Metalurgy questions Isotherm asu sp thru hull metal composition is it seaworthy?

[Eastward ho 24]

I'm eyeing up the Isotherm asu so holding plate unit. I'm a little Leary of the galley sink through hull..... I know bronze is the metal of choice for below the water line. I've been in trying to decide if the thru hull will be safe. Crib my understand there's a sacrificial zinc attached to it. Here's the info I have on it's composition. Any one care to weigh in? I'm outfitting my down Easter 32 boat for extensive cruising and it's in salt water year round. I'm trying to make her as low maintenance and safe as possible. My galley drain is well below the waterline. I'm being a little uneasy about this through hull...opinions? Facts? Here's an attachment of the specs for the thru hull

[tkeithlu]

Wow! I wish everything I have under water had specs like that. They've gone way out of their way to reduce the potential for corrosion. Back off a minute here and think about the general safety of your boat in the realm of underwater corrosion. Assuming that you've done the bonding between everything (including this through hull and your anodes) and have loaded up with anodes, the only additional step you might consider is investing in a silver corrosion reference electrode. They cost $100-$125. You hang it over the side, and connect your voltmeter between it and those bonded parts. You need a volt or more. If you've got it, there's nothing under the waterline corroding except your anodes. Enjoy yourself, or at least worry about something else.

[Typhoon]

Just go with an air cooled system . Much more reliable and you can use it when you are on the hard .

Regards John

[hellosailor]

Eastward-
I would suggest that IsoTherm's main concern is protecting their cooling loop, not so much the thruhull.
When I went looking into "proper bronze" thruhulls a decade ago, some of the top names said their alloy was proprietary (as if a college chem lab couldn't unravel that) and others insisted that brass and bronze were the same thing, the only difference being exact ratios and those can and do overlap in standard alloy definitions.
I wound up thinking that genuine Marelon, glass reinforced nylon, is actually the way to go. It isn't perfect, no, but it eliminates the electrolysis question and if you don't install them where someone or something is going to whack them...not such a bad way to go.

Then at least you'll only need to worry about putting a zinc in there to protect the cooling loop. You may lose the fridge, but that won't sink the boat.

[OzePete]

Raw water (sea) and 12VDC power should never mix.
We manufacture both air and air/ water cooled 12VDC systems with thousands in service, so we are not prejudiced one way or the other. We could never understand why anyone would use raw water, adding another level of maintenance with current corrosion and therefore system destruction always a possibility, let alone having yet another hull penetration in some cases!
Contrary to what some say, water cooling is superior in many installs especially for tropical use or when the condensing unit is located in a hot or air restricted area. Water is a far better medium for disposing heat than air.
Our 'water cooled system has fresh water circulation through the condenser to boost the air cooled condenser as required. We only recommend for re-cycling fresh water from the boats tank with the 1/3 amp micro pump supplied, not raw water.
Like John says use an air cooled only system unless your situation demands water cooling also.

Cheers OzePete Ozefridge | 12 Volt Refrigeration Systems

[iseadreamer]

15 years ago we plumbed our Isotherm refrigeration to one of our three fresh water tanks. No more zinc corrosion. No more cooling system maintenance. Can be used on the hard. What's not to like?

[Pueo]

I've had two Isotherm SP systems on board for over 10 years. Not one problem or hiccup. No heat from the air cooled system in the boat, much smaller systems, quiet, low amp draw. I use one system for refrigeration and one for freezer. They are set up so I can switch them out if needed.

[hellosailor]

Several people have mentioned using their fresh water tanks to cool the refrigeration (cooling water) lines. Any problems with keeping those lines clean, or access for cleaning them, in the tanks? Any tank growth issues?

[robert sailor]

You won't have problems with the quality of bronze, it's good stuff. I had that exact system on our boat for 4 years. I didn't like replacing the special zinc every 6 months and cleaning the thruhull so I temporarily put an air cooled radiator in to check on power use...We are in the tropics but we do have a very well insulated and sealed fridge. There was really no difference in power use so this year i pulled it and went to an air cooled system. No more diving and a simpler system.

[strandte]

I have read about people cooling their refrigeration systems of in a fresh water tank. I see there are at least one person here on this thread that uses this technique on his boat. I'm interested in knowing more about how large the fresh water tank is, how many liters fridge and freezer is cooled in this tank and what kind of temperature the water tank acquire. Is the tank an in hull GRP tank or a stainless steel free standing tank which would cool off in the air internal to the boat?
I'm tempted to try this solution my self, but I have concerns about higher bacteria growth in the tank due to higher temp and also leakage of cooling fluid into the fresh water tank. Would one have to have a water maker to keep the tank topped up to keep the cooling working optimally, or does it work satisfactory with eg 50% full fresh water tank? Is the water from this tank used for drinking water?
I hope several others here have interest in this questions just like me, and that the questions isn't to far off the main issues discussed here. In other words, I hope this post isn't seen as a high jack of the thread.

