Grunert AR-50-12

[Tommee]

I have an ancient Grunert AR-50-12 fridge freezer. It is 12v & runs off it's own 12v motor. This unit has been BRILLIANT!!! It is 40 years old & has never missed a beat! Remarkable. I live onboard & run it for 1- 1 1/2 hrs twice a day & it makes ice & does everything one would hope for. Very sadly it has just started making a dreadful noise which appears to be coming from the flywheel. It is still working normally at present but I feel the end is in sight. Sounds like a bearing, but I took the fan belt off & turned the flywheel manually & it sounded ok so might be more internal. I don't have any breakdown photos of the unit to see whats inside, just the manual for installation etc. I guess this may be terminal as the unit runs on Freon R12 which is unobtanium.
If anyone has any knowledge of this unit can they shed light/hope on this?
Ok, it owes me nothing & fridge experts have been telling me to ditch it for years, but why, when it has always worked so well? You won't get anything that is built these days to be so reliable.
Can anyone offer advice on a replacement please? I really like the running it twice a day aspect as I have a genset for power & only 1 solar panel for trickle charging the batteries. I really don't like fridge unit's that cycle on & off, they seem noisy & annoying. The spec on the present unit says it runs up to 5cu ft freezer capacity & 12cu ft fridge capacity.
As always any help, advice greatly appreciated.

[stormalong]

I used to have the same or similar system. 12 volt 40 amp Grunert tied to two holding plates, one freezer, one refer. Ran twice a day, controlled by a sprinkler timer I modified to do the job so that I did not have to run the engine. 300 watts of solar kept it running. Couldn't run the freezer because the power draw was to high to keep both going on solar.

I started having problems with the compressor and had to replace it with a used takeout. That compressor was no longer made and service parts are not made either.

I saw the handwriting on the wall and during a major refit I replaced it with two Adler-Barbour cold machines. Tremendous improvement. Low current, constant cycling has much lower impact on the batteries and I can run both freezer and refer when I want the freezer. Constant cycling translates to a 33% duty cycle for a five cubic foot refer and 50% duty cycle for a 2.5 cubic foot freezer. The temperature remains constant unlike the holding plate system.

I did that in 2009 and it has run great ever since. I did have to replace the freezer unit about five years ago because my installation did not account for drainage of condensation from the freezer when not running it. The pool of water in the box caused the evaporator plate to corrode.

A side benefit to replacing the Grunert is more space in each box and a tremendous weight savings. Each holding plate was incredibly heavy - hard to lift out of the boxes and the compressor skid was also very heavy to get out of the cockpit locker where it was mounted. Combined I estimate the system weighed 300 pounds.

[Bowdrie]

It would pay to have a tech evaluate the system.
Just a hunch, but the noise may be in the motor rather than the compressor.
Fortunately, both motors and compressors are available from "R Parts", but there are other companies which have rebuilt units, (internet searching).
For that matter, any good automotive starter shop should be able to re-build the motor without any trouble, (just a simple DC brush motor).
Yes, there are many ways, (mostly weight and space,) in which the newer 12V units are quite nice, but a BTU is still a BTU and no free lunch.
Your system, should you decide to keep it, (subject to evaluation,) is a system that is intuitive and can be serviced anywhere in the world with simple tools and a gage set.
R12? it IS still obtainable, but at high cost in the 1st world countries, but all over the 2nd and 3rd world R12 is alive and well.
That said, a good flushing and oil change(s) will allow an R12 unit to use the newer refrigerants, some of which are "drop in" replacements.
I wouldn't just "automatically" condemn your unit without some further investigation, those popular "mouse power" Danfoss units with their microprocessor controls and pressed aluminum evaporators are not cheap, nor are they anywhere near being an "end all, be all" device.
Another avenue may/might be the replacement of the, (I believe,) 1/2HP unit with an AC hermetic compressor, which might mount on the same baseplate in place of the existing compressor/motor combo, (the fan set-up needs to be accounted for).
Or just a complete 1/3>1/2 HP 120 AC condensing unit hooking up to the existing cold plates.
Such a system can run for many years but will need an inverter to run it away from the dock.

https://www.rparts.com/index.php?cPa...l2893te1mtnv95
https://www.rparts.com/index.php?cPa...tv156p9jd33kd2

[Tommee]

