We continue to have problems with our engine-driven refrigeration
system, and wondered if anybody knows what we might be doing wrong. We
keep on blowing up compressors -- either they start to leak after a
couple of months use, or they fail (i.e., no longer bring down the
low-side pressure to a vacuum). We know it's not from 'slugging' ice,
because we routinely monitor the state of the return line about 4 feet
from the compressor, and it's never frozen. When the compressors leak,
we naturally don't know it until the fridge doesn't cool anymore, when
we look at the sight glass and see it's empty. This entails running
the system for 5 minutes or more, empty, because that's how long it
takes for liquid to appear in the sight glass when the system is full.
Is that a long enough time to ruin the compressor? The last time we
opened the system up, we found some black residue blocking one of the
filters at the expansion valve. Any idea how dirt could have gotten
into the system? Maybe from a compressor going bad? How do you clean
it all out?

what Freon's are you using? Was it a R12 system that you converted to 134A?
Is there a high pressure switch that opens the clutch? Who's system is it?

More questions then answers right know.


"Akka" wrote in message
oups.com...
We continue to have problems with our engine-driven refrigeration
system, and wondered if anybody knows what we might be doing wrong. We
keep on blowing up compressors -- either they start to leak after a
couple of months use, or they fail (i.e., no longer bring down the
low-side pressure to a vacuum). We know it's not from 'slugging' ice,
because we routinely monitor the state of the return line about 4 feet
from the compressor, and it's never frozen. When the compressors leak,
we naturally don't know it until the fridge doesn't cool anymore, when
we look at the sight glass and see it's empty. This entails running
the system for 5 minutes or more, empty, because that's how long it
takes for liquid to appear in the sight glass when the system is full.
Is that a long enough time to ruin the compressor? The last time we
opened the system up, we found some black residue blocking one of the
filters at the expansion valve. Any idea how dirt could have gotten
into the system? Maybe from a compressor going bad? How do you clean
it all out?

"Akka" wrote in news:1155451606.008019.324930
@h48g2000cwc.googlegroups.com:

We continue to have problems with our engine-driven refrigeration
system, and wondered if anybody knows what we might be doing wrong. We
keep on blowing up compressors -- either they start to leak after a
couple of months use, or they fail (i.e., no longer bring down the
low-side pressure to a vacuum). We know it's not from 'slugging' ice,
because we routinely monitor the state of the return line about 4 feet
from the compressor, and it's never frozen. When the compressors leak,
we naturally don't know it until the fridge doesn't cool anymore, when
we look at the sight glass and see it's empty. This entails running
the system for 5 minutes or more, empty, because that's how long it
takes for liquid to appear in the sight glass when the system is full.
Is that a long enough time to ruin the compressor? The last time we
opened the system up, we found some black residue blocking one of the
filters at the expansion valve. Any idea how dirt could have gotten
into the system? Maybe from a compressor going bad? How do you clean
it all out?



I'll make some guesses.....(c;

Make sure there is a loop in the return line from the cold plate to the
compressor for residual freon to collect in and boil off (you don't see
moving freon freezing the outside of the line).

Make sure the suction side of the cold plate is the TOP of the cold
plate, sucking freon gas off that has already boiled. I've seen a couple
hooked up upside down that blew the compressor sucking liquid.

Does it have a dryer bottle on the system to get the residual water out
of the liquid line? The bottle may have come apart inside, filling the
expansion valve with material you're seeing. When it becomes clogged,
the expansion valve opens and may pass the stuff onto the compressor
through the cold plate, jamming the compressor, but not very likely.
Replace the dryer bottle, anyway.

OK, you've put the vacuum pump on the system and sucked all the air out,
right? (I say this in jest as I met 3 who thought, wrongly, they could
just blow the air out with freon, which won't work.) How much
refridgerant OIL did you pump in before charging it?? Oh? It needs
special OIL?...(c; Yes, it does, or the compressor will lock from lack
of lubrication. Many don't know it. They just start filling it with
freon and run it dry....not good.

