Which Reefer System to Choose

[Cpt Mark]

Hi all,

As you may recall my 25 year old Grunert R-12 system died, not to be resurrected. I tried a huge Snomaster drop in ice chest thingy that freezes ice cream, great refrigeration but for cruising purposes just too small.

So, take it out and rebuild the refer box I had and install a new system. Ugh. My box is about 10 cf. It was way too deep before so will be a bit smaller.

Started looking at Isotherm and contacted their gurus for info. Based on reports here started looking at Cool Blue and had a very good talk with them. then I ran across Nova Kool also from this site and they look good.

Cool blue uses holding plates with the expectation that they kick on 4 times a day using around 40-45 amps in the tropics where I'm headed. The other 2 use thin plate condensers which will cycle on/off all day but according to specs use about the same amount of energy.

Cool Blue around $2700
Isotherm around $1300 (one large bendable plate
Nova Kool $1000 (3 plates connected)

Nova Kool only uses a a Seacop BD 35 but can build one with a BD 50.

All will will freeze to around 15f and hold a spillover. Cool Blue says if only used as a freezer, sized accordingly, it will keep ice cream frozen. Not sure about the others. Not a deal breaker but... lol

Looks like I could get 2 nova kools reasonably and have 2 separate systems. BTW- Cool Blue said the total energy draw would be the same with 2 units as one. the box size is the box size and you're only cooling "x" cf.

I'm looking for opinions from our refer experts and those who have/had any of these systems.

Thanks,

[a64pilot]

Even if you insulate a 10 cuft box exceptionally well, it’s unlikely that a single bd50 will be able to be anything but a fridge.
A single BD80 can do it as a spillover, but really what makes a lot of difference is the R value of your box.
Best is two systems, one for the fridge half likely a bd50 and a BD80 for the freezer half if your wanting to keep ice cream, that takes below zero temps, which is tough.

[Cpt Mark]

Originally Posted by a64pilot

Even if you insulate a 10 cuft box exceptionally well, it’s unlikely that a single bd50 will be able to be anything but a fridge.
A single BD80 can do it as a spillover, but really what makes a lot of difference is the R value of your box.
Best is two systems, one for the fridge half likely a bd50 and a BD80 for the freezer half if your wanting to keep ice cream, that takes below zero temps, which is tough.

Thank you. yes, Ice cream is ridiculously tough and really not the primary goal. Maybe an frozen dream lol.

So there are 2 styles of systems. One uses cold plates, runs less and the other uses evaporator plates and runs more. Is the cold plate system really that much better? This is where I'm struggling. I can put in 2 of the evaporator plate systems for the cost of the holding plate single system.

All manufacturers are saying their systems will work in 90 degrees etc.

[john61ct]

Most people say that in and of itself, the eutectic holding plate technology does not deliver Ah per day greater efficiency.

But energy savings can be tremendous if your charging times are (mostly) during "free excess" power generated, like solar output after the battery bank is full, or from running ICE sources for other reasons.

Ozepete has detailed data that **his** eutectic system was **much** more energy efficient than evaporative plates, but some here expressed skepticism no one tried to replicate the test.

Aside from cost issues, I would choose based on service and support, and Rich wins on that score hands down as confirmed by hundreds across all the forums.

[a64pilot]

It’s really not as simple as just hold over plates vs thin plate evaporator.

The hold over plates original design was I believe intended to be primarily an engine driven large compressor removing a huge amount of heat from a significant amount of eutectic fluid, and then over night the large mass of frozen fluid would keep food cold until the next day and the engine was again run.
However there is more to a system than the evaporator, there is capillary tube systems which are very sensitive to refrigerant charge, so much so that it’s an art getting the charge level correct and there are thermal expansion valve systems that are not at all sensitive to refrigerant level, then does a system have a filter / drier? Finally a system, is well a system and the condenser that never gets much press is as important as the evaporator, plus how is the condenser cooled and is it sized large enough? Is there any additional compressor cooling?
Finally how many proprietary pieces does a system have, meaning can you get replacement parts easily of are they only available in one place?
Finally how is the support? That to me is vital. Any system you consider buying from the Windlass to the Radar or refrigeration etc., before you buy, give customer support a call and see who you are talking to, if it’s a call center that the best they can do is open a service ticket for you, or their answer is box it up and send it in and we will inspect for warranty, I’d give them a pass, cause that’s not going to help much out in the sticks.

