Integrated Hot Water Heating System

Integrated Hot Water Heating Systems Integrated hot water heating systems, also known as combination water and space heating systems, use the energy from the space-heating unit in your home to heat water.

Quick Links:
How to buy?
What are my Options?
Energy Saving Tips
What do I ask a contractor?
How much can I save?

How to buy?

When purchasing an integrated hot water heater, there are four main components to consider:

Efficiency. The efficiency of an integrated hot water heating system is determined by its combined appliance efficiency rating (CAE).
The CAE typically ranges from 0.59 to 0.90.
The higher the CAE, the more efficient the model.
To compare different systems, look for the highest CAE possible.
For new models, a CAE of .85 of higher is recommended.
 
The sizing of a combination system involves different calculations from those used for sizing a separate water heating or space heating system. Generally, in indirect systems a smaller storage tank can be used for tap water; and less hot water “reserves” are needed because a space-heating boiler heats up water very quickly.

Sizing your system accurately is very important; it is easy to generate water that is too hot if the unit is not sized correctly. A qualified plumbing and heating contractor is suggested to size and install a hot water heater.

Back to top

What are my Options?

There are two different models: tankless coil, and indirect water heaters. Each uses boilers and hot water heating systems to produce domestic hot water. Since the system has one source of energy, integrated units are typically easy to maintain and most modern models are relatively high in efficiency.

Tankless Coil Hot Water Heaters. A heating coil or “exchanger” is installed in the main furnace or boiler that heats your home. When hot water is needed, water flows through the coils in the boiler and is heated by the surrounding boiler water.

Similar to a demand heater, these models produce hot water on demand, without a storage tank. Because they rely on the heat from the furnace or boiler to produce hot water, they function most efficiently during cold months when the heating system is already in use.

During the summer, when a boiler is usually turned off, these systems are less efficient because the boiler is continually being heated to produce domestic hot water.

Typically these units can last for up to 30 years or more if operated correctly.

Indirect Hot Water Heaters. An indirect water heater uses the heat from the boiler water circulated through a heat exchanger to heat water in an adjacent well-insulated storage tank.

Since energy is stored in a tank, the boiler not only operates less, but also turns off and on less often than a tankless coil hot water heater. This feature increases the efficiency of the unit, and thereby lowers your energy costs. An indirect water heater paired with a high-efficiency boiler and insulated storage tank could result in the lowest annual energy costs, even during the summer when your heating system is not in use. The hot-water storage tanks in integrated systems last longer because they are not subject to the temperature fluctuation and corrosive effects of direct combustion.

Back to top

Energy Saving Tips

Proper maintenance of your combination water and space heating system can optimize its energy efficiency and extend your water heater’s lifetime.

Make sure the boiler is equipped with the following features:

A pressure-only relief valve protects the coil and piping from excessive pressure.
A vacuum relief valve vents the system if a vacuum occurs inside the tank.
A back flow preventer stops boiler water from flowing into potable water systems.
An anti-scald device, also known as a tempering valve or mixing valve, mixes cold water into the hot water to lower the temperature of the water to the desired setting.
For a Tankless Coil,  fix leaks to conserve resources and maximize the life of your system.

Leaks typically occur:
At the tankless coil face area around the temperature sensor
At the tankless coil face where cold water comes in and hot water goes out.
At the tankless coil mounting plate bolted to the face of the heating boiler.
White or other mineral salts produced from evaporating leaky water (typically found at and or below the point of leakage) indicate the presence of a leak.

To repair a typical leak found at the tankless coil mounting plate:
Shut off and drain the boiler.
Cut water-piping connections to remove the coil.
Remove coil and replace the mounting gasket if coil face and boiler face are not damaged.
Return the coil to boiler.
If you notice any signs of leakage, repair it as soon as possible. If severe rusting and flaking is apparent, replacement may be in necessary. When properly maintained and operated, a boiler has almost up to three times the life expectancy of a standard storage water heater.

For an Indirect Heater. Insulate the storage tank and surrounding pipes to lower standby heat loss.

Add an insulating blanket to the storage tank. They cost only $10-20.
Insulate your hot water pipes. Use plastic or foam at least 3/4 inch thick.
This will reduce the energy losses from the tank to the faucet. Energy and water are wasted waiting for the hot water to reach the tap. The water in the pipes will eventually cool, but it holds its heat much longer than it would if the pipes were not insulated at all.

Generally, integrated systems are long-lasting and easy to maintain. The most effective way to save money and energy is to conserve by reducing consumption, and investing in an efficient model. Contacting the installer or manufacturer for maintenance tips specific to your system will only further maximize the efficiency of the integrated system.

Back to top

What do I ask a contractor?

Although most integrated systems are designed for new homes, retrofit units that can work with an existing boilers are available to purchase. When selecting a contractor remember to:

Ask for cost estimates and references. Make sure the contractor understands local permits and building codes to ensure the safety of installation and operation. Requirements may exist such as the use of a double-walled heat exchanger between the tap water and the boiler water to guarantee the safe production of potable hot water.

Back to top

How much can I save?

The Department of Energy estimates that systems employing one heat source for both air and water can reduce domestic energy consumption by up to 27%.

Tankless coil systems have high standby heat losses, whereas an indirect heater operating with a high-efficiency boiler and a well-insulated insulated storage tank is much more efficient than tankless coil models.

Back to top