AIr conditioner pump bonding?

[MikeP]

When I overhauled the ac seawater pump yesterday, I noticed that the pump's manifold (that feeds the water to the 4 ac units) has a bonding fitting on it. This fitting has never been connected to the boat's bonding system. Should it be? The pump motor has a green ground wire that connects to the ac volt ground system which, I would assume, does the same thing...

 

[Angela]

I remember that we addressed this issue once before, and while I cannot remember why, I do recall that the bonding wire was NOT supposed to be attached. Perhaps Ed will remember why. He connected it and then brainstormed with Gil shortly thereafter where they came to the logical conclusion that it was not connected for a very specific (and important) reason. He went back in there right away and took the wire off. I cannot remember why it wasn't supposed to be connected, but he didn't waste anytime getting it off of there.

 

[spcoolin]

If you have a bronze headed pump the manifold will be bonded to the pump by it's threaded connection...

However if you have a March pump with a plastic head this is not true, and the metal manifold will be isolated by the hose & plastic head it is threaded on to...This type installation needs the bond to protect the metal manifold.

Steve~

 

[REBrueckner]

Mike, Bonding and grounding wires are separate systems. The fromer is to connect galvanic protection (zincs) to underwater metal components, the latter is a safety wire to prevent electrical shock to people. They should be kept separate and would ONLY connect at the single common ground point of all systems..dc ground, ac ground, and bonding.

"If you have a bronze headed pump the manifold will be bonded to the pump by it's threaded connection..."

My guess is spcoolin might mean "grounded"....Are the pumps REALLY bonded??? I don't know the pump schematic. Different motors can be grounded in different ways...analogous to some "double insulated" hand drills that don't require a ground wire.

I would recall the thread Angela refers to if I had read it. If anyone has the thread and can post it, I'd be very interested to see and understand it.

I had never thought about it before, but my guess is the copper tubing raw water coils in air conditioner compressors are NOT bonded....and my guess is that is because they are already connected to the air conditioner GROUND via soldered type connections; but if they are connected via non conducting rubber hose sections, which I don't recall seeing on my own cruisair units, then they should likely be bonded. Anybody know what's standard ?? The logic should apply to Angela's post; in my own case, my two a/c units were connected via a hose and tee arrangement.

 

[Boatsb]

grounding and bonding may be two different definitions but if you have a common wire between the 2 systems they are common all through. If I connect a bonded through hull to a grounded device the device is now bonded.

Bonding is for protecting the metals by having the sacrificial anodes in place of metals you would like to keep.

Grounding protects the people on the vessel from stray currents.

 

[spcoolin]

I concur with both above posts...
And I did mean bonded to the pump in the sense that the manifold is mechanically/electrically connected, unless it is a plastic head pump...

To bond or not to bond is the question that I did not answer...Because there are differing opinions on it, and they seem to change...

In my opinion...If it is a plastic head pump & the manifold has no mechanical connection to the pump or otherwise...Yes I would bond that manifold to zinc for galvanic protection...

As far as bonding the pump...Hatteras did it and so does Viking...Even with shore ground connected.

Marine Air states in a big tag attached to new chillers that the warranty will be void if the chiller is Not bonded to zinc...and of course you would ground it to shore as well for electrocution protection...

The dilemma here lies in if that electrical motor (Compressor or Pump) would start leaking to ground...A dead short would trip the breaker supplying the motor...But a small leak (less than breaker rating) would go straight to the bonding system & zincs causing the zinc to erode very rapidly...Once gone, the current would start working on the underwater machinery & thru-hulls until they fall off & sink the boat....

This is another reason I replace all bronze head pumps with March magnetic drive models of similar capacity...They have the plastic/nylon/composite heads/impellers and no motor shaft connection to the seawater to seal (mechanical seal) or to wear out & leak, The impellers don't eat up from erosion or galvanic action, and you only need to tie them to AC power ground because the water never touches the motor in any way (unless the bilge fills)...Plus they just last many times longer than the Oberdorfer or Scott pumps (which kinda shoots me in the foot as far as service) but at least I don't have to worry about leaks...Either Electrical or Water...

Steve~

 

[MikeP]

The grounding system - ac/dc and the bonding system - are, on our 53 at least, linked together. An ohmmeter between a DC ground, an AC ground or a bonded component shows 0 Ohms. That's why I made the assumption that the green ground wire effectively bonds the motor/pump (all metal).

For that matter, the white (neutral) wire has the same 0 ohms reading to ground or the bonding system.

