Breaker tripping

[gonesailing13]

Recently had a new Dometic A/C unit installed. This past night the unit tripped the breaker twice. Checked the wiring and found nothing so flipped the breaker back on and it ran fine. Now twelve hours later the breaker tripped again. Not sure what’s going on. Anyone with advice ?

 

[Choices]

Breakers typically have two trips, short circuit and overload. The short circuit is instantaneous, the overload is time dependent. If a 20a breaker sees 23a it may take hours to trip.

My bet is your new unit is pulling more current than the old one. Assuming the tripping breaker feeds the unit bump it one size up.

If the tripping breaker is a main, might try turning something off to see if it trips again.

Also check connections. A bad wire will cause a resistance, pulling more current.

As a note, each time a breaker trips it usually trips at a lower current next time. So a 20 a breaker might trip at 16a the second trip. A 20a breaker is in spec if it's trip range is 18-22a.

 

[High Wire]

Get a clamp on ammeter that also reads DC amps in 40 and 400 amp ranges. You will use it a lot while cruising.
Verify the amps drawn by your unit when running.

 

[Comodave]

Check all the connections for loose or dirty connection. Agree on the above advise too.

 

[tiltrider1]

If you just recently had it installed you should be checking with the installer. A single 16,000 btu a/c should pull only 13 amps. It would pull more on start up but only briefly. Now if there is more on the circuit than just the a/c. It could explain why the trips are so random. If you had a water heater on the same circuit it might take the heater being on and the a/c starting to trip or something of this nature.

In order to do any meaningful diagnosis I would need to know a lot more. What size is the circuit breaker, wire size, what is on the circuit, circuit length, size of a/c and startup amps required

 

[Mac2]

tiltrider1: Do they list the startup amps on the label? This has always screwed me up in the past. I went by the running amps listed, not knowing of the surge in amps required on startup. Then, like you said, a high load like the water heater, or microwave would trip the circuit breaker.

 

[tiltrider1]

I can’t say about dometic. On my Webasto it is listed as max 13 amps but I see it only pulls 11 while running and peaks at 13 on start up.

 

[OldDan1943]

Time to get the tech out there again.

 

[Alaskan Sea-Duction]

Good advice to check all electrical connections.

few years a go, I had a new unit installed. Same issue on start up. The old Marine Air 12btw pulled 22 amps on start up. I was told it was a bad breaker by the local demetic rep.

I call Dometic and they told me start up amps on the new unit was 23amps. Go figure. They advised to change the breaker and install a "soft start" unit.

Works great. However, in your case you paid a tech to install it, probably for some good boat $$. Make them come out and fix it. That's what you paid for.

 

[STB]

I understand the unitnwas installed recently. But if it ran well for a few days or more and is now tripping the breaker, my bet is something changed.

Something could have been installed badly and gotten loose or otherwise gone bad, or there could be a defective part like a bad breaker, etc, etc, etc.

But, in the case that it ran well for at least a few days before having a problem, my bet is that the seawater loop is clogged, most likely at the strainer or an elbow or the pump inlet or the trhu hull or seacock. I'd try cleaning it all out and verifying good, easy flow.

A pump like other motors draws way more current when stopped or overloaded.

My units usually error out before going over-current, but I have had them, when clogged, both use enough excess current to cause me to trip my boat 30A breaker in circumstances where it normally doesnt (short use of microwave with ACs running) and also cause the AC breaker to trip and blow the AC pump's fuse within the AC controller.

Curiously enough, the AC's breaker most often trips before the pumps fuse blows. The only time it doesn't is if the breaker is already warmest up from having been reset. I thought this was wrong, but when I checked the breaker curve and fuse specs, the behavior seems to spec.

At any rate, if it ran for a while before having the problem....try cleaning that seawater loop well and see if the pump then draws less current and thereby avoids the breaker trip.

 

[High Wire]

You could also have low shore power voltage. Its not uncommon to have 208 volts split to 104 volts. Plays havoc on air conditioning units.

 

[EngNate]

First thing, shut down the power and check the terminals of the circuit breaker. A connection a little bit loose here will generate heat and fool the breaker as these are thermal devices. A half turn with a screwdriver may solve the problem.

 

[CharlieO.]

I have an old a/c unit, I recently found out the breaker trips if I have low or no water flow. Once because I forgot to open the seacock, once because I cleaned the strainer and had air in the water line.

 

[markmuck]

Just curious. How does it do on the generator? Any problems there? How are the connections on your boat for the shore power cords. I just replaced mine today because I was having similar issues. So far so good. Good luck...

 

[TowLou]

Id first check amps to see if the compressor is pulling to many amps or is the breaker going bad.

 

[gonesailing13]

Update ! Talked to the installer today and he knew exactly what the problem was. Seems Dometic has a de-ice mode, when the A/C runs for long periods it will switch to this mode which has a high amp draw. The de-ice mode is only needed on bigger boats than mine with long runs of duct work so he had me go to the push pad and deactivate it.Works fine now.

 

[Comodave]

Update ! Talked to the installer today and he knew exactly what the problem was. Seems Dometic has a de-ice mode, when the A/C runs for long periods it will switch to this mode which has a high amp draw. The de-ice mode is only needed on bigger boats than mine with long runs of duct work so he had me go to the push pad and deactivate it.Works fine now.

Gotta love the easy fixes…

 

[Deckape]

I would still have him come out and check his work . Some how your unit froze up and when to defrost , but he said to delete the safety , Tighten all termials and connections and check strainer .

 

[Jack McGrath]

I have a 16,500 Mermaid A/C and had the same tripping breaker, called the manufacture and they said to adjust the compressor delay to 5 min. my issue the compressor came on too quickly and the delay let the pressure drop before starting, no more tripped breakers!