Total Newbie AC Question

[ddossey]

We picked up our 2009 Flagstaff 27bhss a couple of days ago. Since then we have been messing around in the trailer in the evenings trying everything out. I have 30 amp service in my back yard where I keep the TTso I have been running the AC when we are inside it. This evening, I plugged her in and turned on the AC so it would cool off by the time we went out to eat and came home. We were gone about 2-2 1/2 hours and when we came back the AC was off. It had tripped the breaker in the converter in the TT. We had a cool front come through central Texas so it was only about 96 or 97 when we left The trailer was pretty warm inside so I think the AC had been off for a while. I had it on Hi Cool and Auto. Is it normal for this to happen? I turned it off and reset the breaker and everything is running fine now. Any ideas? It's supposed to be back to normal tomorrow - about 102, so I will give it a test.

Thanks-

Dave

[cat1956]

You may have had a power surge while you were gone. Try it again and see what happens.

[HookupAndGo]

Couple other things... Do you have the 13.5K BTU AC or the 15K BTU unit? If you have the 15K unit, it draws more amps and sometimes that will happen. Also, check the voltage coming into the trailer when the AC is running. If you have weak or small power lines running out to where you plug in the trailer this may cause it.

Unfortunately these things are picky with the power coming in.

[ddossey]

It is the 13.5k unit. I have been running the AC all day and it is 103º right now. So far so good. It hasn't tripped the breaker. I guess (hope) yesterday was a fluke!

[dB*R]

This also has happened to me once. I think we set the thermostat too low at first. From now on, we cool the camper in steps and this seems to work fine now without any issue.

Do yall have a voltmeter inside to see what the voltage is doing? With the A/C on, the voltage in ours drops about 5 to 8 volts vs when its not running. Less volts equals more heat through the breaker via more current.

[MtnGuy]

Originally Posted by dB*R

This also has happened to me once. I think we set the thermostat too low at first. From now on, we cool the camper in steps and this seems to work fine now without any issue.

Doesn't the compressor only operate at 1 power level ?? So if the theromstat is set low, the compressor will stay on longer, but not pull any more amps for any given time ?? Someone enlighten me here, because I do run my AC off a generator occasionally, and if a lower thermostat pulls more amps, then I will start doing things differently.

I do start my AC with the fan in the low position, as I figure that lessens the compressor start-up drain some. Also, I read somewhere to let the fan run a couple of minutes, as the current to the AC will help charge the start-up capacitor, and again lessen the draw on the genny.....but I am not sure about that 1.

[rockwood06]

Originally Posted by mtnguy

Doesn't the compressor only operate at 1 power level ?? So if the theromstat is set low, the compressor will stay on longer, but not pull any more amps for any given time ?? Someone enlighten me here, because I do run my AC off a generator occasionally, and if a lower thermostat pulls more amps, then I will start doing things differently.

I do start my AC with the fan in the low position, as I figure that lessens the compressor start-up drain some. Also, I read somewhere to let the fan run a couple of minutes, as the current to the AC will help charge the start-up capacitor, and again lessen the draw on the genny.....but I am not sure about that 1.

Yes, your are right the only time more power is needed is when the a/c unit first starts up, that's the reason for a start capacitor and the same go's for the fan. The compressor has three connections on it....START, RUN and COMMON. Once the compressor starts it then kicks out the start capacitor and then operates on the RUN mode and at this point the compressor is operating on 1 power level. The problem I see operating an a/c unit in stages to get it to a room set point is that short cycling a compressor will cause damage to it. What people don't know that everytime a compressor starts the life of the compressor is shorten over time, It's like smoking for ever one cigarettes one smoke they loose 2 mins off of there life. I suggest to set your t-stat at a set point and let the unit do it's job. If you find that the unit keeps on running an never reaches set point, by lowering the stat will not make a difference the unit can only remove so much heat, this has to do with the size of the unit and the heat load in the camper. This is why I change out my a/c unit from a 13,500 BTU to a 15,000 BTU @ 95 degrees I could only maintain 74 degrees in the camper with a 64 degree supply air temp with the 13,500 BTU unit. With adding curtains to the windows the a/c unit now reaches set point and the unit shuts down. You find that in the evening when the sun starts to go down and at night your a/c unit will work just fine that's because the heat load has now been reduced and the unit can keep up with the demmand.

[dB*R]

Originally Posted by rockwood06

The problem I see operating an a/c unit in stages to get it to a room set point is that short cycling a compressor will cause damage to it.

Even though the compressor sources most its current on startup, the breaker did not trip as soon as the a/c tried to start. The a/c was on for about 10-15 minutes when it did tripped. Besides the converter, the a/c was the only other thing on. I presumed that the reason for the interruption was because the a/c ran a good while and then tripped on thermal. BTW, I generally stage the temperature down over the course of a day.

[rockwood06]

Originally Posted by dB*R

Even though the compressor sources most its current on startup, the breaker did not trip as soon as the a/c tried to start. The a/c was on for about 10-15 minutes when it did tripped. Besides the converter, the a/c was the only other thing on. I presumed that the reason for the interruption was because the a/c ran a good while and then tripped on thermal. BTW, I generally stage the temperature down over the course of a day.

Here is a problem when staging down the temp over the course of the day, as the day go's on the temp continues to rise and you keep lowering the stat to make it cooler, this makes the fan and compressor work harder by trying to keep up with the rising temps. If you set the stat to a 65 degree level in the morning and leave it there and let the unit do it's job. You will find that 65 degrees may be a little too cool in the morning but as the day go's on your heat load well increase, now humidity plays a big part in this as well as far as confort go's. If the compressor is tripping the breaker that means that the amp draw on the compressor has exceeded the lock rotor amp that it is rated for. A few things to check, make sure the that all electrical connections are tight, if there are any loose connections this will cause a higher amp draw. Wiring can loosen from heated wires and as they cool they can become loose. Check to make sure that the breaker is the correct size for the unit. The other thing that can case the it to trip is if you have experienced a power drop at your camper from land power. I have experienced in extreme high electrical demands, temps in the mid to upper 90's as the a/c is on then next thing I know the hot water heater comes on and the a/c breaker trips, well the first thing that will trip will be the appliance that draws the most power and there could have been a voltage as well.
I work in a Museum in Virginia and it is all most 1,000,000 sq ft and on hot days we pre cool the Museum all night long so our chillers do not have to work as hard by day and we have a thermal storage system (ICE FARM). I do the same in my camper, pre cool in the morning when we go to Myrtle Beach in July, we added curtains to our windows and close them during the day and change out our a/c unit from a 13,500 BTU to a 15,000 BTH. It works well.

[dB*R]

"Pre-cool" eh? I will try this on our next trip to FL. Always something new to learn .

[rockwood06]

Originally Posted by dB*R

"Pre-cool" eh? I will try this on our next trip to FL. Always something new to learn .

I do suggest to install installed curtains in your windows, this helps a great deal with heat load and keep them close all day. I am headed to Ocean City MD this coming week and it is suppose to be hot. I am going to take a surface temperature gun with me and test the heat at the windows from completely open to day/night shades closed and then with all window treatments close to see the effects. The site that I have, my camper will be facing full sun on the curb side, so i will try to be as accurate as possible with time of day and temperature.

[IIFID]

Did you switch the unit yourself? Or did you have someone do it.
I'm planning on buying a 15btu carrier and moving the stock dometic to the front rough in location, the unit is roughed in for two units but came with one and I think the unit is to big for one AC.
I'm wondering how hard it is to install the unit?