Clarifying the term: what do we really mean when you say “biomass load bank”?
The dissipation unit (water/air): creating an artificial load outside the heating season
In some discussions, “biomass load bank” refers to thermal dissipation equipment. In practical terms, you connect a water/air or water/water heat exchanger to dump kW when the network is not taking any heat. The goal is to stabilize the supply temperature, hold a given firing rate, and tune combustion and hydraulics without waiting for winter.
The acceptance load test: validating the boiler plant at nominal operating conditions
On site, people often talk about the acceptance test. You create enough load, then progressively ramp up to nominal output. At each step, record flow and return temperatures, flow rate, ΔT, firebox draft, flue gas analysis, and check that the safeties trip as intended. The deliverable is a report with measured values.
Rented equipment or testing service: the questions to settle before pricing
Before quoting, define the framework. Who supplies and installs the dissipation unit. What useful output (kW) and what hydraulic connections. Which instruments are included (flow meter, sensors, analyzer). How many test hours, who signs the report, and who bears liability in the event of non-compliance. To frame these points when accepting the works, rely on a clear quality checklist.
Why carry out a full-load acceptance test in 2026 (and not just “at part load”)
A biomass boiler cannot be properly set up at low firing rates: real on-site risks
At part load, air and fuel settings do not reflect behavior at nominal output. The result is a setting that looks clean on paper but can drift under full load with CO, unburned fuel, flame instability and tar buildup. The biomass load bank is precisely there to create a constant off-season load so combustion can be set at the right point.
Avoid discovering problems at the first winter peak: breakdowns, fouling, user complaints
Without a nominal-output test, faults show up at the first demand peak. On site, this means safety shutdowns, fouled heat exchangers, flue gas values outside target, hydraulic imbalance, and a plant that is always “catching up.” A full-load test reveals these limits before commissioning.
Protect your liability: traceability and proof of compliance at acceptance
In 2026, what protects you is the paper trail. Formalize a step-by-step test report with temperatures, flow rates, firebox draft, flue gas analysis, and safety tests (overtemperature, low water, draft, emergency stops). The acceptance file becomes enforceable evidence in the event of a dispute.
Preparing the test: creating sufficient load and securing the ramp-up
Sizing the load: dissipation capacity, test duration and hydraulic constraints
Calculate the dissipation power needed to hold the test at nominal output, even outside the heating season. A biomass load bank can be an air cooler, a heat exchanger to a buffer tank, or a temporary loop. Check available flow, pressure losses, valve settings and the ability of the circulators to follow the setpoint.
Setting up a progressive ramp-up: steps, stabilization, checkpoints
Ramp up in stable steps. Stabilize at each level, then record flow and return temperatures, firebox draft, chimney draught, O2, CO, and the status of the safeties. A step is only valid if the parameters remain within the manufacturer’s range and the control system is not compensating at its limit.
| Target firing rate (% of Pn) | Minimum stabilization (min) | Readings to record (no unit) |
|---|---|---|
| 25 | 10 | water, flue gases, draft, O2/CO, alarms |
| 50 | 10 | water, flue gases, draft, O2/CO, alarms |
| 75 | 15 | water, flue gases, draft, O2/CO, alarms |
| 100 | 20 | water, flue gases, draft, O2/CO, alarms |
Organizing the test site: staff, access, fuel, evacuation, risk management
Assign a dedicated team for operation and readings. Secure access to the silo, hopper, ash area, room ventilation and flue gas evacuation. Formalize a risk prevention plan, isolate equipment, provide fire-fighting means, CO detection if the room is enclosed, and a shared emergency shutdown procedure.
Carrying out the full-load test: parameters to record at each firing rate
Hydraulic and thermal: supply/return temperatures, ΔT, flow rates, pressure and control stability
Bring the system up in power step by step, with a biomass load bank if the building demand is insufficient. At each firing rate, hold a stabilized operating point and record the values.
- Supply and return temperatures, calculation of ΔT and consistency with the emitter and setpoint.
- Measured flow rates (primary, secondary), circulator speed, valve positions and balancing.
- Static pressure, pressure evolution during heating, make-up water and expansion vessel performance.
- Control stability. Measured setpoint deviation, oscillations, time to return to stable operation.
Aerodynamics and flue gases: draft, O₂/CO/CO₂, flue gas temperature and draught
At each firing rate, record firebox draft and chimney draught before adjusting air and fuel. A measurement that is not recorded is useless.
- Draft and damper or extractor adjustment.
- O₂, CO, CO₂, plus flue gas temperature and ambient reference temperature.
- Fan speed, fuel size and feed rate, consistency with the analysis.
Safeties and automation: trips, alarms, emergency stop and safe recovery
Test the safeties under conditions close to nominal. The aim is to verify the trip, then a safe recovery without improvised workarounds in the control cabinet.
- Overtemperature, low water, pressure switches, extraction fault, feed fault, ignition fault.
- Emergency stop, acknowledgement, restart permitted only after the cause has been cleared.
- Time-stamped alarms and PLC statuses in the test report.
Formalizing acceptance: test report, measured values and items to have signed off
Minimum report content: step-by-step tables, instruments used, test conditions
A biomass load bank test is formalized in a dated, signed report with a table for each firing rate. Add the list of instruments (combustion analyzer, differential pressure gauge, flow meter, sensors) and their references. Note the test conditions. Fuel, declared moisture content, outdoor temperature, filter condition, control settings, valves in nominal position.
| Firing rate | Useful output (kW) | Primary flow rate (m³/h) | Supply temp (°C) | Return temp (°C) | Firebox draft (Pa) | O2 ( % ) | CO (mg/Nm³) |
|---|---|---|---|---|---|---|---|
| 30% | to be recorded | to be recorded | to be recorded | to be recorded | to be recorded | to be recorded | to be recorded |
| 60% | to be recorded | to be recorded | to be recorded | to be recorded | to be recorded | to be recorded | to be recorded |
| 100% | to be recorded | to be recorded | to be recorded | to be recorded | to be recorded | to be recorded | to be recorded |
Acceptance thresholds and reservations: what you approve (or refuse) at the end of the test
Your thresholds come from the specification, the manufacturer’s instructions and, if applicable, the relevant standard. You approve. Efficiency and combustion stability at full load, draft, overtemperature safety, emergency stop, fan fault, dampers, interlocks. If one safety point does not trip, you do not accept the system. You issue written reservations with a deadline, corrective action and retest.
Archiving and exchanges: send to the client, to maintenance, and keep your evidence
Send a signed PDF plus the raw exports from the analyzer, curves and photos of the displays. Give maintenance the final settings (setpoints, limits, timers, firing-rate parameters). Keep a chain of evidence. Signed version, sending emails, acknowledgements and the minutes of reservation closure. To frame the format and the items to be logged, you can rely on a standard site report.
