Wednesday, April 27, 2011

More Generator Details

     The cooling system is critical to the life and proper operation of the generator. The system is divided into two subsystems - the raw water cooling side, and the closed cooling side. The raw water system is comprised of the thru-hull fitting, seacock, strainer, raw water pump, heat exchanger, and exhaust system. The closed cooling portion is similar to the cooling system of a car, with recirculated coolant, a circulator pump, associated hoses, and the closed cooling side of the heat exchanger. In operation, the coolant carries away the excess heat of combustion, and passes it to the raw water via the heat exchanger. The heated raw water is discharged with the exhaust, which it also cools. Simple enough on the surface, but again, the devil is in the details.
     As I mentioned in the previous post, a siphoning condition can be created, if the generator is below the water line, wherein raw water can bypass the raw water pump impeller, and flood the exhaust system, as well as the generator itself. The resulting engine damage is not covered by the generator warranty. After all, they do describe the proper install techniques in an installation manual - available on the Westerbeke website. It is a good read whether or not you are actually doing an install, and provides a great deal of useful information for marine generator owners. Since I covered the vented loop installation in the last post, I won't get into it again. Just make sure yours is operating properly.
     On the raw water side, I installed all new hoses, and double clamped every joint, with two exceptions. The raw water pump on the generator has a specialty nipple for the hose connection, and it only has room for one clamp. As it operates under negative pressure, I am not overly concerned, but I will keep an eye on it. The Groco vented loop also will not support double clamps, but these hoses are all above the water line in my boat, so again, I am fine with it.
     The muffler isolation mounting was previously discussed, but I should mention that the generator to muffler connection on a 340 like mine is a bit tight. Conventional rubber exhaust hose is a bit stiff, so I used corrugated, wire reinforced blue silicone exhaust hose for this connection. It is expensive, but the enhanced flexibility and longevity makes it worthwhile. You can see a portion of it here:
     It is important to route this hose with a constant downward pitch. Do not create any low spots that can trap water between the generator and muffler. Under rough conditions, that water could slosh back up into the generator, and damage it.
In the picture above, you can also see a yellow-handled ball valve and hose nipple. I made the aluminum block in my milling machine, and threaded the fitting and valve into it, then mounted the assembly next to the generator, to make the oil changes easier. The original Westerbeke setup is simply a hose with an NPT pipe cap on the end, held in a bracket right behind the raw water pump impeller. It is hard to access, blocks the access to the impeller, and would probably result in an oil spill every time the generator needed an oil change. With this modification, all I have to do is connect the hose from my vacuum oil changer to the nipple, open the valve, and all the engine oil is sucked out. The valve has a locking hasp on the handle, so it can't open accidentally. And now, it is much easier to service the raw water pump.
     Last, but not least, are some electrical details. As you know from some older posts, the 4 engine and house batteries were moved out of the engine compartment. The generator battery was not. I placed it just forward of the generator, on a custom machined aluminum battery tray:
     I modified the battery tray to accept a heat shield, which you can see to the right of the battery. This protects the battery from any radiant heat from the generator, and also acts as a convenient mounting point for the wiring and fuel line. Speaking of wiring, you can see two wires that connect to the positive battery post - one for the generator itself (the large red one to the right), and the other for the battery to charger connection. There is a fuse holder in this lead. ABYC recommendations stipulate that a fuse be placed within 7 inches of battery positive terminal connections, with the exception of larger starter cables. The fuse holder meets this requirement. I placed red shrink bands around the wire to indicate its positive conductor status.
    One more thing - the generator fuel system. As you can see, I used metal braid over Teflon line (Goodridge #811 hose) for the fuel system. I will be using this same fuel line on the engines. There is an excellent article written about modern fuel line here:

Take the time to read it - there is a lot of information here concerning rubber fuel hoses, ethanol fuel, and the resulting reactions. The hose I am using is made from Teflon tubing, and is 100% resistant to Gasoline, Ethanol, Methanol, and even Nitromethane. It is 100% resistant to vapor permeation, lightweight, flexible, abrasion resistant, and never needs replacing. It also exceeds all marine standards for fuel hose. There is, of course, a drawback, and that is price. it runs about $10.00 to $12.00 a foot, and the hose ends aren't cheap either. But if you want it done once, and only once, it's the way to go.
     And with that statement comes a warning. Metal braided fuel line forms an electrical connection between the engine/generator and the boat's fuel tanks. If, by chance, the engine's ground cable were to be somehow compromised, and the starter engaged, the braided fuel line becomes the engine ground conductor. The result can be a melted fuel line and potential fire or explosion. If you use metal braided line, there MUST be a break in the circuit between that line and the boats ground. I accomplished this by using a short section of hose, between the fuel tank and the fuel filter, that has a Kevlar braid instead of the metal braid. The engines will be similarly isolated. OK, I'll get off the soapbox now....

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