Abstract
The paper reports on the development of a condensing water heater with a thermal efficiency of 95 percent (based on the net calorific value at maximum rated output) and thermal output of 35 kilowatts. The thermal efficiency of conventional instantaneous water heaters is around 80%. Fitting a highly durable latent heat exchanger to recover even the latent heat in the steam in the exhaust gas gives the unit a thermal efficiency of 95%, a world best for an instantaneous water heater. The unit is equipped with a full primary combustion ceramic burner, reducing emissions of NO_x (crucial to global environmental protection) to 30ppm, half the level of emissions of current low NO_x water heaters. The heater was injected into the market in October 1999.
