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Old 07-25-2012, 07:08 PM   #1
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Troubleshooting RV Air Conditioners


Looks like none of my comments got to you.
First comment:
You said that you turned the thermostat up to turn it off and back down within a minute. That in its self can create a problem because that short period of time does not allow the compressor to equalize. When the AC is running you have a 250 lbs. to 300 lbs. of pressure on the discharge side of the compressor and around 60 lbs. on the inlet side. As you can imagine the motor doesnít like to start against a 5 or 6 to 1 ratio (itís like trying to start a car in gear). Thatís why the newer systems have a 5-minute time delay built into the system.
That being said if the pressures are equal and the voltage is correct you should not need a Hard Start Cap. I would check to make sure that the voltage is over 110 VAC when the AC is running (Check this at the AC unit in the ceiling). A hard start kit is a bandage for something that not correct with the compressor or the power supply feeding the compressor.
Along those lines a 2000-Watt compressor is probably NOT enough to run a 12,000 or 15,000 btu AC. There are a couple of reasons, 1- most 2000 watt Gens are only rated at 1800-Watt continuous duty (15 Amps 120 VAC). A 12,000 btu. Two, the AC that runs at 12 to 13 amps @ 120 VAC has a momentary start up current of 25 to 30 amps @ 120 VAC or 3000 t0 3600 Watts. Starting a motor is like pushing a car the first 10 feet is really hard but after you get it moving itís not so bad. An electric motor is the same because the first few revolutions the motor will draw 2 to 2 Ĺ times the run load amps. Thatís why I say the 2000-Watt Gen is really not adequate for a 12 mbtu. or 15 mbtu. AC even though the run load amps are less than what the max amps are on the Gen.
Now as for low voltage as the voltage goes down the amps go up. Work is a combination of volts and amps which = watts or work. Any motor or inductive component will suffer from this; a 10% decrease in voltage creates a 10% increase in amps. Thatís what burns stuff up NOT the low voltage but the by-product of low voltage, which is high current (amps). Resistive components do not suffer for this problem only happens with inductive parts like motors & relay coils. But thatís not the end of the problem as the voltage goes down and current goes up the wire it's self heats up because of the high current and when that happens the resistance increase and the voltage drops even more.
So as you can see any voltage under 110 VAC will create problems serious problems, in most case low voltages cause more problems that high voltage because of the high current by-product.

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Old 07-25-2012, 07:29 PM   #2
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Next NO Cooling after long run time, IF (key word IF) the compressor is still running you probably have a freeze up problem. Indoor coil freeze up, this is only caused by one thing LACK OF AIR FLOW ACROSS THE COIL when its over 75 degrees outside. This can manifest its self in several ways:
Fan failure
Dirty air filter
Impacted Evap coil (indoor coil). This is dirt in between the fins
Dirty Evap coil surface (indoor coil).
Inadequate ductwork (Not uncommon in an RV). Duct work to small.
Low Freon will not freeze up an Evap coil at normal operating temperatures. That being said if you are low on Freon your compressor will overheat and shut down after 5 to 30 minutes of run time depending on how low it is. THIS IS NOT COMMON and usually results in a burned out compressor in short order.
Now after all of that remember that on a hot day with sun shining in all of your big windows your AC probably will not be able to keep up. If it’s a scorcher keep the shaded drawn on the South side along with the East in the morning West in the afternoon.

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Old 07-25-2012, 07:56 PM   #3
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Location: East Long Island, NY
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Thanks for the AC, volt, amp class...
The prob then - it sounds like with mine is the STOCK run cap and/or start cap maybe/are going bad?
The AC had been running cool/ great while it's running, even in those mid 90 out in the middle of a sunny field days. It's when the AC reached the set T-stat temp (@ night) cycled off and when it tried to come back on later on when T-stat called for it, the AC would trip the 20amp AC coach breaker. Each time I had good voltage close to 120V (on dedicated 30amp service I had run @ my home when tested).... And yes I realize I cycle the AC too soon

And as Maranatha said "A fan timer and a capacitor are relatively inexpensive mods and can't do anything but help reduce the initial surge." - right?
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Old 07-25-2012, 08:11 PM   #4
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While relatively inexpensive to install the capacitator, I took a good look at my warranty & since the trailer is brand new and covered by warranty - any changes to the wiring will invalidate the cool cat warranty I will just have to wait it out....orrrr get a larger generator LOL

sigh...I do think the hard start capacitator would effectively help my Champion 20000 genny run the A-frame's cool cat system - but I'll just let another owner do it to theirs and wait for their findings....

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Old 07-26-2012, 04:35 AM   #5
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i think it depends on how low on freon you are. r-22 at 57 psig will form ice, r-134 at 36 psig will form ice. it starts to form just past orfice reducing air flow and continues to spread dropping the psig fauther untill coilis blocked or compressor quits. i have seen the whole compressor form a ball of ice on it in some applications. rooftop units,residental,etc.
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Old 07-26-2012, 05:49 AM   #6
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This is part of the "Hard Start Capacitor" thread.


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