Chiller recommendations

It sounds to me like you need to get a new air conditioning company. Need to find out what the code is. But if both soft starts are doing it, with 2 new chillers, there's an issue.

It also could be a shorepower issue and the chillers are not getting enough voltage. Also, if the soft starts are winding up too slowly, it could cause issues.

The big question is why does the voltage drop under 200v. Not good. When switching from shore to gen, the system will shut down anyway and should restart. Rotary switches if that’s what you have should not be switched underload. Turn off the air cons and other heavy loads, transfer power and restart

You could run dehumidifiers (maybe rent) while not on board the boat until resolving the shore power problem. We run one along with the ac in the master plumbed with a hose to the shower drain with when at the dock, leave the air handlers running on low for circulation. Keeps the humidity down on the lower deck.

Once a compressor shuts down it takes up to several minutes until the high side equalizes with the low side so they can restart. This delay is programed into either the AC controller or sometimes the frequency drives. Usually the compressors thermal protection trips if a premature restart is tried, they are self resetting once they cool (several minutes)l. Sometimes a breaker kicks or frequency drive locks out, depending on how the system was designed. This might be why the AC tech didn't want the drives to auto reset. If you can program the frequency drives to auto restart set the delay to at least 3 minutes. You should never see 200 volts, I would hunt down that problem. Pascals advice in post 44 should be followed when switching from shore to internal power or back. Generators can have sine wave problems but the grid, at least in the USA is a very stable 60 HZ.

It would be helpful to monitor the shore power voltage too. A 208 volt service, which is a common 3 phase commercial service could easily drop to 200 volts during times of high demand.

The freq drives may be doing their job properly by protecting themselves from low voltage.

Brings us back to the manual. That would tell you the voltage thresholds and whether you can safely lower that parameter.

First a question ? is your boat wired for 3 phase power. 208 volts is usually the high leg ( L3 ) of a 3 phase transformer installation. 208 volts to neutral/ground. L1 and L2 should be 120 volts to neutral/ground and 240 volts between L1 to L2. Unless your wired for 3 phase power you should not be connected to that leg (L3).

It should help. What I think might be happening is that both chillers are coming online at the very same time causing the voltage drop. Check and see if you can change the delay on 1 of the chillers. It's also possible that your 100 amp service is simply not enough and with chiller 1 already running and number 2 coming online the voltage stops dropping. The other side of the coin is when you're away you can run only 1 chiller and it should help. A yacht of your size should have full time crew on it (everyday).

100amp is tight for us (84 Lazzara) in July and August. We can run both chillers and regular loads but add in an oven or a dryer and breaker goes pop.

No error on the Drives though, just the breaker by the glendining. No big deal from late afternoon till late morning when one chiller is enough.

My chillers have temp controls that monitor the chiller loop as it passes each chiller. The temp settings are staggered so that only one unit is called to handle the cooling, but if the high side hits another threshold, the second unit is called to assist. I believe #1 is set at 44/54 and #2 is set at 46/56. The second unit only runs on the warmest of days. The temp settings can be adjusted quite easily for both engage and disengage temps.

I can run both chillers, cook, and wash clothes. Have you looked at the status of the water heaters? Are they creeping up with amperage demand? My Acme system and most transformer both provide a full compliment of voltage, so that helps with the load, too. But I really don't have any trouble aboard if I have the full 100 amp supply.

NO.....If the primary side of a transformer drops in voltage so will the secondary side. IF you install a boost transformer to boost volts you drop down in amperage.

Problem goes away on Gen-Set?
Your ISO transformers in boost mode?

How long does it take the freq drives to bring the pumps to speed?
Can you determine is it when the pumps are coming up to speed or already running?

I understand strange questions, just something for me to chew on in my sleep.

Nothing is for free. you want volts, you have to give up amps. Hence a question in post # 56.

W=VxA
Raise the V, A must go down. The motor will draw it's watts. If not enough of any of these three, things smoke and breakers trip

Even if the frequency drives give you a "slow start" the compressors still will draw any where from 150% to 300% of there ratings for a couple seconds. If that's the case, the AC units may just need capacitors added to smooth this currant draw out for that short period. Search for "hard start AC capacitors".

If the problem in voltage is dockside, take a walk and check the plate on the marina transformer. Likely it's converting to 208, coupled with long runs of wires, and you'll be at 200 at your pedestal. Then you'll have another drop via your shore cord. I've run this exercise after discovering 196 volts aboard. I only had 200 at the pedestal under load. The transformer was providing 208, and the delivery was several hundred feet. I was able to install a 25 KVa boost transformer at the panel, boosting 208 to 240. Now I'm at 230v entering the boat, and my boost aboard kicks that up easily. Problems were solved.

To me, a good HVAC electrician should be able to figure this out in under a hour since its repeatable. The installer or marina might not want to fess up to a obvious problem or doesn't know how to trouble shoot it or correct it. You may need a independent electrician familiar with commercial power ,AC and frequency drives. Just because a person sales and installs a system doesn't mean they understand how it works on a fundamental level.