Alternator Cooling needed?

[bgallinger]

I have had suggestions to install a cooling fan for my 100amp Balmar alternator. Has anyone tried this and how did you mount the fan? Would there be a minimum CFM size to be effective? My Yanmar 3GM30F lives in a relatively small compartment without much wasted space!
Cheers and thanks!

[Rumrace]

I think adding a fan is a weak idea but just about every car has an air scoop for the alternator. Increase the blower sure. There are liquid cooled alternators. I have two very odd alternators a Bosch liquid cooled on a 40hp Yanmar and a “NASCAR” Alt on a high performance boat. With a single engine the alternator is burdened with hydraulics for extra large tabs, steering and drive.
Both alternators came from written off SUVs. BMW X5 supplied one Cadillac Escalade the other.

[sailorboy1]

Originally Posted by bgallinger

I have had suggestions to install a cooling fan for my 100amp Balmar alternator. Has anyone tried this and how did you mount the fan? Would there be a minimum CFM size to be effective? My Yanmar 3GM30F lives in a relatively small compartment without much wasted space!
Cheers and thanks!

Do YOU have a reason to believe you need more cooling? Your boat is reasonably old has it burned up alternators, or if you have an external regulator with an alternator temp sensor has it been reducing the output?

Does your engine even have the belting to run a 100A alternator at 100A? I have a 100A alternator and have it belt limited to 85%. If you don't have an external regulator that you can program I bet you get more value out of installing one than you do with a fan.

Nigel Calder did an article and testing years ago and for his setup a fan helped a lot/ I suggest IF the answers to me questions above are yes that you search it out and read it over the forum approach of opinions.

[ItDepends]

A "fan" doesn't help, it just move around the hot air that is already in the engine room. The internal fan on the alternator is already pretty good at this.

What you want is to direct cooler outside air to where the internal fan of the alternator can pick it up.

Most sailboat engine "rooms" can use a lot more ventilation, so consider it in a good cause.

[wholybee]

Do you have blowers that evacuate air out of the engine room, as required for gas engines, but sometimes also installed with diesel?

That is how I would do it, have a blower that blows air out of the room to an outside vent, and an intake hose that was directed to the alternator.

[hlev00]

My Beneteau 423 has a fan for cooling the engine compartment but I didn't know that when I bought her used as it was non-functioning. I later upgraded the stock alternator to a Balmar 100A which died while I was in the Bahamas, after about 4 months usage. During my testing of what might have contributed to the problem I decided that overheating at least contributed to the problem. The boat already had two ducts so I figured I would cut into one and install a fan. As I was looking for a place to insert the fan, and with some suggestions from other 423 owners, I found the non-functioning fan. After replacing it, the alternator runs much cooler. This also prevents the regulator reducing output due to temperature as much.

Long way to say, yes you should provide a fan, but as others said, you need it to help circulate fresh air. My fan blows in so I direct the duct at the alternator since the rest of the diesel engine is fine with the temps. Others will suggest exhaust.

Harry
s/v Juno

[Madehn]

I used a duct from one of the vents with a bilge blower in it. It has a moveable nozzle that I can use to direct cool air to the alternator or to the hot section of the generator. Used 4 inch pvc pipe for the majority of the duct work with some Ss flexible duct as the nozzle. Works well

[jordanbigel]

Originally Posted by wholybee

Do you have blowers that evacuate air out of the engine room, as required for gas engines, but sometimes also installed with diesel?

That is how I would do it, have a blower that blows air out of the room to an outside vent, and an intake hose that was directed to the alternator.

My boat is equipped with 2 blowers like this (one breaker on the panel turns them both on) never a problem with overheating alternator, even after 4+ days motoring in calms near the equator.

Also, they are 24v blowers, but my boat is 12v - "some guy" once explained to me this would result in longer lasting motors.