by Joe Wallace
Oxygen trim (O2 Trim) is a system that constantly monitors your boiler’s combustion. Unlike your car, your boiler has the ability to run properly without it, so what are the upsides to it? This system can adjust your air fuel ratio based on what it’s supposed to be and triggers alarms or lockouts should the combustion deviate from proper levels. It also helps end users save on operational and maintenance costs.
We have all seen slipping couplings, broken shafts, blocked intakes or other things that have created improper combustion and unsafe conditions. Oxygen trim can prevent those situations from turning into something far worse. When a burner is tuned with O2 Trim, an oxygen level is assigned to each curve point and is stored with that point as a safe oxygen level. While the oxygen sensor continually monitors your burner’s combustion, it can detect any “off-curve” oxygen readings during combustion and adjust for them within reason. Should the oxygen level have a large deviation from setpoint, the control system will alarm and/or shut down the burner before something bad happens. Another safety function of O2 trim is if a very high CO condition is present, the CO will also make the O2 cell read a lower oxygen level and alarm/lockout the boiler.
Preventative maintenance should always be done in your boiler room including boiler tuning, but O2 trim may help save you some money on these visits. Since O2 trim constantly monitors your burner’s emissions and makes small adjustments to ensure proper and safe combustion, some areas have only required tuning bi-annually or less. Your system still needs to be set up by a professional and is certainly not a replacement for your service company, but is a great way to ensure your boiler is running properly between their visits. Due to this continually monitoring, the burner is much less likely to be damaged during operation. Improper combustion can lead to very expensive repairs to your system such as burner component replacement due to being burned up, refractory repairs do to instability and impingement, or a catastrophic boiler explosion. Having oxygen trim drastically decreases the risk of these events for a small fraction of the cost.
While one can tune a boiler for the conditions that exist while they are on site, what happens when the conditions change? The temperature in your boiler room, the fuel quality, hysteresis of control valves or dampers, etc. can cause a variation in your combustion. Often a boiler is tuned with a safety factor to accommodate for these variations which leaves some efficiency on the table. With O2 trim, you don’t have to accommodate for these future variations, therefore allowing you to run your boiler more efficiently. Your return on investment is contingent on your fuel usage and there are several utilities incentivizing the installation of this equipment with rebates as it has been proven to reduce fuel usage.
Oxygen trim is best coupled with a linkageless control strategy. If you have a Preferred Utilities FlexFit or BurnerMate Universal system already installed, oxygen trim is easily added. The return on investment is dependent on your usage and incentive programs in your area and can often pay for itself within a single heating season.
Ask us how you can improve your boiler efficiency and start saving today.