That's two things that make a compressor blow.....no lube oil....and the
biggest cause - pumping LIQUID freon!

The compressor's very low in the system so any liquid freon that didn't
boil off flows downhill into the cylinders made-for-gas-only. You'll
hear a knocking sound as liquid freon hits hot pistons from heat-of-
compression. The freon explodes in the hot cylinders, boiling off
immediately. The pressure the explosion creates is too instantaneous to
flow out the valves into the high pressure outlet. Make a loop in the
hose from the cold plate so that can't happen, so any liquid blown out
the cold plate runs back into the cold plate, hopefully into the TOP of
the cold plate.

Anything sound familiar? What pressures are you measuring on the
Schrader valves?

"Rick" wrote in
:

what Freon's are you using? Was it a R12 system that you converted to
134A? Is there a high pressure switch that opens the clutch? Who's
system is it?



Yes, there's another angle, too! When it's converted to R-134a, you should
see just a SPRAY of R-134a in the sight glass, NOT solid liquid with no
bubbles like R-12 was. R-134a is much more cooling so we don't fill the
system.

http://www.wikihow.com/Fix-Cars-Air-Conditioning
http://www.machinerylubrication.com/...?articleid=310
&relatedbookgroup=Lubrication
http://www.sanden.com/support/servic.../retrofit.html
http://www.everything2.com/index.pl?node_id=1674978

To sum up from everything I can read.....DON'T. If it was working great on
R-12, find R-12. Some sailors brought me back 4 cases of 16 oz cans from
the Caribbean islands for my old '73 220D's 2-cylinder system. They paid
68c/can for it! Damned stuff was made in TENNESEE...LAST YEAR! This
replacement business is a big EPA-sponsored RIPOFF...

The ozone hole over Antarctica got bigger, year-after-year, after the ban.
Another government lie, raising prices. The SUN causes the hole, stupids.

On 12 Aug 2006 23:46:46 -0700, "Akka" wrote:

We continue to have problems with our engine-driven refrigeration
system, and wondered if anybody knows what we might be doing wrong. We
keep on blowing up compressors -- either they start to leak after a
couple of months use, or they fail (i.e., no longer bring down the
low-side pressure to a vacuum). We know it's not from 'slugging' ice,
because we routinely monitor the state of the return line about 4 feet
from the compressor, and it's never frozen. When the compressors leak,
we naturally don't know it until the fridge doesn't cool anymore, when
we look at the sight glass and see it's empty. This entails running
the system for 5 minutes or more, empty, because that's how long it
takes for liquid to appear in the sight glass when the system is full.
Is that a long enough time to ruin the compressor? The last time we
opened the system up, we found some black residue blocking one of the
filters at the expansion valve. Any idea how dirt could have gotten
into the system? Maybe from a compressor going bad? How do you clean
it all out?

When compressors go bad, they usually leave metal flakes at the
expansion valve filter. Black gunge suggests incompatible oil, or
inadequate flushing when changing refrigerant type.
You replaced the dryer/reservoir of course?
You filled with the recommended type and quantity of oil, I expect?
You DO have an electric clutch on the compressor drive, I suppose?
There is a cutout to the clutch for underpressure/overtemp, I expect?

Brian Whatcott Altus OK

All engine driven refrigeration compressors were intended to be used on
automobile air conditioning and not for medium to low temperature
refrigeration. In most cases if a compressor had a good service life in
an automobile it could work in a lower temperature system if the system
is designed correctly. If an engine drive refrigeration system is
designed and installed correctly the compressor will operate for twenty
plus years this is a proven fact. Engine driven systems designed by the
original companies of Crosby and Grunert were still running with the
same compressors, these were installed in the late 1970's.

There are a small percentage of new and rebuilt compressors that do
fail prematurely in the first twenty five hours but repeated compressor
failures are preventable. There are a number of reasons why the engine
driven compressor fail:

Compressor capacity is excessive for the size of holding plates; If a
compressor is putting out enough energy to freeze a 500 pound holding
plates in one hour and the plate only weighs 50 pounds the refrigerant
and oil return will not be adequate for lubrication or compressor
cooling, because the expansion device won't allow the flow. The
colder the plates are the less flow of needed refrigerant and oil.
Remember the compressor was designed for high back pressure
applications.

