Greetings & sorry you are having trouble~

I need a bit more info before I can suggest a fault…

When you say Dual Marine Air system…Does that mean two self contained units on one seawater pump ?

Are they Marine Air, Cruisair, or some other brand ?

What type of controls…Digital or 3 knob ?

How Old ?

Does the breaker trip immediately, or a few seconds after the compressor starts ?

What is the dock voltage with the aft system running ?

Are both units on the same shore cord ? 

Steve~

Cruisair or Marine Air ?

Is one unit larger than the other…If so which one is larger ?

If the aft unit is the smaller of the two and it runs ok…It could be a shore power or breaker (weak) problem.

Marine Air didn't use a start capacitor & relay, and are a bit harder starting than Cruisair's of that vintage…

i would start by opening the electrical box on the unit to look for burnt connections on the run capacitor.

A hard start kit can be added if the compressor is not shorted to ground but it may not last long after that…and then again it could.

Two units on one 30 amp cord is right close to the limit of that cord so good voltage is paramount…especially without a start kit installed.

As you probably know…The lower the voltage…The higher the amp draw.

Is the boat in a marina with a 30 amp source or is it behind a house using an adaptor to plug into a 15 or 20 amp source ?

Steve~

Post edited 11:18 am – May 3, 2009 by Steve Pooler

From what you are telling me…It's not sounding so good…Everything seems to point to a "locked rotor" compressor.

I'm guessing that unit is probably 16,000 Btu…Those compressors can draw up to 75 amps when locked (seized) and this is the reason for the voltage drop and the gen set stumbling…

You can try a Hard Start kit…It's a start capacitor & relay (all in one) that has 2 wires that plug on to the run capacitor (one wire each side)

This gives the compressor a boost to get it rolling over, and it's my opinion that Marine Air should have done this (or a relay & cap) from production…Shore power is frequently not what you might expect in a home or permanent type installation, so any help a marine system can get is good…Unfortunately I think they were considering costs…

If it won't start with a kit…The compressor is locked and will need to be replaced…Question is…What made it fail in the first place ?

Without a running compressor…You can't determine that, as you would need to see systems running pressures with gauges to get any idea.

If it will start with a kit…Yes you or a trained A/C tech can at least see if it was running low on refrigerant, or has a stuck reversing valve with the gauges…

Considering the age of the unit (15 yrs) the question is…Is it worth repair ?

A replacement compressor from Marine Air/Cruisair for that unit (They are both now owned by the same company "Dometic") Costs between $600 to $660 depending on if it is a Reciprocating (piston type) or Rotary model…Add to that labor & freon…That's just to find out if the unit has another problem such as freon leaks, or a bad reversing valve…The repair could get even costlier…

You can physically see the condition of the unit (I can't) so from here it would be hard for me to make a recommendation for repair or replacement…But given what I do know about age and symptoms…I would lean toward replacement to get good service out of your fwd system without having more costly repairs in the near future.

Marine systems live in a different environment than a home system, and have seawater running thru them…Electrolysis is a factor that home systems don't encounter as much as a marine unit…Electrolysis attacks the solder joints in marine units (of which there are many) and is evidenced by the copper turning Black in color…Especially at the solder joints….If you see this on your unit then it probably has a freon leak, and by it running low on freon, consequently caused the compressor failure due to overheating…Compressors rely on freon return for cooling of the compressor (the seawater only takes the heat out of the refrigerant) If one joint is leaking…It's likely that others are too, or not far from it….It only takes a small loss of refrigerant to overheat a compressor…Finding & re-soldering these leak/s can be quite time consuming, and even if you do repair them…They are likely to show in another spot soon…Possibly causing the replacement compressor to fail…

The new "Turbo" units from Dometic (Marine Air or Cruisair) are really a step above what was available in 1994…They are much Smaller, Lighter, Have More Efficient/Powerful Blowers, and Composite Drain Pans that channel the condensate to the drain for less standing water in the pan and less rusting of remaining steel parts such as the bottom of the compressor (another source of freon leaks)

Just this week I replaced a 16,000 Btu unit with a Turbo 12,000 Btu unit….The customer claims it performs better than the old unit ever did with much less noise, and with lower amperage too…The only drawback is the new unit will not talk to your existing digital control so it will need to be replaced as well…Which really is no drawback except for that extra cost of the control & cable…

I know this is probably not what you wanted to read…But it is a change-out that you could do yourself since you are handy…and with the 2 year warranty offered with the new unit…My feeling is it would be worth the money spent as opposed to a repair that may end up as wasted money.

If you do decide on replacement…Your existing duct work will be the deciding factor of what size unit to go with…

Marine Air also used to supply their 16,000 Btu units with a 6″ discharge ring which was never large enough for the air flow of a 16,000 Btu unit…A 16,000 needs 7″ discharge and close to 80 sq in of total grill area…

That's the reason I installed a 12,000 in the boat last week but we can discuss what you have available, and your options if you decide to go that way.

Let me know what you think…and I'll be happy to answer any more questions if I didn't cover something…

Steve~

Post edited 8:35 am – August 17, 2010 by Steve Pooler

Peter~

If the installers replaced a compressor…They would have most likely had to run the unit to check & charge it fully with freon…Maybe only on a bench, but it should also have been run (or at least started for a few seconds) once installed.

If they replaced the whole unit…It's either a low voltage problem, or a warranty problem with the unit….Have you tried it on shore power ?

I would get the unit checked by a qualified tech…Here's a link to a dealer locator that should be able to find your problem quickly.

http://www.dometicenviro.com/d…..hp?l=water

Steve~

I guess what I'm trying to understand here Peter is…Did the unit at least run before without tripping the breaker or heavy amp draw ?

If it did at least run before…Then it may not have been a compressor, but another problem.

How did they test for another problem with the boat out of the water ?

Did it indeed draw high amperage & trip the breaker before the repair ?

If they did replace the compressor it could be wired wrong…Which would show they did not test it before re-install or after…

Was it a boatyard that did the repair, or do you know if they hired a A/C tech/contractor to do the job ?

How much did they charge for the job ?…This would tell me if a compressor was involved (or at least charged for)

Lastly…They could have just added freon to make it cool for the sale…Brokers often will only pay for this, and no more….Running low on freon could and would have killed any compressor…New or Old…How much have you run, or tried to run it since you took delivery ?

Lots of variables here that are all guesses at this point…My crystal ball has been called good…Just not quite that good    Especially if I can't lay hands or eyes on the unit.

Steve~