Are holding plates "old" technology?

[Scaramanga F25]

After cruising for years with 2 independent top brand holding plate systems in the same box, extra insulation etc etc with much maintenance and so-so performance, although some have had better, I discovered 12v Engel refrigerators and freezers. So easy to install and I have had years of
trouble-free use. Completely self-contained units. Just plug it in!
They use this type to fly donor organs in small aircraft in some areas.
I found out years ago about this type of "swing compressor" units from a pilot that flew for Doctors Without Borders.
Very efficient. Box is correctly sized. Lid locks closed.
I cruise in the sub-tropics.
Boat manufacturers should just build the boat with the space.

Do you build your fridge/freezer when you buy a house?

[RaymondR]

The answer to your question is "no", the system of generating power from sunlight and storing it in batteries favours the use of holding plates to store cold for usage during the times that no power is being generated, cold is cheaper to store than electricity.

[zboss]

Rich, is your holding plate always kept frozen at fridge temps?

[SV THIRD DAY]

Originally Posted by zboss

Rich, is your holding plate always kept frozen at fridge temps?

Yes. A freezer plate is set to freeze at -5 to 0 degs F. And a refrigerator plate is set to freeze at 25degs F. All based on the mix of glulycol. (33% for freezer 10% for refrigerator). We know from experience that the plate temp is usually 10degs F colder that the box temp, so that sets up the proper box temps while keeping the eutectic solution from doing the decorating phase change, which costs energy.

The freezer and refrigerator thermostats have different temp bands to always keep the plate frozen, or close to it in the real world.

[[[Oh but Rich...glycol and water are not true eutectics you are a fool....Bla bla bla.... Yes we know science, but it is close enough and does exhibit the properties of temp change without phase change, just not perfect.]]

[zboss]

ok, so you have different plate solutions for different target temps... that makes more sense.

Can you use multiple smaller plates instead of one big plate? I'm interested in building the box before putting the unit in but I'm concerned about the unit fitting through the access hatch.

[skipgundlach]

Originally Posted by zboss

ok, so you have different plate solutions for different target temps... that makes more sense.

Can you use multiple smaller plates instead of one big plate? I'm interested in building the box before putting the unit in but I'm concerned about the unit fitting through the access hatch.

EXCELLENT thought!

I'd have gone back with a problem-solved new Frigoboat keel cooled if I could have gotten my evaporator in the door I left when I built the new box.

But I couldn't, and I have three SS look-like-thin-holdover plates instead.

[SV THIRD DAY]

Originally Posted by zboss

Can you use multiple smaller plates instead of one big plate? I'm interested in building the box before putting the unit in but I'm concerned about the unit fitting through the access hatch.

Absolutely, we do dual freezer plates all the time. The plates are plumbed in series with the expansion valve sensing bulb put on the outlet of plate no 2. That way the Compressor and TXV treates the two plates as one.

What you can't do is run two different temp plates off one Compressor. Because you would only have one controlled with the thermostat.

We have a photo of a dual plate system at the bottom of our holding plate page.
http://cruiserowaterandpower.com/Holding_Plates.html

[CarinaPDX]

Clearly Third Day has this worked out. The important point is that the question is not just holding plate or not, but the system design. His holding plate system is nothing like the jacket-around-the-evaporator "improvement" sold by his competitors. His TXV system is an improvement on the capillary systems typically sold.

Some basic points: the amount of heat that needs to be extracted every day by the refrigeration is ALWAYS going to be equal to the amount of heat that gets conducted or convected into the space (not including cooling down new additions). Holding plates per se don't change this. Better insulation and sealing, top loading instead of side loading, unsealed drains, do have a major impact, so fix them first.

A holding plate, other things being equal, will result in fewer and longer compressor runs. This can result in some efficiency improvement, but ultimately the amount of heat removed is the same. As Third Day noted, the fewer starts should improve product life.

Personally I have a custom system installed in Turkey. It is a basic Danfoss BD35F capillary system with air and keel cooling, and (due to mistaken communication) a holding plate. It works well, but note that the guys who did it knew their stuff. As Third Day pointed out these systems are very critical as far as internal volume, quantity of refrigerant, and pressure drop across the capillary - not really for amateurs. I originally had a problem with the capillary, probably from contamination, so had new tubing installed with a larger/longer capillary (to maintain the pressure drop). Even for an experienced professional (not me), getting the charging right took a bit of time, and an added high pressure port for better instrumentation. The dual condensers added to the confusion. I'm happy with the result, but it was a unique situation. Next time I'll be looking at a packaged system.

BTW my previous system was an Isotherm seawater cooled one. It was complicated without much benefit and in the end very unreliable due to the seawater cooling design. In the future I will stick with keel cooling if at all possible.

For those that are using the Danfoss systems with the Danfoss basic controllers, you should be aware that the compressor speed can be manually adjusted by adding resistance into the thermostat loop. Without resistors the compressor runs at 2000rpm, but can also be set to run at 2500, 3000, and 3500 rpm. So adding a resistor can significantly improve the capacity/reduce run time for those with high duty cycles. The advanced controllers control the speed automatically, which is a benefit. Perhaps Third Day could comment on this.

