Marine A/C
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The friendliest place on the web for anyone who enjoys boating.
If you have answers, please help by responding to the unanswered posts.
If you have answers, please help by responding to the unanswered posts.
Comodave
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I like to use bronze if possible. How many A/C units do you have? Groco makes a raw water manifold. You can Google it.
mvweebles
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Here's the Groco one Comodave mentioned.
https://www.groco.net/products/fittings/manifolds/raw-water-manifold
Note that their description cautions against using it. Also note that some equipment manufacturers will void warranty if their kit isn't provided a dedicated thru-hulls (engines and generators for example). That said, the Groco manifold is engineered so the sum of consumers is less than the inlet size, an important factor.
A separate thru-hulls and strainer is of course recommended, but I like having a central sea strainer. I have a totally oversized manifold of 2-inch seacock and sea strainer with valves hanging off for AC. Works fine.
Peter
https://www.groco.net/products/fittings/manifolds/raw-water-manifold
Note that their description cautions against using it. Also note that some equipment manufacturers will void warranty if their kit isn't provided a dedicated thru-hulls (engines and generators for example). That said, the Groco manifold is engineered so the sum of consumers is less than the inlet size, an important factor.
A separate thru-hulls and strainer is of course recommended, but I like having a central sea strainer. I have a totally oversized manifold of 2-inch seacock and sea strainer with valves hanging off for AC. Works fine.
Peter
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mvweebles
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Five self contained units? Lots of pumps....
As a suggestion, would spend the extra money on 316 SS. It's really a much better alloy for salt water resistance. Fabrication cost is the same.
Good luck. I can't offer more than I have. But I'd be interested in more details on what youre doing, boat, why not go with a chiller system, how you'll power that many units, Etc.
Peter
As a suggestion, would spend the extra money on 316 SS. It's really a much better alloy for salt water resistance. Fabrication cost is the same.
Good luck. I can't offer more than I have. But I'd be interested in more details on what youre doing, boat, why not go with a chiller system, how you'll power that many units, Etc.
Peter
Comodave
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Agree on the 316 S/S. It will take a large pump to provide for 5 units.
mvweebles
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Nope. 316 is pretty much impossible in Ensenada. Need to go to San Diego.
Bmarler - I seem to recall you have a very strong background in marine metals and welding. What's your opinion on stainless vs bronze for seawater applications? I would think bronze if possible as it eliminate crevice corrosion of SS (certainly 304).
If the OP is Ensenada, Casa Plomeria in the city has a decent selection of Bronze fittings. Reasonably priced too.
Peter
Bmarler - I seem to recall you have a very strong background in marine metals and welding. What's your opinion on stainless vs bronze for seawater applications? I would think bronze if possible as it eliminate crevice corrosion of SS (certainly 304).
If the OP is Ensenada, Casa Plomeria in the city has a decent selection of Bronze fittings. Reasonably priced too.
Peter
Turtle Blues
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The most common setup I'm seeing on boats with over 3 AC's these days is a central chiller with a variable drive pump and pressure switch to schedule 80 PVC distribution manifold. Even the chiller unit factory piping is sch 80 on the header.
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ksanders
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So...
I installed three AC units in my boat in La Paz this last spring.
I used one large pump, and three relays to turn it on and off.
For a manifold I used groco check valves to share the through hull with the watermaker.
I installed three AC units in my boat in La Paz this last spring.
I used one large pump, and three relays to turn it on and off.
For a manifold I used groco check valves to share the through hull with the watermaker.
Thanks for the input all we are going to stick with the 304 SS raw water manifold after being told stories of 304 SS being commonly used on long range fishing boats for raw water and no problems were encountered. The parties involved have different opinions on whether or not it would be better to switch it out for bronze or something else next time we go to San Diego, before we head south in two weeks. Thru-hull and strainer used are only for ac. Two pumps for five ac’s.
I’d go bronze. For non heated sea water bronze performs very well. For exhaust, which is heated, and has extra corrosive properties, 316 would be my choice.
316 works here too of course, I don’t think crevice corrosion really comes into play as it’s not buried in a wet environment and starved for oxygen. But the ready availability of bronze makes it an obvious choice for me.
The other consideration is appearance. If the op wants a slick manifold then stainless is the best way to get it. Bronze would be a collection of fittings and look a little more crude.
Turtle Blues
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Below is a cut and paste from the Gemlux website. Please excuse the large type. I'm not trying to shout just don't know how to resize.
What Is 304-Grade Stainless Steel?
304-grade stainless steel is made of 18 percent chromium and 8 percent nickel. It doesn't have the corrosion-resistant molybdenum to decrease the speed of rust from de-icing salt and seawater.
Commonly used applications for grade 304 stainless steel include wheel covers, electrical enclosures, auto trim and moldings, storage tanks, kitchen appliances, and equipment that is not around saltwater, chloride, or strong disinfecting agents.
What Is 316-Grade Stainless Steel?
Grade 316 stainless steel contains 16 percent chromium, 10 percent nickel, and 2 percent molybdenum. The molybdenum significantly reduces corrosion from the salt in de-icing chemicals and saltwater. Grade 316 stainless steel also resists pitting and corrosion from spilled acidic drinks, such as soda, and cleaning materials containing chlorine and other harmful chemicals.