If it’s a smaller company, how long have they been in business? Not real important unless there are proprietary parts, then it’s important.

Properly designed, a thin plate evaporator system can be as efficient as a cold plate, in theory it can be more efficient as it’s cooling the food directly where a cold plate system is first cooling the plate and the plate is cooling the food.

However it’s almost a certainty that all inexpensive systems are always thin plate, capillary tube systems, that doesn’t mean that are all junk, but it’s certainly a lot less expensive to manufacture.

In other words I’m afraid your going to have to do your due diligence and do some reading, this is a good place to start.

Myself, personally I’m a fan of KISS, the fewer the parts, the more common those parts are and how simple is the system to service means a whole lot to me, I’m, not a fan or electronic controls, in my opinion they really don’t do much to increase efficiency and are very often the source of problems.
You want a simple system that you can jumper the thermostat for example until a replacement comes in, or use a computer fan for the condenser until the proper fan comes in etc.
Carry a spare controller, no matter who’s system you buy, that’s the one thing that is irreplaceable and you can’t jury rig

[Cpt Mark]

Originally Posted by john61ct

Most people say that in and of itself, the eutectic holding plate technology does not deliver Ah per day greater efficiency.

But energy savings can be tremendous if your charging times are (mostly) during "free excess" power generated, like solar output after the battery bank is full, or from running ICE sources for other reasons.

Ozepete has detailed data that **his** eutectic system was **much** more energy efficient than evaporative plates, but some here expressed skepticism no one tried to replicate the test.

Aside from cost issues, I would choose based on service and support, and Rich wins on that score hands down as confirmed by hundreds across all the forums.

Thank you, good points all

[Cpt Mark]

Originally Posted by a64pilot

It’s really not as simple as just hold over plates vs thin plate evaporator.

The hold over plates original design was I believe intended to be primarily an engine driven large compressor removing a huge amount of heat from a significant amount of eutectic fluid, and then over night the large mass of frozen fluid would keep food cold until the next day and the engine was again run.
However there is more to a system than the evaporator, there is capillary tube systems which are very sensitive to refrigerant charge, so much so that it’s an art getting the charge level correct and there are thermal expansion valve systems that are not at all sensitive to refrigerant level, then does a system have a filter / drier? Finally a system, is well a system and the condenser that never gets much press is as important as the evaporator, plus how is the condenser cooled and is it sized large enough? Is there any additional compressor cooling?
Finally how many proprietary pieces does a system have, meaning can you get replacement parts easily of are they only available in one place?
Finally how is the support? That to me is vital. Any system you consider buying from the Windlass to the Radar or refrigeration etc., before you buy, give customer support a call and see who you are talking to, if it’s a call center that the best they can do is open a service ticket for you, or their answer is box it up and send it in and we will inspect for warranty, I’d give them a pass, cause that’s not going to help much out in the sticks.

If it’s a smaller company, how long have they been in business? Not real important unless there are proprietary parts, then it’s important.

Properly designed, a thin plate evaporator system can be as efficient as a cold plate, in theory it can be more efficient as it’s cooling the food directly where a cold plate system is first cooling the plate and the plate is cooling the food.

However it’s almost a certainty that all inexpensive systems are always thin plate, capillary tube systems, that doesn’t mean that are all junk, but it’s certainly a lot less expensive to manufacture.

In other words I’m afraid your going to have to do your due diligence and do some reading, this is a good place to start.

Myself, personally I’m a fan of KISS, the fewer the parts, the more common those parts are and how simple is the system to service means a whole lot to me, I’m, not a fan or electronic controls, in my opinion they really don’t do much to increase efficiency and are very often the source of problems.
You want a simple system that you can jumper the thermostat for example until a replacement comes in, or use a computer fan for the condenser until the proper fan comes in etc.
Carry a spare controller, no matter who’s system you buy, that’s the one thing that is irreplaceable and you can’t jury rig

Very good points and info to consider which is why I'm posting here. Manufacturers are not liable to tell you their system is sub par lol

[john61ct]

To be honest in this niche, things are **so** competitive.

