Refrigeration Email I have no good answer for.

[sailjumanji]

Originally Posted by Richard Kollmann

Frost on a refrigerant return line and how close frost gets close to reaching the compressor is always of concern. What is important is frost near the compressor indicates liquid and not gas vapor could damage the compressor. I prefer to know more about the design of this system and what else was done when the new plate was installed.before I give advice about tampering with refrigerant charge.
All refrigerator designs have a low pressure accumulator at the end flow of all types of evaporators to be efficient and to take advantage of refrigerant heat extraction liquid to gas phase change. Larger pleasure boat systems have a separate suction line accumulator to insure liquid phase change and allow small amounts of saturated liquid and oil to return to the compressor this then becomes the primary source of compressor cooling on many designs. Assuming the frosted line is not approaching the compressor at any time during the freezing of the eutectic plate compressor is safe but this condition needs to be corrected.
Again an experienced technician needs to know the type of refrigerant flow control device used on your refrigeration system Capillary tube, a Thermostatic Expansion Valve (TXV) or a low pressure evaporator temperature regulator:
Cap tube refrigerant flow is controlled by refrigerant volume in complete systems which change as ambient temperatures change, too much refrigerant on a warm day and not enough on a cold day.
TXV with its liquid refrigerant storage tank receiver needed to meter refrigerant flow to evaporator as conditions change ensuring the most evaporator heat removed per ounces of refrigerant flow.
Refrigerant flow of a Low Pressure Valve is preset manually to a desired pressure/evaporator temperature.
I prefer when adjusting refrigerant volume on most electrical refrigeration compressor to adjust volume of refrigerant based on compressor current amperage.
On volume of refrigerant in a TXV system with a sight glass keep small bubbles in sight glass until desired evaporator temperature is reached and only then add refrigerant till glass is clear. This method will keep you from over charging unit and allow you to verify later there are no leaks in the system.

The unit is an Indel/Webasto Compact Air-Cooled Refrigeration System.

https://www.indelwebastomarine.com/u...ation-systems/

Looking at the images, it is probably most similar to model 2010. However I know that Webasto also custom bends the cold plate to fit the Seawind freezer box, so that plate might be different. It is L-shaped.

It comes pre-charged, so only need to connect up the system and its properly charged. The Seawind factory installed this unit in our new-build, and it worked fine for about a year until the cold plate had a leak. They shipped a new plate, and a local tech did the recharge. At first too much coolant, which didn't cool properly as well as had freeze back of return line almost to the compressor. Then release some coolant, and the system was able to achieve colder temps as well as the frost line moved back toward the cold plate. But it still freezes (ice form on outside) around 3 ft downstream of the cold plate.

[OzeLouie]

Originally Posted by sailjumanji

The unit is an Indel/Webasto Compact Air-Cooled Refrigeration System.

https://www.indelwebastomarine.com/u...ation-systems/

Looking at the images, it is probably most similar to model 2010. However I know that Webasto also custom bends the cold plate to fit the Seawind freezer box, so that plate might be different. It is L-shaped.

It comes pre-charged, so only need to connect up the system and its properly charged. The Seawind factory installed this unit in our new-build, and it worked fine for about a year until the cold plate had a leak. They shipped a new plate, and a local tech did the recharge. At first too much coolant, which didn't cool properly as well as had freeze back of return line almost to the compressor. Then release some coolant, and the system was able to achieve colder temps as well as the frost line moved back toward the cold plate. But it still freezes (ice form on outside) around 3 ft downstream of the cold plate.

If the system is near cut out temp there should be no frosting on that suction line. Let a bit of gas out but best in small increments (say 3 to 4 second squirts) with the unit running. Do one purge then check again after another 20 minutes running and repeat if frosting persists

[Richard Kollmann]

Originally Posted by OzeLouie

If the system is near cut out temp there should be no frosting on that suction line. Let a bit of gas out but best in small increments (say 3 to 4 second squirts) with the unit running. Do one purge then check again after another 20 minutes running and repeat if frosting persists

I was concern after my long post that he would make a mistake after reading it and let out refrigerant. I gave him advice that would avoid calling technician again.

[sailjumanji]

Originally Posted by Richard Kollmann

I was concern after my long post that he would make a mistake after reading it and let out refrigerant. I gave him advice that would avoid calling technician again.

Hmmm, I read your comment multiple times and while it was quite an education, I missed the advice to fix that you recerences.

[sailjumanji]

Originally Posted by OzeLouie

If the system is near cut out temp there should be no frosting on that suction line. Let a bit of gas out but best in small increments (say 3 to 4 second squirts) with the unit running. Do one purge then check again after another 20 minutes running and repeat if frosting persists

Thanks. Its a pretty low volume system so 3 sec of purge might be a lot.

And why with system running?

[OzeLouie]

Originally Posted by sailjumanji

Thanks. Its a pretty low volume system so 3 sec of purge might be a lot.

And why with system running?

Apologies, I should have mentioned purging from the suction service valve only, and if only for 3 to 4 secs as advised, it is near impossible to 'over do it.
ONLY purge if frosting of the suction line is evident after at least 20 minutes running. (Ignore any momentary frost when a cycle starts)
With system running to allow monitoring and to keep the suction low and therefore we are only purging tiny amounts each time. It is not unusual to have to purge many times if well overcharged but best in small increments as described and you can't go wrong.

BTW a grossly over charged capillary system may not frost the suction line but exhibit very cold sweating instead. This situation usually produces the following indicators: The systems temperature decrease stalls before achieving SET point, high power consumption, high discharge pressure/ temperature and sweating on side of compressor. .

Cheers OzeLouie

[sailjumanji]

Originally Posted by OzeLouie

Apologies, I should have mentioned purging from the suction service valve only, and if only for 3 to 4 secs as advised, it is near impossible to 'over do it.