You can sometimes get away with using 304-grade stainless steel, which is more affordable. However, if you are boating, even on freshwater lakes and rivers, you'll want to use marine-grade 316 stainless steel. You may pay a little more upfront, but in the long run, you'll save money since you won't have to replace your hardware or accessories as frequently.
In addition to marine parts and accessories, manufacturers use grade 316 stainless steel for pharmaceutical equipment, stainless-steel baskets, chemical equipment, medical/surgical instruments, and outdoor electrical enclosures.
What Is 304-Grade Stainless Steel?
304-grade stainless steel is made of 18 percent chromium and 8 percent nickel. It doesn't have the corrosion-resistant molybdenum to decrease the speed of rust from de-icing salt and seawater.
Commonly used applications for grade 304 stainless steel include wheel covers, electrical enclosures, auto trim and moldings, storage tanks, kitchen appliances, and equipment that is not around saltwater, chloride, or strong disinfecting agents.
What Is 316-Grade Stainless Steel?
Grade 316 stainless steel contains 16 percent chromium, 10 percent nickel, and 2 percent molybdenum. The molybdenum significantly reduces corrosion from the salt in de-icing chemicals and saltwater. Grade 316 stainless steel also resists pitting and corrosion from spilled acidic drinks, such as soda, and cleaning materials containing chlorine and other harmful chemicals.
You can sometimes get away with using 304-grade stainless steel, which is more affordable. However, if you are boating, even on freshwater lakes and rivers, you'll want to use marine-grade 316 stainless steel. You may pay a little more upfront, but in the long run, you'll save money since you won't have to replace your hardware or accessories as frequently.
In addition to marine parts and accessories, manufacturers use grade 316 stainless steel for pharmaceutical equipment, stainless-steel baskets, chemical equipment, medical/surgical instruments, and outdoor electrical enclosures.
Thank you for the input. Almost everything used on the boat is marine grade. We will be conducting a case study on the longevity of 304 SS used in the marine environment for salt water plumbing purposes. We will report back with our findings every year.
To add a little to what I was saying here, I’d never even consider using 304 in a sea water fitting. It will absolutely fail eventually.
Turtle blues posted the reasoning behind it. It’s interesting how little the percentage of moly is in the chemistry, but had such a profound effect.
I will use 304 for certain deck fittings, or interior pieces
Even when using 316 you need to be careful. Welded pieces need to have the right filler, and then be passivated to reduce corrosion at the heat affected zone. I think we’ve had some discussion on this topic previously, but it bears repeating.
Turtle Blues
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I will add 1 more comment. Really trying to convince you not to do that on your own boat. A 3rd world fishing vessel is not the standard of quality you should be working too.
I have been working for a couple of weeks now sourcing all parts to completely re-pipe a system on a 100+' yacht. It will be removed in sections and duplicated / prefabricated by a certified welder as much as possible due to clearance issues. Welding is a whole lot easier and safer in the shop. The cost to do this is astronomical and the insurance underwriter is on record requesting material certification sheets prior to commencement and will require a engineer to survey on completion. This is how much of a difference it makes.
I have been working for a couple of weeks now sourcing all parts to completely re-pipe a system on a 100+' yacht. It will be removed in sections and duplicated / prefabricated by a certified welder as much as possible due to clearance issues. Welding is a whole lot easier and safer in the shop. The cost to do this is astronomical and the insurance underwriter is on record requesting material certification sheets prior to commencement and will require a engineer to survey on completion. This is how much of a difference it makes.
ksanders
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I do not know if it was 304 or 316 SS but...
When I went to the boat parts store in Cordova Alaska I realized that all of the salmon boats used SS fittings and pipe for their saltwater plumbing, and the boats had a lot of plumbing for their various systems.
Circumnavigator
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A fast look at McMaster suggests that 316 is 10% to 20% more than 304 in 1.5" fittings. Considering the cost of the A/C units, that's a small premium.
Also remember that if the 304 fails, you will have a saltwater flood which your pumps may or may not keep up with -- so you are risking your boat (and potentially your life) to save a very few bucks.
BTW, bronze is 50% more expensive than 316.
I used schedule 80 PVC for blackwater lines on Fintry and would consider using it for seawater. There's also PEX -- the heating system on Morning Light has it. Both are cheaper than SS.
Jim
Also remember that if the 304 fails, you will have a saltwater flood which your pumps may or may not keep up with -- so you are risking your boat (and potentially your life) to save a very few bucks.
BTW, bronze is 50% more expensive than 316.
I used schedule 80 PVC for blackwater lines on Fintry and would consider using it for seawater. There's also PEX -- the heating system on Morning Light has it. Both are cheaper than SS.
Jim
Circumnavigator
Senior Member
Agreed -- I suggested it above -- but definitely use Schedule 80, which is gray -- not to be confused with PVC electrical tubing which is the same size and color but has much thinner walls. Scd 80 is much stronger than Scd 40 (which is what you will find at Home Depot) This will have seawater in it and you don't want to sink your boat because you fall against the seawater line.
Go to a plumbing supply house or McMaster for Scd 80.
Jim
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