing Energy Losses

Most direct heat loss from water heaters is made up of:

• losses by heat conducted through the tank walls and base
• losses by hot water convection through the hot and cold water feed pipes

The operating efficiency of a domestic hot water system can be improved significantly by designing the system carefully and selecting equipment that generates hot water more efficiently and reduces stack and standby losses. For starters, you might want to lower the temperature of the water in the tank.

Reducing Standby Losses

Standby loss is heat lost to the surrounding air from the water in a domestic water heater and connecting pipes. It is a function of:

• the temperature difference between the water and the surrounding air
• the surface area of the tank
• the amount of insulation encasing the tank

To reduce standby losses, consider the following options:

• Cover the tank with an insulating blanket. Caution: It is extremely important not to insulate over any controls or obstruct the vent connections or combustion air openings. The insulation should not come in contact with the vent connector.
• Install a heat trap above the water heater. This is a simple piping arrangement that prevents hot water from rising up in the pipes, thereby minimizing the potential for this loss.
• Insulate hot water pipes to reduce heat loss from the pipes themselves. Pipe insulation is available in a variety of materials and thicknesses, with easy application to most hot water pipes. Use insulation with an RSI (insulation value) of at least 0.35 (R-4) over as much of the pipe as you can easily access.
• Place the water heater over a layer of rigid thermal insulation to reduce heat loss through the bottom of the tank. This is particularly applicable to electric water heaters and external storage tanks for integrated space and water-heating systems.
• Buy a tank with bottom inlet of cold water

Before carrying out any of these steps, check with your local installer or electricity utility representative to ensure that you will not compromise the safety or operation of the appliance.

Hydronic Systems – Electric

Electric hot water (hydronic) systems deliver heat to a house by means of hot water. They have three main components:

• a boiler to heat the water
• heating equipment – generally baseboards or radiators – in most rooms, often installed against an outside wall
• a pump to circulate water from the boiler through the pipes to the radiator and back again

Central boiler for an electric hydronic system

The boiler in an electric hot water heating system is compact. Its heating elements are immersed directly in the water (as in an electric kettle). Where space is limited, the boiler can be installed on a basement wall, in a closet or under a kitchen cabinet. It can even be hung from basement ceiling joists.

Maximizing Efficiency in Hydronic Systems

There are several ways to improve the performance of hydronic heating systems.

Improving Heat Distribution

Old-fashioned gravity heating systems that circulate water by natural convection are less efficient than systems with a circulating pump. Slow heat circulation may cause house temperatures to fluctuate noticeably between firing cycles. As with all hydronic systems, it can also take a long time to restore the house temperature after a nighttime thermostat setback. In addition, a gravity system cannot circulate hot water to radiators or baseboards in basement living areas, where they would be below the level of the boiler. All of these problems can be overcome by adding a circulating pump and replacing the open expansion tank with a sealed and pressurized expansion tank near the boiler. If you have a gravity system, ask your plumbing and heating contractor about upgrading it.

Balancing the Heat

Manual valve Balancing the heat delivered to different areas of the house is as important with hydronic heating as it is with a forced-air system. Radiators are often fitted with a simple manual valve that can be used to control the amount of water flowing through them. Such valves can be used to vary the heat delivered to different rooms of the house in the same way that balancing dampers are used in a forced-air system.

Automatic valve One device that can vary the heat output automatically is a thermostatic valve, which can be set to control the temperature in any room. This valve, however, will not work on radiators or baseboards installed on a “series loop” system. In such a system, the water must pass through all the radiators on its way back to the boiler. If there is more than one loop in the system, the heat output can be balanced somewhat by adjusting the valves that control the water flow through each loop. The heat output of baseboard units can also be controlled to some extent by regulating the built-in damper, which operates much like the damper in a warm-air register.

Zone control It is possible to reduce energy use in a hydronic system through zone control. This system regulates the temperature of individual rooms with thermostat-controlled valves on each radiator. A plumbing and heating contractor can provide more information about zone control and can install all required equipment when the heating system is installed.

Outdoor reset Conventional hydronic systems usually have the boiler temperature set at 82oC (180oF). In some hydronic systems, it is possible to reduce energy consumption by means of a regulator valve that varies the temperature of the water circulating in the system in relation to the temperature outside. As it becomes warmer outside, the temperature of the water is reduced.

However, some boilers can be subject to thermal shock or corrosion if the return water temperature is too cold. Before applying one of these devices to your system, ask your plumbing and heating contractor whether your boiler can handle it, and if the distribution system will perform effectively at the lower temperature.

Thermostats

The easiest way to save heating dollars is to lower the temperature setting on your house thermostat when possible.

Automatic setback thermostats will adjust your home’s temperature automatically. These thermostats have a mechanical or electronic timer that allows you to preset household temperatures for specific periods of the day and night. As a general rule, you will save 2 percent on your heating bill for every 1°C you turn down the thermostat overnight.

You could program the thermostat to reduce the temperature a short while before you go to bed and to raise it again before you get up in the morning. You could also program it to reduce the temperature for any period during the day when the house is unoccupied and to restore the temperature shortly before you return. A good guide is to have the temperature set at 17°C (63°F) when you are sleeping or not at home and at 20°C (68°F) when you are awake and home.

ENERGY STAR qualified programmable thermostat can help reduce the temperature swing from an average range of 1.5–2°C to 0. 5–1°C, ensuring that the heating system turns on and off as close to the required temperatures as possible. Energy savings from these mechanisms will be maximized and comfort is usually enhanced at the same time.

Combination Systems

Wood-electric

Wood-electric combination furnaces are common in rural areas. These are wood furnaces that contain built-in heating elements that are activated only when the wood furnace cannot meet the heating requirements of the home. Electric baseboard heaters can also be used to supplement a central wood furnace, a wood-oil combination furnace, or a wood stove.

A combination wood-electric furnace

Oil-Electric

An oil-electric combination system consists of an oil furnace with factory-installed electric heating elements. The electric elements supply a large part of the heating requirements, with the oil burner kicking in only during very cold weather.

An oil-electric combination furnace