Refrigeration Upgrade

[daga]

I have a 41' Van de Stadt Norman that I live on full time with my partner. We are currently in Tasmania but this is just the start of our journey and we intend to spend next southern winter in the tropics.

The boat came with separate fridge and freezer, each driven by two circuits: one from a 240VAC compressor and the other from the engine via a Sanden compressor. The engine circuit has failed, at this stage I am not sure why-- the compressor gets very hot but the temp of fridge and freezer remain the same.

Regardless of the fault, I am not happy with the design of the system and would much prefer a DC powered compressor system. So I am using this 'opportunity' to explore how I might upgrade the existing system. I should make clear that the fridge and freezer appear to be well-insulated, in excellent condition, and very well constructed of stainless steel with enormous holding plates. The freezer takes about a week to come to room temp, and that is with the lid open a good deal of the time! The fridge is not quite so good as it has a front-opening door, but it's adequate.

The objective is to replace the existing compressors (both 240VAC and engine) with a 12V DC system that will last at least 10 years. On a previous boat I installed a Danfoss BD35 and it was pretty impressive, but that boat had a smaller fridge/freeze and no holding plates.

For this boat I am looking at the Ozefridge range. From a brief email exchange with Ozefridge I was informed it would be best to replace the existing holding plates with their units. This seems to me like a LOT of work, especially given that the existing holding plates appear to be custom made to the exact size of the respective boxes, and of course there is very limited access to the back of the boxes, which seem to have been built against the inside of the hull.

Advice from a local fridge mechanic was not to bother with a water-cooled Ozefridge but just put in 12V DC compressors with air-cooled condensers using the existing engine-driven refrigerant circuits, and maybe even leave the 240VAC compressor. The only downside I see to this solution is it is not as efficient as the Ozemail. Is that right?

So which is the best alternative? The Ozefridge solution sounds good, but I am afraid the work involved in replacing the holding plates will become a nightmare and take more skill and agility than I have. The ideal solution from my point of view would be to install a couple of Ozefridge units but utilize the existing holding plates. I don't understand why Ozefridge advised against this. Any thoughts?

[Typhoon]

Here's a few reasons you don't want water cooling ,

This is from my web site

Avoid These 5 Refrigeration System Problems

Also holding plates are really designed for systems that can generate large amount of power and are used to store that energy in the form of a frozen holding plate when the engine or shore power are not available. These small 12v systems don't have that power to spare , some manufactures use them to cut down on cycling the condensing unit. These system use a captube to control refrigerant flow and are controlled by evaporator plate temperatures, A holding plate responds slower therefore the compressor will run until desired temperature are reached, cutting down on the number of cycles to bring the box temperature down .

If you don't change your plates , they may actually be to big for your small dc compressors and never reach desired box temperatures. Also how will you control refrigerant flow ? these plates most likely will have a TXV , you will need to go to a captube system as the Ozefridge uses a captube to control refrigerant flow so there entire system is designed around that.

I recommend going with the plates that come with what ever system you decide to use . If you use the old plates the install will be difficult to achieve your desired results , plus you will have to employ a tech to come and install it and redesign the system as he goes , not cheap and tough to find someone like that . Plus you will void any warranty .

A ready to install system you can do yourself with no special skills or tools , they come precharged .


Regards John.

[ben373]

I have installed an ozfridge and they do work well. However, they use about 8 amps when running and the fan is quite powerful and hence noisy. The evaporation side of refrigeration really needs to be matched exactly to the condenser. The fresh water cooled unit is worthwhile but more work to install. Check out seebreeze industries for Waeco equipment. This is a lot cheaper. How big is your fridge?

[a64pilot]

Contact Rich Boren of Cool Blue, he will custom build an air cooled system for you that I bet will keep your existing cold plates

Or maybe John can?

[TheWatchman]

Isotherm 2013 Compact Refrigeration Kit. West Marine $1000. Installed one four years ago, outstanding unit.