Very interesting, thank you. I am away cruising at present & hoping & praying this unit keeps going a while longer. I have today, found a tech who speaks our language & was going to do some research about what I believe you mention, a Danfoss replacement compressor & other options. This guy obviously understands the unit, wants to retain as much as possible & isn't one of the "toss it all out & buy new" brigade.
I have listened to the grinding noise & I don't think it's coming from the motor, I believe it's the compressor. I know absolutely nothing about this problem but am seriously loathe to dump this previously reliable unit. It is perfect for me.
A couple of points you may be able to clarify please:-

You mention AC compressor, do you mean Air Conditioning compressors?. As it happens I have a spare & not needed Cruisair unit in storage. My boat is 110v here in NZ where local power is 240v, so I often "inherit" stuff that imported yachts are dumping...very useful. If that compressor could be adapted that would be a plus.

I asked the fridge tech what that noise might be & he mentioned it could be running low on oil after all these years...maybe dumb question, but is that something I could fix? or will it be a sealed unit.

I wish I could track some R12 but as much as NZ prides itself on being a first World country, I haven't been able to source any & getting some imported may be impossible, Customs here are impossible to deal with.

I will certainly look up R Parts, that is a good link. Many thanks for your time & experience.

[ejs]

I had the same compressor and the same horrible noise, it was the motor bearing, and lasted a couple of weeks making the noise (I was also out and about) before seizing up completely.

[Tommee]

Thanks for that, I have been expecting a seizure any day but am actually weather bound & have been for several days & more to come. 50kts & 4m swells out there...good old NZ Summer weather!

By motor did you mean the 12v motor or the compressor?

[ejs]

The 12 volt motor, the compressor was fine. BTW I was in Minerva reef at the time.

[Bowdrie]

Originally Posted by Tommee

Very interesting, thank you. I am away cruising at present & hoping & praying this unit keeps going a while longer. I have today, found a tech who speaks our language & was going to do some research about what I believe you mention, a Danfoss replacement compressor & other options. This guy obviously understands the unit, wants to retain as much as possible & isn't one of the "toss it all out & buy new" brigade.
I have listened to the grinding noise & I don't think it's coming from the motor, I believe it's the compressor. I know absolutely nothing about this problem but am seriously loathe to dump this previously reliable unit. It is perfect for me.
A couple of points you may be able to clarify please:-

You mention AC compressor, do you mean Air Conditioning compressors?. As it happens I have a spare & not needed Cruisair unit in storage. My boat is 110v here in NZ where local power is 240v, so I often "inherit" stuff that imported yachts are dumping...very useful. If that compressor could be adapted that would be a plus.

I asked the fridge tech what that noise might be & he mentioned it could be running low on oil after all these years...maybe dumb question, but is that something I could fix? or will it be a sealed unit.

I wish I could track some R12 but as much as NZ prides itself on being a first World country, I haven't been able to source any & getting some imported may be impossible,

Although air conditioning compressors have been adapted for reefer/freezer usage it's not an ideal solution.
Air conditioning compressors are designed for high flow rate/high pressure/high temp use, (in refrigeration AC is considered high temp,) and the valve plates are different from units designed for low/medium temps.
Yes, automotive AC compressors have been used for low temp work, but they do it by brute force and RPMs must be kept fairly low for good service/long life.
Oil issues? the oil level can be checked, but both service valves must be closed to isolate the compressor, (the tech will know the process).
R12 in NZ? yeah, I hadn't noticed your location before, yes, I can imagine that getting R12 in NZ would be next to impossible.
Can you post some pics of the unit?
If the noise issue can be isolated to a particular device, then your options/actions can be more defined.

[Tommee]

Not too many fix it places on Minerva Reef, but a great place to be, remember it well.

Still weather bound & as you do, I have been holding a listen to the noise seminar After tuning in with a long screwdriver Votes are it is the 12v motor, not the compressor. I am hoping so as this will be an easier fix for this unit than a compressor problem. Still have to get to civilisation & hope it continues to hold up. Very many thanks to all for your help. I looked up R Parts, great site, thank you for that link.

[ejs]

The PO of my boat had actually purchased a replacement motor bearing, (I think it had gone out before) and I did replace it in Minerva, before all the frozen food spoiled. I had to cut the old bearing off carefully with a Dremel, since I didn't have the right puller. I hammered the new one back on using a deep socket as a drift on the inner bearing race.