Carbon Lighthouse, an energy conservation engineering company, recently contacted us about upgrading our shared client’s gas and oil-fired Cleaver-Brooks boiler combustion controls to achieve better efficiency and less cycling. Their existing boiler’s combustion control maintains the combustion air and fuel ratios with a single-point positioning system.
Single-point positioning utilizes a modulating motor that drives a jackshaft connecting the combustion air damper, gas valve, and fuel oil valve with linkage rods whose positions are held in place by adjustable ball joints. Single point positioning is outdated technology. It doesn’t allow combustion to be easily tuned and plagued by ball joints that loosen and linkages that slip. The frequency of the boiler cycles and how often it operates influences how quickly the ball joints loosen, linkage rods slip, causing the boiler’s combustion efficiency to decrease until the boiler experiences a failure requiring service.
Our customer’s Cleaver-Brooks boiler, a scotch marine four pass fire tube boiler, is an excellent piece of equipment that is capable of greater efficiency by upgrading the single point positioning control system to a parallel positioning control system. Instead of a modulating motor and linkages, a parallel positioning (aka linkage-less) system utilizes independent servo motors, one connected to combustion air damper, gas valve, and oil valve. The valve positioning of each servo motor is made through an interface on a controller. Several companies make parallel positioning controls. For this project, we presented several quotes to the customer who ultimately chose Autoflame’s Mini Mk8 MM (https://www.autoflame.com/mk8_mini/).
Compared to their single-point positioning combustion control system, Autoflame’s Mini Mk8 boasts a 5% to 7% fuel reduction and 10% reduction in CO2 emissions. In addition to these reductions, our customers liked the control’s touch screen interface, lead/lag Intelligent Boiler Sequencing and precise target setpoint control (PID). To further the efficiency upgrades, we installed a variable frequency drive (VFD) controller on the boiler’s combustion air blower motor. The VFD reduces electrical consumption and wear and tear on the combustion air blower motor by modulating the motor’s revolutions per minute (rpm) based on demand. The VFD-controlled motor no longer operates at either 0% or 100%.
Better Efficiency and Less Cycling with a Boiler Upgrade
We completed this upgrade a couple of weeks ago, so it is too soon to measure the Autoflame Mini MK8 and VFD’s impact on efficiency and emissions. However, the Resident Manager observed several changes in how the boilers operate. After the upgrade, the boilers hardly cycle. The steam pressure used to fluctuate as the boilers cycled on and off. Now the steam pressure remains constant. The banging in the radiators and steam piping stopped, and the condensate return pipes are no longer overheating. The boilers are also much quieter, thanks to the VFD.
Autoflame’s MK8 control offers additional expansion options not chosen for this project due to budget constraints. The optional Electronic Gas Analyzer (EGA) https://www.autoflame.com/ega the combustion gases that leave the boiler communicates the findings to the MK8 for real-time automatic adjustments. The optional Digital Transfer Interface (DTI) https://www.autoflame.com/dti remote access to operating history and some settings for up to 10 boilers with MK8 controls.
The NYC DOB is implementing Local Law Code 97 (LL97) as part of the Climate Mobilization Act. LL97 has carbon emission limitations that will apply to most buildings over 25,000 square feet in 2024 and 2030. Upgrading your boiler controls from single-point positioning (aka linkaged) to a parallel positioning (aka linkage-less) system is a great way to reduce emissions. Con Edison is currently offering significant rebates for linkage-less upgrades.
Are you interested in such an upgrade for your building? Please send an email to Info@HeatingNY.com or complete our contact form to find how we can help you upgrade to linkage-less controls and obtain Con Ed Rebates for this and other projects.
1 thought on “Upgraded Boiler Controls to Achieve Better Efficiency”
Great write up! Will be interesting to see the long term savings. Also did you guys do an emissions calculator before hand?