Too large an expansion valve for the evaporator coils in holding
plates; During the off cycle when holding plates are colder than
compressor refrigerant mixed with oil will migrate to the cold plates.
Then after start up with a large valve orifice there will be a quick
flood of this liquid mixture flooding back to compressor causing stress
on reed valves and connecting rods. Some systems must have suction line
accumulators to reduce the liquid return to an acceptable level.

Improper type of refrigerant and oil; Most engine driven refrigeration
systems violate the basic principles of refrigeration, Condensing unit
and return line along with evaporator should be designed to allow
gravity to assist in liquid return, Each component in the system must
be able to match the capacity of the compressor. Oil return will
always depend on miscibility in our boat refrigeration systems, R12 and
mineral oil are miscible, 134a or R12 and polyester oil are miscible
all other refrigerants lack different levels of miscibility at low
temperatures.

Too large of a line in holding plate or anywhere in low pressure side
of system will cause oil accumulation and compressor oil starvation.

Too small of a line or restriction in low pressure side of system will
cause oil accumulation in lines and very low compressor suction
pressure.

"Akka" wrote:

We continue to have problems with our engine-driven refrigeration
system, and wondered if anybody knows what we might be doing wrong. We
keep on blowing up compressors -- either they start to leak after a
couple of months use, or they fail (i.e., no longer bring down the
low-side pressure to a vacuum). We know it's not from 'slugging' ice,
because we routinely monitor the state of the return line about 4 feet
from the compressor, and it's never frozen. When the compressors leak,
we naturally don't know it until the fridge doesn't cool anymore, when
we look at the sight glass and see it's empty. This entails running
the system for 5 minutes or more, empty, because that's how long it
takes for liquid to appear in the sight glass when the system is full.
Is that a long enough time to ruin the compressor? The last time we
opened the system up, we found some black residue blocking one of the
filters at the expansion valve. Any idea how dirt could have gotten
into the system? Maybe from a compressor going bad? How do you clean
it all out?

We have an engine driven/shore power refrigeration system that can be done either way.
The key to our particular system is not to run the engine driven refrigeration more than
45 minutes at a time. We normally do it once in the morning and once in the evening. If
you run it for more time than that, the fluids disappear to somewhere and the compressor
freezes up. We have been running ours that way since we bought the boat in 1998 (on
instructions from the PO who had the same problem as you seem to be having with blown
compressors), and have had no problems with it.

The only other thing is that we always check to see that water is coming out the exhaust
(like we do with the engine). When we run it on shore power the time isn't as critical,
but we do about the same as when we are using the engine. Otherwise it will sometimes
stop itself when it gets really cold, although it doesn't seem to hurt it when it does
that.

grandma Rosalie

S/V RosalieAnn, Leonardtown, MD
CSY 44 WO #156
http://home.mindspring.com/~gmbeasley/id1.html

In article .com,
"Akka" wrote:

We continue to have problems with our engine-driven refrigeration
system, and wondered if anybody knows what we might be doing wrong. We
keep on blowing up compressors -- either they start to leak after a
couple of months use, or they fail (i.e., no longer bring down the
low-side pressure to a vacuum). We know it's not from 'slugging' ice,
because we routinely monitor the state of the return line about 4 feet
from the compressor, and it's never frozen. When the compressors leak,
we naturally don't know it until the fridge doesn't cool anymore, when
we look at the sight glass and see it's empty. This entails running
the system for 5 minutes or more, empty, because that's how long it
takes for liquid to appear in the sight glass when the system is full.
Is that a long enough time to ruin the compressor? The last time we
opened the system up, we found some black residue blocking one of the
filters at the expansion valve. Any idea how dirt could have gotten
into the system? Maybe from a compressor going bad? How do you clean
it all out?


