Frigoboat - The Smoking Gun (or compressor)


This is a tale of the death of a Frigoboat keel cooler installation.

This discussion (or the predecessor) began on this forum, here
http://www.cruisersforum.com/forums/...em-106061.html.
Folks weighed in, but Frigoboat Info took it offline with me, as the problem
was to prove complex.

In the end, we tried just about everything. FI sent me an air cooler, in
case, somehow, the keel cooler was damaged by running it out of the water.
We tried it in replacement of, and then in tandem with, the keel cooler.
The issue got worse. I'll save you the gory details, other than that I had
more than 1000 data points of time, pressures, plus high pressure connector,
low pressure connector, compressor and box temps, over 3 months or so, and
included 2 lengthy evacuations, the second of which was nearly 2 days, and
recharges.

Nothing worked. FI felt that adding a cap tube filter and a filter dryer to
the system would resolve a symptom which was suggestive of something
blocking the system, but which moved from time to time, allowing
intermittent cooling. However, the cap tube filter involved cutting a line
and doing some silver soldering, a task FI felt better reserved for a
talented refrigeration professional. Given the finicky nature of the
Frigoboat systems, due to their size, I felt that one who was specifically
knowledgeable about Frigoboat - including perhaps my coming to Annapolis,
for FI's team, would be best. FI recommended Clay Hansen, of Hansen Marine
Services, we got to the dock literally down the driveway from his shop, and
commenced.

The first week's adventures can be seen in the thread linked above. Nothing
we did changed matters, despite the rather extreme measures we tried. The
case was tried, and the jury was out. This morning, the jury came in.


I killed it. Whether it was running the keel cooler out of the water, or
just the conditions in the yard, Clay, my referred pro - and by now close
acquaintance, as I "assisted" in his work aboard - in consulting with
several other refrigeration professionals, learned why our efforts - which
included the welding in of a cap tube filter, adding a filter dryer,
evacuation and recharge, flushing the system through both service ports,
followed by a nitrogen blast, isolating the evaporator (the suspected
problem point, which was true, but not the "real" problem) and successive
nitrogen blast/suck vacuum on both sides of the evaporator, alternating,
repeatedly, to no avail) - were fruitless.

The oil used in BD compressors changes state if it gets too hot, per Clay's
consultants, who have seen this happen many times, in older systems. It
doesn't happen immediately, which is why it's nearly never seen in new
systems. The first clue (which Clay observed as irregular, and pursued with
his other pros) was that during the flush/nitrogen blow, a yellow oily
liquid came out. It should have been clear, or perhaps slightly brown.

That change of state results in the oil not remaining perfectly liquid. I
don't know the chemistry, but the effect is that it clogs stuff up,
particularly in really small orifices, such as, perhaps, the keel cooler (I
don't know what the size is on the tubing in the keel cooler, but infer it
must be pretty small to allow the lengths needed for cooling in that small
package), and for sure, the capillary tube, which, if not the keel cooler,
in our case, was for sure packed up (see above about attempts to remedy).

Unfortunately, if absolutely all of the contaminated oil were not removed
from the system, it will only happen again, later.

The bottom line is to start over.

If I had it to do over again, I'd not change anything other than to have
something more effective than the very small heat sink and fan on the
compressor, and make very damn sure the system was not run out of the water
(or, perhaps, without an add-on air cooler, which VecoNA supplied for
testing purposes - swapping for the keel cooler, or even in tandem didn't
solve the problem).

As I understand it, if the compressor is kept cool, this problem is unlikely
to occur. If not, over time, it's nearly certain to occur. Whether or not
the Frigoboat air-cooled system, as provided as a single unit, rather than
as an add-on air cooler, would be sufficient to move the enough air over the
compressor to avoid this in the future I can't say. But it's not a box
system which completely encloses the compressor, channeling air, lessening
the air flow effectiveness over the compressor, and so, as it was in the
yard (or would be at anchor, too), with ambient temps close to, or perhaps
exceeding 100F, that might prove problematic, eventually.

At one point in my testing with the add-on air cooler, before I'd hooked it
up, electrically or with refrigerant, I merely directed the air flow from
the air cooler fan on the compressor, and temperatures dropped notably, even
though the heat sink fan wasn't connected (I had to use those terminals for
the air cooler fan). Perhaps severe ventilation would have been enoughto
make my failure not happen - but I doubt it, as we had an AC bullet fan
directed on the compressor during the time it was run out of the water, to
no avail (or, at least, the problem occurred, anyway).

All this presumes that I caused the problem by running it out of the water.
I suppose it's possible that compressor temperatures, as we were in the
tropics for a couple of years of the use of the system, and the compressor's
in the engine room, could have reached that overheat condition without the
added stress of running the keel cooler out of the water. We'll never know,
as I don't care to attempt to duplicate the circumstances; once bitten,
twice $hy, so to speak, and we'll be very different in our new installation.

I have to say, however, that until I stuck my foot in it, the system was a
real pleasure. But perhaps my egregious error can be avoided by others in
the future. To be sure, while I didn't see the caution at the time,
Frigoboat makes it clear you should not run the system out of the water
without - at a minimum - having water running over the keel cooler.
However, there was no mention of the actual consequences. For a techie
(well, interested in everything, and moderately able to understand the
physics and realities), that information would have been orders of magnitude
more effective to me than "don't do this" - with its implication that it
would simply be inefficient, rather than destructive. Stupidly, because it
continued to work a treat, I did that for a time, as, all around it, we were
epoxy fairing, grinding and all that sort of stuff at the time. It can't
have helped, whatever the other instances of high temperatures for the
compressor may have been.

However, in the end, our choice for replacement is a Sea Frost air and
water-cooled (like the air cooler is an option after the fact on Frigoboat
Keel Cooler systems, this will allow, when the Keel Cooler is removed,
installation of another thru-hull for water-cooling as backup or extremely
hot circumstances) system. It solves a problem which would present to
someone retrofitting cold plates and engine-driven systems, that of access
in an already-built box. The evaporator plate which I got (see
http://www.justpickone.org/skip/gall...ze=640&start=0
and onward for what we did initially) couldn't possibly be inserted into our
current box. Whether we have to cut it up to get it out remains to be seen.

The Sea Frost system relies on two separate evaporator plates which will
make it through our existing door opening, and are much deeper (courtesy of
our depth of the box), allowing for the same surface area in a different
configuration, and a different configuration than the troublesome capillary
tube (Frigoboat's solution) to accomplish the superheat portion of the
cycle. That they are also fully stainless steel is encouraging/reassuring,
in that I can't be ham-handed enough during defrosting to damage them, as
could be the case with the typical aluminum evaporator plate (and which was
the reason I chose a SS-fronted plate to begin with, despite it being less
efficient than straight aluminum).

I have no reason to expect other than stellar results with our new system.
And my experience should NOT be a reason not to buy a Frigoboat system - but
it should be a heads-up as to how you treat it, if you do.

L8R

Skip

Morgan 461 #2
SV Flying Pig KI4MPC
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