[Typhoon]

Originally Posted by a64pilot

Contact Rich Boren of Cool Blue, he will custom build an air cooled system for you that I bet will keep your existing cold plates

Or maybe John can?

Hey Pilot , yes I probably could build him a system that would do the job . Sounds like he has got quit the setup with some big plates .
Thanks for the vote of confidence .

Regards John Tully

[SV THIRD DAY]

We do about 4-5 Holding Plate Recycle projects like this per mounth because as long as the holding plates are in good shape they pretty much last forever (or forever defined as your years of boat ownership0.

The process is pretty easy when you boil it down.
You will have a separate 12v air cooled compressor unit for each Box, refrigerator and freezer. You will need a new copper line set to connect the compressor to the holding plates(s). A new 12v thermostat and then some miscellaneous fittings. The hardest part of the entire project is if your current system is running on R12 rather than R134a. IF so, you will need to acetone rinse out the holding plates and replace the R12 expansion valve with a R134a. The old R12 Oil is not compatible with the R124a gas and it will gum up the internals. It's really that difficult, but you will need someone to vacuum down the system locally and perhaps do a little silver soldering for a few fittings if you don't want to use copper/brass compression fittings for your in field connections.

If you want to review the details and get some pricing, just shoot me an email at Info@TechnauticsInc.com and I'll be happy to help.

It's also pretty common for others to tell you to "just replace the whole system" because it really is more work for the company to help walk you through the project than it is to ship out a complete new unit. But why get rid of perfectly working and usable holding plates just to make it easier on the Company? I don't get that...well I do...but it's still wrong in my opinion.

You can download our manual and see how the system plumbs together and how it works, just imagine putting your holding plate in the loop.
http://www.cruiserowaterandpower.com...anual_2015.pdf

We ship DHL pretty much anywhere in the world, shipping a holding plate recycling project out tomorrow to Hong Kong in fact.

Cheers

[RaymondR]

Originally Posted by SV THIRD DAY

We do about 4-5 Holding Plate Recycle projects like this per mounth because as long as the holding plates are in good shape they pretty much last forever (or forever defined as your years of boat ownership0.

The process is pretty easy when you boil it down.
You will have a separate 12v air cooled compressor unit for each Box, refrigerator and freezer. You will need a new copper line set to connect the compressor to the holding plates(s). A new 12v thermostat and then some miscellaneous fittings. The hardest part of the entire project is if your current system is running on R12 rather than R134a. IF so, you will need to acetone rinse out the holding plates and replace the R12 expansion valve with a R134a. The old R12 Oil is not compatible with the R124a gas and it will gum up the internals. It's really that difficult, but you will need someone to vacuum down the system locally and perhaps do a little silver soldering for a few fittings if you don't want to use copper/brass compression fittings for your in field connections.

If you want to review the details and get some pricing, just shoot me an email at Info@TechnauticsInc.com and I'll be happy to help.

It's also pretty common for others to tell you to "just replace the whole system" because it really is more work for the company to help walk you through the project than it is to ship out a complete new unit. But why get rid of perfectly working and usable holding plates just to make it easier on the Company? I don't get that...well I do...but it's still wrong in my opinion.

You can download our manual and see how the system plumbs together and how it works, just imagine putting your holding plate in the loop.
http://www.cruiserowaterandpower.com...anual_2015.pdf

We ship DHL pretty much anywhere in the world, shipping a holding plate recycling project out tomorrow to Hong Kong in fact.

Cheers

I like this blokes advice as he appears to know what he is talking about.

A relatively small compressor running on 12V is going to have to run continuously to pull down a holding plate designed for an engine driven eutectic system so I would put a second fan under the compressor to assist in cooling it.

Once the holding plate is pulled down it should not use any more amp hours to keep down than any other system and you will have a much longer hold over capacity in the event of problems.

My 12V system was rigged up this way and I put a timer on the compressor control so that the compressor would not run at night. Because the compressor only ran during the day when there was lots of solar power available the batteries did not pull down very much and I got a very long life out of them.

