Doing Your Own Air Conditioning

Several recent posts have mentioned installing or revitalizing a/c systems. I have recently done both and hope the following may be of use to those about to tread the same path.

My 1984 DeFever had three self-contained Cruisairs: two originals and one new Stowaway unit installed by the PO. None of them produced more than a dribble of cold air. My a/c guy found the refrigeration side of all three units to be healthy, so the problem(s) were elsewhere.

These units have squirrel-cage fans. The fan blades are narrow strips of metal bent into a shallow "V" about their long axis. Over the years, the "V" fills up with crud so that, at first glance, the blades appear flat. Cleaning and repainting the blades produced a remarkable increase in the fans’ performance.

Even with the fans working properly, there was still precious little air coming out of the vents. The ducting was the Slinky Spring type with a glass wool insulating jacket and welded boxes at the junctions. It seemed that enough run of ducting combined with plenty of changes in direction was using up all the puff that the fans were putting out. The new Stowaway unit was located under the bathroom vanity in the aft cabin and I tackled that first. I re-located the air outlet to make the run as short as possible. 4" PVC waste pipe with two layers of insulation made a nice smooth duct. The result was better than I had hoped: lots of lovely cold air, even on the lowest fan speed. Can you spell duvet?

I had bought two new Pioneer Mariner a/c units when I bought the boat, because I didn't trust the two old Cruisairs. My success with the first unit prompted me to tackle the other two. As I was going to relocate these units, I decided to install the two new ones and put the old ones up for sale. I located the new units as close as possible to the outlets and 4" PVC was again used for the ducting. Both performed beyond my expectations. In fact the unit cooling the forward cabin worked so well that the place was like a walk-in freezer. The manufacturer told me I couldn’t slow the fan down beyond its lowest setting, so I ducted some of the air into the saloon (pic). Here are a few of the things I learned along the way:

When buying new, choose models who’s squirrel-cage fan can be rotated from horizontal through to vertical. Make sure every unit has a bug screen just in front of the evaporator.

If possible locate the units where you have good access to them. Sacrifice some storage space if necessary – you will be glad you did. Leave adequate space for the air flowing into the unit.

Install self contained a/c’s at a slight angle so that the drip tray drains easily. Route the drains directly overboard if possible. If not, then shower sump or pump sump are acceptable.

Provide a separate breaker for each unit. If something electrical goes wrong with one of them it won’t stop the others from working. Fit each unit’s power supply with a GFI receptacle next to the unit and fit the unit with a matching plug. This simplifies installation and subsequent removal. The indicator light on the GFI receptacle gives confirmation of power reaching the unit.

Install a Perko (or similar) sea strainer before the raw-water pump. Locate it where it is easy to see and below the water line so it self-fills.

Small 110v centrifugal pumps make good raw-water pumps for a/c systems. They are quiet and efficient, but they don’t self-prime. Mount below the water line and close to the strainer.

Run the raw-water pump’s power supply to a junction box next to (and above) the pump. This makes changing the pump a breeze.

My pump had a trigger switch which only ran the pump when the a/c’s wanted it. I removed this and replaced it with a conventional breaker and indicator light. One less thing to go wrong – just remember to switch the pump on or off.

Replace the hoses that feed sea water to the a/c units. Make sure there is a proper manifold so that each unit gets its fair share of water.

I recently replaced the two old units in my boat and installed two new Flagship 18.5k btu air/heat units in my boat. Having a hard time keeping the boat in one place because of the air volume they put out. Instillation took less than a day for both and that included running the ducts and putting in new March high volume pumps.

Shoalwaters said:

Several recent posts have mentioned installing or revitalizing a/c systems. I have recently done both and hope the following may be of use to those about to tread the same path.

My 1984 DeFever had three self-contained Cruisairs: two originals and one new Stowaway unit installed by the PO. None of them produced more than a dribble of cold air. My a/c guy found the refrigeration side of all three units to be healthy, so the problem(s) were elsewhere.

These units have squirrel-cage fans. The fan blades are narrow strips of metal bent into a shallow "V" about their long axis. Over the years, the "V" fills up with crud so that, at first glance, the blades appear flat. Cleaning and repainting the blades produced a remarkable increase in the fans’ performance.

Even with the fans working properly, there was still precious little air coming out of the vents. The ducting was the Slinky Spring type with a glass wool insulating jacket and welded boxes at the junctions. It seemed that enough run of ducting combined with plenty of changes in direction was using up all the puff that the fans were putting out. The new Stowaway unit was located under the bathroom vanity in the aft cabin and I tackled that first. I re-located the air outlet to make the run as short as possible. 4" PVC waste pipe with two layers of insulation made a nice smooth duct. The result was better than I had hoped: lots of lovely cold air, even on the lowest fan speed. Can you spell duvet?

I had bought two new Pioneer Mariner a/c units when I bought the boat, because I didn't trust the two old Cruisairs. My success with the first unit prompted me to tackle the other two. As I was going to relocate these units, I decided to install the two new ones and put the old ones up for sale. I located the new units as close as possible to the outlets and 4" PVC was again used for the ducting. Both performed beyond my expectations. In fact the unit cooling the forward cabin worked so well that the place was like a walk-in freezer. The manufacturer told me I couldn’t slow the fan down beyond its lowest setting, so I ducted some of the air into the saloon (pic). Here are a few of the things I learned along the way:

When buying new, choose models who’s squirrel-cage fan can be rotated from horizontal through to vertical. Make sure every unit has a bug screen just in front of the evaporator.

