Condensing water heaters are gas-fuelled continuous flow water heaters that use “condensing technology” to increase their energy efficiency, making them 8-15% more efficient than a standard continuous flow water heater. This extra efficiency is possible as they preheat the incoming water with ‘waste’ heat extracted from the flue gas. This heat would otherwise be expelled from the appliance. This extraction process causes the flue gas to condense into liquid, hence the term ‘condensing water heater’.
Condensing water heaters are usually designed with a secondary heat exchanger along with the standard primary heat exchanger that is in every continuous flow water heater. This secondary heat exchanger allows the appliance to extract more heat from the flue gas
Secondary heat exchangers
Secondary heat exchanges allow the extra extracted into the cold water coming into the appliance. This additional heat exchanger means that the appliance can increase efficiency above 83%, the efficiency at which flue gas begins to condense. Secondary heat exchanges are constructed from stainless steel instead of copper as used in standard heat exchangers as the condensed liquid corrodes copper.
The payback from saving
The big benefit from condensing appliances is lower running costs from energy savings. The energy saving will be a substantial saving on the lifetime costs of the appliance. In a domestic application the savings for an average cost will be between $40-100 per year depending on the hot water usage, the region of the installation and the gas type used. For the average family total saving over the usual 10-15-year life of the appliance will usually cover more than the additional cost of the appliance.
Rinnai New Zealand have two condensing water heaters available. The INFINITY® EF26 is our domestic condensing water heater and will be suitable for most domestic applications. The INFINITY® N Series appliances are our commercial appliances and are designed for commercial applications along with larger domestic requirements.