Main Salon & V Berth Air Conditioning - Complete August 2015

Buy, Install Aft Berth and Main Salon Air Conditioning Rua Fiola had no Air Conditioning as purchased. We had viewed another Vagabond 42 of the same design that had a Main Salon Unit mounted under the curved main salon bench seat, and the Rear Berth Unit mounted under the rear berth bench seat. Both the outlet registers and the return air looked as though they would “short circuit air flow” by poor adjacent register placements. We determined that the main salon should have a unit that also supplied air to the V berth, and that the rear berth register be fully directed in the berth itself. Both return air registers need to be 4 to 6 feet separation from outlet registers. It is not common knowledge that the Return Air path can provide excellent service OR be entirely defeating of good cooling. Sizing air conditioners for the length of the boat and the normal heat load to be experienced is not difficult. Most manufacturers have sizing charts to make it easy. For Rua Fiola based is the SE USA and Caribbean the requirement is for about 25,000 BTU.

This can be done one of 2 ways, a single 25,000 BTU unit or 2 units of 16,000 BTU and 9,000 BTU. The large single unit requires 240 VAC service while the 2 smaller units can both be 120 VAC service. The Amp draw for the single unit is about 11 Amps, while the 2 units draw 23 Amps. The boat is wired for 30A 120V shore power, which is adequate for Air Conditioning loads. At the dock is necessary to add the Battery Charging load as it can be and additional amp draw of 4 amps for the Mastervolt 12/40-3 triple battery bank charger. The sea water cooling pumps draw 2 amps, so this AC load is right at the 30A service limit. We have not tripped the shore power breaker up to this point. We decided that the reality is that normally only one or the other AC units is running and most of the time the charger is in Float mode drawing less than 1 Amp.

The choice of actual unit is either based on prior experience (Marine Air in our case and not very positive) or some part of the sales sheet or specification list that looks important. We chose to buy MarinAire units – MSBA9 and MSBA16, because of high efficiency, low noise and modern digital control of humidity management. Siting the 2 units was challenging with the salon MSBA16 being fitted under the Nav Station table, where it took over an existing cupboard space. The sea water strainer and pump were fitted to the front of the unit inside the same space. The electrical panel had a 50A breaker dedicated for Air Conditioning and that was used. All wiring was based on the requirements as laid out by MarineAire. Mounting the MSBA16 is only part of the job, as the ductwork and registers required to handle Cool Air OUT and Warm Air RETURN have to be configured and placed. We decided that the main salon register would be on the STBD side shelf of the salon and that its air flow be directed by configuring a Flat Screen TV stand as a directing baffle, then from that point air flow was ducted to 2 lower registers in the FWD V berth. Flex ducting of 6” to the salon register and 4” to the V berth was used. The return air register that is below the NAV station draws warm air from the circular cross flow in the salon and through the V berth doorway.

Rear Berth Air Conditioning Installation - Complete August 2015

Mounting the MSBA9 was initially to be in the aft berth STBD lazarette, but when we tried to fit the unit in its prospective space – it would not fit! As a standard part of the Vagabond 42 design of its era the boats were fitted with a 4KW GenSet under the Midships Berth. The one on Rua Fiola had been removed at some time in the past so we opted to commandeer that space for the AC unit and some tool storage drawers. Routing the 6” flex duct to rear berth was physically difficult. When we tested the unit, the air flow path was too tortuous through the rear lazarette so we decided to replace the flex duct in the lazarette with duct board ducting of very generous size. The rear berth unit cools well and the return air path to below the midship berth provides a good separation.

There is no Air Conditioning air flow to the Midship berth itself or to the Galley. To do so would have severely compromised cooling where we wanted it, Salon, Aft Berth and V Berth. In use, both AC Systems are turned on to cool the boat when we arrive at the dock if necessary, but usually we use the MSBA16 during the day and the MSBA9 at night.

The digital wall control units offer a good range of control - equal to that found in current residential units. One of the things liked most is that the AC will recirculate the air on a timed basis. This means that you do not have to run the fan continuously, this periodic refresh mode is very nice.