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Variable Speed Air Conditioners: IBEX Innovation Award Winner

Discussion in 'YachtForums Yacht Club' started by JWY, Oct 5, 2014.

  1. JWY

    JWY Senior Member

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    A change in air conditioning for yachts was presented by two companies and thus necessitated a shared IBEX Innovation Award for the Mechanical System category: Dometic Variable Capacity Chiller (VARC 48) and Webasto BlueCool Variable Speed Chiller.

    The bottom line to both units: low energy start-up, chiller efficiency with a variable output, a reduction of load fluctuations, and quieter more consistent operation. Chillers typically run at either full on or full off which creates sudden swings in power generating high demand from generators. Another major benefit, aside from ultimately creating an interior milieu that meets thermal load demands, is the reduction in total equipment necessary. While a yacht might need a 4 ton (48,000BTUs) chiller, for example, to handle start-up requirements, that capacity is rarely needed on a running mode basis, perhaps in the 1 - 2 ton range. This also can necessitate the downsizing of the generator.

    Comparisons: There is a minor difference in BTU capability. Both units are more compact than prior models and have remote control capability. Dometic offers some innovation design features such as front and back pressure ports that give improved access and greater installation flexibility, straight out water connections without bends or angles, and front and back display modules. Although not yet proven in real-world extended usage, Webasto offers a closed unit which negates the need for a condensate drain. Webasto is a long-standing excellent reputation company so I don't mean to express any doubt; however, a condensation free AC unit is such a dramatic improvement in the marine HVAC systems that it deserves an award of its own. I would like to hear feedback over extended usage on the maintenance issues this unit alleviates.

    Variable speed chillers are being brought to the mainstream of yachting by two well-known companies. Please do further research to appreciate these two new offerings.

    Judy Waldman

    Webasto_product image2.jpg
    Last edited: Oct 6, 2014
  2. AMG

    AMG YF Moderator

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    Not really new, is it? I think the AC from Heinen & Hopman we had more than 20 years ago was with both variable speed and soft start..?
  3. JWY

    JWY Senior Member

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    Lars - I trust your industry knowledge, so maybe it is either a megayacht thing or an across the pond issue although nationality nor size were not a condition of awards. None of us 5 judges could really believe that variable speed chillers haven't been in use before (and we did have a megayacht builder on the team), yet none of us could think of a manufacturer (wanna be a judge next year?) Additionally, the fact that 2 different well established and well funded companies came up with a 2014 innovation simultaneously also pointed to "new in the industry." Both companies had tight wraps so theoretically neither knew what the other had on its drawing board. I checked the H & H website and it does seem like they have the real deal, and perhaps had it first. That would be a "yikes."
  4. Capt J

    Capt J Senior Member

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    In the smaller yacht market, soft start compressors have just become popular in the last 5 or so years. I agree that they help in terms of generator load or popping shorepower breakers. I do prefer multiple chillers rather than a variable compressor one. I've run several boats with 2 or 3 chillers in line and it tends to run off of one then when calling for more a/c the second one comes on and then the thirds.....At least you have a backup in this situation. I've also run a yacht that had 1 chiller and when that went down, you had no a/c at all.
  5. Marmot

    Marmot Senior Member

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    Not just soft starts but variable speed compressors with speed proportional to load along with unloaders and other capacity controls have been in use on larger (not necessarily just megayachts) for years. This is also standard for the "split" units used for domestic terrestrial air conditioning used in much of the world but only fairly recently gaining popularity in the US.
  6. wdrzal

    wdrzal Senior Member

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    Honeywell has had VAVVT (variable air volume , variable temperature) systems for more than 25 years. I would bet you (Judy) have seen systems using DC powered compressors. A lot of companies call this inverter technology with soft start.( Yes Marmont, I know changing AC power to DC is done with a rectifier) Does inverter technology just sound cooler than rectified technology ? With DC compressors you can slow them down just by lowering the voltage. With AC powered compressors you need to lower the frequency, say between 30 to 60 hertz to change the output, but frequency drives are expensive.

    You need ~400 cfm of air flow over the coil per ton (12,000 btu) . If you lower the output of the compressor you must also decrease air volume. If you have too much air flow over the coil it loses its ability to condense water out of the air, not enough and it freezes solid.

    As to a Air conditioner with no condensate drain, where does the water go ? Do they evaporate it back into the air?:confused:
    Last edited: Oct 5, 2014
  7. Marmot

    Marmot Senior Member

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    The inverter in air conditioning systems is just one part of the process. AC is rectified to DC which is then reconstituted to AC by the inverter at the frequency required to produce the desired compressor speed. The inverter component is "new" to this application and is why that term is used to describe the method of control.

    The same system has been used for decades for electric propulsion and many other industrial control applications.