What you need is AN ELCTRIC CLUTCH on that compressor, so that it only
runs when the Refer needs to cool itself. Almost every Car A/C has
one, and for the same reasons you NEED one. Also does you compressor
commect to the rest of the system with some kind of vibration proof
hoses or flexable piping? Now there is a novel idea. Keeping the engine
vibrations out of the refer system.

Me

Larry and all other responders,

Thanks for all the advice. We learned a lot from it.

On the R12/R134a issue: too late. We converted from R12 to R134a years
ago, and the system was working fine with R134a for a long time -- now,
no longer. When we installed the last compressor (marked clearly
'R134a' all over it) last month, we evacuated the system and put in a
new dryer, a big accumulator, and of course, gas. The compressor comes
with oil in it, as does the gas, so we didn't add any more.

We put in enough R134a to just barely fill the sight glass -- maybe
that was too much! The expansion valves are on the original factory
settings -- 2 turns closed from fully open. There are 2 low spots
below compressor level in the low-pressure copper tubing: one where the
tube runs under the floorboards from the fridge to the engine
compartment, and one at the bottom of a full loop just before the
compressor.

When we last charged the system, we had 140 psi on the high side, and
something below atmospheric pressure on the low side, when the system
was running and the plates were cold. When we closed the valve on the
high-pressure side, we got 150 psi on the high side and a full vacuum
on the low side. That was the day before the compressor blew. Now it
doesn't draw down to a vacuum (only to about atmospheric pressure) and
doesn't hold the pressure differential at all, after shutoff. So we
figure it's blown.

We didn't hear any knocking sound before the compressor blew but of
course the engine was running at the time and the engine room is
sound-insulated from the cabin. Initially, we did see a light fast
flow of freon across the bottom of the sight glass, then nothing. We
waited 5 minutes, turned off the system, hooked up the gauges, and
discovered we had no pressure -- and a blown compressor.

We don't have a high-pressure valve. We do have an electric clutch,
but in practice it never cuts out because we never run the fridge more
than about an hour at a time, to avoid freezing the lines. We also
check fairly regularly after we've recharged the system with R134a that
we're not frosting the return lines.

So right now I'm concentrating on three possibilities: (1) we may have
overcharged the system, causing fluid to be forced through the
expansion valves and back into the compressor at startup; (2) the
expansion valves might be clogged up and the compressor starved for oil
because of the lack of a return supply; or (3) the new compressor
simply blew -- we discovered that 3 of the nuts on the compressor head
weren't fully tight. But that in itself wouldn't cause the compressor
to fail, would it?

The gunk on the valve filters certainly could have come from
incompatible gasses. We used to get the unit refilled from time to
time by 'professionals' and we're pretty sure at least one of them put
in the wrong gas. That was 2 years ago, but still ...

So, what to do? Apparently, compressors can't be repaired (though it
sure looks like one could replace the head gasket), so we have to buy a
new one. When we do, we'll open up the valves and inspect them,
replace the dryer, vacuum-pump the system, then barely fill it until we
see liquid running across the bottom of the sight glass. What else?
More oil? Lighter-weight oil because of the low operating
temperatures?

Akka wrote:
Larry and all other responders,

Thanks for all the advice. We learned a lot from it.

On the R12/R134a issue: too late. We converted from R12 to R134a years
ago, and the system was working fine with R134a for a long time -- now,
no longer. When we installed the last compressor (marked clearly
'R134a' all over it) last month, we evacuated the system and put in a
new dryer, a big accumulator, and of course, gas. The compressor comes
with oil in it, as does the gas, so we didn't add any more.

I thought when r134a came with PAG oil and POE is usually recomended
for marine use. Maybe I'm wrong ...


When we last charged the system, we had 140 psi on the high side, and
something below atmospheric pressure on the low side, when the system
was running and the plates were cold. When we closed the valve on the
high-pressure side, we got 150 psi on the high side and a full vacuum
on the low side. That was the day before the compressor blew. ...

150 pounds sounds real high to me. My system, a DC powered Tecumseh
compressor, runs at about 95 psi on the high side. This corresponds
to a temp about 20 degrees hotter than the cooling water.