Saturday, October 27, 2012

It's Freezing In There!


The Saga of the SeaFrost refrigeration system.

When we visited LUX in March 2011 for a week-long cruise around Tortola, we found that the refrigeration system wouldn't stay cold enough to keep our food safe. Unfortunately, we were there on a holiday and the local charter management staff found Alfred, who supposedly knew how to diagnose and repair refrigeration systems. Well, Alfred didn't know a lot. We wound up with a completely broken compressor that wouldn't run. Our temporary solution was to use an ice chest for our food. Upon return to Nanny Cay, another refrigeration person quickly diagnosed a bad compressor, which is what we had diagnosed as well. The new compressor and installation cost about $1400 (ugh!) It then worked correctly.

When we went back in May to bring LUX back to the Chesapeake, the refrigeration system was working, but not as well as we wanted. It was ok for keeping food safe, so we decided to investigate further when we were home.

What was clear is that there was a slow leak. We bought a gas detector and a refrigeration gauge system from Harbor Freight Tools to help us diagnose and repair the source of the leak. We found several suspect connections and were able to tighten them, vacuum the system, and recharge it with 134R refrigerant. The gas detector hasn't indicated any leaks more recently.

The collective wisdom of the Leopard catamaran mailing list on Yahoo was to add refrigerant slowly. The lines should frost all the way through the system. During the discussion, it was funny to hear someone else with a story about Alfred at Nanny Cay, with similar results. If you get any refrigeration system work done on Tortola, be suspect of anyone named Alfred.

After about a month, we found that we needed to add more charge. The loss of refrigerant (i.e. cooling) seemed to correlate with the number of times that the system was fully defrosted. Warming up the entire system to ambient temperature seemed to accelerate the loss of refrigerant. We checked the resistor that determines the run speed of the compressor and there is already a resistor in place that causes it to run at high speed.

An infrared thermometer shows that the exhaust air is 20 degrees warmer than the intake air. We reversed the fan so that air is first drawn over the condenser, then over the compressor. This seems more efficient than the default configuration, though we don't have any actual measurements to back it up.

On one of the recharges, we noticed a small "Pfftt" sound when the low pressure service port cap was removed. The schrader valves are deep in the fittings, so we had to make a trip to the local HVAC supply shop to get a tool to replace them. There is a nice tool that allows replacing the valve without discharging the system, but unfortunately, it didn't fit the Sea Frost system. However, the schrader valve tool that is part of it could be used to tighten the valves. We found that they could be tightened about 1/10 to 1/8 of a turn. So far, so good, but the system hasn't been running long enough for us to know for sure. The freezer is working well, but still runs all the time. We think it should be running half the time.

Door Gaskets

Refrigerator Door, Door Liner, and Taped Refrigerator Opening
We also thought that the door gaskets could be replaced, perhaps providing better seals than the gaskets that are now eight years old. We ordered gaskets that looked like the proper cross-section (number P-2099-8) from Exact-A-Line Gasket, Inc, in Canada. The gaskets arrived and are very nice. We let them sit out for a few days to resume their normal shape after being twisted in the shipping box.

The inner fridge door and gasket are held in place by pan-head screws, which don't seem like the right kind of fasteners to use. It seems to us that flat-head fasteners, countersunk into the door liner would be better. Surprisingly, the door itself isn't fully insulated. The insulation is concentrated in the inner liner. We used plastic taped over the door to keep the cold air in the refrigerator while the door surgery was under way. All three are shown here.

The new gasket fit the refrigerator door extremely well. Unfortunately, when we reassembled the door, we found that it didn't compress as much as the old gasket and that we could only shut the door by sitting on the floor and pressing the door closed with a foot. The door wouldn't stay latched. And in addition, about 1/8 of the gasket was not making contact with the door facing, which is really not good.

Off came the new gasket and back went the old gasket, after it was thoroughly cleaned and inspected. The old gasket is still in good condition. It is flexible and seems to seal all around. The replacement was to eliminate the seal as a source of air leakage, more on the freezer compartment than the freezer compartment. As a result of the work, we replaced the screws with counter-sunk flat-head screws, which should help the lay of the gasket on the door.

There are other gaskets available from Exact-A-Gasket and we'll be contacting them to discuss options and see which one works best for us.

Update 2/22/2013

We have since found coolergaskets.com, and their profile 702 looks like an exact replacement for the existing Leopard 40 refrigerator/freezer door gaskets. Another option is their profile 494, which is about 1/16-inch shorter in height and has a 5/8-inch wide face. The wider face would have a lower pressure (lb per sq in), but may seal better due to the larger mating surface. Both of these gaskets are gray, not white. One of the cruisers is going to try this gasket to see how well it works. We won't be able to try new gaskets until June 2013, when we bring LUX back from the Bahamas to the Chesapeake. 

Our door measurements are:
Freezer: 15.0 in wide X 23.25 in high
Fridge:  17.5 in wide X 23.5 in high
George on Matador said that he measured the Freezer as 15.25 wide, and the other measurements the same as ours. John on 2AWESOME was able to get our Exact-a-line gasket for the freezer to work, but had the same problem that we had on the fridge door. So the 15.0 in measurement worked for John's freezer (we had not tried the freezer gasket after the fridge door didn't work).

Additional Update on 8/2/2017

We found that the refrigeration system would gradually lose effectiveness after a period of not running it. After some discussion, we decided that there was a leak in the low pressure side. When we turned the system off, the higher pressure in the low pressure side would leak refrigerant. So we called Nate Horton (Horton Marine Services in Annapolis, MD) to take a look. He quickly found a leak at the brazed connection of the low pressure (blue) maintenance connector by pressurizing the system with nitrogen. It was a quick fix and it worked well for a couple of years. This spring (early 2017), we noticed that it wasn't working as well as it had in the past. It sat all winter without running, so maybe there's still a slow leak somewhere. We had some left over refrigerant in a container with a fill hose, so we added it - about 1/3 of the can. That restored the operation and the plates get frosted again like they used to.

We have also lined the refrigerator and freezer with double sided TechFoil. It's like bubble wrap with aluminum foil on both sides. Inexpensive insulation and it doesn't consume much space. We lift it to allow it to dry underneath when we defrost the freezer.

We also added the digital control, which seems to have made a big difference in how well the freezer performs. It runs a bit over 50% of the time.

  -Terry

No comments: