Refrigeration unit replacement - Price vs Performance

[CarinaPDX]

For just a couple of years of cruising I would definitely go with a simple, lower price system. If you were building or equipping a new boat it would be another matter, and in that case it would be worth considering the premium systems. YMMV

As one refrigeration tech explained to me, any system should last the life of the compressor without maintenance. The problems arise from manufacturing design or defects, such as debris left inside which can block the capillary tube (if equipped), installation mistakes, or damage. I would add that any system that includes a salt water pump is going to need more maintenance, and should be avoided. Personally I am using a custom bronze "keel cooler", which exchanges heat between the refrigerant and the sea water passively, and has been great for more than 10 years. However, some keel coolers made with sintered materials have a poor track record; design is everything.

While it may be a PITA, if efficiency is your goal (particularly if you are depending on solar) there is no substitute for bringing the insulation up to snuff. The best, most efficient designs can't possibly save as much as improving the R-factor by, say, 50%, and likely you could do much better from your marginal (IMHO) insulation. Most marine systems use the Danfoss BD-35 or BD-50, and for good reason; at this point I wouldn't consider anything else. Assuming a properly sized heat exchanger and evaporator, and adequate ventilation, there isn't going to be a large difference in efficiency - the insulation determines the amount of heat that enters and must be removed, and with the same compressor and technology they will perform similarly. Smart controllers/thermostats can make modest improvements, but they can be added to any system if desired.

If it were me, I would put in a basic system for about $1k and go cruising - no point in installing a high end system into a poorly insulated box. Then when time allows upgrade the insulation, and after that perhaps a better controller or thermostat. It might be worth having a pro do the install if you can find one. If you are doing it yourself first check that the copper tubing is still annealed (softened) - bending older copper tubing can be a nightmare. I would be very reluctant to anneal myself as I would think that would have a bad effect on the refrigerant. (BTW I am only a cruiser who has fought these battles - best to listen to the pros.)

Greg

[glcalahan]

I will weigh in as I just ordered insulation several hours ago. My experience with Norcold cold plate system has been Excellant but obviously nor in league with systems mentioned. My first box/plate conversion (as a live aboard) was in a DownEaster 38' and worked great for 11 yrs till boat was sold. I used 4 layers of Dow Blue insulation. My second install was in my Catalina 30 again as a live aboard 8 yrs and worked flawlessly. I am now restoring a '72 Pearson 33 and found a newer Dow insulation called Thermax Sheathing. 4'x8'x2" is R13. I will double and have R26 and line inside of box with aluminum flashing and seal seam. BTW....cost? $60 for Thermax and $650 for the Norcold. Please refrain from flaming over the Norcold but the first 2 may still be working!

[john61ct]

My understanding is the compressors pretty much last forever.

So saying that should be the *first* component to fail seems to be an unrealistic expectation.

[BluJu]

Originally Posted by CarinaPDX

If it were me, I would put in a basic system for about $1k and go cruising - no point in installing a high end system into a poorly insulated box.

Greg

Thanks for the feedback, Greg, that's also how I feel. We had issues with the previous system so I don't even have a good feeling for what I can expect in terms of the box's insulation. The evaporator surface area of the NovaKool system I'm looking at is rated for a box volume almost twice as large as mine, so I'm hoping it will compensate for the presumably poor insulation of the box.

[BluJu]

Originally Posted by Richard Kollmann

BluJu, I have followed the different pleasure boat refrigeration designs for over twenty five years. I would like to know why your E Z Kold machine needed to be replaced. The E Z Kold design with the exception of their water cooled option failures was a one of the leading efficient systems and almost comparable to Technautics Cool Blue machine with holding plates. E Z Kold’s water cooling condensers I believe is what caused them to fail. Did you ever use the water cooling on your unit?

The Nova Kold is one of the top performing basic efficient systems. If you can take advantage of their mutable evaporator plates in a small spillover box you will be satisfied with a Nova Kold BD 50 unit in the tropics. Solar energy storage without holdover plates is less effective than wind generators because of daily energy hours available.

Basic less expensive uncomplicated refrigeration is simple to maintain anywhere in the world as long as you avoid unnecessary unproductive gadgets. Unfortunately there is no way anyone can prove what configuration of components are best for your refrigeration needs. SO KEEP IT SIMPLE..

Thanks Richard. My E Z Kold machine had a refrigerant leak that I could not track, though I did not try very hard. It was water-cooled, so the issue may have been there. Because of the age of the system, our cruising plans and because a reliable, worry-free system was a must on our boat (my wife is very peculiar about fridge temp!..), I decided to go for a new system.

Can you explain what you mean by "mutable evaporator plate"?

[BluJu]

Originally Posted by ayates

Attached is a little table I put together a year ago when comparing ice box conversion refrigeration units.