ONLY purge if frosting of the suction line is evident after at least 20 minutes running. (Ignore any momentary frost when a cycle starts)

With system running to allow monitoring and to keep the suction low and therefore we are only purging tiny amounts each time. It is not unusual to have to purge many times if well overcharged but best in small increments as described and you can't go wrong.



BTW a grossly over charged capillary system may not frost the suction line but exhibit very cold sweating instead. This situation usually produces the following indicators: The systems temperature decrease stalls before achieving SET point, high power consumption, high discharge pressure/ temperature and sweating on side of compressor. .



Cheers OzeLouie

Got it. Thanks

[Bbolino]

I spent a 40-year career in the HVACR business
These small systems not only don't need they should not have receivers or sight glasses. If the manufacturer thought it needed them, they would have installed them.
They are single capacity compressors and the minor refrigerant flow volume that occurs from load and condenser capacity changes is easily handled in the condenser.
The starting point to correcting a problem in a system like this is put it back to the way it was when it was built. Recover whatever refrigerant is in it (leak test it first), evacuate to a deep vacuum and then weigh in the correct amount of the correct refrigerant. This type of system is what we call a critical charge system and even an ounce or two of refrigerant can have a huge effect on performance.
Without knowing the more about the system and having more readings little diagnosis can be done, but 30deg C is 86 deg F which suggests that no work is being done. the pressure readings suggest an R-12 system which hasn't been used in probably 25 years. Any of the likely refrigerants would display pressures much higher than that.
Likely diagnosis is short of charge but don't just add - fix the leak, evacuate and re-charge

[OzeLouie]

Originally Posted by Bbolino

I spent a 40-year career in the HVACR business
These small systems not only don't need they should not have receivers or sight glasses. If the manufacturer thought it needed them, they would have installed them.
They are single capacity compressors and the minor refrigerant flow volume that occurs from load and condenser capacity changes is easily handled in the condenser.
The starting point to correcting a problem in a system like this is put it back to the way it was when it was built. Recover whatever refrigerant is in it (leak test it first), evacuate to a deep vacuum and then weigh in the correct amount of the correct refrigerant. This type of system is what we call a critical charge system and even an ounce or two of refrigerant can have a huge effect on performance.
Without knowing the more about the system and having more readings little diagnosis can be done, but 30deg C is 86 deg F which suggests that no work is being done. the pressure readings suggest an R-12 system which hasn't been used in probably 25 years. Any of the likely refrigerants would display pressures much higher than that.
Likely diagnosis is short of charge but don't just add - fix the leak, evacuate and re-charge

These small systems fall mostly into two groups with the vast majority ( nearly all) being capillary fed and a diminishing few being TX valve fed. A liquid receiver followed by a sight glass and proper filter dryer is essential for TX valve systems. Some early commercial TX systems also used 'try-cock' test points on the receiver but that practice has long gone.

Capillary systems do NOT and should not use a liquid receiver and a sight glass but should have a PROPER filter dryer and suction accumulator. The system referred to in the latter part of this thread is a capillary throttled type and the advice provided is correct.

[RaymondR]

Originally Posted by Bbolino

I spent a 40-year career in the HVACR business

These small systems not only don't need they should not have receivers or sight glasses. If the manufacturer thought it needed them, they would have installed them.

They are single capacity compressors and the minor refrigerant flow volume that occurs from load and condenser capacity changes is easily handled in the condenser.

The starting point to correcting a problem in a system like this is put it back to the way it was when it was built. Recover whatever refrigerant is in it (leak test it first), evacuate to a deep vacuum and then weigh in the correct amount of the correct refrigerant. This type of system is what we call a critical charge system and even an ounce or two of refrigerant can have a huge effect on performance.

Without knowing the more about the system and having more readings little diagnosis can be done, but 30deg C is 86 deg F which suggests that no work is being done. the pressure readings suggest an R-12 system which hasn't been used in probably 25 years. Any of the likely refrigerants would display pressures much higher than that.

Likely diagnosis is short of charge but don't just add - fix the leak, evacuate and re-charge

Could be full of air rather than refrigerant, but the solution is the same anyway.

[Richard Kollmann]

Originally Posted by Bbolino

I spent a 40-year career in the HVACR business
These small systems not only don't need they should not have receivers or sight glasses. If the manufacturer thought it needed them, they would have installed them.
They are single capacity compressors and the minor refrigerant flow volume that occurs from load and condenser capacity changes is easily handled in the condenser.
The starting point to correcting a problem in a system like this is put it back to the way it was when it was built. Recover whatever refrigerant is in it (leak test it first), evacuate to a deep vacuum and then weigh in the correct amount of the correct refrigerant. This type of system is what we call a critical charge system and even an ounce or two of refrigerant can have a huge effect on performance.
Without knowing the more about the system and having more readings little diagnosis can be done, but 30deg C is 86 deg F which suggests that no work is being done. the pressure readings suggest an R-12 system which hasn't been used in probably 25 years. Any of the likely refrigerants would display pressures much higher than that.
Likely diagnosis is short of charge but don't just add - fix the leak, evacuate and re-charge

Bboline, This thread wondered around inventing facts and not looking for enough information that would help this boater. You were correct small refrigeration in a reasonable environment mean ambient temperatures from 60 to 80 degrees F perform well with a Cap tube refrigerant flow controller. It is a fact if ambient temperature decreases below or above design temps the superheat efficiency inside evaporator will change. No one asked the size of compressor all we new was it was smaller than 1/2 HP and larger than a small Danfoss BD compressor. It is the normal practice for mobile refrigeration like this one to use a TXV, liquid receiver and sight glass.