Condensing boilers and water heaters

Boiler installer

When was the last time you got your heating system’s efficiency checked? The efficiency of old furnaces and boilers is less than 70%. The fuel savings from a new model with a 90 percent or greater efficiency might have a quick payback and also reduce common maintenance issues that keep you awake on icy winter nights. Condensing heaters and boilers are generally available from the majority of manufacturers.

How is this overall efficiency achieved in comparison to traditional equipment, which normally function at 80 to 85 percent? Steam is produced as a byproduct of the combustion of fuel oil, propane, and natural gas. 1 gallon of fuel oil creates around 0.98 gallons of water, 1 gallon of propane produces approximately 0.82 gallons, and 1 cu ft of natural gas produces approximately 1.16 gallons.

This hot water vapour, which has a temperature of 200 to 300°C, generally moves up in the stack and is vented into the air in a non-condensing boiler or furnace, along with the other pollutants. The high temperature is required to avoid excessive flue condensation and boiler damage from acidic condensate.

In the flue gas exhaust system of a condensing boiler, an additional heat exchanger causes water vapour to condense back into a liquid. This technique may capture up to 8000 Btu of heat per gallon of condensate, which is close to 13% of the original fuel energy. If an air-to-air heat exchanger is installed, the condensate either warms the incoming air or pre-heats the water (if an air to water heat exchanger is used).

After the heat has been removed, the low temperature condensate water can be discharged through a corrosion resistant piping (often PVC), effectively removes the need for a chimney.

Condensing boilers require low return water from radiators to function properly. At 54°C, only 15% of the water vapour condenses, but at 16°C, more than 90% of the water vapour condenses. A root zone system with return water at temperatures ranging from 25 to 30°C is an example of how it will operate effectively.

The humidity of the air also has an impact on the efficiency. Condensing boilers may reach an efficiency of 95 percent or more under the correct operating conditions.

Most condensing heating units contain modulating burners that can operate at various firing rates. The firing rate is adjusted to the heat load required to provide the optimal performance by using integrated control. This ensures that even at high firing rates, the efficiency will never be lower than that of a traditional boiler.

Because there is less water in the jacket of today’s boilers, they are substantially smaller than older and larger conventional counterparts. Because they are self-contained, much of the wiring and plumbing are installed before you receive the unit. This significantly lowers installation time.

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