Does your boat have an Isotherm System?
If so, do you know how it works?

“It’s the little things you may not recognize when you’re buying a boat,” says Dave Lerbs of Indel Webasto. “Like how the refrigerator on your boat really works.”

If you own one of the 160+ known boats worldwide with Isotherm’s products, then you know your refrigerator/freezer is the best of the best. But, do you know how it works?

At IBEX I had the opportunity to talk with Dave Lerbs of Indel Webasto. Here’s what I learned.  The main thing is they save batteries using ASU, ISEC and ITC technology.

Automatic Start Up (ASU)

Boaters have used ASU technology for 30+ years. It works with both 12v and 24v systems.

Indel-Webasto Isotherm Refrigerator/Freezer with top and front doors

Isotherm Refrigerator/Freezer with top and front doors

And shields itself form unplanned polarity setbacks. The ASU checks the voltage level through the electronics mounted on the compressor. Each compressor can run at three speeds; slow, medium and fast. When the engine is running it adds an additional voltage of around 14 volts. This causes the compressor to run at the highest rate of speed. “At that speed,” says Lerbs, “it cools quicker and has more capacity.”

“What this system does is recognize when you might be typically cruising. You start the engine in the morning and pull up the anchor. Then you go outside the harbor and you sail for the remainder of the day with no engine on. During that time the engine is on. It’s running the compressor at the highest rate of speed and it’s cooling down that plate so that it’s almost like an artificial block of ice. It’s like putting an extra block of ice in your refrigerator so the compressor runs less. When it does run, it runs at the slowest rate of speed which consumes the least amount of battery. So, the combination of those two can reduce battery consumption by 50%.”

Indel-Webasto Isotherm two-draw and single door refrigerator

Isotherm two-draw and single door refrigerator

Indel-Webasto Isotherm Refrigerator; looking inside from top

Isotherm Refrigerator; looking inside from top

Isotherm Smart Energy Control (ISEC)

ISEC works like ASU. Yet, ISEC recognizes all the unused voltages on the boat. The ISEC uses several sources like the engine alternator, solar panel and wind generator. Then the ISEC takes that surplus power and runs the compressor at a higher speed. The high speed brings the temperatures in the refrigerator and freezer down. Both the food and beverages absorb the extra cold air. It acts like a cold-holding system for when the system runs on battery power alone. In absence of surplus power, the ISEC module slows down the speed of the compression. It allows temperatures to return to their normal state. This saves battery power. With the new ISEC kit, old becomes new state of the art energy efficient.

Self-Pumping System (SP)

Water cool models can carry heat away. That means it doesn’t exchange ambient air temperatures. So that frees you of stuffy compartments and things like that where it would limit air cooling. The water cool systems include a through hull which is like a keel cooler in the way it cools. Then you have a sea water pump that works similar to how air conditioning works. It brings water in cooling the condenser, then goes back over the side.

Indel-Webasto Isotherm Refrigerator w/two sliding draws

Isotherm Refrigerator w/two sliding draws


“The SP system is unique for Isoterm,” says Lerbs. “It’s a patented system that replaces the through hull used in the galley sink drain. Once you compress refrigerant and it gets up to around 150 degrees F, you need to remove that heat.” You remove that heat by one of two ways; blowing air across the condenser or in contact with the water using the SP System. Sailors love this system because it frees them of worrying about their ventilation and pumps.

Intelligent Temperature Controller (ITC)
Indel-Webasto Isotherm Stainless Steel Refrigerator

Isotherm Stainless Steel Refrigerator

They’ve also now taken that to one more step. This is a brand new Isotherm Intelligent Temperature Controller (ITC). It gives you a digital display of what the temperature is in the fridge. Now you can manually control the speed of the compressor. You don’t have to have surplus power or anything. If you want to supercharge or supercool your refrigerator you can just hit it on the max mode or if you want to be in economy mode, you’ll lock it into that. You’re also sensing the air temperature.

“Ask anyone at Indel Webasto Marine,” says Lerbs. “Energy is a precious resource on board any boat or yacht.”

Disclaimer: Photographs are from display at IBEX, not necessarily paired with the technology shown here

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