[OzePete]

Originally Posted by daga

I have a 41' Van de Stadt Norman that I live on full time with my partner. We are currently in Tasmania but this is just the start of our journey and we intend to spend next southern winter in the tropics.

The boat came with separate fridge and freezer, each driven by two circuits: one from a 240VAC compressor and the other from the engine via a Sanden compressor. The engine circuit has failed, at this stage I am not sure why-- the compressor gets very hot but the temp of fridge and freezer remain the same.

Regardless of the fault, I am not happy with the design of the system and would much prefer a DC powered compressor system. So I am using this 'opportunity' to explore how I might upgrade the existing system. I should make clear that the fridge and freezer appear to be well-insulated, in excellent condition, and very well constructed of stainless steel with enormous holding plates. The freezer takes about a week to come to room temp, and that is with the lid open a good deal of the time! The fridge is not quite so good as it has a front-opening door, but it's adequate.

The objective is to replace the existing compressors (both 240VAC and engine) with a 12V DC system that will last at least 10 years. On a previous boat I installed a Danfoss BD35 and it was pretty impressive, but that boat had a smaller fridge/freeze and no holding plates.

For this boat I am looking at the Ozefridge range. From a brief email exchange with Ozefridge I was informed it would be best to replace the existing holding plates with their units. This seems to me like a LOT of work, especially given that the existing holding plates appear to be custom made to the exact size of the respective boxes, and of course there is very limited access to the back of the boxes, which seem to have been built against the inside of the hull.

Advice from a local fridge mechanic was not to bother with a water-cooled Ozefridge but just put in 12V DC compressors with air-cooled condensers using the existing engine-driven refrigerant circuits, and maybe even leave the 240VAC compressor. The only downside I see to this solution is it is not as efficient as the Ozemail. Is that right?

So which is the best alternative? The Ozefridge solution sounds good, but I am afraid the work involved in replacing the holding plates will become a nightmare and take more skill and agility than I have. The ideal solution from my point of view would be to install a couple of Ozefridge units but utilize the existing holding plates. I don't understand why Ozefridge advised against this. Any thoughts?

Daga, the reason why Ozefridge recommend that you replace the eutectic plates is simply because those plates were engineered originally for a much larger capacity condensing unit. Possibly also a different refrigerant, possibly contaminated and simply DO NOT come close to matching the evaporator tubing size, and hence refrigerant velocity, required for ANY of the DC condensing units offered today. As you would have been advised by Ozefridge, connecting to your existing evaporator(s) would work but could lead to evaporator oil retention and therefore compressor damage.
At Ozefridge we supply systems that are correctly engineered and coupling an Ozefridge condensing unit to evaporator(s) of unknown value is not something we do.
As for comments made by some regards problems with capillary systems.. rubbish!
Of all the fridges, freezers and air conditioners we own or have ever owned, they have almost all been capillary systems. So when was the last time your fridge, freezer etc had a capillary tube problem? My money is on NEVER!
Cheers, OzePete, Ozefridge

[Typhoon]

Originally Posted by OzePete

Daga, the reason why Ozefridge recommend that you replace the eutectic plates is simply because those plates were engineered originally for a much larger capacity condensing unit. Possibly also a different refrigerant, possibly contaminated and simply DO NOT come close to matching the evaporator tubing size, and hence refrigerant velocity, required for ANY of the DC condensing units offered today. As you would have been advised by Ozefridge, connecting to your existing evaporator(s) would work but could lead to evaporator oil retention and therefore compressor damage.
At Ozefridge we supply systems that are correctly engineered and coupling an Ozefridge condensing unit to evaporator(s) of unknown value is not something we do.
As for comments made by some regards problems with capillary systems.. rubbish!
Of all the fridges, freezers and air conditioners we own or have ever owned, they have almost all been capillary systems. So when was the last time your fridge, freezer etc had a capillary tube problem? My money is on NEVER!
Cheers, OzePete, Ozefridge

Hi Pete.

