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Montana_1424 05-31-2005 06:33 PM

AC Tripping Breaker
I had a problem in Flordia, with the AC tripping the breaker when turing on. I was on 50 AMP service, which my rig is. I thought it was just the RV park, but this past weekend, I did the Hunter Thermo upgrade, at another park with 50 AMP service. The first time I turned the AC on, it tripped the breaker. Couldnt get it to do it again, but I am getting concerned. Used the AC plenty last season with no problem what so ever. Any insight on this would be appreciated.

Bowie 06-01-2005 04:24 AM

A handy list of average amps for typical appliances which we received from our camp may provide a clue to the problem at hand.

Air conditioner 12.5 amps
Converter (with nothing on) 1.5
Electric water heater (6gal) 12.5
Electric refrigerator 4.0
Microwave 12.5
Electric coffee pot 9.0
Toaster 10.0
Hair dryer 10.0
TV 2.0
Electric fry pan 10.0
Iron 10.0
Food processor 6.0

If the AC, frig, water heater are in use (29 amps) and you throw in the coffee pot, fry pan and someone drying their hair (29 amps), making some bacon in the microwave (12.5 amps) might get you in trouble. Do you know what difference the thermo upgrade adds to your system? Check to see what else was in operation when the AC coming on tripped the breaker. Not to say that there isn't another issue--but we've all been in the over-applianced mode at one time or another. Let us know what you discover!

sreigle 06-01-2005 08:14 PM

Ed, your rig is pretty new so I wouldn't think the compressor would have a problem. I've seen older rigs, including one we had, where the compressor kicking on would seriously dim the lights and sometimes pop a breaker. It had to do with the bearings (I think) in the compressor getting dry and requiring more amperage to fire up the compressor. This is probably a longshot for yours but thought I'd mention it anyhow.

toolmanroy 06-01-2005 09:13 PM

We had a similar problem and Roy took the end of the trailer power cord apart and found some moisture and a cobweb. After he cleaned it and plugged it back in it stopped tripping the breaker.

Harold & Teresa 06-02-2005 04:30 AM

ED, my farther-in-law also has a 2004 Montana and he was having the same problem. He had a mobile RV service tech check it out and it was a bad compressor. Someway the tech was able to test the amp draw and if I remember correctly it was pulling like 24 amps. He has been waiting on Dometic to send him a new unit for around 2 weeks now.

Montana_1424 07-21-2005 12:10 PM

Well, now I am in Myrtle beach, and the aC is tripping the breaker again, not doing a very good job of cooling wither. Went up on the roof and saw no signs of freeing, however, the drip pan under the compressor is full of water, not really draining that well. Could this cause the breaker to drip? I am starting to think it is a bad compressor. Any help would be appreciated, again. as it is pretty hot here (90 degrees plus).

Countryfolks 07-21-2005 12:40 PM

Which CB is tripping? It may be the breaker itself. they sometimes fail and start tripping at lower amps than rated. Keep in mind the AC draws about 20 amps or so [maybe more] when it first starts.


Broome101 07-21-2005 12:46 PM

You mentioned you did thermostat upgrade. Did you have this problem before the upgrade on the stat? If not something may be wrong with your thermostat if it just started doing it after the install, just a thought.

sgf 07-21-2005 01:07 PM

Being a hvac tech I will throw my 2 cents in here,when the un it starts it will draw more amps, probably around 28-30,when up to speed the unit will probably draw around 10-12,this is called RLA or running load amperage.If the compressor was bad and tripped every time right away I would say the compressor was shorted out to ground,if it trips occasionally but starts you may have what we call a hard starter,it could be a tight compressor, bad run capacitor or resriction in the system.If it tries to start but does not it would draw LRA or locked rotor amperage which may trip the breaker but the overload built into the compressor,some are externaly wired should pop first.In your case if the drain pan is full of condensation it sounds like the compressor is running,so you may have a loose wire, weak breaker bad overload, LOW voltage,that is a biggie, the lower the voltage, the higher the amp draw will be.Also a bad motor will cause the amp draw to creep up,if this is a new unit I would have someone check yur voltage and wiring to make sure it is ok,if it is the a/c unit from domectic should have a five year warranty.Good luck.Also make sure your filter is clean and the outside coil is clean and free of leaves and dirt.

