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Isotherm Compact ASU 3701 Refrigeration Kit


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Delivery within 2 - 3 weeks.
Model # 12731709 | Mfg # 43701EE100000

Advanced electronics that monitor available battery power and adjust the three-speed compressor for greatest efficiency and cooling power distinguish this system. The stainless steel holding plate will refrigerate a box up to 7cu.ft. and it utilizes an air-cooled compressor for easy installation. ASU systems for larger or smaller boxes are available by special order.

Chilling Medium: Holding plate Power Requirements: 6A 2 12V DC; 3A @ 24V DC Cooling Capacity: 7cu.ft. Dimensions: Compressor: 12"L x 6"W x 6"D; Holding plate: 14"L x 11"W x 2-1/2"D Weight: 40lb. Plumbing Connections: Compressor: Quick disconnects; Holding plate: 6' precharged copper tubing with quick disconnects Electrical Connections: Hardwires to 12V or 24V DC electrical system Seawater Cooling Required: No Warranty: Five years

Isotherm Compact ASU 3701 Refrigeration Kit

Amperage 6 Amps at 12 Volts DC
Best Use Small to Medium Refrigerators up to 7 Cubic Feet
Capacity Up to 7 Cubic Feet Refrigeration
Condenser Cooling Air
Dimensions 6" Width x 12" Length x 6" Depth
Family Isotherm
Plumbing Connections Quick-Connect Couplings
6' Precharged Copper Tubing
Refrigeration Component Compressor
Shape Horizontal
Warranty Details Five Years

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by PowerReviews
Isotherm Compact ASU 3701 Refrigeration Kit

(based on 2 reviews)

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Reviewed by 2 customers

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Previous Review is Wrong

By Captain Blue Water Cruiser

from Florida, Bahamas, Caribbean, Mexico

Comments about Isotherm Compact ASU 3701 Refrigeration Kit:

I have this system and feel I must object to the previous author's contentions! In spite of misleading complaints, the author of the previous 'review' states that the ASU works for his spillover after installation mistakes were corrected.

The Isotherm catalog clearly states 'fridge' for ASU models listed and the West Marine site clearly states the best use is "refrigerator". The manual covers all systems and all scenarios, including the ASU for freezers (the part numbers end in a '3'). Holding plate systems are better suited for refrigerators as the holding plate acts like an artificial block of ice. The ASU refrigerator holding plate goes down to 14 degrees F on the surface (freezer models go down to zero degrees on the plate surface). In the case of this review, the refrigerator ASU model was not the best choice to cool a freezer AND a refrigerator as the author is attempting to do, even though he is currently doing so successfully after he corrected the installation mistakes. The ASU would probably do better if the box were better insulated as a freezer and the seals were not allowing humid air inside the box as indicated by complains about frosting.

Further, misleading mistakes quoted in the review include installing the temperature probe incorrectly, to miscalculating the partition height on a spillover and later having to correct his error with a fan, to losing refrigerant on install (it only holds 4 ounces), not understanding auto fill gauges are not for refrigerators, to the fact that ASU runs the compressor on high speed when there is a consistent flow of voltage above 13+ volts such as when an engine is running and charging the batteries, that solar will not produce 13+ volts when the batteries are at peak charge, and on and on. It is unfair to blame Isotherm for installation mistakes. Isotherm has great products and service. When installed properly, Isotherm refrigeration products are the best!

Service and delivery comments:

Delivery to the West Marine store saves on shipping charges. It is convenient and dependable without worrying about packages left on your doorstep.