"problems with capillary systems.. rubbish! " ?

The forums are full of people having troubles with there systems that use cap tubes for a metering device .

This is one .

Procedure for removing a blockage on Frigoboat cap tubes | Jeanneau Owners Network Forum

And land dwellers have trouble as well .

Capillary Blocked?

Just google it ! , wow ! seems like a little speck of dirt can really ruin your day .

If this happens to your fridge at home , not problem. If you are the San Blas Islands ? Hmmm..... you may have trouble .

Regards John Tully

[Suijin]

Marine refrigeration professional cage match.

[botanybay]

Interesting that here in the United states almost all split evaporator/confensor air conditioning systems installed since 2007 have txv installed.

The reason is to make a mandated efficiency level, the valves are not mandated, the target efficiency level is.

From what I can find online a retrofit of an average split home air-conditioning system to add a txv results in between 15% to 25% reduction in energy consumption on the unit retrofitted.

These retrofit kits are produced by Danfoss as well as others.

The push back is from air conditioning service companies whose technicians sometimes don't understand the more complex txv vs a fixed metering device.

I suspect a similar effect is being seen in these refrigeration compressors.

However, does the $100 cost for the part (end user single part cost) justify the energy savings.

I have been trying (for fun) To work through the thermodynamics of the trade from data sheets and measured heat load for my box.... perhaps soon...

I suspect that the flat plate evaporator may not have a consistent enough heat load for the valve to respond correctly but that is purely a guess at this point.

This might suggest why the cool blue and coldeh systems have either a small holding plate or a thermal mass of copper (can't tell how the coldeh evaporator is constructed but looks like a good bit of copper)

There are probably box/heat loads where it helps and ones where the downside is primarily cost/complexity which could impact reliability.

Still tinkering with numbers, may start a new thread if my spreadsheet shows something interesting.

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[Typhoon]

Originally Posted by botanybay

Interesting that here in the United states almost all split evaporator/confensor air conditioning systems installed since 2007 have txv installed.

The reason is to make a mandated efficiency level, the valves are not mandated, the target efficiency level is.

From what I can find online a retrofit of an average split home air-conditioning system to add a txv results in between 15% to 25% reduction in energy consumption on the unit retrofitted.

These retrofit kits are produced by Danfoss as well as others.

The push back is from air conditioning service companies whose technicians sometimes don't understand the more complex txv vs a fixed metering device.

I suspect a similar effect is being seen in these refrigeration compressors.

However, does the $100 cost for the part (end user single part cost) justify the energy savings.

I have been trying (for fun) To work through the thermodynamics of the trade from data sheets and measured heat load for my box.... perhaps soon...

I suspect that the flat plate evaporator may not have a consistent enough heat load for the valve to respond correctly but that is purely a guess at this point.

This might suggest why the cool blue and coldeh systems have either a small holding plate or a thermal mass of copper (can't tell how the coldeh evaporator is constructed but looks like a good bit of copper)

There are probably box/heat loads where it helps and ones where the downside is primarily cost/complexity which could impact reliability.

Still tinkering with numbers, may start a new thread if my spreadsheet shows something interesting.

Sent from my SM-G935V using Cruisers Sailing Forum mobile app

An educated consumer , our best customer.

Yes refrigeration is a steep learning curve for sure , understanding liquid/vapor/pressure and how it all goes together to make something cold is a little bit confusing and not for every one. But it is not a "black art"

Here's a little light reading.

http://icemeister.net/backroom/wp-co...ed-Version.pdf

One reason we don't use one .

Yes , the plates I build are all copper , nothing else .There thermal conductivity is second to none , twice that of aluminum and ten times that of stainless . They have no hold over capacity at all . They respond very quickly to heat loading in the box and just as well when the compressor runs and responding to the refrigerant flow . A huge benefit is the ability to defrost the system quickly . Remember ice is an insulator robbing energy from your system. People leave far to much ice on the holding plates , and I can understand that , it takes a very long time to bring a holding plate up to temperature to release the ice . As for a consistent heat load for the valve to operate , this is a not an issue, the sensing bulb itself has a damping effect as it regulates the TXV .

