AquaAir Chiller Keeps faulting

Odd that it would prevent other types of growth and not barnacles. Chlorine output might be low? No doubt the bromine tablets work, I switched to them after you posted using them over concern with metal corrosion shortly after replacing both chillers.

My neighbor was having high pressure alarms on his AC.
Replaced the raw water pump cause it was old.
Same alarms.
Disconnected suction hose, plenty of water gushing.
Found the interior of the suction hose would collapse when pump was on.
I do not know the type of hose it was tho.

So if you are changing the pump, maybe change the suction hose too.

Had that same problem on a Hatteras main engine a while back. Would get hot at speed.
Old hose laminate was sucking in and collapsing.
It does happen.

I run 10 tons of chiller, and I'm set up with two Oberdorfer 1hp centrifugal pumps mounted just below the water line with valve controls and an A/B power switch to allow me to switch over periodically from one pump to the other for all of the obvious reasons. I feed them with a 1.5" dedicated through-hull plumbed to a 2" strainer as overkill for the point of raw water restriction. I keep a handful of strainer baskets aboard and rotate them periodically, like weekly during warm months and monthly when cooler.

Heck, eBay, Grainger, whatever is convenient. The Oberdorfer units are so simple to rebuild and maintain. I just buy parts as needed. Seals, impellers, capacitor, whatever is needed. So simple. And with the spare already in place, I'm not going to be forced into a hot ER to grind through the effort.

Of course, first you need to know the various part numbers.

1/2 HP sounds like it's not enough flow for the raw water side. You need to speak to someone real knowledgable or you need a really good tech. Try calling Ocean Breeze and asking what size pump you should have for the raw water side.

Are you getting cold air out of the vents when it's anchored? Is your insulation in the engine room sweating? If so, it may be that the chillers are working properly in the engine room, but the chilled water line insulation is insufficient AND cannot overcome the heat of the engine room or you lose a lot of BTU's in the engine room before it even gets to the 1st air handler.

If you're at anchor in calm water, what's different? The heat of the engine room and you have a generator running. I've always found chiller boats struggled a little when the engine room is hot because the compressors are in the engine room. I keep coming back to the boat is under a/c'd. what's your chilled water loop temperature, at the dock and at anchor? You should be able to get that from one of the displays inside the boat.

I try to match pumps up, be them for raw water, circulation, fuel polish, etc to share the same motor. Then it’s a matter of inventorying pump parts and one motor as spares. KISS.

I’m running two fives in series, total of 10. Loop temps run 44 to 54 on #1 and 46 to 56 on #2. Goal is to keep #2 from short cycling and only running when the sun demands it. I’ll alternate units in sequence periodically to keep use balanced.

My setup is also stacked. My pumps are at the bottom. #1 is roughly sitting atop the water line above them. #2 is sitting atop #1, and all raw water ends up at that upper level, splitting and feeding each heat exchanger with cool water, but combining at the same "elevated" point before running downhill and overboard. That split and lift calls for some extra help with the push of water. I wouldn't want to use less pump than I have.