The combustion ability of a burner relates to it’s ability to burn the fuel it’s using completely, and this is tested by measuring the amount of excess air and unburned fuel in the burner’s exhaust product.
It makes sense that it’s the burners that show low levels of unburned fuel and low excess air levels that have the best efficiency ratings overall. This also relates to a burners given ability to avoid what’s known as “stack temperature” and means that the burner has a higher “thermal efficiency”. This is not the same as combustion efficiency.
A burner that’s producing excess air levels of about twenty five percent is said to be running at a pretty high level of efficiency. A burner operating at these levels is going to result in lower quantities of unburned fuel. This of course will also depend on the burner and boiler combination being used.
Burners that are designed with superior functionality can even get to an even lower excess air level of about fifteen percent. This is another reason why it’s important to ensure clients understand the benefits of installing a well designed system to begin with. The savings long term are more than worth the extra investment up front. Here at Heat Control London, we’re always keeping this in mind when dealing with new customers looking install a brand new boiler system.
Having such a system not only increases efficiency remarkably, but also the emission load is much lower, which means you’re saving your money, and helping lower your carbon footprint at the same time. The benefits are plentiful.
When a burner runs at the minimum excess air level possible, then this means that a lower amount of heat from the overall combustion process is needed to heat the excess combustion air, this in turn increases the amount of energy that’s available for the load, as well as reducing the amount of necessary fuel needed to raise the whole processes temperature of the system. Again in terms of being helpful towards lowering an environmental impact, this reduces the harmful production of NOX (nitrous oxide) and other toxic emissions.
The Basic Elements Of The Combustion Process
In most cases, an engineer will setup the burner so that it has sufficient excess air so as not to run out of combustion air in the process of burning fuel. Here’s a quick run down of the factors that can have an impact on this combustion process over time:
Due to the fact that it’s not really possible (unless you’re running some kind of commercial operation where it’s viable and necessary) to have constant monitoring by an heating engineer, it’s necessary to have a monitoring system such as what’s known as “oxygen trim” incorporated into the system.
Basically, o2 Trim systems monitor a burner systems oxygen levels present in the stack at any given time, and then search for an optimal efficiency level of that given appliance so that it can run at high efficiency levels.
The better o2 Trim systems these days will have the ability to learn and improve their performance, and therefore improve the system’s efficiency, despite condition changes that may come up over time.
The atmospheric conditions can have an impact on the air density, and also impact the fuel to air mix. This will invariably have an affect on how efficient the system is at burning fuel, and impact cost and environmental outputs over time.
Burner settings can “drift” off their initial values over time because of continuous operation without breaks or maintenance checks. This can mean that more air needs to be introduced to make the burner run properly. This of course can negatively impact the efficiency of the burner over time.
What’s known as the “calorific value” of a fuel can change over time, and similarly to the barometric conditions, this will have an impact on efficiency and performance.
o2 Trim technology when used can have a very positive effect on a system’s efficiency levels. Co2 trim can add even more to these positive gains.
Similarly to o2 Trim tech, Co2 trim uses a detection method based on the chemical and catalytic properties of the output of the burner.
While the technical details given here may go above and beyond your understanding levels if you’re a consumer hoping to improve the efficiency of your system, there’s nothing to stop you referencing the basics here, and ensuring that you get your professional heating engineer to apply some of these setups to your current system.