Marine A/C installation

[paj637]

I am contemplating installing a 6.5K Mermaid reverse cycle unit that I recently aqquired (for almost free) in my 2006 . I want to minimize underwater hull penetrations and am considering placing a 500 gph live baitwell pump or similar inside the ballast tank that would pump seawater cooling to the a/c unit and then discharge it overboard as normal. The baitwell pump will need to be submerged and should easily be able to handle the run time needed for my anticipated use. One added benefit of this method is being able to pump my ballast if need be. ( would of been handy over this New Years trip in the upper FL Keys when I beached too shallow) It would require me to install a 4" access in the top of the ballast tank to install the pump and plumbing. The ballast tank gate valve would need to remain open while a/c was running. I also could send the condensation back to the ballast tank or exhaust overboard with a enductor setup like the meramid condensator. Looking to install the unit in the stbd V berth stowage area. Any thoughts?

[mastreb]

Presuming that you don't intend to use the AC while on the water, this sounds like a good idea. A problem you may run into is that the v-berth is the "top" of the ballast tank, so depending on how much weight you're displacing, the water level in the tank may not come up to the pump. You will likely need to have a tube going a few feet into the ballast tank to guarantee that you won't gulp air. Given that, you could probably just go through the existing vent hole under the port vberth and do away with making any kind of penetration (which is what I would do). If a 1/2" clear flex tube will do the job, I'd use that, and just pull the tube out to seal the vent hole when you get underway.

You can't pump ballast out of the ballast tank or run with the gate valve open safely because the boat is unstable unless the ballast tank is completely full, so this would be for dockside use only. I like it!

[paj637]

The inexpensive bait well pumps are not self priming and need to have their suctions submerged. I would only use the A/C on the hook with a generator or in a marina. My ballast pumping was geared towards being able to remove it to refloat the boat earlier if I ever get stuck again on the bottom when I anchor shallow/beach stern to the shore. Usually due to the incline, opening the stern gate valve will not drain ballast.

[DaveB]

The smallest Mermaid is the 5.5 and use to be the 5.0 that I installed with thru hull and strainer.
I wouldn't try to put a fitting in your Ballast tank as the water outside is much cooler. Best to put a tru hull Brass ball Valve Seacock at lowest point close to center hull outside of waterballast tank.
Keep in mind you will have to keep your ballest tank open to get cooling water in.
Your Idea for cooling the coils for refig. or aircondition is good. much better than air cooled but only a step better.
Closed ballast will generate a lot more heat in cooling the system.
Thru hull seacock with water strainer still is best for AC and refig. cooling below 26-27 N Latituide.
I use fans and EdgeStar portable Refig. to keep me and others happy.
When in the Keys in July, I will bring the 5000 btu Air (In Companion way hatch) and get a slip at Pennikamp for $30 a day and plug in.
Dave

I am contemplating installing a 6.5K Mermaid reverse cycle unit that I recently aqquired (for almost free) in my 2006 . I want to minimize underwater hull penetrations and am considering placing a 500 gph live baitwell pump or similar inside the ballast tank that would pump seawater cooling to the a/c unit and then discharge it overboard as normal. The baitwell pump will need to be submerged and should easily be able to handle the run time needed for my anticipated use. One added benefit of this method is being able to pump my ballast if need be. ( would of been handy over this New Years trip in the upper FL Keys when I beached too shallow) It would require me to install a 4" access in the top of the ballast tank to install the pump and plumbing. The ballast tank gate valve would need to remain open while a/c was running. I also could send the condensation back to the ballast tank or exhaust overboard with a enductor setup like the meramid condensator. Looking to install the unit in the stbd V berth stowage area. Any thoughts?

[paj637]

Dave, it's me...Phil. I would keep the ballast gate valve open.

[mastreb]

I wouldn't try to put a fitting in your Ballast tank as the water outside is much cooler.

This would be the case if the water intake and exhaust were both in the ballast tank--it would quickly not work at all as the ballast tank water heats up.

