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bigdave720's avatar
bigdave720
Explorer
Jun 24, 2015

AC help needed

I got my previous low voltage problem taken care of. Holding in the 118 to 120 range now. New problem is my 14 year old Coleman Mach 15k ac.

I've had both sets of coils cleaned. New gasket installed due to small leak. Air coming from the vents stays right around 53ish degrees until outside temps start getting into the mid to upper 80's. At that point vent temps start increasing into the mid 60's. Once outside temps get into the 90's vent temps get into the 70's. Now I realize that is fairly normal. Problem is that once outside temps get into the 90's ac starts tripping the 20 amp breaker it runs on. Basically I have to shut it down completely from around noon until around 6pm daily with the current heatwave we've been experiencing for the past couple of weeks. I've replaced the breaker but that didn't help. What do I check now or am I to the point of needing to spring for a new ac?

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  • Fulltimer50's avatar
    Fulltimer50
    Explorer
    Jun 24, 2015
    golf_bears wrote:
    If I understand your problem based on the info you've provided you are running a 15k AC unit on a 20 amp circuit. At high outside temperatures the AC unit keeps running and trips your 20 amp breaker.

    A 15k AC unit needs about 22 amps to kick start it. So if it runs almost continuously when outside air is at 90 degrees it makes sense that the breakers are overloaded and too hot.

    You need that AC unit running on a 30 amp circuit.


    I dont know about your numbers but ACs run on 20 amp circuits. As are my two and every one I have ever had (5-6).
  • C_Schomer's avatar
    C_Schomer
    Explorer
    Jun 24, 2015
    You need to use an amp clamp/meter and verify the current draw and voltage and go from there. The breaker needs to be HACR rated... heating/AC/refrigerating. I also use thermocouples to check for proper refrigerant flow/temps. It's really easy to check subcooling and superheat that way and see if the filter/strainer or cap tube is restricted. Your symptoms would make me look for a restriction or dragging fan motor... after cleaning the coils. I wish I had a dollar for every drier I've replaced on old systems and made them work like new again! I've added a SUP hard start to a RV AC that had a high amp compressor but that only made it last another 1 - 1 1/2 months. That old AC might not be worth spending very much on it. Craig
  • golf_bears's avatar
    golf_bears
    Explorer
    Jun 24, 2015
    If I understand your problem based on the info you've provided you are running a 15k AC unit on a 20 amp circuit. At high outside temperatures the AC unit keeps running and trips your 20 amp breaker.

    A 15k AC unit needs about 22 amps to kick start it. So if it runs almost continuously when outside air is at 90 degrees it makes sense that the breakers are overloaded and too hot.

    You need that AC unit running on a 30 amp circuit.
  • ksg5000's avatar
    ksg5000
    Explorer
    Jun 24, 2015
    When your running AC are you connected to shore power or running off of generator? As temps go up more people on the grid turn on their air conditioners and that can sometimes make the power supply sag which will contribute to air conditioner problems.
  • allen8106's avatar
    allen8106
    Explorer
    Jun 24, 2015
    Sounds like as the load increases the compressor is drawing too many amps and tripping the breaker once it reaches the breaker limit. A couple of causes, not in any particular order.

    Compressor is starting to fail.

    Loose wire connection somewhere along the electrical system of the compressor. At the breaker, at the compressor etc.

    Clogged outdoor coil causing the compressor to work too hard in high heat conditions. Make sure the outside of the coil is free of tree cotton etc. I use a 3" paint brush with the bristles cut short to about 1-1.5 inches to clean the cotton off of my coil. Flush the coil from the inside out with a water hose.

    Damage to outside of coil not allowing for proper air flow. May need to comb coil.

    There may be a few other causes I am missing.

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