The sub-par got wiped out long ago.

Minor differences, slightly different factors.

Question is, which one picks up the phone 6am Vanuatu time on a Sunday and is happy to patiently step you through the troubleshooting process?

Doesn't charge for it?

What's that worth over the next ten years?

[Uncle Bob]

Do yourself a favour, send an email to ozefridge and ask them the question.

[SV THIRD DAY]

Originally Posted by Cpt Mark

All manufacturers are saying their systems will work in 90 degrees etc.

Not exactly.....
Once you hit 90-degs with the Critical Orifice systems you start losing condenser efficiency. However the CoolBlue system will not lose condenser efficiency until the ambient temp hits above 120-degs. That is a Huge Difference for systems designed to operate in the tropics. Why...how can CoolBlue claim this? It's the difference in design between a capillary system vs an expansion valve system. In a Capillary system you have to match the size of your condensing unit (Radiator) with the size of your evaporator. But on a system with a thermally adjusting expansion valve, you do not need to balance the condenser and evaporator. So this means you can dramatically oversize the condenser to allow for greater heat dissipation. It's not magic or sales hype, it's just good refrigeration system design for boats going to the Tropics, which is our target market.

[Richard Kollmann]

A 35 ft cat would have the refrigerator in the main cabin and not in one of the pods where amount of insulation is always a problem. The 25 year old 12 volt Grunert refrigerator if ¼ HP drew 14 amps, if it were a ½ HP system it drew 31 amps. Grunert 12 volt units larger than ½ HP were interlocked to prevent them from running unless a alternator or generator was running. All of these units produced surplus energy this is why eutectic energy storage plates where used instead of standard evaporators.

Then considering a replacement for these older large 12 volt refrigeration systems with asmall 12 volt systems is how much energy was consumed daily to satisfy the box temperatures you desired then. If the old system in a tropical climate consumed over 200 amp-hrs per day the replacement small twelve volt compressors will lower the daily amperage by maybe 25%. My point is there is little if any surplus energy produced by small 12 volt BD compressors. The first question that needs to be answered is the boats Direct Current power grid sufficient enough to support all of your house DC power along with 12 volt small refrigerator compressors. Do not fall for the poppycock that eutectic plates are more efficient than properly sized evaporators or cycling compressors have to be less efficient than those with eutectic plates.

My recommendation is you should address your DC power grid first battery capacity alone is not enough always add alternative electrical energy first because even with a 150 amp-hr alternator and 800 amp-hr battery bank managing daily power management would be difficult to support the added 10 cubic foot refrigerator Freezer.

The age and moisture content of most old box insulation is important. The divider that separates refrigerator section from freezer need to be at least an R value of 10 in order to provide a area temperature difference of at least 25 degrees F. Reducing the interior size of box with moisture proof closed cell insulation will reduce energy demand.

Once you addressed the power requirements I would recommend 60/40 percent refrigerator freeze box powered by two Nova Kool units with BD50 compressors. If lid opening size permits I would install their large bin box shaped evaporators high in each freezer refrigerator compartments for redundancy if needed. This also provided a quick freeze section in freezer. As cruising climate temperatures change I recommend either a means of switching compressor speeds manually or by up grading the compressor module Designed for the Danfoss AEO module design for BD50 compressors.

[Cpt Mark]

Originally Posted by Richard Kollmann

A 35 ft cat would have the refrigerator in the main cabin and not in one of the pods where amount of insulation is always a problem. The 25 year old 12 volt Grunert refrigerator if ¼ HP drew 14 amps, if it were a ½ HP system it drew 31 amps. Grunert 12 volt units larger than ½ HP were interlocked to prevent them from running unless a alternator or generator was running. All of these units produced surplus energy this is why eutectic energy storage plates where used instead of standard evaporators.

