Gas Condensing Water Heaters

Known as gas condensing boilers they are high efficient water heating systems with energy efficiency of over 90%

Gas condensing water heaters are high efficient units that are designed with the energy factor (EF) of over 0.9, which is much higher than on conventional tank-type (0.6) and tankless units (0.82).

Residential gas condensing water heaters are very popular in Europe, where they are usually called condensing boilers, combi boilers and cylinders. And, for example, in UK, combi boilers are found in close to 70% of homes.

Government legislation and higher demand are driving the need for greater energy efficient water heating systems, or condensing boilers.

There are also well known in North America for commercial use... and because of all its benefits, rising gas prices and lower costs for operation, condensing models are becoming more and more popular in the residential water heating application as well.

Condensing water heaters - How they work

Condensing hot water heaters are fuel fired units with the very similar water heating process as conventional models. The problem with the conventional heaters, the most popular heating systems in NA, is that too much energy and heat is wasted when the gases are vented out.

The very smart solution comes with condensing or such energy efficient water heaters where the heat of the flue gases is recaptured and used, so less heat / energy is wasted. They achieve this high efficiency by removing the heat from the burning fuel and also cooling the products of combustion.

That is why condensing boilers have to have larger and more efficient heat exchanger than traditional boilers and some other additions.

The water vapor produced by the burning of gas in the boiler, condenses back into liquid water, releasing the latent heat of vaporization from the water. Because latent heat is a significant source of energy, condensing boilers have efficiency ratings up to 98%.

Good example is Weil-McLain that offers the Ultra Gas condensing boiler with efficiency ratings up to 98% in low water temperature applications.

Video: AO Smith Vertex - Condensing Heater - 96% Efficiency


condensing water heaters

Tank-type condensing water heaters are equipped with a super performing helical heat exchanger, which is completely surrounded by water. A typical example is AO Smith Vertex. This fully-condensing design heater provides a high 96% thermal efficiency and performance that rivals much larger heaters.

The flue spirals around and inside the tank so that the combustion gases spend more time releasing the heat until the water vapor in the gas — a natural by-product of the combustion process— condenses, releasing even more energy. The spot where the flue exits the tank is barely warm to the touch.

The main disadvantage of these high efficiency water heaters is the higher initial investment, but since they are very economical, it can repay that extra cost in energy savings.

The condensing boilers are the most environmentally friendly heating systems, with reduced CO2 and NOx emission. They feature a stainless steel heat exchanger, which is usually larger than conventional or dual burners, providing longer life and much better performance.

They are not complicated to install. One additional installation requirement that is needed is a pipe to drain away the condensate.


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Buying tips and benefits

It is time for you to buy a new hot water heater; by planning ahead and doing a little research you or your plumber / installer will need some time to investigate about condensing water heaters and select the right one.

Being relatively new, for you and most users, condensing heating systems might need more time for installation, troubleshooting and maintenance.

Since gas condensing water heaters have the efficiency of over 90 % you don't have to think is it energy efficient or not. They are.

Also, these models have the first-hour rating much higher than conventional heaters, with the same capacity.

Reminder: First-hour rating is another important factor when selecting the right heater, it measures how much hot water you can get during the busy hour.

No need to buy a larger tank type heater, as you are getting better performance with condensing hot water heaters.

When comparing these condensing heaters with over 90% thermal efficiency, to conventional tank-type, which are with 80% of thermal efficiency, the expected energy saving is at least 10%.

Note: ENERGY STAR qualified gas condensing water heaters are expected to reach the market later in 2009.

Popular manufacturers

weil mclain condensing boilers

Weil Mclain condensing boilers, Ultra series 3 gas boilers, models UG-80, 105, 155, 230, 310 combined with an indirect fired water heater tank.

All of these condensing boilers are with high grade stainless steel burners; operate in low temperature condensing applications and with the thermal efficiency of 92-93%.

AO Smith Vertex model GDHE-50, is direct vent condensing water heater with 96% thermal efficiency. With the capacity of 50 gallons, Vertex delivers hot water output that exceeds 75-gallon atmospheric gas heater.

Laars heating systems have two types of indoor, direct vented and room sealed residential condensing water heaters; 9600 HWG, with sizes from 150-250 Mbh and Summit SMW with size range 199-257 Mbh.

Per Laars you can reduce operating costs by 40% when you switch from conventional heating systems. Thermal efficiency of 96% is achieved through the low mass heat exchanger that eliminates standby and radiation loss. Using them with storage hot tank is ideal if you need a high volume of domestic hot water.

Polaris is a high efficiency gas fired water heater available in 34, 50 and 100 gallons tank, with power direct vented technology, thermal efficiency of 95-96% and very low standby heat loss.

Condensing tankless water heaters are becoming more and more popular due to its convenient size and ability to produce hot water with high energy efficiency. Popular condensing tankless brands are Navien NR-240A (CR-240A) with 96% energy efficiency, Noritz has N-0842 model (new number is Noritz NRC111 where the EF factor 0.92 for natural gas and Rinnai manufacturer has a RU98 model with the 0.93 EF.

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