So I couldn't see any reason to separately bond a component that already has the green ground. Along the same lines - and we've had this discussion before, it does seem to me that a metal exhaust collector/pipe should be bonded if it is connected to the engine with a rubber hose...

 

[Boatsb]

If one bond wire is good then 2 are better. if one should fail there is backup.

 

[REBrueckner]

spcoolin posts : "As far as bonding the pump...Hatteras did it and so does Viking...Even with shore ground connected."

Could you explain what you mean by "bonding"?? Is there a dedicated wire from the pump to the bonding/galvanic system??....NOT the one used for a/c electrial ground??



"grounding and bonding may be two different definitions but if you have a common wire between the 2 systems they are common all through. If I connect a bonded through hull to a grounded device the device is now bonded"

And that is BAD if there are multiple connections which can induce unwanted voltages where you don't want them......this has been discussed ad nauseum here, see Nigel Calder....and ABYC standards....

"The grounding system - ac/dc and the bonding system - are, on our 53 at least, linked together."

Yes, all boats should have a SINGLE ac, dc, and bonding ground point. Most boats have lightning ground there too, not the best practice. But not via multiple connections all over the boat, ONLY at the SINGLE common bonding point.....again Calder explains it. This is ABYC standard and has been forever.

"This is another reason I replace all bronze head pumps with March magnetic drive models of similar capacity..."

I had the magnetically driven March pump and would never use 120volts at seawater any other way....I do not know other pump systems....but I agree with the magnetically connected arrangement.....I have yet to see a superior connection. .

"... it does seem to me that a metal exhaust collector/pipe should be bonded if it is connected to the engine with a rubber hose..."

That metal COULD be connected via bonding strap to the engine, but there is little to no reason. There is virtually no electrical conduction via water in such a location, water there is present only when the engines are running...If it were a ferry running 24 x 7, ok, then it would make sense.

 

[spcoolin]

spcoolin posts : "As far as bonding the pump...Hatteras did it and so does Viking...Even with shore ground connected."

Could you explain what you mean by "bonding"?? Is there a dedicated wire from the pump to the bonding/galvanic system??....NOT the one used for a/c electrial ground??

"grounding and bonding may be two different definitions but if you have a common wire between the 2 systems they are common all through. If I connect a bonded through hull to a grounded device the device is now bonded"

And that is BAD if there are multiple connections which can induce unwanted voltages where you don't want them......this has been discussed ad nauseum here, see Nigel Calder....and ABYC standards....

"The grounding system - ac/dc and the bonding system - are, on our 53 at least, linked together."

Yes, all boats should have a SINGLE ac, dc, and bonding ground point. Most boats have lightning ground there too, not the best practice. But not via multiple connections all over the boat, ONLY at the SINGLE common bonding point.....again Calder explains it. This is ABYC standard and has been forever.

"This is another reason I replace all bronze head pumps with March magnetic drive models of similar capacity..."

I had the magnetically driven March pump and would never use 120volts at seawater any other way....I do not know other pump systems....but I agree with the magnetically connected arrangement.....I have yet to see a superior connection. .

"... it does seem to me that a metal exhaust collector/pipe should be bonded if it is connected to the engine with a rubber hose..."

That metal COULD be connected via bonding strap to the engine, but there is little to no reason. There is virtually no electrical conduction via water in such a location, water there is present only when the engines are running...If it were a ferry running 24 x 7, ok, then it would make sense.

It's been my experience that Hatteras will connect the "Oberdorfer" bronze headed A/C pump to the Zinc Bonding system as well as AC ground...Viking Yachts will also....

Steve~

 

[Angela]

My "blueprints" tell me differently. There is not bonding wire to the pump.

 

[REBrueckner]

I just reread this thread to recheck facts...and did not remember seeing this.....spcoolin posted:

"...The dilemma here lies in if that electrical motor (Compressor or Pump) would start leaking to ground...A dead short would trip the breaker supplying the motor...But a small leak (less than breaker rating) would go straight to the bonding system & zincs causing the zinc to erode very rapidly....."

that's a very good description....a small electrical motor leak might also go directly to raw water and cause electrolysis of the equipment.... and is why I do not like electrically active devices (like electric motors) that are in direct contact with sea water (via a metal shaft and metal impeller for example) ...


But for me it's no dilemma: such electrical devices which are connected via narrow diameter hoses to raw water are UNLIKELY to experience galvanic corrosion. And if they were subject to it, it is only during period of operation when cooling water is present. Bonding is unlikely to provide such electrically isolated systems good protection and as spcoolin points out increases the chance of electrolysis (stray current corrosion)....

