Cummins/Onan 275 DFBF Generator Set

1. Turn idle speed potentiometer clockwise 20 turns, then 10 more turns.
2. Turn run speed potentiometer clockwise 20 turns, then 10 more turns.
3. Turn gain potentiometer fully counterclockwise.
4. Turn droop potentiometer fully counterclockwise for isochronous operation.

1. Close the main line circuit breaker and apply approximately 1/4 rated load.
2. Verify engine speed is constant.
3. Turn GAIN potentiometer clockwise slowly until engine speed is not constant.
4. Turn potentiometer counterclockwise until constant speed is achieved.
5. Turn counterclockwise an additional 1/2 division.

⚠ Ignition of explosive battery gases can cause severe personal injury; always connect battery negative last.

⚠ Do not smoke while servicing the batteries.

1. Use two, 12 volt (Type 8D) batteries for a normal installation.
2. Connect batteries in series: negative post of first battery to positive post of second.
3. Connect the negative (–) battery cable last to prevent arcing.
4. If no built-in charge circuit exists, connect a separate trickle or float charger.

⚠ Do not connect generator set directly to any building electrical system; connect only through an approved isolation switch or paralleling device.

1. Bolt load wires to the appropriate terminals on the generator terminal block.
2. Terminals are stamped U, V, W and N (U, V, W = L1, L2, L3; N = L0).
3. Route generator output leads through current transformers CT21, CT22 and CT23 for meter operation.
4. Balance loads so current from each line terminal is about the same.
5. Ensure each line current is within 10 percent of median value and below nameplate rating.

⚠ Verify at least 12 inches (305 mm) clearance between exhaust pipes and combustible materials.

1. Check ventilation and exhaust systems.
2. Check all mechanical connections.
3. Fill the coolant, lubrication and fuel systems.
4. Prime the lubrication and fuel systems.
5. Check the fuel system for leaks.
6. Check the lubrication system for leaks.

Tools: Leveling bolt, Lock nut

1. Place isolators on support structure; shim or grout so all bases are within 0.25 inch (6 mm) elevation.
2. Loosen side snubber lock nuts so top plate is free to move vertically and horizontally.
3. Place genset onto isolators, aligning skid mounting with threaded isolator hole.
4. Insert leveling bolt through skid into isolator to adjust clearance.
5. Turn leveling bolt until nominal 0.25 inch (6 mm) or greater clearance is achieved.
6. Adjust leveling bolts until set is level and sufficient clearance remains.
7. Lock leveling bolts in place with lock nut.
8. Snubber nuts may remain loose to provide better isolation.

⚠ Handle filters with care; install recommended replacement part if damaged.

1. Loosen fasteners and remove air cleaner housing end cap.
2. Remove air filter element from filter housing.
3. Blow low pressure compressed air (30 psi/207 kPa) through element from clean side.
4. Hold nozzle at least 1 inch (25 mm) away to avoid damage.
5. Soak filter at least 15 minutes in water and Donaldsons D1400 solvent.
6. Rinse with clean water, air dry, reinstall; replace after two cleanings.

⚠ Do not use antifreeze with an anti-leak formula.

1. Close the shutoff valves.
2. Unscrew coolant filter and discard.
3. Apply a light coat of lubricating oil to the gasket surface.
4. Install new filter; tighten by hand until seal touches head, then 1/2 to 3/4 turn.
5. Open the shutoff valves.

⚠ Do not open a radiator or heat exchanger pressure cap while the engine is running.

1. Remove the radiator pressure cap and monitor the coolant level on first start.
2. Add coolant as trapped air is expelled and the level drops.
3. Replace the pressure cap when the coolant level is stable.

1. Remove wing nut, flat washer and rubber washer; lift cover and swing away.
2. Lift out breather element, vapor element and gasket.
3. Clean all parts with approved solvent; dry with compressed air 30 psi max.
4. Inspect all parts and replace if necessary.
5. Reassemble filter assembly, replace cover and secure.

⚠ Contact with hot coolant can result in serious burns.

1. Remove the cooling system pressure cap.
2. Fill system with water or water/antifreeze mixture.
3. Start engine and monitor coolant level with cap removed.
4. Add coolant as trapped air is expelled.
5. Replace pressure cap when coolant level is stable.

⚠ Excessive air pressure could split the radiator core; apply gradually.

⚠ De-energize engine coolant heater before flushing and cleaning.

Tools: Flushing gun

1. Clean system with sodium bisulphate or oxalic acid per supplier instructions.
2. Neutralize and flush with clean water.
3. Open upper and lower radiator hose connections and install radiator cap.
4. Attach flushing gun to lower hose; let water run until radiator is full.
5. Apply air pressure gradually; repeat until water is clean.
6. Remove thermostat; flush engine block until water runs clean.
7. Replace thermostat and all hoses; refill cooling system.