  • Was this a gift?:
  • No

(13 of 15 customers found this review helpful)


Doesn't function like Manfacturer claims

By Unhappy Owner

from Pacific Northwest


  • Compressor Quality
  • Ease of installation
  • Small Size Compressor


  • Asu Controller
  • Cannot Be Frig And Freeze
  • Poor quality control
  • Thermocouple Placement

Best Uses

  • Fridge On Power Boat

Comments about Isotherm Compact ASU 3701 Refrigeration Kit:

The quick couplers are a clever idea for ease of installation, and we were able to get them connected without loss of coolant. However, on start-up, we encountered our first problem - the unit as shipped did not have sufficient refrigeration charge to completely freeze the plate, even in manual mode. By talking to tech support, we learned the behavior indicated the unit needed more coolant - apparently it left the factory without enough. Adding more coolant required a refrigeration technician with commercial gear since it appears to not be possible to buy an adapter to go from a can of coolant easily bought at an auto-parts store, to the fitting on the compressor. (The automobile A/C world does not use the same standard fittings as the rest of the refrigeration world does - called your local fridge tech and ask if you doubt me)

Our next problem was we could not keep the well-insulated undersized (for this model) box cold enough for safe food storage (per the manual's guidelines). Isotherm product literature states "The ASU technology detects when a surplus of power is available and uses it to freeze the cooling plate." "If your boat is a sailing yacht and the engine is used for short periods only, we recommend the installation of a fridge or refrigeration system equipped with Isotherm ASU control and a cold-holding plate." This has not been our experience on our sailboat, with our solar panels. Even when we have ample stored power, the ASU controller will not keep the holding plate frozen when in Auto mode. If you can keep your batteries charged (i.e. solar or wind generation) then you do not want this poorly programmed ASU controller since it cannot automatically control the compressor in the manner stated in the manual. In fact, I cannot imagine a scenario when the ASU controller in auto mode would be useful given how poorly it operates. (No, we do not have big voltage drop between the batteries and compressor.) We worked hard to ensure it was not our error with this unit, we used it for 3 months keeping close records of its behavior and it seems totally erratic.

We contacted Isotherm USA technical support, and were told the ASU controller cannot be used for a freezer - and definitely not for a freezer/fridge combo, which is exactly why we bought it based on this statement from the Isotherm 3701 product manual intro: "A moveable partition should be installed in the box to allow the frozen food section surrounding the cold plate to be reduced to the smallest space possible so that the correct temperature of 4 - 6° (39 - 43°F) can easier be maintained in the refrigeration section." Later in the manual, there is a whole section on how to create a freezer partition within an ice box. When I pointed this out to the US tech support rep, he contacted the factory in Italy and then informed us it would only be possible to use the unit as a freezer if we changed the DIP switch settings on the compressor so the controller would run to a lower setpoint AND we changed the solution in the holding plate to avoid cracking the plate when the liquid freezes more completely at this lower setpoint. So much for the marketing literature that claims the holding plate is filled with a magic eutectic solution with a freezing point below 0C - (eutectic means the plate should freeze at a given temperature, not over a range of temperatures, so changing the setpoint should not alter the volume change with freezing, presuming the original setpoint was below the freezing point of the eutectic solution reportedly in the holding plate).

Also, the thermocouple is installed on the topside of the holding plate, and it becomes embedded in ice build-up quickly if you sail in an area with some humidity (and you run the controller on Manual so the plate will actually freeze.) This means the thermocouple does not properly sense the temperature in the box until the ice build-up melts, by which time the box is too warm for safe food storage. So we had to free the thermocouple from its clamped position and mount it in our box in a manner that allows it to sense the box temperature near the plate, not the ice build-up-on-the-plate temperature. I suppose this also puts us at risk of rupturing our holding plate as this is equivalent to lowing the setpoint - but come on, just how is this fridge supposed to be useful!?!

So all in all, the isotherm marketing literature for this unit is full of misleading statements at best - though I consider them to be just flat-out lies.

The only good thing about this unit is the compressor from Danfoss. It's small and quiet. All the stuff that Isotherm added on seems to be faulty.

In the end, we installed a small fan between the freezer and fridge compartments on a separate temperature controller that creates more air flow between the freezer section and fridge section when the fridge gets too warm, and we only run the ASU controller on manual. If our batteries are getting a little low, we turn down the setpoint to control the compressor speed and runtime. When the batteries are fully charged or we are running the motor, we turn up the setpoint to freeze the plate solid. So it is use-able to us now, but what a fiasco it has been to get it working to even this degree. The isotherm ASU 3701 definitely does not work as described on the tin.

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