If possible locate the units where you have good access to them. Sacrifice some storage space if necessary – you will be glad you did. Leave adequate space for the air flowing into the unit.

Install self contained a/c’s at a slight angle so that the drip tray drains easily. Route the drains directly overboard if possible. If not, then shower sump or pump sump are acceptable.

Provide a separate breaker for each unit. If something electrical goes wrong with one of them it won’t stop the others from working. Fit each unit’s power supply with a GFI receptacle next to the unit and fit the unit with a matching plug. This simplifies installation and subsequent removal. The indicator light on the GFI receptacle gives confirmation of power reaching the unit.

Install a Perko (or similar) sea strainer before the raw-water pump. Locate it where it is easy to see and below the water line so it self-fills.

Small 110v centrifugal pumps make good raw-water pumps for a/c systems. They are quiet and efficient, but they don’t self-prime. Mount below the water line and close to the strainer.

Run the raw-water pump’s power supply to a junction box next to (and above) the pump. This makes changing the pump a breeze.

My pump had a trigger switch which only ran the pump when the a/c’s wanted it. I removed this and replaced it with a conventional breaker and indicator light. One less thing to go wrong – just remember to switch the pump on or off.

Replace the hoses that feed sea water to the a/c units. Make sure there is a proper manifold so that each unit gets its fair share of water.

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Mike, VERY informative post. Well done!

I'm currently in the middle of an A/C install myself and certainly agree with everything that Mike mentioned. A couple of other thoughts: I looked carefully and measured all the existing ductwork and return air. They all met the specs for the Webasto FCF that I'm installing, save for the return air grille, which had about half the square inch area it should have. Since I doubt that there is a whole lot difference between manufacturers, I have to chalk it off to a half-a**ed original install. If the unit does not get enough return air, it will choke down all the supply outlets and greatly diminish airflow. I'm glad that I took the time to verify as things just seem to run better when you read and follow label directions. I didn't want to dump condensate into the bilge (again, the original installation) and came across the "Condensator" from Mermaid. This is an elegant (albeit pricy) solution to moving condensate using a small venturi to suck the condensate and then mix it with the cooling water outflow. Family obligations this weekend, but will complete the install next week and report back.

RickH

I like some of the information you provided.... We have a 16.5BTU AC in our salon, and it comes out of two ducts....one right above the unit and the other about 11' away.... The ducting is the silver accordion type...similar to dryer vent hose.. I don't think the output of the vent is as good as it should be.

Using PVC pipe that is insulated just might do the trick!! It should make the salon AC more efficient and keep temp down and save on electricity!

JAT said:

.............Using PVC pipe that is insulated just might do the trick!! It should make the salon AC more efficient and keep temp down and save on electricity!

Click to expand...

Good insulation is essential. Without it the surface of the pipes will run with water condensed out of the air. I used what Keith described as "foam/foil house sheathing (from) Home Depot". It is thin bubble-wrap with a foil skin on each side. To stick foil to pipe, and to itself, I used the very sticky double-sided basting tape marketed for use with acrylic fabrics like Sunbrella.

The stuff I described is rigid, different from the bubble wrap stuff. BTW, some friends down the pier used that bubble wrap stuff on their windows with the metallized side to the glass. The metal "fused" itself to the glass and everything we have tried has not removed it, so be careful. Razor blades, glass polish, acid and base compounds, etc. have not worked.

I'm in the same boat so to speak. Have to replace the AC unit in my island Gypsy. The compressor failed and the unit being 7 years old makes it worth replacing the entire unit. Any suggestions as to suppliers and type of unit is most welcome I want to get this done this winter so that the coming summer will be cool.

We installed 2 - Vector Turbo Series Air Conditioners from Dometic. No SS pans and efficient. Full on, each 16K AC draws 10.4 amps. Expensive, yes, but there are a few internet dealers if you search them out.

Another model and brand to look at. Although cost is an important issue, I want to be sure to get a unit that will hold up a bit longer than 7 years.
Thanks for the info

The decision tree is getting harder since a lot of the smaller companies have been swallowed up by the big guys. According to the Dometic web site, Cruiseair, Marine Air and Dometic are all one company.

Marine Leisure - Dometic

save for the return air grille, which had about half the square inch area it should have.

Good call!

Many air cond dont work well because of poor return air.

Remember heating the cabin may be 70F and the circ water 180F over 100 deg of delta T ,(difference) plenty to do the job.

With air cond the cold air is held to 40F or so as -20F would ice up the unit in a few min.

With 80F in the cabin and 40F cool air to do the work the amount of work that can be done is reduced.

So the more inside air that can be fed back to the evaporator the cooler it can eventually get.

A second concept for the DIY folks is a too big unit is a poor choice as if the unit cycles of /on too rapidly there will be little drying of the interior air.

For great drying a smaller unit on almost 100% of the time with a second unit keeping the temperature as desired works best.