AC question

[captbuddy]

While in Marco Island, I had a AC guy come out and check my master stateroom AC. Didn't know my v-berth ac was not working and needed a capacitor. Found out my master AC compressor is toast. Yesterday in Dunedin, I got to the marina and turned on V-Berth and Salon units. Did not think the Salon unit was putting out. It took a while to start cooling so I put a termomater in the vents. It got down to about 59 deg in both the salon and v-berth. Should it be lower than that or is that normal?
Thanks,
captbuddy

 

[SKYCHENEY]

I think the rule of thumb is to measure the inlet air temp and the outlet air temp. Ideally there should be about 12-14 degree difference between the two.

 

[Canuck Dennis]

My air goes down to under 50 at the coil discharge

 

[captbuddy]

Sky,
I put the thermometer in the return vent and there was a 20 degree difference. 79 going in to 59 coming out.
captbuddy

 

[Angela]

Sky,
I put the thermometer in the return vent and there was a 20 degree difference. 79 going in to 59 coming out.
captbuddy

That delta sounds decent for a hot summer day in Florida. That's about what I get and it's very comfortable inside. During the daytime, the AC runs almost constantly and rarely satisfies to shut off. As soon as the sun goes down, however, it gets bone chilling cold in here.

Edit: Just went and checked for the heck of it. This time of day is my warmest. I've got 72 going in and 51 coming out, if that helps for comparison. So maybe you are a tad on the warm side.

 

[Boatsb]

Thanks sky at least we have one informed answer.

Theory and reality collide on ac systems. A 12- 14 degree drop is a good target. Thats air temp not coil temp. It has a lot to do with the air velocity and the coil efficiency. If you getting better than 15 degrees drop dont sweat it. Just check that the coils dont ice. Thats a sign of low freon.

Its not rocket surgery so dont over think it.

 

[Canuck Dennis]

Cruiseair suggests 20 Deg diff. health advisory for conditioned space is 10 deg diff to o/s air temp. cooling space

 

[captbuddy]

Again, yesterday we got back to marina and it took the salon unit a very long time to start blowing cool air. I'm talking at least 30 minutes. When it started it came down again to about 59deg. Could a capasitor be causing this delay.
captbuddy

 

[Canuck Dennis]

Most systems have two capacitors, one is hard start and the other is a run cap. you need to test both to see if one is faulty, usually if the run cap is toast, nothing happens, if the hard start is toast, then the run cap may not be able to start the compressor and will usually overheat, trip breaker or just burn up. If the compressor does start but takes a long time to produce cooling then suspect low charge.

 

[captbuddy]

Is it possible for the triggers to go bad and cause the compressor to start for an hour or so. Again tonight it took a long time and I finally heard the unit kick on after I turned it off and on about 3 times. It runs find after it kicks on. I will try and replace the triggers since I think I have them if I can find where I put them. That is unless someone tells me for sure, that is not my problem.
captbuddy

 

[Canuck Dennis]

I ain't got no triggers on my systems, so, I am zero help on that one. If the compressor starts and runs for a while, then it's not capacitors..problem somewhere else.

 

[MikeP]

It's worth checking the connections at the triggers to be sure the problem is not just loose/corroded fittings. ALSO, I once had a similar problem that turned out to be the main power wire at the compressor itself. The connection is under cap on the side of the compressor (at least on my cruisers) and the fitting in question - a male/female type of fitting - had basically arced itself in to being very erratic. I cut the wire back to good copper/tin and installed a new fitting and that eliminated the problem.

With any sort of electrical problem, unless the cause is obviously a faulty component, the related connections are always among "the usual suspects."

 

[Boatnut]

usually when there is a wiring problem and the compressor is not getting it's required power, it will heat up pretty quick, surely shorter than an hour. As previously stated low freon may be the problem, or if present possibly the reversing valve. If you know how, put a voltmeter on the incoming power leads (wires) on the unit and read the voltage when it is not working compared to when it does work. If the start cap is bad the compressor won't start, and if the run cap is bad the unit may run slowly, and usually get hot, and draw more current causing the incoming power to drop.

 

[captbuddy]

Thanks everyone for your help. Boatnut, I really appreciate your help but you are talking way over my head. I have the meter but when you say run cap & start cap, I'm lost.
captbuddy

 

[Boatnut]

Thanks everyone for your help. Boatnut, I really appreciate your help but you are talking way over my head. I have the meter but when you say run cap & start cap, I'm lost.
captbuddy

Honestly I am sorry if I lost you, it was not intentional. With the problem you are having I do not think you have a problem with either cap (capacitor). The caps are an electrical part used to help start a motor. Why and how I will not bore you with.

You never know in a forum the level of knowledge of anyone you are trying to explain something to. If I confuse anyone just send me a private message. I am always willing to explain and help if I can.

 

[captbuddy]

No problem Boatnut. Can you tell me what the triggers do?
captbuddy

 

[fixin-to-cruise]

Triggers are essentially relays but they are similar to transistors in appearance except that they have an additional terminal. Typically one takes the low power level from the control PC board and switches the power on/off to the compressor and another one for the fan. They are typically mounted on the wall of the control box as a heat sink.

Capacitors help the motor... One cap helps it start and one helps it run. They are cylindrical, about an inch diameter and 1.5 inch long. They are located inside the control box near the motor and are cheap - about $3-5 each.

If you hear the motor try to start for a second or so it could be a bad "start cap". If the motor gets hot and shuts down after getting really hot it could be the "run cap". If you hear nothing it could be the trigger which is also known as a triac or SCR.

You can replace these parts yourself. The caps are not hard if access is available. The triacs require a good soldering iron.

 

[Boatnut]

Fixin explained it very well, you can think of the triac or as they call them triggers, as basically a solid state relay. Easy to replace just don't use a large soldering iron or gun, too much heat will destroy them. A 25 watts iron is about as large as you want to use.

One other thing you can not test a triac with the load disconnected, they will not turn on. Typically these devices tend to short out, often followed by burning up, finding them can sometimes be pretty easy. If the triac is shorted the load will run as long as there is power to the circuit.

 

[SKYCHENEY]

Other than a start capacitor, there are 3 parts that could be bad/going bad. They are: Triac, trigger, and time delay.

I just had this happen last week. I got to the boat and it was over 100 degrees inside. I turned on all 4 A/C units and the big salon unit would run for about 3 minutes and then the compressor would go off. I replaced the Triac first but the result was the same. Next, I put in a trigger and the unit ran fine and cooled the boat off in about 30 minutes.

The time delay(if you have one), will delay the compressor from starting for up to 6 minutes(I think) so that all compressors don't start at the same time. If this is going bad, it could keep the compressor from starting, but you can bypass it and tell.

 

[Boatnut]

Sky,

Can you tell me what the triggers are? Typically a trigger or trigger circuit creates the pulse to turn on the triac. I am still off shore working so I don't have any drawings with me.

captbuddy, it sounds like you have a bad connection in the wiring, or possibly a bad solder joint on the board. If you had a bad start capacitor the unit would hum, and get quite hot if left on for an hour.It could be a bad compressor but doesn't sound like it.