Generator Cooling

As mentioned last Tuesday, for some time now I have been contemplating changing how our diesel generator is cooled. As with most projects I like to take my time working out the pros and cons, before proceeding. Having chewed the cud over this for most of this year, and having discussed it with fellow boaters, I finally bit the bullet and went ahead with the changes yesterday.

Further reference to “engine” in this blog is the engine part of the generator, which is actually a 3 cylinder Yanmar.

As supplied, our generator comes complete with a closed water cooling circuit, using a heat exchanger, to transfer the heat to another source of cooling. As marine generators are designed to draw cooling water from outside a boat, and in most cases this is salt water, it is not a good idea to have salt water passing directly through an engine, hence the heat exchanger. To this purpose as well as the water pump which is an integral part of the engine which is used for the closed circuit, a second water pump is fitted and driven from a second fan belt which is for the raw water circuit.

Now Hadar has 2 separate cooling tanks built into the hull, one for our National engine and one for the generator engine. When we installed the generator we connected the appropriate skin tank to the raw water circuit, as supplied, thus resulting in having 2 completely separate cooling circuits. The one through the engine is pressurised the same as with a car engine, with a pressure cap on a small tank on top of the engine, same as found on the top of a car’s radiator. Now unless I strip down the shelf unit which surrounds the generator, and remove all the toolboxes on the top, I cannot get to this tank to check the water level easily. The raw water circuit though has an external header tank which is easy to get to for checking and topping up.

Directly cooling the engine has quite a few advantages as listed in my previous entry in this blog on Tuesday. During the week I picked up the parts I needed to complete the task from Homebase down in the town, and yesterday we set about changing it.

It was quite a simple task really. Fortunately the 2 pipes from the skin tank come very close to both of the sections of pipe of the closed circuit which I had to connect to. This was achieved fairly easily without much effort, which makes a nice change for us! Having changed the piping, I then removed the fan belt which drives the raw water pump. With all the changes completed we topped the water up, and ran the generator to check for any water leaks, amazing, no leaks! With the simplified water piping we were able to rearrange the sound proofing, to reduce the generator noise within the boat.

The real test was running the generator last night fully for the first time. It was definitely quieter with the rearranged sound proofing, and ran successfully without stopping due to over heating for a full battery charge session, result. Only time as to how much effect removing the raw water pump from the system has on fuel consumption. I know from my car rallying days, that getting more power from an engine hinges very much on reducing what an engine has to drive. For example, back when I was rallying, car engine radiators were cooled by a mechanical fan fitted to the front of the engine. these fans could use as much as 5bhp from the engine. these mechanical fans were removed and replaced with electric fans (which are fitted as standard to cars these days I believe). As the fan usually only needs to work when the vehicle is not moving and getting natural air flow, these electric fans only work when a car is stationary, when it is most needed, thus they do not operate when the car is in motion, saving at least 5bhp.

Having completed some major jobs recently, I can now concentrate on finishing my latest rag rug.

Keith.