Seawater pump/motor

[Seas the Moment]

Folks, my 220V Orberdorfer seawater A/C pump/motor went bad. I shipped it to Depco for rebuild. They called back and said the pump was shot and motor was ruined from water damage. The tech said the bronze pump was "rose" colored and corroded indicating electrolysis. I had a "hot spare" and all is working. Here is question, there is a 10gauge wire between the pump casing and a bolt on engine. Is this a proper place to ground/bond the pump? I want to get out in front of this before this happens again.

Thanks

 

[Pete]

The AC power to the pump should be 3 wire boat cable. Most often red/black/green wires in a jacket.The green wire should be attached to the case and run back to AC panel joining all other ground wires on a ground block. Green wire AC grounds are tied to the bonding system at one common point. My opinion is this separate bonding wire from the pump case to the bonding system is incorrect.

BTW, do you have a green wire connected to the pump case running back to the AC panel also? If so, this wire to the engine block is creating a parallel path for all AC grounds to the bonding system.

Pete

 

[GJH]

I wired my motoras Pete described and ran a bonding wire from the pump head, not the motor. to the copper bonding stip there in the pump well. I figured they ran the bonding strip there for a reason. That bond was mssing the first few years I had the boat, and I managed to crud things out in a simialr way yours was (some OS issues were added [OS= Operator Stupidity])

After installing the new pump and bonding it, no signs of issues or corrosion in the ensuing three years or so. The original pump was OEM, so I guess the proof will not bear out for a few decades. You should ask Depco and Sam's for their opinion.

 

[Pete]

Is the pump section electrically isolated from the motor on this unit. I have not seen one. If the motor and pump are not electrically isolated, then neither should be bonded, as this will create a parallel path for all AC ground to the bonding system with a path through the unit's case.

Pete

 

[Angela]

I used to go through the Oberdorfer pumps, too, but mine was a problem of developing a pinhole leak in the pump head - got it in the same spot over the same amount of time, in three new pumps. Now, I have a March pump and it does not corrode since it is made of some sort of fancy plastic. Somewhere, I learned, but cannot remember why it was, but it wasn't supposed to be connected to the bonding system. I can't explain it, but I think it had something to do with by doing so, the AC got connected to the DC system, but I can't be sure of that. I just remembered that it didn't go there. Right or wong, I can't say for certain, but I have a March pump now, so it doesn't seem to matter anymore. I think I'm on my third or fourth year with the March. I was going through Oberdorfer heads every year.

 

[Pete]

I can not think of an exception to the rule that NOTHING powered by AC power should be connected DIRECTLY to the bonding system on a boat in the sizes we have and constructed of fiberglass. The green wire ground is the proper path to the bonding system, and only the green wire ground . And always validate that the green wire ground at AC devices has continuity to the bonding system (through the proper path). Use a multimeter one probe on the case of the device where the green wire is attached and the other probe to the bonding band on the stringer nearby. Check AC voltage, DC voltage (both should be zero) then the lowest ohm scale and it should read zero. Anything different needs investigation. You will likely need to scratch the probe tip on the bonding band to get a good connection to the copper.

Pete

 

[GJH]

Good points Pete. I did so when I hooked it up. I forget what Angela's root cause was on her pumps; all I know is that my first Oberdorfer lasted 30 years until I killed it via OS and the next one was like new three years after install. And I should note that pump got used two or three hundred days a year.


And one other thing, the AC DC and bonding system all meet at a common ground point.

 

[Seas the Moment]

Thanks guys! I will do as Pete and George suggested... thanks again!