Cleaver-Brooks - Complete Boiler Room Solutions

Take Control of Your Savings

Tip Sheet: June 2016

Key Facts

  • To improve boiler efficiency, consider upgrading the control system
  • An advanced control has enhanced diagnostic tools and remote capabilities
  • Select a control that meets minimum and maximum load-demand requirements without excessive cycling

To improve boiler efficiency, it is important minimize system heat loss. If a boiler pressure vessel is in good shape and retrofitting is an option, one key area to upgrade is the control system. New developments in boiler controls create opportunities for substantial efficiency gains.

Following are options to help an existing boiler system produce measurable efficiency increases and fuel cost decreases.

Parallel positioning. Many boiler burners are controlled by a single modulating motor with jackshafts to the fuel valve and air damper. This arrangement, set during startup, fixes the air-to-fuel ratio over the firing range. Unfortunately, environmental changes such as temperature, pressure and relative humidity alter the fixed air-to-fuel ratio, making combustion inefficient. To account for these conditions, boilers with jackshaft systems are typically set up with a high amount of excess air. This higher excess air level reduces boiler efficiency and, over time, linkages wear – making repeatability impossible. To solve this problem, consider incorporating parallel positioning into the control system. It’s a process using dedicated actuators for the fuel and air valves. Burners that incorporate parallel positioning can be set with lower excess air levels. Energy savings of up to 5 percent can be realized by introducing a parallel positioning system.

O2 trim. Another way to ensure peak efficiency is to use an oxygen sensor/transmitter in the exhaust gas. The sensor/transmitter continuously senses oxygen content and provides a signal to the controller that “trims” the air damper and/or fuel valve, maintaining a consistent oxygen concentration. This minimizes excess air while optimizing the air-to-fuel ratio.

Variable speed drive. Variable speed drive enables a motor to operate only at the speed needed at a given moment, rather than a constant 3600 RPM as a drive runs. This speed variance results in the elimination of unnecessary electrical energy consumption. A variable speed drive can be used on any motor but is most common on pumps and combustion air motors of greater than 5 horsepower. These drives also produce quieter operation compared to a standard motor, and they reduce maintenance costs by decreasing the stress on the impeller and bearings.

Lead lag. Lead lag sequences the operation of multiple boilers, matching system load. Lead lag enables the boilers to operate at peak efficiency, reduces cycling and decreases maintenance and downtime.

There are several key features of newer control systems, including centralized operation, remote capabilities, enhanced diagnostic tools and an emphasis on energy efficiency. More specifically, an advanced system will improve operating efficiency at all loads, but particularly at part load, where a conventional control system cannot closely manage boiler operations. By installing an integrated control system, a facility can expect to see better performance, enhanced safety, lower maintenance and reduced operating costs.  

A key benefit of an advanced control is that a boiler can be remotely monitored and manipulated.  Operators can monitor boiler status via email, text messaging, voice mail, the Internet or an internal system. In the event of a boiler system alarm or malfunction, the control system can automatically alert an operator in a nearby or remote location, permitting the more efficient use of an operator’s time. 

When researching an advanced control system, ensure that the one selected is compatible with the facility’s boiler/burner. It is vital that any control integration system does not compromise or change the safety interlocks on the boiler. To ensure the correct control system is installed, consult the boiler manufacturer’s trained service technician and the building management system supplier.

It is also critical to select equipment that meets minimum and maximum load-demand requirements without permitting excessive equipment cycling. Control strategies must be determined through a complete understanding of systems to ensure available output capacity for a given period of time with an associated load demand.

To learn more about boiler controls, or find a Cleaver-Brooks representative near you, visit cleaverbrooks.com.