Montana_1424 07-21-2005 02:07 PM

sgf, thanks for the info, that helped a lot. I did alrady call the place I bought it, and from what I said, they seem that the compressor is bad also. Someone is coming to look at it tomorrow. This did not happen before my thermo upgrade, however, I switched back to the old thermo and the same thing was happening. I did notice that this started happening when I started using the hot water heater on electric instead of gas. I switched back to the propae, and the same thing was happening. I guess I just have to sweat through one night until they come tomorrow to look at it.
Again, thanks for all the info. Tyring to sell this unti so I can get my new one, so I need to make sure everything is tip top shape.

Glenn and Lorraine 07-21-2005 02:35 PM


quote:Originally posted by sgf

...........LOW voltage,that is a biggie, the lower the voltage, the higher the amp draw will be.....
Low voltage was my problem just 3 weeks ago. After an AC tech explained about the low voltage causing a higher amperage draw I purchased the Autoformer and have had NO problems since than. With the heat wave SE Penna is having I haven't turned the AC off in 3 weeks. Thank you Hughes Autoformer!

Get yourself a meter and check your voltage at the campground connection. Best time to do this is mid-day when the electric usage is at it's highest. If it is low voltage there is a Camping World in Myrtle Beach, they may have an Autoformer in stock if you should want to give it a try.

Charlie 07-21-2005 03:13 PM

We purchased one of the plug-in volt meters from CW and it is plugged in all the time within easy view so that we know what the load is inside the trailer and how much is available to use.

Montana_1424 07-21-2005 06:08 PM


What exactly is an Autoformer?
Also, an update, I had the AC turned off most of the day. I turned it on around 8 PM Tonigh,t (It is now 11 PM) and it has been working fine. I am sure it is only a matter if time. I have a tech coming to my site in the morning. I think I will invest in a volt meter. What voltage should I be getting, just 110?

Thanks again, and Glenn, if you can let me know what an autoformer is, I am going to be going to CW at some point this weekend (There is not one is Syracuse, so I always go when I am here).

Thanks again.


Montana_2785 07-22-2005 05:36 AM


quote:Originally posted by kozzy45


What exactly is an Autoformer?

It is a transformer that is setup to automatically transform (boost) its output voltage by 10% when its input voltage drops below some value (I think I've seen people say 118 volts???).

Why do we want this?

AC electrical devices, and in particular induction motors (like you have on the compressor of your air conditioner) are rated to run at a particular voltage, drawing a particular amperage. The size of the wires in the windings are sized for THAT amperage. The motor is rated, thusly, to produce a particular amount of mechanical power in order to turn the compressor.

When your park power is not able to supply the correct voltage (bad wiring, too many other RV's on the system, etc...) the motor in your air conditioner is still trying to produce its rated power. Since the voltage has dropped, the only way it can continue to produce the power is to draw more amperage. Simple formula (over simple for AC power but gives the concept) Voltage times Amperage equals Power. As voltage drops, amperage must increase.

For comparison, a DC motor will simply slow down and produce less power if the voltage drops. An induction AC motor will attempt to maintain the same speed due to the 60 cycle nature of AC power. It wants to stay mechanically (rotationally) syncronized with the 60 cycle sine wave of the electricity. That attempt to maintain speed is what causes amperage to go up.

If the voltage drops too far, then the amperage it draws will overload the size of the wire used in its windings and it starts to run hot. If overloaded too much you let the smoke out and the motor is ruined. Note: It is a well known fact that electronic devices are made with smoke in them as a critical manufacturing raw material. For proof, just note that electronics are ruined when you let the smoke out... ;):D:D:D

So, we use the autoformer (a simple step up transformer) to increase the voltage to the air conditioner so that the amperage it draws is lower and more in line with its design.

