Act like you are the design engineer for a boats refrigeration

[Freedom45]

Look into Engle.
I put two of the drop in units in my boat, worked flawlessly across the Pacific and through out the tropics and are still going strong, very efficient, about 2.5A 12V each.
They also make a DIY retrofit for existing box.

Cheers

[Typhoon]

Originally Posted by tml

Richard
The 110 volt system is a SA 2 which uses a 1/4 hp motor drawing 3 amps. It is air cooled with 134A refrigerant.
Originally it was installed with 2 freezer plates and a spill over fan with thermostat to control refer temp. This didn't work well and couldn't keep the freezer cold enough.
Cleave at Seafrost suggested that the insulation be up graded. I couldn't get my head around that 4" of insulation in a well built box wasn't good enough. I should of course have taken his advice!
At some point he got tired of my sniveling and made me a good price for an additional plate for the refer which I installed. Basically we just overpowered the box with refrigeration. It worked well but after 20 years or so I figured out that it was under performing and solar powered aspirations were not going to be attainable..
Last year replaced 75 % of the insulation with new and not surprisingly performance was markedly better. Just now replacing the top and hatches insulation and expect another bump up.
The engine drive compressor and the SA 2 are totally separate and can be run individually or at the same time. They each have their own black box flow control.
I believe but not certain that the flow goes from compressor to freezer plate # 1 then to freezer plate # 2 and then to refer plate before return.
The cold plates are aluminium 18" x 12" x 3"
Thanks
Tom

When running on just shore power does the SA-2 keep up and keep your boxes at the desired temperature?

Regards John
www.coldeh.com

[Richard Kollmann]

Originally Posted by tml

Richard
The 110 volt system is a SA 2 which uses a 1/4 hp motor drawing 3 amps. It is air cooled with 134A refrigerant.
Originally it was installed with 2 freezer plates and a spill over fan with thermostat to control refer temp. This didn't work well and couldn't keep the freezer cold enough.
Cleave at Seafrost suggested that the insulation be up graded. I couldn't get my head around that 4" of insulation in a well built box wasn't good enough. I should of course have taken his advice!
At some point he got tired of my sniveling and made me a good price for an additional plate for the refer which I installed. Basically we just overpowered the box with refrigeration. It worked well but after 20 years or so I figured out that it was under performing and solar powered aspirations were not going to be attainable..
Last year replaced 75 % of the insulation with new and not surprisingly performance was markedly better. Just now replacing the top and hatches insulation and expect another bump up.
The engine drive compressor and the SA 2 are totally separate and can be run individually or at the same time. They each have their own black box flow control.
I believe but not certain that the flow goes from compressor to freezer plate # 1 then to freezer plate # 2 and then to refer plate before return.
The cold plates are aluminium 18" x 12" x 3"
Thanks
Tom

An 8 cu foot combination box with a 12 volt hermetically sealed compressor is on the edge for cruising below Latitude 25 but the engine drive as a booster if you need it is the best of both worlds. I would consider at least 300 watts of solar power if you have room for it.

The question that needs to be answered for the small 12 volt compressor to use the existing plates is the outside diameter of evaporator tubing inside each plate. Mistakes have been made before using plates on small compressors when coil tubing is sized for a higher velocity compressor oil return flow.

[tml]

John
The SA 2 keeps up even in Bahamas with water temp at 87 F. Before I replaced and added insulation it struggled and ran constantly. Now a 50 % to 75% duty cycle.
The challenge is to keep the refer box from freezing while keeping the freezer
box between 0 and 10 degrees F.
Tom

[tml]

Originally Posted by Richard Kollmann

An 8 cu foot combination box with a 12 volt hermetically sealed compressor is on the edge for cruising below Latitude 25 but the engine drive as a booster if you need it is the best of both worlds. I would consider at least 300 watts of solar power if you have room for it.

The question that needs to be answered for the small 12 volt compressor to use the existing plates is the outside diameter of evaporator tubing inside each plate. Mistakes have been made before using plates on small compressors when coil tubing is sized for a higher velocity compressor oil return flow.

Richard
The SA 2 copper tubing is smaller than the copper tubing from the engine drive compressor, I assume the coils in the cold plates are the same. I will measure the diameter when I am on the boat tomorrow. My guess is that they are 1/2" for the engine drive and 3/8" for the shore assist.
I have 300 watts of solar which should be 400 in short order.
Tom

[AuroraGH]

Originally Posted by Freedom45

Look into Engle.
I put two of the drop in units in my boat, worked flawlessly across the Pacific and through out the tropics and are still going strong, very efficient, about 2.5A 12V each.
They also make a DIY retrofit for existing box.

Cheers

Sadly the drop-in units are discontinued. Can you point me to a source for the DIY? Person on the phone at Florida location said they don't make anything like that. Just the complete portable cooler boxes or front loading fridges.

[Dockhead]

Originally Posted by a64pilot

. . . However if I had to do it again, I think I would seriously consider Nolex’s solution, that is a commercial off the shelf 12V cooler / freezer. That gives you the closest I believe to easy, good and cheap, and beyond warranty, heck with fixing it, they are cheap enough you can just go to a box store and buy another, the good ones are surprisingly rugged and long lasting.. . .

It's somewhat off topic, but I agree with you on this.

After nine years of living with a highly complex cruising boat, the value of simplicity and genericness in systems has grown in my system of values.

