Energy efficiency can be improved with combination boiler/hot-water heater
The selection of a residential heating system is an investment that the homeowner will have to live with for a very long time. Those who have owned all-electric homes, advertised as an advanced and integrated solution to power and fuel needs, know firsthand how technologies and energy costs can shift in only a few years. HVAC professionals also have to be aware of how newer and better technologies are essential to serving their customers’ long-term needs.
Today, as the realization sinks in that energy efficiency is both urgent and imperative, HVAC professionals cannot afford to be caught stuck with old-tech, energy-inefficient home and water heating.
Today, in colder climates such as Canada, Northern Europe and the Northeastern U.S, there is a resurgent interest in the use of boilers as a heating system that not only provides for winter comfort efficiently, but can also replace the energy-draining hot water heater at the same time.
‘The energy efficiency of conventional furnaces is around 80 percent,” said Harry West, a heating system consultant in Toronto. ‘Using the latest boiler technology can boost that efficiency close to 90 percent and get rid of the expensive water heater at the same time.”
West, who managed heating equipment sales and service for Imperial Oil (a Canadian subsidiary of Exxon) for 30 years, said that residential boiler design has come a long way in recent years.
‘In the past, boilers were designed as a low-cost approach to home heating,” he said. ‘As a result, boiler construction was very basic and somewhat inefficient. But now there are residential systems that will very efficiently supply heat, hot water, melt snow for walkways and driveways, and even heat a swimming pool, all from one high-efficiency boiler.”
A significant improvement came with the adoption of commercial boiler heating system designs in recent years. The Fleetline Aqua-Matic, manufactured by Brant Steel of Brantford, Ontario, adheres to commercial design basics, such as high efficient horizontal boiler design, and also offers compact size and features that make it easy to install and service.
This type of boiler runs on oil, LP gas or natural gas, achieves up to 89-percent combustion efficiency and over 82-percent Annual Fuel Utilization Efficiency.
Residential customers who are concerned about return on investment and service life should expect that newer, high-efficiency boiler models also include warranty coverage. The Fleetline Aqua-Matic, for example, includes a 20-year warranty.
Connie Newland, a resident of rural Ontario, Canada, decided to replace her old oil-burning forced-air furnace last year. The catalyst for the change, though, was being able to dispose of her old electric-powered, 70-gallon water heater.
‘It didn’t make sense to heat our water with electricity any longer,” she said. ‘It was simply too expensive. So, we installed an (oil-fueled) Aqua-Matic system. This system supplies all our domestic water heating as a priority, as well as our space heating during winter months and air-conditioning during the hot summer months. The boiler, an integral part of the furnace and smaller than the electric hot water tank, heats the water much faster than electricity, yet it is much cheaper to run.”
Rebecca Vanderpost of Brantford, Ontario, moved into a home that already had an Aqua-Matic boiler with an in-floor heating system.
‘The furnace in our previous home kept breaking down, always in the middle of the night,” she said. ‘The new system is very reliable. We love the in-floor heating.”
Vanderpost added that the unit also heats the pool during the summer months, and that while she and her two daughters enjoy taking long showers, they never run out of hot water.
Less mass, better loading
One of the reasons most users don’t run out of hot water is improved system design, which also allows the system to perform multiple functions and to react to changing priorities.
‘Because this system normally eliminates the need for a separate water heater, you save the energy it would otherwise take to keep heating, for example, a 70-gallon water heater all day long,” explained Mark Offenhammer, Brant Steel president. ‘When you come home from work and want to jump into the shower, there will be hot water available immediately through the boiler’s domestic water coil. However, if you were to draw a bath, the volume of hot water needed to fill a bath would override the house heating function for a short period.”
According to heating system consultant West, proper loading and low water mass (volume) are important contributors to the efficiency of a combination boiler-water heater.
‘Let’s assume that you have an efficient boiler to start with, such as the Aqua-Matic,” West explained. ‘Now you want to maximize the use of the boiler and make it very cost-effective. If a boiler is well-loaded, it runs longer and is more efficient. However, a boiler with a very low load factor will lose efficiency. So, to maximize efficiency you could load the boiler to handle domestic water and in-floor heating during the winter and then in summertime switch the in-floor heating load over to heat the swimming pool.”
West said that you also want to be sure that you can pour the heat into the boiler and transfer it quickly. Keeping a low mass of water inside the shell-and-tube heat exchanger results in better efficiency than having to maintain the temperature of a 70-gallon water heater.
‘A low-mass boiler with only 10 to 12 gallons of water inside it will heat-up very quickly. You get better performance and it starts pumping hot water sooner,” he explained.
People today are increasingly viewing their homes as among their most important assets. Therefore, the choice of clinging to an outdated, inefficient and expensive heating system may have more serious consequences.
Not only does that homeowner have to foot the cost for energy that is higher than necessary, but they are also asking others to do the same when it comes time to sell the house.
‘I believe that the value-added aspect of these more advanced boiler systems is very substantial,” Offenhammer said. ‘Today’s homeowner wants to have a house with environmental amenities: a clean air-filtration system, or a snowmelt system, more efficient air-conditioning or an efficient swimming-pool heater.”
Offenhammer pointed out that some of those functions seem to be restricted to more expensive custom homes, but that isn’t necessarily so. A snowmelt system, which typically requires that the driveway or walkway be concrete or interlocking brick, adds functional value and safety, but also improves the curb appeal of the house.
‘On the other hand, if the house has the antiquated heating system, you get the opposite effect,” he said. ‘As for the HVAC contractor or architect, there is another issue: Will they adopt this new two-for-one home-heating technology as a highly practical long-term solution? If not, they may not benefit from what promises to be an important system for the future.”