Smoke from air conditioner

[dohenyboy]

Have a question that is out of my expertise and so I ask for help.
Started one of the airconditioning units yesterday. Its a Marine Air 16K model from their compact line. Do not know how old it is, but I gues at least 5-6 years. Had not been run for about 3 months. Temperature was 90 F, was powered by 7.5kW generator. Only other load was the airconditioning circulating pump.
After a few minutes, I noticed smoke coming from the cold air vent, smelling like burnt motor. The breaker tripped.
Later that day I removed the cabinet cover and started the unit again. On these models there is a rotary switch with "Start"--only runs the blower-- and "Run"--compressor runs as well. This time I started it on "Start" to see if smoke would come out (indicating the blower was bad). No smoke. Switched to Run and no problem.
Since I am unable to reproduce the problem, I don't know what to repair. Why would smoke come out one time and not the next time. What would cause the smoke, just a motor wearing out? I thought it would have been caused by motor overload, but it did not smoke the second time. If its the blower, should I replace it now, or just wait till it happens again? What else could cause the smoke? Or could it be the compressor? Do I have some other intermittent wiring problem?

[hellosailor]

Generally smoke is a bad thing, indicating a motor has seized up or is about to. And then if a breaker doesn't trip, you have a fire.

It *could* be the motor had something in it (bugs, mouse nest) that has now been burned off but I still wouldn't trust it without eyeballing the whole thing real close, or getting it out to a motor shop to see if it needed overhaul. Could be you just "burned off" a problem area in the insulation or coils in the motor--leaving a raw spot that will cause more trouble in the near future. (Motor, blower, whichever.)

Electric-driven compressors generally are sealed and won't make smoke. Bottom line is, you need eyeballs in there to look for the charred parts before you can use it with both eyes closed again.

[ebs001]

If you have an amprobe, take a reading on the fan motor and check it against the FLA of the motor. If it's high you have a bearing problem and will need to replace the motor soon. It could be as HS suggets bugs etc but the fact that you smelled "burnt motor" sounds like it had something to do with the fan motor, not a burning mouse - they smell different. This could also have been something jamming the motor. Check in the motor location to see if anything is loose that might have jammed the motor.

[dohenyboy]

Thanks for the responses. Since the boat is kept quite far from me, I think I will try to buy a replacement blower, rather than make another trip to troubleshoot the blower or try to get it repaired. Its just as easy to install a new blower as it is to take out the old one, check it out and reinstall. I just wanted to narrow down the problem. I think I will look at the wiring too and check for excessive voltage drop.

[CapnHand]

Originally Posted by hellosailor

Generally smoke is a bad thing

Electric things run on smoke. If you let the smoke get out, they usually won't run anymore.

[Valiente]

I'll follow this, as I have the 12,000 BTU model, and it's about the same vintage.

Have you considered corrosion at the leads creating heat and resistance at start-up? Those units eat a vast amount of amps in the first couple of seconds of running and I suspect if the wiring is compromised in any way, heat, and not cool air, would result.

Do you have a March pump in the same compartment bringing in the raw water? That could be a place to look, as they draw a large AC load on start-up, and could be strained if there was a marine beastie stuck in the circuit.

This is my model: http://www.mmair.com/marine_division...ir_conditioner

and this is my pump (a great pump, by the way):

MARCH LC-3CP-MD:

* Liquid cooled, Maroon epoxy encapsulated (open air or submerge)
* 3/4" Inlet, 1/2" outlet (5/8" hose)
* 1/20 HP motor - 2.2 amps @ 110v
* 220v available - 50hz OR 60hz needs to be determined

[sailaway21]

You should check the startiing capacitor on the motor. It is the most likely culprit for high draw on the start windings of the motor. Having sat for some time you may have some corrosion or such causing binding, and it may start fine now. Starting seperately pretty much confirms an excessive amp draw was present. What reason and on which unit? You'll need an amp probe and an ohm meter for further details to that question.

[camaraderie]

I'm with Val on this one. Check the pump!...and check for a blockage or partial obstruction in the water line.