I really can't complain about my refrigeration -- two Isotherm SP systems original to the boat whose only fault so far in 17 years (knocking on wood here) has been that they lose a very small amount of gas, requiring me to use Richard Kollman's excellent (thanks Richard) instructions to gas them up -- once a year.

Yet the problems which can befall these systems can be highly complex requiring parts, tools, equipment, expertise -- a real problem in a remote area.

I REALLY like the idea of using a completely self-contained generic commercial unit like Noelex is using, which you can just toss out if it breaks, and which you can just replace every five years or so to be sure that they don't do so unexpectedly. It means designing the galley differently to accommodate the slide-in boxes. It's one less fixed installed system requiring maintenance and just waiting to spoil a cruise by breaking down. Our Noelex is a clever fellow.

[Freedom45]

Originally Posted by AuroraGH

Sadly the drop-in units are discontinued. Can you point me to a source for the DIY? Person on the phone at Florida location said they don't make anything like that. Just the complete portable cooler boxes or front loading fridges.

As far as I can tell, they are still available
Engel Website

[AuroraGH]

Originally Posted by Freedom45

As far as I can tell, they are still available
Engel Website

Huh. Engel USA tells me they are discontinued (called em on the phone). I wonder if I can just import a couple myself from AU? I will send an email to ask.

[Richard Kollmann]

Originally Posted by tml

John
The SA 2 keeps up even in Bahamas with water temp at 87 F. Before I replaced and added insulation it struggled and ran constantly. Now a 50 % to 75% duty cycle.
The challenge is to keep the refer box from freezing while keeping the freezer
box between 0 and 10 degrees F.
Tom

The refrigerator plate is going to get very cold at times because the frozen solution's eutectic freeze point does not control actual refrigerator box temperature. All three plate temperatures are controlled by the thermostat located in freezer set to below zero degrees F. Bulk energy is stored in refrigerator plate only until the liquid is phased to ice. After the phase change is complete and compressor is still running the refrigerator will quickly drop in temperature with almost no additional energy stored in plate.

To control the low temperature of this plate from freezing product in refrigerator a portion of plate can be covered to slow down the heat absorb by plate's large surface area.

[Richard Kollmann]

Originally Posted by tml

Richard
The SA 2 copper tubing is smaller than the copper tubing from the engine drive compressor, I assume the coils in the cold plates are the same. I will measure the diameter when I am on the boat tomorrow. My guess is that they are 1/2" for the engine drive and 3/8" for the shore assist.
I have 300 watts of solar which should be 400 in short order.
Tom

There are two design problems to consider in your desire to convert the 1/4 HP 110 volt AC compressor system over to a 12 volt BD compressor.
1. The Btu capacity of the 1/4 HP compressor and condensing unit is around 60% larger than the BD50 condensing unit at temperatures needed to freeze the plates in tropical weather. For the BD50 compressor running at maximum speed it might need to run all the time. The unknown value is how is the added insulation going to decrease the daily Btu requirements.
2. SeaFrost standard earlier holding plate evaporator coils were 1/2 inch OD for engine drive and 3/8 inch OD coil for what was called back then the shore power 110 volt system. We know that the BD80 and BD50 return refrigerant flow is restricted to 1/4 inch OD line sizes and the practice of using 1/2 inch OD eutectic tubing may have cause BD80 compressor oil starvation. If you follow the text book theory that the compressor manufacture sets the standard size of all the low pressure tubing in a system the Danfoss BD low pressure tubing would be no larger than 1/4 inch OD tubing.

[Freedom45]

Originally Posted by AuroraGH

Huh. Engel USA tells me they are discontinued (called em on the phone). I wonder if I can just import a couple myself from AU? I will send an email to ask.

A quick search shows plenty of U.S. suppliers....Amazon etc

[Dymaxion]

If the issue is being able to properly cool 3 compartments (freezer,drinks,main fridge) would it be possible to put the freezer plate(s) and master thermostat in freezer and use small fans, ducting, and 2 more local thermostats to maintain the drinks and fridge compartments? A powered "spillover" system with thermostats. Idle speculation, no expertise at this end.

[OzePete]

Originally Posted by Dymaxion

If the issue is being able to properly cool 3 compartments (freezer,drinks,main fridge) would it be possible to put the freezer plate(s) and master thermostat in freezer and use small fans, ducting, and 2 more local thermostats to maintain the drinks and fridge compartments? A powered "spillover" system with thermostats. Idle speculation, no expertise at this end.

Exactly correct Dymaxion, a thermostatically controlled fan circulating refrigerated air into an adjacent compartment is the simplest method and easiest way to properly control cabinet temperatures.

Like this... The First is a simple thermo-fan install. The other is with a ss heat exchanger and matching remote controller panels.



Cheers OzePete Ozefridge | 12 Volt Refrigeration Systems

[Typhoon]

Originally Posted by Dymaxion

If the issue is being able to properly cool 3 compartments (freezer,drinks,main fridge) would it be possible to put the freezer plate(s) and master thermostat in freezer and use small fans, ducting, and 2 more local thermostats to maintain the drinks and fridge compartments? A powered "spillover" system with thermostats. Idle speculation, no expertise at this end.

Not exactly sure what you mean by 3 compartments , But we do 2 compartments all the time.

Our setup is just like Pete's .

Proper insulation in the dividing wall crucial in achieving freezer temperatures . Also a system that is capable of removing enough heat at the reduced efficiency temperatures on the freezer side.

Regards John.
www.coldeh.com