Installing A/C in an A32 V Berth


After a lot of thought, the best place for me to install the unit was close to power and water under the port side salon seat.
A hole as large as possible was cut in the top of the seat and the draw and draw facing was removed, after seeing how much space was above the draw, I also cut out the top of the starboard seat and put a shelf in.

The next job was to find a unit that would fit. After a lot of measuring and making cardboard boxes to manufacturers specifications I found the best fit to be the Mermaid 9000 BTU Reverse Cycle.


I epoxied (to water proof it) a piece of 3/8” plywood the size of the base of the unit. This was affixed to the liner as close to the water tank bulkhead as possible. A small corner of the liner had to be cut away to allow the board to lay flat.

A transition box was fabricated from plywood. This would allow for a 6” straight through vent (that Mermaid said is required) with a 4” vent off of the side. This Box was fitted to the front of the A/C unit and on the front of this, a 6” round plastic collar was glued to accept the 6” plastic pipe. A 4” aluminium elbow (Home Depot) was attached to the side of the box.

The next job was to cut the holes for the air ducts:

  • 6” hole through the bulkhead in line with the A/C unit into the head cupboard.
  • 6” hole through the front of the cupboard beside the head
  • 4” hole through the bulkhead behind the water tank
  • 4” hole underneath the chart table behind the water tank.
  • 2” hole into the head cupboard to accommodate the wiring harness.
  • 1” hole in the liner to allow for the condensation drain pipe

A hole was cut on the base of the A/C unit by the condensation drain. This was to allow for the condensation drain pipe to be led to the bilge.

The condensation pipe was attached to the A/C unit and the whole assembly was carefully shoe-horned in and screwed down.


A 6” collar was glued to the back of the hole beside the head and the two 6” collars connected with 6” flexible plastic ducting (Home Depot).

A 4” semi-flexible ducting (Home Depot) was used to connect the 4” elbow to the vent under the chart table.


4” vent grill (marine store)

6” vent grill (Home Depot) the closest size that would cover the 6” hole

Return vent (home Depot) The closest size that covers the area were the draw trim was removed. The only colour available was white so it was sprayed brown.


The control box was mounted in the head cupboard.

The wiring harness was feed through 2” hole and plugged into the control box.

#12 wire was fed from a spare 15-amp breaker that I had on the AC panel and connected to the control box.

The FX-1 thermostat was mounted over the nav station with the wiring being fed back to and plugged into the control box.


I fabricated a manifold for the head intake, it now supplies water to the head, wash down pump and the A/C unit.

As a side bar the wash down pump also supplies water to a sprayer (Home Depot) in the head to wash the head and also the galley to spray the worst off of the dishes before washing to conserve water while at anchor.

The intake line is connected to the 110V pump that is hard-wired to the control box. The water pipe is then led to the A/C unit. All the hoses that I used were 5/8” reinforced PVC. This is over-sized to Mermaid’s requirements, but I wanted to reduce pipe line friction and back pressure because of the underwater discharge.


I did not want to discharge through the hull above the water line. I’ve been tied up next to boats running air conditioning at night and it can drive you crazy, so I enlarged the through hull for the sink in the head to a 1 ½” ball valve and connected the A/C discharge to that with a ‘Y’ going to the sink. A ball valve was installed in the sink drain just in case there was any back pressure to push water up into the sink and hence into the boat. As yet there hasn’t been a problem, the only time the valve is closed is if the boat is left for an extended period with the A/C running.


The system was turned on and for 1 ½ hours the whole thing work perfectly, then the coils froze up stopping any air flow. I called the Ontario distributor that sold me the unit. He told me that everything that I had done was wrong and that it was not his problem, that he only sold me the unit and that I would have to deal with the manufacturer. As you can imagine, at this point I wasn’t feeling too good.

I contacted Roger Williams Product manager of Mermaid Mfg. and I can’t say enough about how helpful and positive he was, promising to stay with me until things were resolved.

He reviewed pictures and a description of what I had done and said that basically what I had done was correct. In the end it was determined that the A/C unit was not cycling off to allow the coils to defrost as the thermostat was mounted away from the air flow . The cure was to mount a remote
temperature sensor in front of the coils behind the return grill and connect it to a plug inside the control box.

I’m now in the process of finding ways to distribute the cold dense air throughout the salon and V berth.

The hot air is not a problem as it rises and seems to work better than two 1500 watt heaters.

The head gets so cold that when my wife uses it she turns off the A/C because where the grill is it will freeze your you know what off. I think that I have solved the problem of cooling the V berth. I installed a 3” 12 volt muffin fan in the bulkhead.

The solution for the salon will be to keep the head door closed to force the heavy cold air up over the top.

Plugged into a 15-amp dock outlet, I can run the A/C and boil a kettle at the same time without tripping the breaker.

What were my costs?

Through Hull $49.71
½” ball valve $8.53
Bronze Cap $2.00
Seacock $153.67
Brass Nipples $12.97
Brass Hose Adapter $3.94
Total: $230.82 (this cost is because I wanted to discharge below the water line)

A/C, FX-1, Pump $2403.00
Return Grill $14.40
4” duct $10.16
4” elbow $4.25
4” vent $10.00
Hose & clamps $45.80
Return grill $16.16
Brown Paint $5.29
6” flanges (2) $20.00 $2529.06
Total $2759.88

Note:  some small items may have been missed or donated