Scroll Compressors

Yeah, Marine air and Cruiseair both offer soft start compressor kits.......

Most major marine air conditioning manufacturers have products utilizing scroll compressors @ 2 tons and above such as Dometic, JD Nall, Heinen & Hopman. anything below 2 tons would be a reciprocating hermitic or semi hermetic piston type compressor. Manufacturers pair Scroll and screw compressors with variable frequency drives to allow the compressors to start with no starting amperage inrush above the normal running amperage. VFD's vary the compressor speed anywhere from 100% to 70 % and are used on sea water pumps also for cooling the condensers.
New technology has become available to the marine market and is being utilized now that will make the above compressors obsolete along with their expensive and troublesome VFD's and Danfoss has the patent on this new "Turbocor" compressor (Google) It's a centrifugal unit that only has two moving parts and uses magnetic levitation bearings and has exceptionally low wear due to limited mating surfaces & no mineral oil in the crank case. These compressors are now finding their way into the product line up of Dometic and Heinen & Hopman and are still not sized for the 120 ft motor yacht but rather large installations of 80 tons or more but Dometic is expected to introduce a chiller using a 40 ton unit this year and this will be a game changer over the old hermetic, screw's & scroll's of years past.

Never seen a scroll that wasn't in a hermetic case. Scrolls and rotary hermetic compressors are only available up to 5 tons in single phase, at least with the companies I deal with. IF 20 ton of AC are needed I would design a system with 4... 5 ton units and 2 to 4 air handlers. That way a single compressor failure won't cook the entire boat. I like redundancy.
Screw and semi-hermetic compressors are a whole different class and price range as they are for commercial to industrial applications.


VFD's are expensive ,there use would be for commercial semi-hermetic or screw compressors. Soft start inverter technology is the way under 5 ton hermetic market is going.

I tried to get these used on an H and H plant. The answer was a firm NO. To many problems and too easy to damage by untrained folks adding gas etc.

I heard similar stories from a giuy I know who works in Qatar as head Fridge guy for a big operation.

We have ended up with 4 x Bitzer Screw Compressors that will need a mW to run them if starting from scratch and the chilled water temp is high.

While soft starts are less expensive they cant modulate frequency under load and therefore cant give you variable compressor speeds for optimal energy savings such as night time when the cooling loads are reduced by a large factor. Over a short period of time the initial start up costs of a VFD will be paid for by the savings of reduced energy consumption. I will say that soft start inverters are more reliable due to the fact that they don't work as hard and only come into play at start up and shut down where a VFD is under constant operation through the cycle start, run, stop.

H & H lists Turbocor compressors as part of their chiller offerings on their web page?

I know , That's where I first saw them. Our project has been running for a while now so maybe things have changed but that was the answer 12 months ago.

It will be interesting to see where this technology goes and if they do scale it for 40 ton chillers and below. The engineering behind the turbocor certainly is solid and the 3,000 plus units in the field now have had great results but if a system becomes to reliable than its usually not good for the after sales of parts and service. Just like your avatar of a plate cooler, The Average service costs if done by Cat for a 3512 's plate coolers removal & cleaning and minimal parts is $4,500 ? I don't think the shell and tube units were that needy , they just didn't generate the revenue of parts sales at service time.. Every time a Capt. clutches in and makes that big cloud of dirt and gravel around the boat there's either an engineer crying or a Cat dealer smiling...

Ain't that the truth!

Its of one of the first Series 2 3516's used on a yacht.

I have recently heard of a quote to clean a pair of them from a CAT Dealer in Fl at $17,000- thanks but no thanks.

CAT Plate Coolers are quite easy to clean as long as you are careful and make sure the gaskets and gasket seating areas are clean when re assembling, they also have the distinct advantage of not being buried under the floor plates like many of their shell and tube colleagues.

These days that should not be seen so often now the FARC is no longer manually set.

As a guy with some MTU experience I guess you would be ecstatic with unbridled joy and a sense of triumph if one of those blew as little smoke as a CAT.