New Use For Old Rooftop AC!

[bob stout]

The AC unit was still good on my 25' 1977 Pace-Arrow moho so I decided to install it in my garage above the ceiling, I spend a lot of time in my garage so why not put the old AC unit back to work, I know corny idea but don't judge me yet, lol! I ran a new outlet off the kitchen circuit and mounted it about 6' from the AC unit and mounted the controls about 12' from the AC unit, I wired on a 3 prong plug to the AC unit wiring so I could unplug it when needed! Surprisingly the AC unit works great and blows cold air but there's one issue, after kicking on the AC the plug I wired on starts getting hot after about 10 minutes! I was told RV grounding is different from house grounding, something about the neutral being bonded or something or could the controls be a problem because of the distance they are from the AC unit? I don't know so that's why I'm asking you guys for help! Has anyone ever heard of someone else using a RV AC unit in their garage?

Can't judge a man for trying to stay cool in this Phoenix heat, unless he's hurting others in the process, lol! 

[Tony durfey]

Hi, I do not believe grounding is the issue.  AC units work on shore power which is the same as any house.  Sounds more like a wire size issue to me.  To much draw=amps though a to small wire will make heat aka hot wire/plugin.  Best I can say without knowing amp draw, wire size, ect.  Hope this helps, Tony, Joy and Cool Paw Luke

[Matthew Tritt]

I agree with your take, but I suspect that the real issue is with the plug that was added. Many of the new batch of universal electrical bits from the hardware store are very light-duty and cheaply made. I would check the ampere rating on the label and then pull it apart to check that the wires are properly captured by the attaching screws. My personal bet is that the wire is fine strand THHN and the attachment points are simply screw heads that aren't compatible. One way to correct this is to tin the wire ends (solder) and bend them in a loop that can be completely captured by the screw heads.

Matt

[bob stout]

Well Mr. Tritt you were right! I replaced the plug with a sturdy universal one and it works fine, no more overheating! I knew I had it wired right so it was driving me nuts trying to figure it out! I'm glad it was a simple fix!  

[Matthew Tritt]

Good. All it took was a bunch prognosticating. ;-)

[Keith Gigabyte]

Not to be a nosy guy, but I am an electrician with 21 years experience.  I see a couple problems here.  First the kitchen must only have kitchen outlets on the circuit.  depending on when your house was built, this may or may not be the case.  The rules were changed in the 70's.  Next problem..the wire size to you kitchen may be 14 or 12..14 will handle 15 amps and 12 will handle 20..I have not seen you  ac unit but it probably pull at least 10 amps so if you wife plugs in a mixer while you have a/c running..pop goes the breaker.  third and definitely a injury risk is the grounding and neutral separation.  In a house or any branch circuit outlet..ie campground..the neutral and ground must be a separate wire.  if your running off generator power the ground and neutral is the same wire..im sure im confusing you but with the neutral and ground the same in the house, there is a possibility of a shock.

[Richard W. Cobbs]

Yes Keith, you are confusing Me anyways.  The OP refered to not bonding the neutral and the ground wires in an RV.  He did not say that they were the same wire.

[Matthew Tritt]

Um hummmmm..... Since this was about running an old RV A/C unit in a house, as I recall, you need to know the BTU rating of the appliance. If it just happens to be a 13,500 BTU unit, they run with about an 8 amp draw and have a start-up surge of around 14 amps - maybe 15. The abandoned AC circuit in the RV will have a breaker in it that was properly sized to use with the unit - probably a 20 amp. To find the right size breaker for this circuit you take the max input surge (15 amps) and multiply it by 1.20 (the .20 is the safety factor) and get 18. Since finding an 18 amp breaker is not likely, 20 amps will do without a risk of allowing too much current to flow in an undersized conductor. As far as isolating the neutral and ground wires goes, just remember that the intended function of the ground is to act as a secondary path to ground in case of an interruption in the neutral side of the service. This means that if the neutral and grounds are commonly connected (as was the case for many, many years under the National Electrical Code), there is a CHANCE, not a certainty, that should the neutral connection fail, the ground could fail as well along with it, thereby causing a potential safety hazard. In most of the world where 50 Hz, not 60 Hz, is the standard, there is NO ground lug on residential plugs and receptacles at all. Since the people who live in these areas (Europe, the UK, Scandinavia, Asia, Australia and New Zealand, etc) appear to be doing just fine, and do not suffer from rampant electrocutions as the norm, it is possible to surmise that our paranoid US electrical code might have a few holes in it's collective logic.