The CREST Combustion System
The fully modulating CREST Condensing Boiler introduces a low-NOx combustion system with a stainless steel heat exchanger and a highly unique, patent pending dual-system burner design with up to 25:1 turndown. The top-mounted, single micro-metal fiber burner actually serves as two combustion systems in one, each with its own blower and gas valve assembly to power the combustion process based on demand.
For example, in a two million Btu/hr CREST Boiler, the upper portion of the burner fires first, with 5:1 turndown, and modulates from 80,000 to 400,000 Btu/hr. When demand exceeds 400,000 Btu/hr, the lower portion of the burner fires and modulates from 320,000 to 1.6 million Btu/hr. In addition, both burners can fire together and modulate up to the maximum two million Btu/hr input.
Introducing the Wave™Through extensive research and design, Lochinvar has taken fire-tube technology to a new level with the CREST Boiler’s patented Wave™ 316L stainless steel fire-tube. According to the company, the Wave is larger than other industry fire-tubes, which means CREST requires fewer tubes and welds. Its exclusive design and unique wave pattern provides superior heat transfer in every fire-tube, creating turbulence to “scrub” maximum heat energy from the flue gas products before they leave the heat exchanger.
Each fire-tube is welded into the CREST’s heat exchanger vessel and surrounded by water. The burner fires heat energy and combustion products downward into the fire-tubes, which efficiently transfer the heat to the water flowing up inside the vessel. With one pass, the heat is effectively stripped from the flue products, bringing the water to condensing temperatures as it flows out into the system. Condensate is drained into a stainless steel collector and piped to a suitable drain in the floor, while exhaust vents through the bottom of the unit.
The innovative design of the Wave also enhances the life of the heat exchanger by allowing the fire-tubes to flex, operating stress-free without the adverse effects suffered by traditional fire-tube boilers.
SMART TOUCH + CREST
CREST is equipped with Lochinvar’s SMART TOUCH user control, the industry’s most advanced operating system loaded with superior features and benefits that provide ease of installation, operation and data retrieval. Its sophisticated technology offers unequaled control and monitoring via the eight-inch, multi-color touchscreen display. In addition, SMART TOUCH enables CREST to communicate seamlessly and in real time with building management systems by utilizing an on-board MODBUS protocol.
Another benefit of the SMART TOUCH operating system is its built-in cascading sequencer. CREST is capable of sequencing up to an eight boiler system using a simple two-wire, daisy-chain connection, which eliminates the cost and uncertainty of using a separate, third-party sequencer. One boiler functions as the leader and modulates to capacity. Increasing load then cascades to additional “lag” boilers in the sequence as needed. This lead-lag rotation shifts the “first on” boiler every 24 hours, distributing equal run times to each unit.
The ability to sequence up to eight boilers that each have as much as 25:1 turndown means that the combined system has the potential of operating with modulation of up to 200:1 turndown. A bank of eight two million Btu/hr CREST models can provide as little as 80,000 Btu/hr and as much as 16 million Btu/hr of heating output, resulting in greater seasonal efficiencies.
Low on Flow Rates, High on Venting Flexibility
CREST allows system designers tremendous flexibility to vary the flow rate through the boiler. With options for installation with primary/secondary piping or in a full-flow arrangement, CREST can operate at flow rates as low as 20 GPM up to a full 350 GPM flow rate, which means it can service systems that operate with widely fluctuating flow rates depending on demand.
In addition, CREST offers a wide variety of horizontal and vertical venting options with increased vent lengths and configurations. With six unique venting options, CREST provides exceptional flexibility for placement of units within the building as it permits direct-vent air intake and exhaust runs up to 100 equivalent feet.
For more information on the new CREST and Lochinvar’s other condensing boiler models, visit www.Lochinvar.com.