However, if you draw from the ballast tank and dump overboard with the gate valve open, the ballast tank will remain very close to out-side water temp as new water is drawing in at the same rate that its being pumped into the A/C. I believe that's the plan. Even in the case that you started with warm ballast tank water it would quickly circulate through to the ambient water temp.

The heat would only be different if the ballast tank were a closed system. I think it's a pretty good idea personally. Where do you intend to run your drain line? You'd want it away from the stern so you're not pulling the warm water back into the ballast tank.

Also consider that if you forget to open the gate valve, you will run your pump and heat exchanger dry. Be sure that won't damage anything.

[DaveB]

Hi Phil, Great Trip to the Keys, nothing like good Sailers having a Campfire or two in the Keys.
As I mentioned Gate Valve open on the hook.
Dave

Dave, it's me...Phil. I would keep the ballast gate valve open.

[DaveB]

Since you are going to put in a sea cock why go thru water ballast? best to keep that water ballast as one container and go outside it with a truhull.
You still need a water strainer and tru hull seacock...better to keep them seperated for safety and seperation.
Out side the ballast you don't have to open ballast and forget closeing it next sail.
I wouldn't want all that nasty tuff in the Ballast tank cooling my AC or refig.
Dave

I wouldn't try to put a fitting in your Ballast tank as the water outside is much cooler.

This would be the case if the water intake and exhaust were both in the ballast tank--it would quickly not work at all as the ballast tank water heats up.

However, if you draw from the ballast tank and dump overboard with the gate valve open, the ballast tank will remain very close to out-side water temp as new water is drawing in at the same rate that its being pumped into the A/C. I believe that's the plan. Even in the case that you started with warm ballast tank water it would quickly circulate through to the ambient water temp.

The heat would only be different if the ballast tank were a closed system. I think it's a pretty good idea personally. Where do you intend to run your drain line? You'd want it away from the stern so you're not pulling the warm water back into the ballast tank.

Also consider that if you forget to open the gate valve, you will run your pump and heat exchanger dry. Be sure that won't damage anything.

[paj637]

I envision putting in a 4" access port in the top of the ballast tank near the vent to be able to access the baitwell pump on the bottom of the ballast tank.

Installation inside the tank would do two things: 1) make a through hull penetration for pump suction not needed and 2) allow me to pump the ballast tank overboard if I ever needed to.

The discharge out of the A/C unit would go overboard via a thru-hull above the waterline on the stbd side fwd of the head fwd bulkhead.

My only question remaining is whether or not the baitwell pump would have enough suction head sitting in about 6 inches of water to not suck air from time to time?

Anyone know how deep the tank is in the vicinity of the vent plug on a 2006 ????

[Russ]

Since you are going to put in a sea cock why go thru water ballast? best to keep that water ballast as one container and go outside it with a truhull.
You still need a water strainer and tru hull seacock...better to keep them seperated for safety and seperation.
Out side the ballast you don't have to open ballast and forget closeing it next sail.
I wouldn't want all that nasty tuff in the Ballast tank cooling my AC or refig.
Dave

I agree with Dave. That seems like a lot of effort to avoid a thruhull fitting. Sucking up who knows what kind of junk from the ballast tank can't be good (bio animals, fiberglass leftovers from factory). Below the water line thru hulls are not that bad.

If that's your concern, toss a hose over the side to draw water in and keep the ballast tanks as ballast tanks. You could pull it through the engine well and drop it in the sea when A/C is needed. That's how I run my washdown pump. I toss the intake over the back when I need it.

[paj637]

OK, let me bare my soul. I beached last month and was stuck on the sand at Short Key while mostly everyone left. (John, not like you beached! ) If I could have pumped my ballast tank, I could have floated off in short order, This seems like a way to kill two birds with one stone. At the most, I can see running my a/c for 3-5 days at a shot. Not much time for fouling to be an issue. Also, the access cover on the ballast tank would allow me to clean the suction of the pump just as easy as cleaning a raw water strainer.

[mastreb]

Do it. Report back. Worst case it doesn't work and you then make a through hole fittIng. Earth continues to rotate about its axis as if nothing had happened.