Broken AC - Re-install myself?

[jpeac2]

Hey All!

LONG time reader and finally signed up and making my first post. Thanks for everything you all have made this forum into!

Unfortunately did not winterize our perfectly good Marine Air VCD 16k/2 AC unit last year and are paying the price now. Beneteau Oceanis 351.

Couple questions:
1. If we bought the same unit again and just took out the old and put in the new - is that something easy enough that I could do it? No changes to the existing install.

2. I am not entirely sure we had the right unit as it never seemed to dehumidify. It almost seemed to do the opposite. Based on what I have read a 16k but unit is right for our boat. Somewhere i did read that if you have the wrong size AC unit (bigger is not always better) it will cycle incorrectly and in the process not do a great job de-humidfying. So my question is how much should the AC unit de-humidfy?

3. Are most of the brands of pretty good quality? Or are there some manufacturers of marine AC units I should avoid?

Thanks for your help!

[belizesailor]

Just dropping in a new unit is not hard. Just make sure you get the electrical connections right. If you are not confident working with AC electrical then get a pro to help with that part...not worth frying the unit, or yourself, to save a few bucks.

[motion30]

if it were me I would see if I could just buy the cooling coil that circulates the water

[redsky49]

Originally Posted by jpeac2

Hey All!

LONG time reader and finally signed up and making my first post. Thanks for everything you all have made this forum into!

Unfortunately did not winterize our perfectly good Marine Air VCD 16k/2 AC unit last year and are paying the price now. Beneteau Oceanis 351.

Couple questions:
1. If we bought the same unit again and just took out the old and put in the new - is that something easy enough that I could do it? No changes to the existing install.

Absolutely! I can go over the details if needed.

2. I am not entirely sure we had the right unit as it never seemed to dehumidify. It almost seemed to do the opposite. Based on what I have read a 16k but unit is right for our boat. Somewhere i did read that if you have the wrong size AC unit (bigger is not always better) it will cycle incorrectly and in the process not do a great job de-humidfying. So my question is how much should the AC unit de-humidfy?

In a mild climate, a 12,000 btuh unit might work, but 16k btuh will not be excessive. Answer is partly based on local design conditions. The unit will indeed de-humidify, but only if operating in cooling mode (or dehumidifying mode if so equipped). I would certainly look at the details of the initial installation. Numerous reasons why the unit is not adequately removing moisture from the air, but I would start with a hygrometer to adequately document the temp and humid levels.

3. Are most of the brands of pretty good quality? Or are there some manufacturers of marine AC units I should avoid?

If you replace with the same unit you will not have to modify the ductwork connection, seawater hoses, electric, etc. While there are differences between the various manufacturers, it is in the details, and the major players seem relatively comparable - some better values than others.
Thanks for your help!

When dehumidifying, there should be a stream of condensate (water) being expelled. Verify flow first off. Discharge could be into bilge but preferably should go to separate sump/overboard discharge.

Where are you located?

[Sailmonkey]

Originally Posted by motion30

if it were me I would see if I could just buy the cooling coil that circulates the water

You can, but if water got into the freon this is false economy.




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[Sailmonkey]

Where are you located?

IMHO 16k could be too large for the volume of the hull and not allowing the compressor enough run time to really pull some moisture out of the air.




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[redsky49]

Originally Posted by Sailmonkey

Where are you located?

IMHO 16k could be too large for the volume of the hull and not allowing the compressor enough run time to really pull some moisture out of the air.

Sent from my iPhone using Cruisers Sailing Forum

It all depends. Here in northern Florida, 16k would be merely adequate.

Sometimes, just reducing the fan speed allows more time for the supply air to be in contact with the coil, increasing the water removed from the air.

Could be the OP leave dorades and ports open, and the unit will never operate successfully under such conditions.

Maybe the unit is not set level and the condensate drain pan is sloped the wrong way.

Not rocket science, but does require some attention to details.

[jpeac2]

Great feedback everyone. Much appreciated.

Myself and the boat are in Chicago.

Will be tough to take a hygrometer reading with the current broken unit but I would be curious to see how if the install may affect the humidity.

It generally seemed to become more humid when running the AC. I could be nuts but when we would run it all night and wake up in the AM it seemed to be the opposite of dryer.

[GordMay]

Greetings and welcome aboard the CF, jpeac.

16K seems pretty big for a 35 ft. boat.
Does the AC short cycle?

A rough "rule of thumb" for sizing marine air-conditioning (for use in sub-tropics) is between 14 (below decks) to 17 (above decks, glazed) BTU/H for each cubic foot of interior conditioned volume.

A (theoretically) perfectly-sized air conditioner will run continuously during the hottest 2.5% summer design (outdoor) temperatures.

Don't buy an oversized unit. An over-sized unit short-cycles (turns on & off too rapidly), so doesn’t properly de-humidify*, and uses more energy (starting currents).

Make sure any ducting and grillework is sized large enough to allow low-velocity air distribution.

➥ http://www.cruisersforum.com/forums/...tml#post305561

[sailorman7225]

With new purchase/install keep in mind which company is recognized as having superior customer support.

[gbohner]

Free 18k Marineair without wall thermostat control. It was located behind the sofa in my salon and was getting noisy. We replaced it with same model to cut down the noise. It was working fine. Located in Stuart, FL

[gbohner]

RE: Free AC, contact guy, gbohner@aol.com

[woodboy12]

I am not all that mechanically inclined, but decided I would try and give replacing my defective A/C unit a shot. My decision was made easier after the person quoting the price wanted nearly $1000 to install the new unit. The old unit I had was pretty self contained and since I was able to order almost exactly the same unit, it was mostly a plug and play operation.

The unit I was replacing was about 12 years old, so the company (Mermaid Manufacturing) had made a few improvements on the the new unit. This required that I change out the electrical box that came with the new A/C unit. There was only 4 wires to change on the included electrical box. The rest was pretty much plug and play.

I replaced the unit in the main stateroom of a 42 PDQ catamaran, so I had ample room to work. Also the unit was only a 6,500 btu unit so it was not too heavy. It took me about 4 hours to muddle through the process. I think I could do it much quicker now that I have done it once.

I would factor in the space you have to work in, if you can get pretty much the same unit, the price a professional would change, and how much you value you personal time.

That was my experience, I hope it might help you decide.

[bobw100ton]

On most sailboats with moderate sunlight through hatches and portholes we find multiplying the cubic ft of open air space times 15 (assuming 85% humidity at 90dg F) will provide you with a good number for total BTU's. In the tropics its common to find over sized equipment creating a cold mildew environment below. This is caused by bringing the ambient air temperature to dew point too fast (causing surfaces to be wet) rather than wringing out the moisture as it passes through the evaporator and falls into the condensate tray.

Self contained units very greatly in the amount of painted steal and un-insulated steel blowers (rust through quickly) along with efficiency (watts/BTU) of the compressors and heat exchangers used. I prefer the mold injected bases over steel. Cupranickle should be the only material used in a marine condenser. Not all blowers rotate, you may need to specify horizontal or vertical. More sophisticated models have a dehumidify setting allowing for much less power usage when your not driving for temperature. Many units do not cycle the pump with the compressor, the pump runs 24/7. The way the compressors are soft mounted and Cu tubing is "tromboned" is the single biggest reason for the wide variation in Db levels between manufacturers. Just some considerations.....

[keepondancin]

Does the condensate water get discharged overboard, or into the bilge?