Chiller help

Unfortunately your replacement options are going to be VERY limited because of lack of space. Shame on whoever built that boat. Personally that would be a deal killer for me. Going to a single chiller may be easier space wise but you will loose redundancy. Right now if loose one chiller you can still juggle cooling by turning off stateroom air handlers during the day and the saloon at night

Upgrading to two 30k, if they even fit, will only increase Amps and breaker popping

You shouldn’t have to replace the units

Do they both start fine on shore power?
Have you tried to put a full load on the generator using stove, oven, etc. to see if the breaker holds. Sometimes generators with dirty filter will stumble a bit when a load is applied. This results is lower voltage, higher amp and POP!
When coming back from a run and the ER is hot, does the problem occur when on shore power. If not, then it s not a heat issue
Try to watch the amp meter when each chiller starts.

Could also be a bad capacitor.

But wait there is more. Last summer i was having shorepower issues when both chiller would run on the boat I run... took me a while to solve the issue and I m not 100% sure of the fix. It was a combination of installing a new 100amp shore power plug, descaling and also replacing the sea water pump which had a badly eroded impeller.

I wonder if "soft start" modules on the compressors would help.

Yep..
AND Consider soft start kits.

I would have soft starts on every chiller boat, as you have the seawater pump kick on and the chiller startup usually at the same time. The soft start modules aren't that expensive to add to an existing chiller.....$700-1000 usually.

You really need to diagnose exactly what the real issue is before throwing 1000's of dollars at it. How long has it been since you descaled them? If they haven't been descaled in a long time, that will make them draw a lot more amps. Also, both chillers should not be kicking on at the same time, the startup temperatures should be about 2F apart. The boards are in the Dometic boxes in top right of the picture closer than the chillers. Loosen the screw, take cover off and there is a digital circuit board in there, this is where it displays error codes (HP/LP) etc. but also where you set the cut in/cut off pressures. Also, how long has it been since the generator has had both fuel filters changed as well as a tune up (valve adjustment etc.)? The first place I would start is putting a good clamp on amp meter on each chiller and getting it to cycle and seeing what startup amps it's pulling and what running amps each compressor is pulling. There should be a plate/sticker that will tell you what both "SHOULD" be. If 1 of the above mentioned items is not close to that you've found your problem. Next move onto the circulating pump and the sea water pump and test them. If all of those are close to rated amps, you really need to focus on the generator, check cycles and see what's going on with it. I agree with Pacal, if a generator isn't running correctly and gets a large load, rpm's drop too much, amps skyrocket and boom the breaker pops. If the chillers haven't been descaled in a year or so, I would do that too with the Trac fluid.

If I was replacing them, I'd go with dometic, 2 units, and larger if you can go to 36k btu's with soft start compressors. That way the entire boat should run on one chiller, but you also have to have a good a/c guy check the system and make sure that oversizing will not cause the 1 unit to short cycle because the air handlers aren't big enough to utilize it. Before doing this, you really need to add up all of the BTU's each air handler is. What boat is it in? My guess would be a Neptunus.

I wouldn't consider anything but a dometic. Period.

Your pictures show the newer 410 condensing stations. If there running at all, you have the best and probably just over due for some maintenance.

A couple of months ago we lost a chiller on the 84 Lazzara I run.. CrapAir 72k BTU (or 96k..!forgot) Only 9 years old... new one was over 16k so i had my AC guy rebuild it for 12k. New parts, same warranty. I trust the guy... been using him for 15 years

Plan B if I had the time would have been to use a Flagship Marine chiller. I installed two 36k chillers on my own boat. Better built, simple design, no proprietary circuit boards. About 12k for a new one but would have taken longer to build so I went with rebuilding the CrapAir.

Hearing that you intend to sell the vessel in 3 yrs or so it would make sense to not redesign the wheel with a new installation footprint and plumbing wise. Have your tech trouble shoot the amperage inrush problem, (compressor stall?) de-scale and fit both units with variable speed frequency drives and or unloader valves and you should be fine.

I wouldn’t go with anything Italian or imported. Stick to well known brands. Swapping brands is going to be a plumbing nightmare.

I don’t like cruisair because of all the proprietary control boards and electronics. This is why I picked Flagship for my boat, it s all basic relays and switches available off the shelf Construction is solid stainless steel with large drains for the pans, not stuff that flakes off after a year. The air handler pans are slanted to eliminate standing water

Only gripe about their air handlers is that the blowers are single and can be a bit loud although there are work around.

+1 for Flagships equipment IF you decide to retrofit. Quality equipment at a fair price and parts easily sourced.

I ran a few boats with flagship. The technology was rudimentary at best. Well built, BUT the blowers were noisier than hell and a single speed. The staterooms sounded like you had a hair dryer on high, and whatever they were mounted on vibrated like hell.....woodwork.....bed....or closet...... Like they can't figure out how to put a simple rheostat on them and isolation mounts in 2019? The self contained units, the compressors were hard mounted to the pan, everything was hard mounted to the pan and it made the beds vibrate like nobody's business and noisy. The thermostats were household units that had no way of displaying any error codes of the units (high pressure/low pressure). Plus there is no service network So you're paying someone to learn the unit in order to fix it, then track down the parts. One boat I ran the Flagship marine units had high pressure switches on self contained a/c's that you had to manually push a button to reset them. And, each unit was a pain in the rear to get to. It also had thermostats that if the AAA battery went low in it, wouldn't turn the compressor on but the fan would run and no indication the battery was low. But the noise and vibration would be the main reason I wouldn't touch one. It's 1960's technology. Please tell me one yacht manufacturer that installs Flagship marine in their new yachts?

The dometics have titanium raw water loops so descaling the chillers doesn't degrade the raw water loop. They're quiet, they're well engineered, and the circuit board monitors the unit and displays the error codes. Plus easy peasy to install new units with existing plumbing. My guess is your repair is going to cost a lot less than replacing the units.

Frigomar I wouldn't touch because the Italian part and parts.

I have got 3 new Dometic regular AC’s recently installed and I contemplated other brands but kept coming back to the widely available service network. Had a warranty issue away from the original installer and another Dometic dealer came and fixed it and there was no moaning about doing warranty work. Sometimes the manufacturers dont want to pay the dealers the going rates for warranty work which obviously serves as a disincentive. I have got 2 more units to go but they are not used much but when I do switch them out I will go Dometic unless something great comes up between now and then.

You may also consider your resale in 3 years. Lesser known brand or well known brand.
Fix what you have.
K.I.S.S.

+1

This sounds like typical factory stuff from some builders. While entirely possible it was done after the build, I highly doubt it. I once ran a new Italian 55' yacht that had the forward VIP air handler in the forward bilge, it simply had a return vent in the floor and no ductwork, the plastic waste holding tank was also in this semi sealed forward bilge!!!!!!!!!!!!!!!!!!!!!