SGKane
Virgina
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Joined: 03/12/2006
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First a little history:
Our rear AC unit has always had an incorrect Thermostat. The one back there has a setting for heat and there is no heater associated with that thermostat. With this thermostat the AC only worked with it set to ‘cool’ and ‘auto low’. Any other settings the compressor would not kick in but the fan would run but always the same speed.
Recently, we had an opportunity to visit my brother at his cabin at the lake. We plugged our 30-amp plug into an ungrounded 115 outlet. When wet and bare footed from the lake we get a small amount of current from touching any metal on the bus. The rear AC quit running on the 2nd night. The compressor would hum but the fan would not start spinning. After playing with it, I could start the fan by with a little spin but it would not start up by itself. I called a local RV Dealer and he suggested replacing the capacitor, which we did, still the same problem.
We gave up and I figured I’d look at it when we got home. After getting home I replaced the motor and still the same thing. I then put in the old capacitor and everything works. Now the AC works on ‘Cool’ and ‘Auto Low’ as well as ‘Cool’ and fan set to ‘low’. When I switch to fans to either auto high or high fan the fan now increases in speed but the AC Compressor cuts out.
Here is my theory:
Being on an ungrounded circuit the capacitor went bad. Replacing it had no effect since we were still on the ungrounded circuit.
Replacing the motor helped in that we now get both a low speed and high speed.
After letting the old capacitor sitting in my toolbox it was allowed to “drain” thus becoming workable again.
Now that we’ve replaced the motor, IF we replaced the thermostat with the correct one, we could have AC on high settings as well as low?
I’m not an electrician or an AC guy so I’m really curious if this all sound correct? If so, when we return next year does it make sense to ground the bus to earth prior to plugging in?
Thanks so much in advance,
Gordon
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SGKane
Virgina
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I probably should have mentioned that this coach is a 1996 and I have no reason to suspect the AC unit has ever been replaced.
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othertonka
Stockton, CA
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Joined: 11/15/2003
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First of all you could be a little low on Amps by only plugging into a 15 amp 110 circuit. Your AC will probably draw more than that at start up. And if you used a long extension cord the power will further be reduced. To do your trouble shooting, it would be best to be pluged into a good 30 amp outlet so you can be assured you have ample Amps to start the AC. And yes I would not plug into a ungrounded outlet, it is dangerous.
Othertonka
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dougrainer
Carrolton
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Joined: 06/11/2007
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Ungrounded plugs would not cause your problem. I assume you have Coleman(RVP) AC units. You have a 12 volt wiring problem, not a 120 voltage problem. Your Tstat is not connected correctly to the AC control board. Either you have an Incorrect 12 volt wire or the Tstat wires are not connected to the correct terminals on the AC control board. From your description, I would suspect low 12 volt positive causing your problem. The Tstat is not an Incorrect one if you think that because it has a 'Furnace(heat) selection. They use the same tstat even if there is no furnace connected. What I would suggest you do, is look at and label the wiring on the front AC and tstat, then compare to the rear to see if it is the same. The ONLY difference between the 2 will be the extra furnace wire on the front Tstat, but all other color codes will be the same. What I would suspect is your problem is an Inadequate ground wire to the control board in the rear AC. NOT a good ground, but a "floating" ground. Doug
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Golden_HVAC
Fulltime, CA, USA
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Joined: 08/19/2003
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Hi,
Next time you have a tingle in your feet, then pound a tent stake into the ground, and attach it to the metal frame of the RV with some wire or car jumper cables. If you still feel a tingle, pour a gallon of water onto the tent stake, so it will conduct power better than your feet.
Also turn over the plug from your RV into the 2 wire receptacle, that might make the RV grounded.
Another thought is to buy a 3 wire receptacle and install it at the cabin. If it is a RV receptacle, 30 amp @120 volts, all the better.
If the cabin already has an electric stove, and you have a 50 amp RV, plug in there! You might need to run the wires out the kitchen window, but you can run both A/C at once! You could also get a 50 to 30 amp adapter, and then use the electric stove receptacle and have a properly grounded 30 amp receptacle.
Fred.
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T_Bone
Arizona
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Joined: 09/20/2001
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Hi Gorden,
Sounds like to me you had a intermidant open neutral at the cabin. A open neutral is the most dangerous condition that can exist for electrical problems.
A ground is a safety wire for a open neutral. The hot wire is protected by the breaker/fuse. A open neutral is protected by the ground wire.
As Doug stated your T-stat is not wired correctly. They used the combination T-stat so they wouldn't have to stock more than one T-stat and is very common to do.
Sounds like to me you need to hire a sparky for the cabin.
T_Bone
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Bob Landry
Austin, texas
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T_Bone wrote:Hi Gorden,
A ground is a safety wire for a open neutral. The hot wire is protected by the breaker/fuse. A open neutral is protected by the ground wire.
The function of ground and neutral are separate and unrelated. An open neutral is not a safety hazard, it will simply cause the devide to not operate. If the ground and neutral are tied together, which they should not be, the outside case of the appliance would become hot should the neutral open. Otherwise ground does nothing but shunt stray voltage to ground.
Also, to the previous poster. Reversing a two prong plug will not crate or remove a ground. With two prongs, there is no ground.
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T_Bone
Arizona
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T_Bone wrote:Hi Gorden,
A ground is a safety wire for a open neutral. The hot wire is protected by the breaker/fuse. A open neutral is protected by the ground wire.
Bob Landry wrote:
The function of ground and neutral are separate and unrelated.
In my statement, a ground is acting just as I stated, the ground is protecting from a open neutral condition.
Bob Landry wrote:
An open neutral is not a safety hazard, it will simply cause the devide to not operate.
"If" this was a true statement, please tell me where in the NEC that it states you can install a switched operator in a neutral line circuit.
Bob Landry wrote:
Also, to the previous poster. Reversing a two prong plug will not crate or remove a ground. With two prongs, there is no ground.
That statement we both agree on!
T_Bone
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Bob Landry
Austin, texas
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First, where did I mention anything about installing any kind of switch in the neutral line? I didn't..Wires open on their own, by breaking, being cut, connections working loose, etc..
Second, explain exactly how does a safety ground protect against an open neutral and what it it protecting against. If a neutral wire opens, no hazard is created. The device or appliance just stops working.
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T_Bone
Arizona
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Bob Landry wrote:First, where did I mention anything about installing any kind of switch in the neutral line? I didn't..Wires open on their own, by breaking, being cut, connections working loose, etc..
Hi Bob,
That is exactly what your are describing as if you could install a switch in a neutral line. It doesn't matter how the neutral becomes open via, switch, break, cut, loose, etc; as there all one in the same condition.
Bob Landry wrote:
Second, explain exactly how does a safety ground protect against an open neutral and what it it protecting against. If a neutral wire opens, no hazard is created. The device or appliance just stops working.
A good example would be a common table lamp. Before they required a jones plug(polarity plug) cord and recepticle to be installed, very dangerous conditions could exist:
Without a jones plug, the outside of the metal fixture bulb holder could be "hot" depending on which way the plug was incerted into the recepticle.
If the neutral line became open and the user touched the metal fixture case then touched a ground source, they could be electrocuted. Thousands of deaths by this type of problem was very common before the NEC and UL required a jones plug cord and recepticle.
With a jones plug and recepticle, then only the center conductor would be "hot" under all conditions. In order to be electrocuted, one would have to remove the bulb then touch the center condutor inside the metal fixture with one finger then grab onto a ground source.
The jones plug and recepticle was a huge safety feature improvement.
T_Bone
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