Heat Exchanger, to bond or not

[lwarden]

Working on sorting out my bonding and noticed the HE's are not bonded. Thru-hulls are Marelon so not bonded, only rudder, rudder ports/glands and struts are bonded directly to a divers plate. Shaft and rudders have zincs as well as trim tabs which are not bonded. Just want to make sure about the expensive HE which I would think should be bonded.

 

[boomerang]

I was waiting for more clarification but no one has replied so I'll go ahead and ask. What do you mean by bonding the heat exchanger? Do you mean the engine? Most have sacrificial zincs and are bonded via being bolted to the block so maybe you mean the ships domestic water heater? I've seen some with a bonding wire attached to the case but ours is not, with no noticeable issues.

 

[Bacchus]

Does the HE have its own anode?
If so it protects the HE and it isn't necessary to bond (connect) to engine or other metals protected by a common larger anode.
My tyranny HE is actually mounted using rubber but it has its own anode that protects the tyranny HE better than a distant common anode could.

 

[lwarden]

Does the HE have its own anode?
If so it protects the HE and it isn't necessary to bond (connect) to engine or other metals protected by a common larger anode.
My tyranny HE is actually mounted using rubber but it has its own anode that protects the tyranny HE better than a distant common anode could.

Yes, the HE has a zinc. So it sounds like it may be OK isolated from the main bonding grid as long as that is in place. The mounting to the engine is not isolated but probably not a great connection. There is a stud on the HE with no bonding wire so this is what makes me think it is intended to be bonded.

 

[Bacchus]

Yes, the HE has a zinc. So it sounds like it may be OK isolated from the main bonding grid as long as that is in place. The mounting to the engine is not isolated but probably not a great connection. There is a stud on the HE with no bonding wire so this is what makes me think it is intended to be bonded.

Just a thought but you may actually be better off leaving the HE isolated as long as it has its own anode.
What I'm wonder is if its bonded to other "systems" whether those could cause the HE anode to sacrifice earlier than expected and actually leave your HE less protected. We are taking very small V differences with galvanic corrosion and relying on a bonding wire to a remote anode may not provide as much protection as an anode that is close by.
With a stand alone HE you will get a feel for a normal rate of decay of the anode and should be able to time replacement fairly well.
Others likely know more about the fine points of protection (boatpoker?)

 

[Lepke]

You get galvanic corrosion any time there are dissimilar metals in salt water. Engines that don't have protection, I add. A problem I've seen in Detroits that has sections of their salt water system separated by hose is the formation of white powder or crystals at the connection points. Bonding the pieces together ends the problem.
In my boat, seacock, engine HE, and salt water pump are protected by zincs. But when checked, cast iron strainers (separated from seacock and pump by hose) had no baskets. PO said they kept dissolving, but did nothing about the problem. I had new baskets made, bonded everything and now no problem.

 

[fgarriso]

Try this from the ABYC.