[Eastward ho 24]

Air cooled sounds good... Although I am putting access to the water tanks and I have (2 )50gal tanks so I think I may be a good candidate for the tank cooling. I'm with you on that any one care to share how this is done? I'd there a big difference in power draw? between water cooled unitd and the water cooled ones?

[boatpoker]

35% zinc content makes this a sacrificial anode. Scares the heel out of me.

I love how their specs give specific metals content for all other metals in the alloy but when it comes to the zinc they say .... "the rest".

PS. I'm a Certified Marine Corrosion Analyst.

[fabricator-ken]

I have had installed since 2009 the Isotherm through hull cooling unit. It works done have never had an issue with it. Changed the anode only once in that time whilst we sailed around the world.

[OzePete]

Originally Posted by strandte

I have read about people cooling their refrigeration systems of in a fresh water tank. I see there are at least one person here on this thread that uses this technique on his boat. I'm interested in knowing more about how large the fresh water tank is, how many liters fridge and freezer is cooled in this tank and what kind of temperature the water tank acquire. Is the tank an in hull GRP tank or a stainless steel free standing tank which would cool off in the air internal to the boat?
I'm tempted to try this solution my self, but I have concerns about higher bacteria growth in the tank due to higher temp and also leakage of cooling fluid into the fresh water tank. Would one have to have a water maker to keep the tank topped up to keep the cooling working optimally, or does it work satisfactory with eg 50% full fresh water tank? Is the water from this tank used for drinking water?
I hope several others here have interest in this questions just like me, and that the questions isn't to far off the main issues discussed here. In other words, I hope this post isn't seen as a high jack of the thread.

Great topic. I and my company have manufactured many thousands of both air cooled and air / water cooled refrigeration systems so not prejudiced one way or the other.
Firstly no 'one size fits all'! Some projects are fine operating as air cooled only while others would function better with water cooling if they are to be used in the tropics or the refrigeration condensing unit is located in an air restricted or hot area. The task is to get rid of heat!
Many water cooled only systems use a vague raw water cooled condenser. We are against this method as there are better alternatives than exposing your refrigeration system to the real possibility of being destroyed by corrosion (SC electrolysis), the additional maintenance and lack of condenser control.
We use a hybrid system where our AW480 system operates as an air cooled system until the condenser temperature reaches 43C. At which time a micro pump recycles fresh water through food grade materials, from the boat's tank. This method ensures that air cooling is always available for the compressors electronic driver and can operate as air only if needed.
Our heat exchange involves a unique condenser which has two coil passes for refrigerant and one for water. The water collects heat from the refrigerant via the condenser fins therefore there is NO direct contact of refrigerant to water.The micro pump when engaged adds 1/3 of an amp (12VDC) to the consumption but this is more than compensated as the compressor consumption drops approx 1.2 amps with the water cooling on.

Sketch of Condenser (Plan View)
This is how the Ozefridge air / water cooled system works but this is difficult to apply to an existing air cooled system.
One suggestion, albeit crude, for adding water cooling to and existing system is to add a 'detour loop' of say 1/4" copper tubing from the compressor discharge pipe. Allow enough tube in the loop to have say two meters coiled inside the boats water tank. This process would require some silver soldering, system evacuation and re-gassing so should be done by a qualified fridgie.

It should be noted that the water cooling advantage is dependant on many factors enough to say that the hotter the environment the more important water cooling assist can be. For example an air cooled only condenser will run with a high side pressure of up to 175PSI in the tropics, this reduces to under 130PSI with water cooling in the same situation.
To explain why: An air cooled condenser in a 40C environment runs at least 50C, this is approx 175PSI (All past Danfoss and now Secop data is at 55C condensing temperature).
Water is cooler than air, usually less than 35C, and with a much better heat transfer rate, a water cooled condenser is far more efficient in these tropical conditions. So if intending to head to the tropics and you want refrigeration when it's most needed, simply boost your fan capacity by *increasing fan size / thickness or add water cooling. *Note: If increasing fan size, best to power via a relay from a separate 12 VDC supply switched from the Motor drivers now fan circuit, and not from the motor driver itself.

Cheers OzePete www.ozefridge.com.au

[bsurvey]

what a waste of money

buy marelon and stop worrying you'll never have to replace them