Exhaust
A big difference between the existing generator and our updated system is the exhaust. The existing generator exhaust is called a dry stack system which is just an exhaust pipe that exits to the outside air. In the case of the Fir, this is a 5-inch pipe that runs about 30 feet horizontally and another 30 feet vertically. We will keep this system for the existing Detroit Diesel 671 that we are keeping as a backup.
For several reasons, the existing dry stack will not work for our upgraded, primary generator system. First, our proposed system is a scaled system that only produces 50KVA at anchor. At this rate, the exhaust from a single motor producing 65HP would most likely cool and condense in a 5-inch exhaust pipe 60 feet in length. The condensate could run down the pipe and into the engine. This would be especially problematic if we take on diesel fuel with higher sulfur content than is available in the United States because sulfur exhaust derivatives can be highly corrosive. Second, the stack on Fir is located over the prime event and recreation deck. We want to avoid the noise, smell, and potential condensation spitting in this area.
Our solution is a modern, wet exhaust system for the new generators. Seawater brought into the engine’s heat exchanger is sprayed into the tail of the exhaust pipe to cool exhaust gases and muffle sound. The combination of water and gas then enters a traditional waterlift muffler. The waterlift muffler produces a gurgling, burping sound often associated with boat engines at idle. In our case, the waterlift muffler pumps the exhaust to an exhaust separator. Water is expelled below the waterline. Gases are expelled above the waterline. We turned to Dan at Soundown to design and build the exhaust system.
The exhaust system as designed by Soundown. Note the drawing shows our plan to have two Kohler generators stacked.
Controls
Fir’s original electrical system was controlled in the Engine Room. We will eventually produce a video showing all the controls for the original generator. In short, you start the Detroit Diesel 671 without an electrical load. Once warm, the Woodward controller is engaged and the RPMs rise to around 3,600. At this point, you fine-tune the controls to produce 450 volts at 60 hertz. Manually closing the circuit breaker makes the power available to the master bus. “Generator #1” (our backup system) will continue to work in this way.
The new Kohler generators are regulated by the Decisionmaker 3500 controller mounted to the generator. This setup supports a remote display and controller in the Wheelhouse. A motorized circuit breaker automatically brings the unit online once the engine is up to speed and electrical production has stabilized.
Our first step was to run the emergency stop buttons for the new generator. This is a very simple, two-wire system. The generator will only run if the circuit is closed so any break along the run will cause the generator to shut down. Chris wired in the original stop switch located just outside the galley. He then added a new leg to the circuit for an emergency shutdown switch in the Wheelhouse.
Joe and Chris wired the remote display and control panel. We initially set-up the display in the engine room with the control wires coiled up on the generator. There are not a lot of connections but getting it right did require a call to Kent at Boatswain’s Locker. For the generator to produce 450 volts (Fir’s native voltage) we needed a few minutes from Kent and an engineer. Kent was happy to help even on a Saturday morning.
The other wiring was installed temporarily. Eventually, the Kohler auto paralleling bank of generators will feed into the existing lines used by the previous “ Generator #2". For this initial test, the output of the single Kohler is wired as a direct replacement of the previous generator.
Sound Comparison of the Old and New Generators
In the future, we will go into more detail. For now, this video is of our initial testing. We open with Generator #1 (Detroit Diesel 671) in operation. We then take Generator #1 offline at the main panel and shut down the motor. We follow by starting the Kohler generator and connect it to the main bus.
There is an obvious difference in sound. Less obvious is the reduced vibrations from the new unit. Also, the Kohler generator responds almost instantly to changes in the electrical load. Again, we will get into this in detail in upcoming reports.
Implications of the New Generator
Getting the new generator online should start a flurry of progress. Previous owners jury-rigged many basic systems so that they could run on 115VAC electricity from small home generators. Since we now have 450 Volt 3 phase generators, the original configurations can be restored and run as intended. One example is the pump for the potable water pictured below.
The PVC pipe from the main potable water system is feeding a standard 115V well pump. Now that we have 3 phase current, we can remove the well pump and restore the piping to the original system.
Over the next several blogs, we will show how we revise the operating systems to function as were designed. Stay tuned for updates.