Holding plate freezer 12v recommendations

[a64pilot]

For $3,500 I’d at least try.
Then any replacement may not really be all that much better, once you get it running right anyway.

[Typhoon]

We recently built a small system for a customer with a very small box. The plate was only 12x6 inches all copper .

This was formated for a refrigerator and setup as such . It performed so well in testing that I built another one just for me to tinker with.

It is running as I write this, in our test box. Now 78 hrs in and amp hr usage at a mere 22Ah or just under 7 Ah in 24 hrs. The box is 7 cubic feet !! with R30 insulation and a "not so good lid" The shop is a little on the cool side at 67 degrees and temperatures in the box are being held between 1C to 3C.

Sorry for the thread drift but my point is I will try to get this large box down to deep freeze temperatures this weekend . All this testing is being done with R134a and one of our stock BD35 condensing units .

So a single 12x6 copper plate in a 7 cubic R30 box trying to get to 0 degrees Fahrenheit or -18C .

I will keep you posted . Also note that all ours systems are TXV based.

Regards John.

[Richard Kollmann]

There are limitations in evaporator freezing temperatures with 134a refrigerant. Small compressors lack the mass refrigerant flow at temperatures -16 degrees F and colder. As evaporator temperature is reduced so will the mass Btu flow of refrigerant be reduced. Once compressor Btu cooling of evaporator and refrigerated box is equal to heat loss of insulation box temperature will not get any colder no mater how long compressor runs. The most energy efficient evaporator pressure with 134a is 6.3 psi resulting evaporator temperature of zero degrees F. Holding plates with small 134a compressors trying to operate at subzero temperature are not as efficient as standard evaporators because there is an additional 10 to 20 degree of heat loss in eutectic solution phase change.

Refrigerant 502 was commonly used in boat freeze plates in the past but the Danfoss BD compressor is only approved for 134a. Holding plates serve only one purpose to store surplus energy and these small compressors rarely produce surplus energy.

[TJ D]

Originally Posted by Richard Kollmann

There are limitations in evaporator freezing temperatures with 134a refrigerant. Small compressors lack the mass refrigerant flow at temperatures -16 degrees F and colder. As evaporator temperature is reduced so will the mass Btu flow of refrigerant be reduced. Once compressor Btu cooling of evaporator and refrigerated box is equal to heat loss of insulation box temperature will not get any colder no mater how long compressor runs. The most energy efficient evaporator pressure with 134a is 6.3 psi resulting evaporator temperature of zero degrees F. Holding plates with small 134a compressors trying to operate at subzero temperature are not as efficient as standard evaporators because there is an additional 10 to 20 degree of heat loss in eutectic solution phase change.

Refrigerant 502 was commonly used in boat freeze plates in the past but the Danfoss BD compressor is only approved for 134a. Holding plates serve only one purpose to store surplus energy and these small compressors rarely produce surplus energy.

This is precisely my understanding and experience. I know that there are some tweaks, and some systems are better than others. ColdEh seems to have it dialed in nicely.

But, the bottom line for me is that I don't like the low-draw compressor running all the time. I'd rather give a holding plate a big hit at a time of my choosing.

I'm not sure that any of the little Danfoss-based systems will do that job.

Still looking for a recommendation on this kind of system, by the way... Anybody got one?

[Typhoon]

I think Seafrost would still be your best bet for an engine drive system . They sold lots of them .

Regards John

[TJ D]

Originally Posted by ColdEh Marine

I think Seafrost would still be your best bet for an engine drive system . They sold lots of them .

Regards John

Not looking for an engine drive... 12v only. '

I just talked to SeaFrost, incidentally, and they confirm that the temperatures that I'm seeing are about what they've designed their system to operate at. 0 at the plate during operation/20 degrees in the box average is in the ballpark for the 134a systems.