I just reread Calder, Second edition, and his discussion on this issue is vague for several reasons...he does point out that in electric devices which are bonded, the bonding cable chould be the same size as the dc ground or ac neutral in case the bonding cable is called on in the event either of these fail and the bonding conductor becomes a current carrying conductor.

Another issue Calder does not mention in the bonding section is the increased likelihood such bonding connections can pick up lightning strike remnants which might damage such bonded equipment. The way Hatt's are wired, that's a distinct possibility. And even in larger more modern yachts where the lightning ground system is more likely to be kept separate, with it's own isolated external ground plate, such unwanted pick up is still possible.

A magnetically coupled raw water a/c pump eliminates almost all of the above concerns.....that's precisely why they have the indirect (magnetic) coupling!!!!!!!!!!!!!!!!!! It's an analogous concept to an isolation transformer.....

 

[spcoolin]

Since A/C pumps are below the waterline...A manifold mounted on top of that pump is likely to be at least partially below the waterline...

Many A/C condensing units (not Hatteras per say) are also below the waterline with only the seawater discharge point above...

Fan motors are mechanically/electrically coupled to the condensing (compressor) unit thru the copper tubing that supplies the Air handler with refrigerant...

So actually it's not just the pump that could leak or short to ground & thus the water, if the condensing unit or pump, is bonded to the zinc bonding system...
Any one of three motors could cause problems by leaking IE: Fan, Compressor, or Pump...

The problem with not bonding the A/C system is Galvanic action attacking the solder joints that make up a A/C system thus causing freon leaks...
Because of the dissimilar metal joints it is generally the first place a slight problem will show up...And is evident by the solder joints turning black.

Steve~

 

[rsmith]

I had a friend that was electrocuted when he grabbed the shaft when the boat was on the hard. The result of the investigation was that the grounds and the bonds were tied together. There was a question that the marinas ground system was not properly wired also.(Wildwood Yacht Basin 1970's)
As a result I always connect a set of auto jumper cables to the props then to a ground. If ones not available I pound a piece of metal rod into the dirt.110 volt pumps that come in contact with salt water are a problem which is why I also use the magnetic drive pumps. plus if they get crap in them and jam they just slip and dont burn up

 

[sgharford]

As a result I always connect a set of auto jumper cables to the props then to a ground. If ones not available I pound a piece of metal rod into the dirt.

That's a great idea that I'm going to borrow! I got shocked pretty bad earlier this season installing new props due to reverse polarity condition at boat yard outlet. Got me pretty good as props just reconditioned, both hands on them as I was setting onto shaft. Thank God I was in a squat position instead of knees in the wet dirt beneath me.

 

[Robby]

Roger Brought this up at the Hatt school this year.He reccommended grounding any boat on the hard.There was some talk about some boats having Isolators and some dont.Hopefully Sky or someone else that was in the class will jump in here.We had quite a discussion about it.Robby

 

[MicroKap]

Roger W. had said that when the boat is on the hard, just to be on the safe side he takes a length of chain and wraps it around the shaft and hangs it so it touches the ground.

 

[sgharford]

Roger W. had said that when the boat is on the hard, just to be on the safe side he takes a length of chain and wraps it around the shaft and hangs it so it touches the ground.

Like that idea even more - set it and forget it.

 

[Robby]

I cant remember everything that was said but some boats need it and some dont.Sooooooo-Whats its gonna cost you to GROUND your Boat.A short lenth of wire to the ground on the box or to a lenth of steel rod driven in the ground?This whole thred seems to try and disquinish between grounding and Bonding:To me as a mech grounding is bringing the vessel(dont make a damn if its a boat spaceship or car)directly to earth.Bonding can be from one component to another and then to earth or in this case dicipated along the lines of a boat at sea.I hate to bring this up but I am a airplane Mech.We have static wicks to dispose of static electricity generated by friction of the mass of air over the vessel.So like I said earirly ground your boat,its cheep Ins.

 

[Banshee36]

Great Thread. I have a march Sealed and watercooled AC pump. I noticed when running one day that a fine mist of water was spraying out of the pump somewhere. Last week took the pummp out and noticed the stainless steel tubes that cool the pump motor when corroded. Well at 600.00 to replace I coated the tubes with marine tex just to buy a little time to get a new pump. Just curious, any one else had this problem.
JW