flue condensing boiler efficient supply temperature

Figure 1 depicts a typical efficiency curve for a condensing boiler relative to return-water temperature. Two main points can be gleaned from Figure 1. First, operating a boiler with a return-water temperature above 140 F yields a peak thermal efficiency of roughly 88 percent. That means it basically is performing like a non- condensing boiler.

Dec 16, 2013· In any case, partially condensing boiler systems are still more efficient than noncondensing boiler systems and should not be a basis for ignoring the benefits of condensing flue gases. Heating hot water systems are forgiving systems when they are designed within the constraints of the equipment being used.

Aug 13, 2018· The word “condensing” refers to the fact that these appliances are able to extract heat from the combustion process so efficiently that the flue gases leaving the boiler are at a much lower temperature than in a conventional boiler. The temperature of these flue gases is low enough that they actually condense inside the heat exchanger.

Condensing boilers often are a practical choice because they recover additional heat from condensing flue gas, boosting efficiency into the range of 88 to 99 percent. Surprisingly, a condensing boiler is one of the most misapplied elements of modern hydronic systems. A typical efficiency curve for a condensing boiler is shown in Figure 1.

Nov 01, 2019· While it may seem counter-intuitive, a lower water return temperature makes reheating and recycling energy more efficient. While traditional (non-condensing) boiler systems require water return temperatures to be higher than the condensing temperature of the flue gases (to avoid corrosion) condensing boiler systems using heat exchangers are now

Operating with a supply water temperature of 180°F and a return water temperature of 140°F, the boilers never operated in condensing mode and the actual boiler efficiency was around 85%, far from the 98% efficiency advertised by the vendor.

A condensing/modulating boiler however will generally have flue gasses somewhat less than the supply temperature (but of course higher than return temp). That's the condensing part doing its job of extracting the most possible heat from the flue gas.

Jan 22, 2020· For the condensing boiler to operate at maximum efficiency, the secondary heat exchanger’s surface needs to be equal to or below the dew point temperature of …

Jun 19, 2012· The first cost of condensing boilers is higher than that of the traditional noncondensing boilers. Therefore, the challenge the designer faces is to ensure that return water temperature to the boiler stays below 130 F; otherwise, boiler efficiency drops and the condensing boiler operates in noncondensing mode.

File Size: 800KB ANSI Standard Z21.13 tests and rates condensing boiler performance with an 80˚F (27˚C) boiler entering water temperature (EWT) and a 100˚F (55˚C) temperature rise (delta-T) to produce a boiler leaving water temperature (LWT) of 180˚F (82˚C). Condensing boiler performance is dominated by the boiler EWT. Figure 1 below shows a typical

Low temperature loads, such as radiant slab heating, require supply water temperature in the range of 27°C to 50°C (80 – 120°F). Low temperature loads are the best match for condensing boiler systems as their return water temperature is low and provides the most opportunity for obtaining high boiler efficiency.