Generator got wet, now what ?

[Dustoff44]

Due to a @#+*## Rule float switch failure and a very heavy rain my generator room flooded to 10" on the Onan 15kw MDJF. No water got into the engine or wet the main circuit boards. After extensive drying out the gen started and runs fine, Voltage was 240 and went down to 170 after 5 minutes
Any sugesstions as to the problem.
*Just installed 2 Ultra SR float switches

 

[ThirdHatt]

Your armature is damaged/corroded. Been there, done that. First time bought new Westerbeke armature for $2850. 14 months later it happened again, then I found Broward Armature who sells them for about half that. Call Broward Armature in Ft Lauderdale, FL and have them send you a rebuilt one. Tell them Byron from Louisiana sent you. Then send your old core back. I toured the factory and they know what they are doing.

Good Luck!

 

[rswirtz]

I came home from work one day and my boat was sitting on the mud off my dock, and my neighbor across the cove hollered "Rick, your boat sank" well the run-about had sprung a link in that I/O rubber boot thing. I dragged it out, took all my used oil out of the garage, pulled the plugs, cranked her over to get the water out of the engine. Pretty cool the way the water shoots outta the plug holes, ran about 4 oil changes through it with my old oil. And everything was fine for the time being. The only thing that ended up needing replacement was the starter, which goes to show, that electrical stuff is more subject to damage than the mechanical stuff. (oh, the boot needed replacing too)

 

[TedZ]

There are short circuit procedures that are used to dry out gen end components that are quite effective. You need to talk to the gen end manufacturer but a direct short and running the generator for 30 or so seconds is a typical procedure...sounds crazy i know.

First you need to confirm voltage regulator and exciter test voltages. If they are ok, check with the manufacturer before you take it apart and spend the $$ for a new armature.

Ted

 

[Passages]

There are short circuit procedures that are used to dry out gen end components that are quite effective. You need to talk to the gen end manufacturer but a direct short and running the generator for 30 or so seconds is a typical procedure...sounds crazy i know.

First you need to confirm voltage regulator and exciter test voltages. If they are ok, check with the manufacturer before you take it apart and spend the $$ for a new armature.

Ted

A direct short sounds...yes, crazy.

Definately talk to the manufacturer before attempting that one.

 

[REBrueckner]

I assume you are taking fresh water here...salt water is another matter. with fresh water immersion, letting electrical things dry before run, or spraying with a dispersant, can sometimes cure otherwise likely issues.

I'd be inclined to restart the genny and see what voltage you get. Especially if a few days have passed and things have had time to dry out.
I can think of several scenarios where upon restart you might just luck out and get your 240 volts back....Talk to the armature place before disassembly and see if the conditions you see are likely armature related issues. It could be another issue; less likely things have happened.

 

[REBrueckner]

On a related issue, I see you have a 58 YF..so I guess your genny(s) is in the bilge under the galley floor. I would NOT, repeat, NOT trust my genny(s) to a single bilge pump.

If you can't stop the source of the rainwater intrusion , can you mount the genny higher without undo effort? I'd urge you to add another bilge pump with a separate outlet, mount maybe maybe six inches above the current one, even if it only pumps to another compartment...saving another outlet hole thru the hull. An alternative is to alarm the bilge water level with another float switch.

The thought of a genny subject to a single bilge pump would cause me to lose sleep!

Good luck!!!

 

[yachtsmanbill]

Tug generators get wet too often, even non use dampness will produce a fault.
We wrap them in plastic with enough open for some air and point a heat lamp at the gen end for a few days and they usually respond well. A blow drier will accelerate the cure as well. Couple of cute 25kw 2-71s here. DC units, but its like apples and watermelons ws

 

[TedZ]

A direct short sounds...yes, crazy.

Definately talk to the manufacturer before attempting that one.

There are many imported generators that are shipped by boat and the absolute first thing you do is run them at full speed with a short circuit. All you have to do is download some manuals, the procedures are clearly outlined.

You still need to check with the manufacturer if the manual is not clear on the procedure.

This quotation is a little more conservative but is not the typical drying method. "On AC generators, drying current may be provided by driving the units at less than rated speed with the terminals short-circuited and excited with very low values of field current. Here again, this should be done only by those with experience in such methods."

Low megging windings are always short circuited on new generators and run at full speed to heat them up to dry them.