Thanks! I only mentioned NovaKool and ColdEh Marine because I found they are at the end of the price range for evaporator plate systems. But I've looked at the systems listed in the table

[bobfnbw]

What about replacing the entire unit with something like the Isotherm DR190 refrigerator drawer ? 6.7 CuFt dual drawer using 700 watts in 24 hours. Dual voltage. Stainless steel. No rebuilding a box, just cut old one out and replace... maybe.
Anyone have experience with this type of refrigeration?
Thanks,
Bob

[Typhoon]

Nice unit the isotherm very user friendly . 700 watts in 24 hours almost equates to 60 amp hrs . They do not mention the ambient temperature but I'm sure they measured it at 72 F . You can probably double that when it is 90F. Poor insulation and inherent cap tube design inefficiencies at higher condensing temperatures .

Regards John

[Richard Kollmann]

BluJu, High end refrigeration means expensive and not necessarily reliable, worry free in cruising world salt air environments. I place more importance on compressor condenser cooling and location than insulation as long as there is no moisture in the insulation. If you can not improve insulation by adding to it increase the refrigeration size and boat’s electrical power grid. Your selection of a BD50 compressor and hopefully a evaporator capacity to match is a good starting point. Alternative energy from wind and solar is a good beginning. I know of boats with small refrigerated boxes that have crossed oceans with just a wind generator for power. For a two year cruise I would recommend new and not aged batteries with as much amp-hrs of capacity as there is room for. You will also require some type of battery monitor.
As to location of air cooled refrigeration unit it needs to be located in a position where air interring condenser does not return warned air again to condenser inlet. I also like the evaporator flexibility, efficiency and price of your choice in Nova Cool. I earlier said mutable plates, what I meant was twin plates. These Nova Cool dual plate evaporators come in either a box configuration or they can be installed on two box walls. Box size and lid opening size will limit the size of evaporator. Also the final Btu size of evaporator will limit the efficient Btu of box cooling produced by compressor. The final Btu balance between evaporator and compressor is reached by thermostat controlling evaporator temperature not box temperature and compressor speed.

[Typhoon]

Enlarging your battery bank and adding extra charging capability is an expensive solution to overcoming a poorly insulated box .

Not only is the equipment expensive , but batteries have a life span as well as alternators. Maintenance cost will rise going this route.

Re-insulating your box may seem like a daunting task , but the materials are cheep and the maintenance cost are nothing , other then the occasional door seal. Better then buying new batteries every couple of years. Now you have a efficiently running system that will not put your power grid to task. This in turn will save you much more money in the end.

Regards John

[glcalahan]

Dow Thermax Sheathing
4'x8'x2" = R13. Cost $60

[Typhoon]

Originally Posted by glcalahan

Dow Thermax Sheathing
4'x8'x2" = R13. Cost $60

Exactly, Thermax is a polyisocyanurate rigid board

We just did a test using this against XPS , both work well in an icebox . I personally lean toward the XPS , it is less hygroscopic. But I have used both in combination.

http://www.cruisersforum.com/forums/...st-193232.html

Regards John

[john61ct]

IOW polyiso needs encapsulation against moisture, at least good vapor barrier(s).

And polyiso's R-value is not so good against very cold temps, so 20% thickness or max 1" of XPS can help *on the inside* in the case of a fridge.

[Richard Kollmann]

Originally Posted by ColdEh Marine

Enlarging your battery bank and adding extra charging capability is an expensive solution to overcoming a poorly insulated box .

Not only is the equipment expensive , but batteries have a life span as well as alternators. Maintenance cost will rise going this route.

Re-insulating your box may seem like a daunting task , but the materials are cheep and the maintenance cost are nothing , other then the occasional door seal. Better then buying new batteries every couple of years. Now you have a efficiently running system that will not put your power grid to task. This in turn will save you much more money in the end.

Regards John

John. I tried to come up with a refrigerator design system concept based on information provided by BluJu :
Want a spillover system 3.4 cu ft refrigerator and 2.5 cu ft freezer.
Plan cruising in tropics for 1 to 2 years.
Two adults and two children on board.
Present box insulation a guess maybe R 12
Does not have the time to replace insulation.

Upgrades and projections to meet the owner refrigeration requirements.

Worst case daily Btu 4200, design consideration in summer tropical climate condition.
Thirty to 50% of the additional daily Btu consumed is do to the increased liquid requiring refrigeration in the tropics.

Doubling the insulation R value could increase its performance by fifteen percent.
I have found selecting the right refrigeration and upgrading boat’s power grid is far more effective than redoing the insulation. Unless insulation is full of moisture and only then replacement is necessary.

Cruising below 26 Latitude should always be considered as tropical conditions.

[a64pilot]

It’s possible to get very good results with a custom system that may not be as possible with an off the shelf system. I have a 14 cu ft spill over that is approx half and half fridge and freezer, and a BD 80 compressor with a Cool blue dual cold plates in a factory ice box with 30 yr old insulation. It could do much better with better insulation, and maybe one day I will get around to that.
For an off the shelf answer, maybe a complete retrofit box from Engel or similar may be worth considering. This was just the other day, I can’t get temps quite this low in Summer in high temps of course.