Note: AN AUTOFORMER DOES NOT CREATE POWER!!!!! It only changes the nature of the electricity on its output. Ignoring the small losses in the transformer itself, what you will see is

pp = park plug
ao = autoformer output

Lower Voltage(pp) * Higher Amperage(pp) = Higher Voltage(ao) * Lower Amperage(ao)= Power Used.

Since the autoformer will be seeing the low voltage and high amperage on its input side, the winding of its internal transformer will be made of heavier wire than what is in the motor of your air conditioner and will be OK.

Note that for a purely resistive device, like a toaster (oven), electric fry pan or coffee maker, the lower AC voltage only results in less heat as these will NOT draw a higher amperage like the air conditioner will. That means that low voltage will not hurt these things, but it will take longer to toast the bread or to make the coffee. So the performance of these appliances will be noticeably better with the autoformer when park voltage is low.


Glenn and Lorraine 07-22-2005 04:49 PM

Once again Eric has jumped in and explained the whole Autoformer thing. I could have done the same thing but in my case I am as dumb as a rock when it comes to such stuff fancy electrical stuff. I only bought the Autoformer because of what I have read on the internet and a camper next to me was already using one with great success.

Thanks Eric another great post.


quote:Also, an update, I had the AC turned off most of the day. I turned it on around 8 PM Tonigh,t (It is now 11 PM) and it has been working fine. I am sure it is only a matter if time. I have a tech coming to my site in the morning. I think I will invest in a volt meter. What voltage should I be getting, just 110?
The above is a very good reason to look at low voltage. During the daylight hours is when you will experience the low voltage. During the evening as offices and industries shut down for the day the voltage will return to a more normal level. In our case each evening we had 118 to 120 volts but during the day time hours this same voltage dropped to under 105V. During the day most business' are operating at full power and putting an overload on the power companies. The power companies can put out just so much and we begin to experience voltage loss.

You could also pick up at voltage meter, as mentioned in another reply, and plug it into any inside receptacle for an instant voltage read. The cost for the meter will be about $20.00.

Montana_1424 07-22-2005 06:56 PM

Thanks guys for all the great information, the autoformer souds like a great idea, but at 550 fot he 50 AMP model, will need to wait a little for that, but a great explaination on what it does Eric. I think i will also invest in the volt meter. I was just at CW today and forgot all about it. Needless to say, thanks to Meyers RV in Syracuse (Where I bought my RV), Holiday Kamper Myrtle Beach (The people that did the work today) and Camping World Myrtle beach (They had the unit in Stock), my AC was replaced today due to a bad compressor, at no cost to me but 2 bottles of water for the repair team, all warrantee.
thanks to those guys big time, and thanks to all of you for the good information.

keham 07-22-2005 07:18 PM

I just was reading through one of the AC trouble shooting guides and remember seeing where low voltage is one of the first things to check for.


sreigle 07-23-2005 04:03 PM

Ed, if you're not near CW, I got my plugin volt meter at Walmart for under four bucks. It says Line Voltage Monitor on the front. I also have a VOM but the plugin meter is right where I can see it from my chair and is worth having.

Montana_1424 07-24-2005 04:31 AM

Well, the new AC unti tripped the breaker last night. I am starting to thinkn this is a voltage problem at the park. I am on my way out now to invest in the line meter, and probably an autoformer. I am hoping that is the problem and it will fix it up.

richfaa 07-24-2005 10:02 AM

Everything should work OK with a input voltage of between 104 and 130 volts..Good surge protectors are set to trip at those levels. An Auto transformer is a good buy..Good explaination by Eric//Ohms law E=IXR E being voltage I being current (amps) and R being resistence Amps is the killer and as Eric and Ohms law states low voltage= higer amps Rv parks and Campground are not known for good steady power a voltage meter in your unit is a must. Autoformers ARE expensive but so is a new A/C or Fridge.Autotransformer is a good insurance policy.I will have one in the new fiver.

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