With only a day to spend — and a little encouragement from my friends at HPAC Engineering — I focused my attention at this year's International Air-Conditioning, Heating, Refrigerating Exposition (AHR Expo) in Orlando, Fla., on what is new in boiler/burner technology. To those vendors I might have missed, I apologize — there was a lot to see in a day.

TRENDS

In general, the industry appears to be working toward increased boiler efficiency and reduced emissions. Improvements are coming through better burners, more-precise fuel-air controls, greater turndown, and the use of variable-speed technology. Manufacturers are offering materials of construction other than cast and ductile iron, steel, and copper, using stainless steel and even aluminum as primary construction materials. Boiler-combustion and burner-management controls appear to be moving toward better integration with other building systems through more interface options. The use of mechanical linkages and adjustable cams to control fuel-air ratios is being replaced slowly with linkageless systems using actuation with precise position control and feedback to digital control systems. Increasingly, burner technicians are able to set aside some of their wrenches in favor of a laptop computer.

SPECIFICS

Peerless Boiler has added two sizes and an improved control board to its Pinnacle line of compact, high-efficiency, natural- and LP-gas, direct-vent hot-water boilers. Supply and return temperatures, flame signal, and fan speed (firing rate) can be viewed on the improved LED digital display module. A switch to “service mode” enables contractors to manually control firing rate. An optional interface module allows external control of outdoor reset, multiple temperature set points, and the sequencing of multiple boilers. Also available is PC software to display boiler status and fault history. Current capacity offerings are up to 399 MBH. This is worth a look, if the pressure rating and capacity range fit the needs of the system you are planning.

Autoflame Engineering Ltd. added a new module to its Micro Modulation line of linkageless combustion controls. The devices provide fuel-air-ratio control with three-parameter (O2, CO2, and CO) trim, PID pressure or temperature control, and intelligent boiler sequencing. Burner management/flame safeguard can be integrated, along with flue-gas-recirculation control. Autoflame offers a Johnson Controls Metasys or Modbus gateway for integration with other systems.

Autoflame demonstrated its new intelligent water-level control, which incorporates redundant level probes and an advanced control strategy.

Raypak was exhibiting its Hi Delta line of high-efficiency water heaters. The units are up to 98-percent efficient with an optional separate condensing heat exchanger, depending on the entering-water temperature. The units are advertised with NOx emissions of less than 30 ppm. The capacity range is 300- to 2,340-MBH input, with pre-engineered stacking multimodule versions with higher capacities available.

John Zink Company LLC was exhibiting its Gordon-Piatt low-emission gas and oil burners:

  • The RMB Series, which is designed to produce single-digit NOx emissions when firing natural gas or similar gaseous fuels and available for boilers ranging in size from 200 to 1,000 boiler hp.

  • The I-F Series, which is rated for NOx emissions of less than 30 ppm with firing gas and less than 78 ppm with light oil and available for boilers ranging in size from 100 to 1,000 boiler hp.

  • The Z-Series forced-draft gas burner, which produces less-than-20-ppm NOx with natural gas at 3-percent O2 without flue-gas recirculation and is designed for boilers ranging in size from 9.25 to 125 boiler hp.

Patterson-Kelley was exhibiting its new Mach series of condensing gas boilers, which are certified at 92-percent efficiency based on the operating conditions specified for testing under ANSI Z21.13/CSA 4.9, Gas-Fired Low Pressure Steam and Hot Water Boilers. The cast-aluminum sectional design caught my attention. The boilers are available in capacities ranging from 300- to 1,000-MBH input. Their burners are designed for full modulation with 5-to-1 turndown and high-efficiency, low-NOx operation. Controls are microprocessor-based, with an on-board touch pad and computer interface.

Gasmaster Industries Inc. was showing its expanded line of one-pass, high-efficiency, condensing, radial-pulse boilers in the range of 200,000 to 8,000,000 Btuh. An optional round metal-fiber premix burner can be specified to provide NOx-emission values in the single digits. The combination of a throttle mechanism, efficient heat exchanging, and radial-pulse combustion enables thermal efficiencies in the 94-to-98-percent range, depending on inflow temperature. Stainless-steel construction makes the units worth considering for applications where fire or water-side corrosion are an issue.