Greg

[Frugal]

To add a few more facts to your decision making.
I run a 12/24 volt Danfoss Frigiboat compressor through an aluminium evaporator plate into a two compartment 3.5 cubic meter pretty well insulated top loading box.
The main box runs at just on accumulating ice on the evaporator IE 0 deg.
and the second box linked by a thin partition and a 10 cm hole keeps non freezable perishables at around 5 deg.
The compressor is air cooled and runs in 12 volt mode.
It has a rheostat control that allows it to run at 2000 rpm ( 3.8 amp) up to 3500 rpm using 6.8 amps.
In 2009 I ran the unit at 3500 rpm for 115 days and averaged 133 a/h per day. The unit ran hot and was hard to keep cool.
For the last 1,000 days I have run it at 2,000 rpm and have used 47.8 a/h per day average. It cycles around 50% with a couple of small computer fans assisting the airflow.
Ambiant air temperatures are typically, tropical, with 20 deg overnight rising to 30+ deg during the day.
The units consumption is remarkably similar to the output of 260 watts of solar panels over the 6 years of records.

In summary the main factors are:_
1. Excellent insulation.
2. Top loading access.
3. minimal rpm on the compressor.
4. Good circulation of cooling air.
5. Reduce ones consumption of ice cold beer, hence cooling load.

Hope the above makes sense and if you are passing, welcome to check the veracity of the cold beer.
Cheers

[Rick01541]

We have one of the older engine driven compressor and AC driven plate system (1998). The engine driven compressor with sea water cooling works great. We never use the AC system and have considered removing it. We are coastal cruisers and running the refrig while motoring in and out of harbors usually is sufficient for our needs. However, there are days where we have little to no motoring time and would like to add battery driven refrigeration in addition to keeping the engine driven system. What is the best way to do this? I'm not sure what drives the AC side of the system but can I simply replace what I assume is an AC compressor somewhere in the system with a DC compressor of the same size?

[Scrimshaw4]

IMHO the Sea Frost DC holding plate system with one compressor slave valved to both the refer and freezer thermostats is an OUTSTANDING system. Been running mine for 17 years with NO problems. It is, as others have also mentioned, CRITICAL to have the best insulation and gasket seals to maintain box efficiency. If you have a dark hull and the boxes are outboard additional insulation is recommended. Also remember to close your lids SLOWLY so as not to blow the cold air out from thye lid compression. The advantage of DC is you can leave the boat and the refer system will self tend.

[SV THIRD DAY]

Originally Posted by Rick01541

would like to add battery driven refrigeration in addition to keeping the engine driven system. What is the best way to do this? I'm not sure what drives the AC side of the system but can I simply replace what I assume is an AC compressor somewhere in the system with a DC compressor of the same size?

We do that all the time on dual cooling loop holding plate systems like you have. You can just replace the AC Compressor with a 12v DC Compressor and then have the best of both worlds:
A) the rapid cooling and "free" cooling BTUs when your engine is running while motoring or ru ning the engine at anchor for battery charging
B) the self temp regulation of a thermostat controlled system running on 12v.

Of course we would need to make sure the Compressor size matches your box, but it is a pretty easy swap out project. Email me a few photos of your current system along with a measurement of your box so I can calculate the cubic foot size, and how much insulation you have. I will be happy to shoot you some technical specs for the project along with pricing.
Info@technauticsinc.com

[undercutter]

Originally Posted by Scrimshaw4

IMHO the Sea Frost DC holding plate system with one compressor slave valved to both the refer and freezer thermostats is an OUTSTANDING system. Been running mine for 17 years with NO problems. It is, as others have also mentioned, CRITICAL to have the best insulation and gasket seals to maintain box efficiency. If you have a dark hull and the boxes are outboard additional insulation is recommended. Also remember to close your lids SLOWLY so as not to blow the cold air out from thye lid compression. The advantage of DC is you can leave the boat and the refer system will self tend.

Or you could just beef up your inverter to be able to handle the loads for the AC fridge and add a smart start to the system. We have both AC and DC driven compressors and both are sea frost but we hardly use the DC at all as the AC will pull the fridges down so fast and the DC cycles far more often even though we set the temps higher on the thermostats. I wonder whether this isn't actually less demanding for power in the end.

[newhaul]

Originally Posted by crazyoldboatguy

A Danfoss with an evaporator plate may well run nearly continuously in the tropics, so it isn't starting up and shutting down as often, if I have read that right. The compressor can slow down and act quite efficiently with the variable speed capacity. I have heard those compressors are quite robust, despite their tiny appearance. Less moving parts (capillary tubes instead of valves) and all that.

Running a holding plate with solar power and batteries is discouraged from what I have read. The convenience is that folks only need to run their generator in the am and pm to recharge the plate. I won't have a generator and will not use my propulsion motor for that purpose.

I've got a lot of learning to do. And a lot of thinking.

We have a cool blue system and have been running it off of our 200 watt solar array since march with no other battery charging. Use we are in the pnw but with 400 watts solar I'm sure it would be doable anywhere in the world. IMO

[jcapo]

Originally Posted by crazyoldboatguy

Running a holding plate with solar power and batteries is discouraged from what I have read.

No reason not to run a Cool Blue style or a larger compressor system with solar and wind but you need more than a couple of group 31 batteries to do it.

I run my DIY 1/2HP 12V split freezer/reefer holding plate system with solar and wind. During the peak southeast summers it uses 80 to 100AH daily that 390 watts of solar and an old Fourwinds wind machine takes care of most days.

Its 15 years old now. The small Danfoss compressors were not a consideration those days and probably not today for my box sizes.