onan update

[flydixie1415]

Never Give The Ship. We Just Completed A Non-scientific Test By Running Three Of The Smaller Ac Units To See If We Would Over Heat. After 45 Minutes Of Running Time We Experienced No Overheating Problems. At This Point We Shut Off The Three And Ran Only The Main Salon Ac, After 22 Minutes- The Gen Shut Down From Over Heating. This Makes Believe That Somehow The Ac Is Affecting The Gen, Does Any Thing Make Sense To You More Experienced Mechanics Out There. Bt The Way, The Main Ac Works Fine When On Shore Power. We Await Your Wisdom.

 

[Genesis]

Heat exchanger on the genset is dirty, assuming you have checked the impeller. If the H/E is clear (pull it and look) then the next place to check is the exhaust water injection elbow for obstructions.

Just like a main engine - more load = more heat, you can't get rid of it the unit overheats and shuts down.

 

[CharlieJ]

I think PoohBah is on the right track but a bit more info would be helpful.

What was the electrical load when running the three smaller units and what size are the units? What was the electrical load when running only the large unit and what size is it?

 

[jim rosenthal]

This is just a suggestion, but do all three of your AC units get their cooling water for the seawater side of the AC coil from the same source? What you may have is a "steal" syndrome where the large AC unit is pulling cooling water away from the genset if they are on the same seawater inlet line. They should not be on the same through-hull for cooling water. Some boats are plumbed like that, but they should not be. Every consumer of seawater on the vessel ought to have its' own source of seawater- one for the AC system, one for the genset, etc. While Hatteras may not have set things up that way, funny things happen to boats when they leave the factory. Let us know what you find.

 

[Nonchalant1]

Check the current draw of the 3 smaller units vs. the one big one. If the draw is more from the big one, it's more likely a generator problem. If the draw is equal or less, it's more likely a raw water constriction problem, as suggested by by Jim Rosenthal above.

Originally, I couldn't find out why my Onan 15Kw was overheating. I replaced all hoses, put in new impeller, cleaned the shower head, pulled the heat exchanger and had it boiled out at a radiator shop, all to no avail. Then, a year later, when I removed both water pumps to rebuild them, I found 3 old impeller blades, from previous owners, stuck in the raw water supply elbow after the raw water pump. The two impellers I had changed had no blades missing!

Good Luck,

Doug Shuman