The only reason it sounds nuts to you is you do not install generators...i do.

Ted

 

[REBrueckner]

On my prior post I should have also suggested that you can't really tell if it's the armature or the fixed, non rotating coils ..is it called the stator ??...that may be the problem. If you disassemble the genny end, a visual inspection MAY give you the answer..if not, some testing is in order.

 

[TedZ]

The terminology on our type of generators is revolving field, rotor, stator.

This .ppt is a little basic but, for generators, pretty good. It will define the terms.

www.owlnet.rice.edu/~nava102/presentations/lesson15.ppt

One of the things to realize that short circuiting a generator output to dry out fields or rotor does not blow a fuse...surprisingly. The reason is there are no fuses to blow internal to the generator. This is why you see melt downs when generators feed improperly fused or shorted circuits.

Also surprisingly, there is a lot of copper in these units so if you hear a generator governor go wide open and you suspect a short you have time to get to the main and disconnect it. Let the generator run so the heat is dissapated. Seldom is there damage to the generator unless it happens for more than 30 seconds...which is quite a long time.

Just FYI's.

Ted

 

[yachtsmanbill]

In laymans terms, isnt it just shorting the 3 stabs at the disconnect? Is there a way to easily measure temperature rise on the stator, or is that by an amperage calculation? My 20 kw westerbeke was under fresh water for a day, and although its not cooperating, once I can get it to run
I want/need to do a bunch of circuit testing REAL SOON upon startup. Any suggestions? Externally its very dry having been above for close to two years. ws

 

[TedZ]

At the disconnect is fine with like a jumper cable. You need to know from the gen end maker whether they want you to go from leg to leg or each leg to ground assuming it is a 240 VAC unit.

The generator revolving field and rotor should be ok. Circuit boards, exiter etc. need to be checked at the voltage test points. If they are ok try it. If it is not putting out the appropriate voltage it should and the regulator voltage is good, then i would get it hot by the short circuit method. Again check with the manufacturer, but generally about 20 to 30 seconds works. May have to do it two or three times depending...let it cool in between. There is no good way to monitor the temp in the field that i know of. If it was not generating properly and you get a melt down in 20 seconds, it could not be saved in any event and you have not done any harm as a rewind (not a good idea IMHO) or replacement is necessary anyway.

Good luck.

Ted

 

[yachtsmanbill]

Electrical end to be dry tested first to eliminate any internal problems. I dont have a meggar, but what could I expect on an ohm meter? Also, if you dead short the unit, what will the governor ask for? Clemency or death by ROO ROO The pic is in the units control box. It quite a bit drier now. ws

 

[TedZ]

Wow! This doesn't look too good.

The governor will go wide open...run the diesel first to warm it up.

Again the resistance units for fields etc. should be in the manual. Problem is they are not too reliable for damp windings with high resistance numbers.

I would make sure all of the components such as those in the photograph are serviceable. I think the rotor and fields are going to be the least problematic and can be dried out. The components on boards need to be checked as do connections that have crimp nuts, tape etc. Diodes should be ok.

Good luck.

Ted

 

[captddis]

For no apparent reason I have had a few generators fry themselves just after start up with no load applied. In all cases there was no warning. None of them ran away instead they bogged down and black smoked. Then the dreaded acrid electrical smell. Just had a Lamarche charger do this last week as well. Turned on and smoke poured out of the transformer!
Westerbekes usually do not tolerate water in the windings. In most cases it is not cost effective to redo the backend on old generators. I always reccomend replacing them. That is what I plan for my old MDJF when it gives me a problem.

 

[TedZ]

In my experience you are absolutely right. Redoing (rewinding) gen ends is generally unsatisfactory in the long run. I know there are exceptions.

The longer the generator sits idle, the more chance of a melt down at startup WITH NEW GENERATORS. Older gen ends have a tendency to almost never do that but i understand your MDJF did it. Too bad. Good gen end, lousy engine.

Ted

 

[TedZ]

Sorry. As i re-read your post i realize the MDJF is still going.

Ted

 

[captddis]

Yeah after 24 years it still does everything it should. It is on its third exhaust elbow, second regulator board, second fuel pump and third seawater pump. Not bad for all the use and time. and it burns almost no oil between changes. I also have a spare gen.I can't justify replacing it until it breaks!