Lead-Lag Modular Boiler Systems in California
Two or more boilers run as one plant, with Autoflame intelligent boiler sequencing or sequencing controls from other manufacturers bringing boilers on and off to follow the load. Designed, built, and installed by McKenna.
Code-built boilers and vessels
Code repairs and alterations
Factory-authorized Tech Center
Factory-authorized Burner Tech Center
Fifth generation, family-owned
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McKenna Boiler Works, Inc. designs, builds, and installs lead-lag modular boiler systems across California. Instead of one large boiler sized for peak load, the plant runs two or more smaller boilers as one system. With Autoflame Mk8 MM controllers, which come as a standard option on new McKenna boilers, Autoflame intelligent boiler sequencing runs the plant, holding header pressure or temperature, staging boilers with the load, keeping a standby boiler warm, and rotating the lead boiler. The Autoflame DTI links plant data to the building management system. McKenna also adds sequencing to existing multi-boiler plants. Call (323) 987-1816 or email info@mckennaboiler.com.
Why modular
Why run several smaller boilers instead of one large one.
A boiler sized for peak load spends most of its time well below it. At light load it sits at low fire or cycles on and off, and every cycle adds a purge, a light-off, and thermal stress on the boiler.
One 800 HP boiler with 4:1 turndown can only fire down to 200 HP before it starts cycling. Two 400 HP boilers with the same 4:1 turndown can follow the load down to 100 HP, because one shuts off and the other keeps modulating.
When one boiler is down for service, inspection, or repair, the others carry the plant.
Running a modular plant
How a modular plant runs.
- Boilers stage on as the load rises and off as it falls
- Each running boiler fires in its efficient range instead of cycling at low fire
- Capacity can be sized so the plant carries its load with one boiler out of service
- One boiler serviced or inspected at a time while the others carry the load
- Room to add a boiler later as the plant grows
- Smaller boilers fit through doors and into tight boiler rooms more easily
Typical configuration
One Autoflame DTI links every boiler to the plant
Autoflame DTIData transfer interface, touchscreen
Mk8 MM controllersUp to 10, one per boiler
Mk8 EGA analyzersUp to 10, reading O2, CO, and CO2
I/O modulesUp to 10 for added inputsInstalled, set up, and serviced by McKenna Boiler Works, Inc., a factory-authorized Autoflame Tech Center.
Product images courtesy of Autoflame Engineering Ltd.
Autoflame sequencing
Intelligent boiler sequencing with Autoflame controls.
Each boiler’s Autoflame controller reads its own firing rate and the plant’s load, and the controllers talk to each other. The DTI ties up to 10 Autoflame controllers together, stores the combustion data, and sends plant data and alarms to your building management system.
The sequencing holds header steam pressure or hot water temperature, decides how many boilers run and how hard, keeps a standby boiler warm so it can pick up load, and rotates the lead boiler on a schedule.
Lead-lag sequencing, live
Plant demand follows the production schedule. The lead boiler carries light loads, a lag boiler joins for normal production, and the third boiler waits in hot standby until a peak needs it. Header pressure holds near setpoint.