Among the products exhibited by Cleaver-Brooks was the new Promethean line of fire-tube steam and hot-water boilers in the 100-to-800-hp range and the Clearfire full-condensing hot-water boiler in the 750-to-1,800-MBH range.

The Model 4WI Promethean steam boiler on display featured an ultralow-NOx burner, combination firing, parallel positioning, O 2trim, and the new programmable-logic-controller-based Hawk ICS boiler-management control with Level Master water-level control for safety and modulating feedwater control.

The Clearfire is a modular vertical fire-tube package incorporating stainless-steel and extended heat-transfer surfaces. The unit is rated for efficiencies to 98 percent when fully condensing. The integral premix burner affords 5-to-1 modulation on natural gas.

Buderus Hydronic Systems was showing its SB316 line of stainless-steel condensing boilers. The boilers are of a forced-draft, three-pass fire-tube design, with gross outputs in the range of 484 to 4,079 MBH.

Buderus also was showing its GB142 compact, gas-fired condensing wall-hung heater, which is similar to European models I have seen. These units have a cast-aluminum heat exchanger and electronic controls, provide for both space heat and domestic water, and are offered in capacities of up to 198.8 MBH.

Ajax Boiler Inc. was showing its Atlas Series condensing boiler/water heater, which is offered in 1,000- and 1,500-MBH sizes. These units offer 97-percent thermal efficiency and fully modulating 6-to-1 turndown and feature a single-path copper-fin heat exchanger.

Aerco International was displaying its line of high-efficiency, high-turndown modular condensing boilers and a new boiler-management system (BMS) capable of controlling up to 40 boilers. The BMS offers great potential for integrating with building-automation systems because 35 points on each boiler can be exposed over the Modbus interface. The literature states that a ±2-F distribution-hot-water-temperature tolerance is maintained by the control system under normal load conditions.

Power Flame Inc. was exhibiting its Nova line of low-NOx burners, as well as a new burner control panel that uses circuit-board-mounted, rather than discrete, control components.

Honeywell Environmental and Combustion Control Division was demonstrating a gas-valve proving system that uses a pressure sensor to monitor the rate of pressure decay or increase between dual gas valves.

From Honeywell, I learned that a new interface to 7800 Series combustion controls that offers Ethernet IP communication will be available later this year.

Fulton Thermal Corp. was showing its new Vantage direct-vent, high-efficiency condensing boiler, which has a capacity of 3,000 MBH and comes with a linkageless combustion-control system. The burner is rated for a 5-to-1 turndown. Other features of note include a sealed, direct-vent combustion system.

Fulton also was showing its new RB Series horizontal three-pass wetback fire-tube boiler, which is offered in the 60-to-300-hp capacity range.

Weishaupt Corp. was exhibiting its line of gas, oil, and combination burners and controls.

W-FM 100 and 200 linkageless controls were designed with plug-in connections for external components. Also of interest are the integrated gas-valve proving system, which enables a “ventless” gas train; the internal or external PID modulating controller; the 200 Series' O2-trim module; and the multiple-protocol digital communication interface.

Weishaupt's multiflam dual-fuel burners employ a primary oil nozzle and three or four secondary ones to burn oil with a blue flame. NOx emissions without flue-gas recirculation are advertised at 30 ppm for natural gas.

Spirax Sarco's newest offering is a ceramic insulated blue cap for its line of thermodynamic traps. The idea of the insulating cap is to slow trap cycling in cold weather or rain to increase trap life.

Watson McDaniel has added a humidifier panel and manifold to its steam-specialty offerings.


Timothy M. Scruby, PE, is a senior controls, commissioning, and mechanical engineer with 24 years of experience in areas ranging from laboratories, museums, and archival storage facilities to industrial HVAC, boiler- and chiller-plant, and process work. He teaches a course on advanced HVAC-system commissioning.

Coming in June: HPAC Engineering's biannual Boiler Systems Engineering supplement, a publication of the American Boiler Manufacturers Association.

For HPAC Engineering feature articles dating back to January 1992, visit www.hpac.com.