Then considering a replacement for these older large 12 volt refrigeration systems with asmall 12 volt systems is how much energy was consumed daily to satisfy the box temperatures you desired then. If the old system in a tropical climate consumed over 200 amp-hrs per day the replacement small twelve volt compressors will lower the daily amperage by maybe 25%. My point is there is little if any surplus energy produced by small 12 volt BD compressors. The first question that needs to be answered is the boats Direct Current power grid sufficient enough to support all of your house DC power along with 12 volt small refrigerator compressors. Do not fall for the poppycock that eutectic plates are more efficient than properly sized evaporators or cycling compressors have to be less efficient than those with eutectic plates.

My recommendation is you should address your DC power grid first battery capacity alone is not enough always add alternative electrical energy first because even with a 150 amp-hr alternator and 800 amp-hr battery bank managing daily power management would be difficult to support the added 10 cubic foot refrigerator Freezer.

The age and moisture content of most old box insulation is important. The divider that separates refrigerator section from freezer need to be at least an R value of 10 in order to provide a area temperature difference of at least 25 degrees F. Reducing the interior size of box with moisture proof closed cell insulation will reduce energy demand.

Once you addressed the power requirements I would recommend 60/40 percent refrigerator freeze box powered by two Nova Kool units with BD50 compressors. If lid opening size permits I would install their large bin box shaped evaporators high in each freezer refrigerator compartments for redundancy if needed. This also provided a quick freeze section in freezer. As cruising climate temperatures change I recommend either a means of switching compressor speeds manually or by up grading the compressor module Designed for the Danfoss AEO module design for BD50 compressors.

My Grunert was a 3/4 hp 120 volt AC system. I have a 4kw get set on board and am adding solar and maybe wind.

The original box is out and gone. Replacing the 25 year old 4"foam with at least 4" and maybe as much as 6" depending on box final size.

As I read the specs, it appears that either the Nova Kool or the Cool Blue will not use that many amps per day. 50? Am I wrong in how I interpret their literature?

Thank you

[Cpt Mark]

Originally Posted by SV THIRD DAY

Not exactly.....
Once you hit 90-degs with the Critical Orifice systems you start losing condenser efficiency. However the CoolBlue system will not lose condenser efficiency until the ambient temp hits above 120-degs. That is a Huge Difference for systems designed to operate in the tropics. Why...how can CoolBlue claim this? It's the difference in design between a capillary system vs an expansion valve system. In a Capillary system you have to match the size of your condensing unit (Radiator) with the size of your evaporator. But on a system with a thermally adjusting expansion valve, you do not need to balance the condenser and evaporator. So this means you can dramatically oversize the condenser to allow for greater heat dissipation. It's not magic or sales hype, it's just good refrigeration system design for boats going to the Tropics, which is our target market.

Thank you for the info. I spoke with you on the phone last week and have watched some of your videos as well.

[SV THIRD DAY]

Originally Posted by Cpt Mark

My Grunert was a 3/4 hp 120 volt AC system. I have a 4kw get set on board and am adding solar and maybe wind.

The original box is out and gone. Replacing the 25 year old 4"foam with at least 4" and maybe as much as 6" depending on box final size.

As I read the specs, it appears that either the Nova Kool or the Cool Blue will not use that many amps per day. 50? Am I wrong in how I interpret their literature?

Thank you

Having a NovaCool in our test box, it's the classic difference of a Critical Orifice vs Holding Plate system in terms of power usage, even more so at the warmer temps when the small condensing unit starts losing efficiency above 90-degs. For a 10CF Box, one BD 50 compressor unit just won't keep you happy, that's where the larger BD80 compressor I believe is a must for a box that size if you want to stick with one system vs two. If you don't have the BTU removal capacity in the compressor to start with, it doesn't matter how "efficient" the system is...you can't beat the laws of physics.

[sailcrazy]

Following. Our smaller boxes (4.5cf refer+2.5cf freezer) both run off a 3/4hp AC single compressor with a solenoid switching valve, but we need to operate our genset 2x ea day to pull the boxes down. Consideration of the holding plates physical size vs evaporator plates is also a real factor in a smaller box configuration; the extra space the holding plates occupy really reduces useable food storage space.