They do sell a 404 unit that should see plate temps at -15 to -20, more easily yielding lower box temps. It comes in the same footprint as the BDXP, and is a straight swap, so this is an option if I can't figure out a good holding plate solution.

They offer a 12v holding plate system, but it's really pricey. And also very heavy compared to the GB setup. Weight is always a concern for us.

[Typhoon]

You must be thinking of this system. Lots of kick and lots of amps . They occasionally come up on ebay for sale . One just sold on this forum. Is this to heavy ?

https://www.seafrost.com/DC%205000.html

Regards John.

[TJ D]

Yes, that's the one. I think that the cost to purchase and get it to Europe will be a bit high, though. The package runs about $6000. Shipping will add a lot too, plus install. I'm hoping to not see a bill pushing 10k for another freezer. I'll probably learn to love my crappy little Danfoss if this is my only option...

It's also a bit on the heavy side, about 80lbs all in.

[sailor bum 2020]

You should research Nova Cool system

[Nightcrawler]

The running on of the compressor we experienced with our new SeaFrost was due to loss of refrigerant on a loose fitting. Once it was sealed and recharged our compressor barely runs. Now in the vein of full disclosure - we have a cold plate refrigerator - but the issue may be the same. Constant compressor is not normal. Cleave has been a lifesaver for us.

[Richard Kollmann]

One has to think removing a unit that drew 45 amps and replacing it with a 3 to 8 amp per hour Danfoss compressor may not have been a good idea. The comparison is not complete without knowing hours per day that GB system ran? To determine how good insulation was, how often in 24 hrs and how long was compressor run? Large compressors systems with large eutectic plates are normally the answer for problems like yours on a 50 ft boat.

[rbrentp]

I had to rebuild my box. 5" of insulation with an R30. I have a BD50 and uses a very large plate that could be bent in a U and wraps around half the box at the bottom. I can set the unit to COLD and make ice cream to hard to spoon out. It uses 134a. I use the bottom of the box as freezer and the top have as fridge. Not has fancy as a side by side but the contents stay frozen at the base. Amp draw is minimal once the desired temp is reached.

I haven't tried the "how cold will it go" test as Non spoonable ice cream was my goal.

I live in Houston and with a water temp of 90f in the summer and air at 100f I get a pretty good differential.

My gut says something is wrong with the set up. I have seen it where a few PSI high or low in the system makes a huge difference in cooling.

[TJ D]

Originally Posted by Richard Kollmann

One has to think removing a unit that drew 45 amps and replacing it with a 3 to 8 amp per hour Danfoss compressor may not have been a good idea. The comparison is not complete without knowing hours per day that GB system ran? To determine how good insulation was, how often in 24 hrs and how long was compressor run? Large compressors systems with large eutectic plates are normally the answer for problems like yours on a 50 ft boat.

In tropical conditions, I'd estimate the GB system sucked down 70-90AH/day for the freezer. But, it didn't matter that much, because we typically run the engine for an hour a day at anchor, so at least half of the amperage use was covered by our very large alternator- we do not use 100% of the alternator's output potential for charging, so the GB basically ran for free for that period.

That's really the big difference. We don't have the advantage anymore of that big kick that we once did.

I'll be the first to admit that if I had this to do over again, I would not have gone the way we did.

Now that it's broken, I have the opportunity to fix that error. Hence the thread.

I should also say that I don't have any hard feelings toward SeaFrost-(Well, I'm bummed that the control module failed at 18 months, but that's Danfoss). I listened to a contractor who, in retrospect, didn't really understand our usage profile.

[Bill Seal]

Amp draw at 12 volts DC: 41 amp. hours (492 watts)

???????????????
Amp hours per what? Minute, hour, day, year?

[TJ D]

I would like to reiterate that I am not looking for advice on troubleshooting my existing system. It broke, and I will be replacing it with something else. There's no need to try to diagnose it. I have spoken with the manufacturer, and according to them, the temps that I have been seeing are consistent with their specifications.

Thanks, friends.