Refrigerator Venting on an AT34

In recent hot weather, the NovaKool refrigerator on my AT34 has not been able to maintain the ideal 38-40degF temperature. It was running closer to 50 deg, which was turning much of our food into science experiments….

Janet called the helpful people at NovaKool, (the Canadian phone number is 604-523-6515, and their website address is www.novakool.com). When she told them it was an American Tug, they right away said “It needs more venting.” They’ve seen this issue before (both with American and Nordic Tugs – must be a Seattle cold-weather thing !). Nova Kool specifies a total of 120 square inches of ventilation for the type of fridge that we have (60 square inches at the top for venting out the hot air and 60 square inches at the bottom for letting in the cooler air). This is actually specified in the user’s manual on page 4. On my boat (hull #48) there is a narrow grill above and below the fridge for ventilation. This provides about 80 square inches in total ventilation – 40 at the top and 40 at the bottom. To make matters worse, if you subtract the restriction from the grills (as the manual suggests), the actually ventilation is about half that.  In addition, the Nova Kool representative recommended that the ventilation be towards the back rather than at the front, as it is in our installation.

It looks that the factory has added more ventilation on more recent boats. I found that “HeartTug” hull#95 has narrow slots routed into the cabinetry below the microwave as well as a vent above the microwave.  While I’m sure that this improves the situation, this still does not get you to the recommended total of 120 square inches of ventilation.

The NovaKool representative suggested that we perform the following test to see if venting was the cause of our poor performance.

1.   Get a fridge thermometer so that you can see exactly how it’s doing.  (We keep one in the fridge as well as the freezer.)

2.   Make sure the fridge has been recently defrosted so that there is no heavy frost build-up on the cold plate at the top of the fridge. (We defrost the fridge weekly in warm weather and every 2-3 weeks in cooler weather, depending on the frost build-up.) The Nova Kool rep mentioned that if you consistently have a heavy frost build-up, then the problem may be the seal around the door. 

3.   Remove the fridge from the cabinet, set the thermostat to #4 and leave it out in the salon area overnight. (It generally takes about 8-12 hours to see a noticeable difference in internal fridge temp when you make any changes, such as changes to ventilation, defrosting, or changes to the thermostat). 

4.   If the fridge cools down to an appropriate temperature, then the problem is ventilation.  If not, then it’s time to start looking for a NovaKool technician.

How to remove the refrigerator:

1.   Remove the quarter-round trim strip on the left hand side of the fridge - closest to the steps.  (8 long screws)

2.   Remove the cabinet door closest to the freezer.  This makes it easier to get the fridge out without dinging the door in the process.  (4 screws in the 2 hinges).

3.   Remove the 6 short screws holding the fridge in place.

4.   Pull the fridge aft a short distance, then lift it up over the short wood base trim piece.

Additional Ventilation:

Intake air:

We cut a 9in X 16in hole in the side of the cabinet, just above the top step, starting about 1in above the carpet and 1in back from the corner molding. This puts the intake right next to the compressor, which is in the space between the fridge and the freezer.  

We purchased a teak vent cover from West Marine to cover the hole.  Even with a hole this size, we figure that we only get about 39 square inches of effective venting from this hole. The louvered opening is 6.5 x 12 inches or 78 inches in total. I divided that by 2 to account for the louvers, giving us an effective venting size of 39 inches.  This together with the existing 20 inches of effective venting gives us a total of about 59 inches of effective venting – or very close to the recommended 60 inches.

Note: Be sure to have the vent cover that you plan to use BEFORE you cut the hole, so you know what size to cut.!

Outlet air:

As noted in the beginning of this article, later AT34s have factory-installed vent slots above the fridge (i.e. behind the microwave). They also have a grill in the middle of the countertop surface above the microwave. To remove the microwave and see if you have this venting, lift the front edge up and pull it out. Caution: it’s heavy (25lbs ++). A second person is needed to unplug it from the outlet once you’ve pulled it out. To reinstall the microwave, reverse the procedure: the front feet fit into ‘sockets’ in the woodwork to hold it in place.

As we did not have this venting, we started searching around for a solution. We came across a vent with a collection box arrangement in West Marine. The collection box has two 3 inch holes to which we attached some air vent hose and ran them down to two 3 inch holes cut into the bottom of the microwave cabinet.  This has the added advantage of allowing the hot air from the fridge to vent past the microwave and directly out into the cabin, behind the starboard pilot house seat. We like having the vent hole on the side rather than on top of the microwave cabinet, as we could imagine the problem of small things falling through the vent if it is on top of the cabinet.

We drilled two 3 inch diameter holes in the back of the microwave shelf as well as an exit vent in the back of the microwave area. The first picture shows the holes cut in the bottom of the microwave cabinet and the long slot cut in the back of the cabinet.  The second picture shows the venting parts installed inside of the cabinet.

These pictures show the external vents – behind pilot house seat (back of microwave cabinet) for the exhaust, and on the side of refrigerator cabinet for the intake.

Part numbers:

We calculated that each of the 3 inch holes gives us an effective venting area of about 9.5 inches.  Since there are two holes, that gives us 19 inches. Since the outlet vent cover has an opening of 34 inches, I figured that we effectively added a total of 19 inches of venting with our new solution.  This, combined with the current effective outlet vent area of 20 inches on top of the fridge gave us only 39 inches – still short of the required 60 inches. 

The Nova Kool representative said that this was OK as long as we installed a small vent fan on one of the holes which would effectively increase the venting.

Fans:

I installed a 3in diameter computer fan under one of the 3 inch holes to extract air.  I wired this to the existing fan. 

The NovaKool representative told me the control unit is rated to switch up to 0.5amps (A) of fans.  There is already a 6in unit installed at the back of the fridge that is rated at 0.28A.  The 3inch fan that I added is 0.1A, so I’m comfortably below their limit.

I noticed that the existing fan was installed on the starboard side of the fridge, set to blow air starboard to port across the compressor. Since we now had a big inlet vent on the port side of the fridge, I removed it and relocated it to the port side, just behind the new grille I installed, and reversed it to pull air IN.

This is the view from the back of the unit, showing the fan relocated to the port side to pull air in.

The cylindrical black thing is the compressor.

The black box with wires is the control unit.

The Result:

 A much happier fridge and the end (hopefully) of our science experiments – at least in the fridge!

Jeremy Bell.     AT 34 #48 “Tardis”