As for cost, yes these TXV systems are much more costly to build , not just the valve itself but also the receiver drier , sight glass, twin' Noctua' fans and now we are free to over condense the refrigerant and use a huge efficient condenser. Ours are all copper as well, no aluminum fins . Thin aluminum plates with captubes attached come in by the truck loads and are very cheap. The cost on the parts alone in our system are in excess of what you would pay for complete captube system from say, NovaKool .

As for reliability , check the warranty of the systems you are looking at, that should say it all .


Regards John Tully

[Richard Kollmann]

Hybrid Engine Drive and 220 volt electrical compressor decisions whether to repair or down grade to 12 volt should be carefully studied before making a major mistake. Live aboard 41 foot cruising sail boats intended to be operated in warm climates with separate freezer and refrigerator boxes are not good candidates for 12 volt refrigeration, because of daily energy requirements.

Your present refrigeration unit’s capacities together are around maybe 9,000 btu per hour. Experience and Danfoss BD35 to BD50 application compressor performance figures limit Btu of these 12 volt compressors to 200 to 800 Btu per hour depending on box temperature and compressor operating speed.

My advice Before replacing present systems with a 12 volt system is, have the system designer/seller post a System performance Bound for complete system cost at your bank.

[botanybay]

Originally Posted by ColdEh Marine

An educated consumer , our best customer.

Yes refrigeration is a steep learning curve for sure , understanding liquid/vapor/pressure and how it all goes together to make something cold is a little bit confusing and not for every one. But it is not a "black art"

Here's a little light reading.

http://icemeister.net/backroom/wp-co...ed-Version.pdf

One reason we don't use one .

Yes , the plates I build are all copper , nothing else .There thermal conductivity is second to none , twice that of aluminum and ten times that of stainless . They have no hold over capacity at all . They respond very quickly to heat loading in the box and just as well when the compressor runs and responding to the refrigerant flow . A huge benefit is the ability to defrost the system quickly . Remember ice is an insulator robbing energy from your system. People leave far to much ice on the holding plates , and I can understand that , it takes a very long time to bring a holding plate up to temperature to release the ice . As for a consistent heat load for the valve to operate , this is a not an issue, the sensing bulb itself has a damping effect as it regulates the TXV .

As for cost, yes these TXV systems are much more costly to build , not just the valve itself but also the receiver drier , sight glass, twin' Noctua' fans and now we are free to over condense the refrigerant and use a huge efficient condenser. Ours are all copper as well, no aluminum fins . Thin aluminum plates with captubes attached come in by the truck loads and are very cheap. The cost on the parts alone in our system are in excess of what you would pay for complete captube system from say, NovaKool .

As for reliability , check the warranty of the systems you are looking at, that should say it all .


Regards John Tully

One of the things I have been trying to work out in my head is where the bulk of the efficiency gain is coming from.

I definitely understand a holistic approach and that the sum of the parts makes for an efficient system.

What I am curious about is do these systems get better efficiency due predominantly to
1) TXV holding the evaporator superheat at a fixed value , allowing the compressor to have reduced load later in the cycle at higher delta T
2) higher heat transfer from refrigerant to box or plate than the aluminum evaporators.
3) Short cycling compressor results in loss of energy during the first part of each cycle.

An interesting experiment would be to swap out the copper evaporator with an aluminum evaporator which is sized to reflect the reduced thermal conductivity. I.e. surface area in proportion to the difference in thermal conductivity. (Not one with an internal fixed orfice, similar to the copper)

I really like the robustness of the non aluminum evaporator, just thinking about the physics of the problem.

I suspect the biggest effect is the TXV as it removes the sensitivity to condensing temperature over a broad range.


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