Chiller troubleshooting

Follow up on my breaker curve thread

https://www.yachtforums.com/threads/schneider-breakers-curve-type.35015/

it wasn’t the breaker... I replaced it and it still trips. Need to come up with a good troubleshooting strategy.

system has three dometic chillers but for some odd reason the dometic control box only has two inputs from the main electrical panels. 1 input for chillers 1 and 2, second input for chiller 3 and the two pumps. As per the diagram in the cruisair box, each chiller should pulls 23 amps and each pump about 8amps. So each input is well within the main panel 63 amp breakers capacity. The chillers use freq drives so no start up load

Problem is that when both chiller 1 and 2 are running, the 63 amp breaker on the main panel trips sometimes after 30 minutes... sometimes after 8 hours.

started happening about 2 weeks ago

if I disable either of them, it doesn’t trip but while two chillers do the job after 7Pm... by 10 am I need all three

trying to come up with a troubleshooting strategy... I m thinking of using the Max function on a Fluke clamp on meter to see if I can see a spike.

each chiller is protected by a 40 amp Breaker inside the cruisair box so in theory I could increase the amperage of the main panel breaker but I just don’t like the idea

any suggestion?

They were replaced 3 years ago so when is no issue. Recently cleaned and when running they re only pulling about 42 amps combined which is less than the 46 the dometic data shows and far less than the 63 amp breaker capacity.

Replacing the individual 40 amp breakers with 30 amps is a pretty good idea, I may try that next of the clamp on meter doesn’t yield any clue.

If anything since I replaced the 63amp breaker, the problem has gotten worst, tripping after as little has 30 to 60 minutes.

this is the graph on my phone get from the monitoring sensor on the loop. On the left, yesterday afternoon you can see the peaks when the breaker had tripped and then quick drop as soon as it was reset. Around 8Pm, I shut down chiller nr 1 so loop temp came back down slowly. Starting around 10 am, 2 chillers were not enough and temp started rising. At 15:31 I restarted chiller nr 1 and you can see the quick drop.

then the up and down ecah time the breaker tripped and was reset

Descaled a month ago, coil temperatures are fine and even. They re on freq drives so no startup surge.

Been monitoring start up and run amps for either chillers and combined. Well within specs.

When running one at a time, no tripping.

Indeed I check all the visible wiring, nothing obvious including in the chiller control cabinet. That’s why I need to narrow it down to one chiller.

I m going to be lowering the breaker rating so no risk of melting any wire

Pressures were checked recently, after cleaning the raw water side and were fine.

After running on just chillers 2 and 3 for 18 hours, I restarted nr 1. After 20 minutes the breaker for 1 and 2 tripped. I was in the ER re inspecting everything again. Breaker just tripped without any external indications like a noise or anything. Overall amps had been holding steady before tripping.

now running on chillers 1 & 3

I don’t have to measure the air temp at the air handler... with chillers the loop temp tells the story.

with all three chillers it comes back down to between 49 and 52 degree depending on the time of the day and sun

on two chillers it doesn’t drop below 60 in the afternoon. Not low enough to really cool the boat as it should.

No they re at 49 or 50.