Hx zinc and bonding

weekendrken

weekendrken

.
May 7, 2011
281
C - 30 # 3573 Lake NormanNC formerly Bflo NY
Hi RC,

Interesting dilemma - to prevent wear on the Hx, many recommend putting thin rubber (bicycle tube) between the Hx and mount/clamps. But Seakamp warned - then it's not bonded to the engine.

What's your take/recommendations, and it's not bonded will the anode protect the Hx?

Ken K
 
Charles Erwin

Charles Erwin

.
Jan 30, 2012
1,123
Nor'Sea 27 "Kiwanda" Portland/ Anacortes
Ken -

I am seriously curious. Did Seakamp explain why "bonding" - in this case an electrical connection between the motor block and the exchanger - would be useful?

The Seakamp or SanJuan Engineering heat exchangers I have seen have pencil zinc anodes. With healthy anodes the exchanger is protected from galvanic corrosion.

Further - seawater is kept separate from the motor so the only electrolyte the exchanger and the motor have in common is coolant - same as a car or truck.

If "bonding" is required then I reckon you could make a jumper wire from the exchanger to the motor and still use rubber mounting isolation material.

Charles
 
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Maine Sail

Maine Sail

.
Feb 6, 1998
11,672
Canadian Sailcraft 36T Casco Bay, ME
Under normal use the pencil zinc is all that is necessary. Owners get lazy though.... On my own boat I have an Earth lug on the HX just in case I forget to change the pencil zinc in a timely manner. This just runs to the engine Earth...

If you are really concerned about it you can add a 5/16" ring terminal under the end cap bolt and run a green wire to the engine Earth. Still the best option is to keep up with the pencil zincs...

Keep in mind all these HX are painted so any bond through brackets would need to be made where the paint has been removed...
 
weekendrken

weekendrken

.
May 7, 2011
281
C - 30 # 3573 Lake NormanNC formerly Bflo NY
Maine Sail said:
Under normal use the pencil zinc is all that is necessary. Owners get lazy though.... On my own boat I have an Earth lug on the HX just in case I forget to change the pencil zinc in a timely manner. This just runs to the engine Earth...

If you are really concerned about it you can add a 5/16" ring terminal under the end cap bolt and run a green wire to the engine Earth. Still the best option is to keep up with the pencil zincs...

Keep in mind all these HX are painted so any bond through brackets would need to be made where the paint has been removed...
Click to expand
RC, admitting here that I don't fully understand under what circumstances there is and is not protection to which components -- so just to be sure that I understand this correctly (and as I had thought) the pencil anode protects the Hx -- no matter whether the HX is bonded to the block or not?

If that's so, I can't see why Seakamp would recommend that it be bonded (or as they said 'grounded' to the block.) (but I am going to find that out!) (tho I am told that newer ones have a bolt or stud for a bonding jumper.)

I think I need to find a good, but easy to understand, primer on galvanic corrosion. It seems that bonding the Hx and pencil anode to the block, would amount to attempting to protect the block and all else by sacrificing the pencil?

Ken
 
Charles Erwin

Charles Erwin

.
Jan 30, 2012
1,123
Nor'Sea 27 "Kiwanda" Portland/ Anacortes
After a bit more thought -

A low resistance electrical path between the heat exchanger and the motor is important but this is really not part of galvanic protection. ABYC bonding rules literally read require all metal components to be bonded. There are exceptions but heat exchangers are not listed among them.

Apart from those rules - just about everything that involves a fixed power systems has all its metallic parts bonded - even aircraft, spacecraft. Cars and trucks also have bonding straps from part to part - they look like little woven copper jumpers.

One assumes this bonding is primarily to prevent corrosion caused by stray currents not galvanic currents - and zincs alone won't last long exposed to stray current.

One thing is for certain - bonding the heat exchanger with a jumper if you insulate the mounting bracket sure won't hurt anything.

Charles
 
weekendrken

weekendrken

.
May 7, 2011
281
C - 30 # 3573 Lake NormanNC formerly Bflo NY
Charles Erwin said:
Ken -

I am seriously curious. Did Seakamp explain why "bonding" - in this case an electrical connection between the motor block and the exchanger - would be useful?

Charles
Click to expand
Charles,

Here is the most-recent exchange.... seems they don't know "why". just do it.
I would say that a bonding jumper would be the best answer -- as you say it can't hurt.

Ken

My understanding is that. bonded or not, the Hx zinc or magnesium pencil anode will protect the Hx, whether it's bonded or not.

Is that not so -- i.e., why is bonding it necessary? And besides, with everything painted, the body would have to be scraped to clean metal for the mount to actually create a reliable bond.

Thanks,
Ken​

Hi Ken we have been asked this many times . is always best to be in contacted with engine when possible On generators we have a ground stud on our heat exchangers and does seem to extend life I have came to a point to let the customer do what they see best. Seems no one has ever pinned down the electrolysis issues . there are all kinds of publications on it and they all have their own opinion.​
 
Maine Sail

Maine Sail

.
Feb 6, 1998
11,672
Canadian Sailcraft 36T Casco Bay, ME
Guys,

The bottom line is this::eek:



At least 5 dissimilar metals in a Westerbeke HX..... It is then filled with an electrolyte!:doh:

If the pencil zinc breaks or wears away the HX can eat itself. Many owners ignore the pencil zincs....:cussing:

If you can it certainly won't hurt to run a bonding wire to the engine block..... As I mentioned before just place a ring terminal under the end cap bolt & run a green wire to the block / Earth, and you're now bonded to the shaft zinc to help save the HX.....
 
weekendrken

weekendrken

.
May 7, 2011
281
C - 30 # 3573 Lake NormanNC formerly Bflo NY
Maine Sail said:
Guys,

The bottom line is this::eek:

.....
Click to expand
Definite bottom line - it will be protected w/ thin rubber, and a 10 awg bonding wire directly to the block or a (paint-free) Hx mounting location/bolt. Thanks, RC!

Ken
 
M

MWybo

.
Apr 19, 2013
13
Cabot 36 Shelburne, NS
Is the engine still Earth if one uses a flexible coupler for the prop shaft ?

If not how does one provide an Earth ground with the use of a flexible coupler ?

Thanks
 
Maine Sail

Maine Sail

.
Feb 6, 1998
11,672
Canadian Sailcraft 36T Casco Bay, ME
MWybo said:
Is the engine still Earth if one uses a flexible coupler for the prop shaft ?

If not how does one provide an Earth ground with the use of a flexible coupler ?

Thanks
Click to expand
You jump across it or use a shaft brush. This would be required under standards such as the ABYC, when a flexible coupling is fitted.

"ABYC P-6 Propeller Shafting Systems


6.5.5.2

If a non-conductive flexible coupling is used, an alternative means of grounding the shaft must be provided."
 
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