Who uses a 30 amp to 20 amp step down plug and runs the A/C?

Hi:
We have a new to us toy hauler.  It is 30 amp so I went to the local RV supply to get a 30 amp step down to a 20 amp so I could test everything out at home.  When I bought the plug the salesman said DO NOT TURN ON THE A/C when you plug into your house electric because the adapter plug will melt.  Two people at work say they plug their 30 amp trailers into their house 20 amp and run the A/C all the time with no problem.

Can I and can't I plug my 30 amp TH into my house electric using the 30amp to 20amp step down plug?

Thanks for your help

I did just that for several years until I installed a dedicated RV outlet at our cottage. Give it a try and check the adapter after an hour or so to see how warm it gets. I found the "dog bone" style adapters hold up better than the "hockey puck" style.

You can run your A/C on 20A but the adapter won't melt.  If you draw more than 20A the circuit breaker in the house will trip.  Just don't try to run much else while the A/C is on.

Actually you will be running it on 15 amps since that is the output of most outlets around you house. I lived in Las Vegas in a friends driveway for several months for several winters plugged into a 15 amp circuit with a 100 foot extension cord. I ran the A/C, my big screen and the surround sound all day long without an issue.

Like Tom said, you're probably plugging the adapter into a 15 amp rated outlet, even if the breaker on the circuit is 20 amps.  You can legally feed several 15 amp outlets from a 20 amp breaker - the assumption is you'll have multiple devices plugged into the various outlets and no one outlet will carry more than 15 amps.

A true 20 amp outlet has one of the blades oriented horizontally, like this:  ( - | ).  There's also a combination 15 or 20 amp outlet where one side is T shaped to take either a 15 or 20 amp plug, something like this:  ( -|  | ).

But if you plug into an outlet with two vertical prongs ( | | ) it's a 15 amp outlet.  If you draw 20 amps from it the outlet's contacts will overheat, which in turn transfers heat to your adapter's prongs.  Often the first sign of overheating is melting of the soft rubber adapter around it's prongs, so you'll hear comments about the adapter melting.  But in fact it's the outlet that's overloaded.

The other issue you have to watch for is low voltage while the air conditioner is running.  All wire loses some voltage when you pull current through it, and smaller wires lose more voltage than larger wires so the problem is more acute when you plug into a lower rated circuit.

The air conditioner's compressor motor can be damaged if the voltage goes below 109 volts.  The motor draws extra current to make enough power at the lower voltage and the windings overheat.  Often the damage doesn't show up immediately, instead it is cumulative and causes the A/C to fail further down the line, earlier than it should.

So bottom line is you MAY be able to run the air conditioner on a 20 amp circuit.  It depends on several factors including what other appliances the circuit is feeding, the length of wire between the outlet and the circuit breaker box and the length of cord between the RV and the outlet - in both cases, longer wires will lose more voltage when loaded. 

The critical factor is to be sure the voltage in the rig stays above 109 volts while the air conditioner is running.

SeilerBird said:

Actually you will be running it on 15 amps since that is the output of most outlets around you house. I lived in Las Vegas in a friends driveway for several months for several winters plugged into a 15 amp circuit with a 100 foot extension cord. I ran the A/C, my big screen and the surround sound all day long without an issue.

Click to expand...

you are most lucky that this worked because running through 100 ft cord you will lose a little power and  most Rv AC units will draw a good 12-13 amps upon starting up hot plus the TV and surround use a little power. I believe you but I have never had any success with any of my RV doing this .usually the 15 amp breaker will pop as soon as the AC trys to start when its hot. I had my swimming pool pump+ salt water chlorinater on a 15 amp breaker and had to change to a 20 amp breaker because when warm it kept triping. How did u keep the batterys charged because its impossible to use a converter,AC,Tv.Surround system through
a 15 amp circuit  never mind add a 100 foot cord to boot??

buchanan said:

you are most lucky that this worked because running through 100 ft cord you will lose a little power and  most Rv AC units will draw a good 12-13 amps upon starting up hot plus the TV and surround use a little power. I believe you but I have never had any success with any of my RV doing this .usually the 15 amp breaker will pop as soon as the AC trys to start when its hot. I had my swimming pool pump+ salt water chlorinater on a 15 amp breaker and had to change to a 20 amp breaker because when warm it kept triping. How did u keep the batterys charged because its impossible to use a converter,AC,Tv.Surround system through
a 15 amp circuit  never mind add a 100 foot cord to boot??

Click to expand...

I am a retired union electrician and I realize it might not work, but the fact is I used it for many months. Naturally I checked the cord for warmth many times but never had a problem. It was a 1985 Allegro so I am assuming the A/C probably pulled around ten amps. The TV and the surround were probably 200 watts so I was safe. And it was only a 14 gauge 100 foot cord. The batteries were charged with the battery charger that came with the RV. I never looked at it because it always worked.

SeilerBird said:

I am a retired union electrician and I realize it might not work, but the fact is I used it for many months. Naturally I checked the cord for warmth many times but never had a problem. It was a 1985 Allegro so I am assuming the A/C probably pulled around ten amps. The TV and the surround were probably 200 watts so I was safe. And it was only a 14 gauge 100 foot cord. The batteries were charged with the battery charger that came with the RV. I never looked at it because it always worked.

Click to expand...

like I said I believe you but have never had success trying what your doing and have never seen it ever work? I seriously just can not see how a roof AC especially trying to start hot, A converter charging batterys and all the well running a tv and stereo system all run through a small wire(14gauge ) 100 foot  cord serviced by a 15 amp breaker.If u did u did I just cant see how that would fly? however it is what it is. I have tried just running the roof AC(one) on a few of my past and present units and 15 amp breaker pops.My current ac breakers are 20 amp

I run one A/C (and usually nothing else) on a 15 amp plug 20 amp breaker all the time (well much of the time) when I am not on 50 amp sites.  Yes, the plugs do sometimes get a bit warm but I have never had one melt.

Suggestion.. In days o old plug bodies were Bakelite, you can still find some that are either metal or bakelite wrapped. These do NOT MELT, get a dogbone and if the plug melts,, Pop on a new plug.. You can also get 20 amp plugs.

NOTE also,,, Recently I set up with both teh converter and the A/C on a 30 amp line... And yes, I tripped the 30 amp breaker.. ONE A/C (13.5 amp) one volt meter (Few mA, too little to matter) and the converter, PDI 9180 with wizard.  Of course I do not know how "Anemic" the vintage circuit breaker was.

One AC on a 20amp breaker will work fine! but that's not what SeilerBird is claiming? NOT even close. Hes using ac and multi other things through a 14 gauge 100 ft cord and all through a 15 amp breaker BIG difference

I've done the same as Seilerbird on a couple of occasions, using a 100 ft. 14 gauge cord to plug into electrical power while volunteering at my favorite railroad museum.  Like he said, it can be made to work.  But it depends on a couple of factors.

The biggest factor was being able to plug into an outlet that was physically close to the breaker box.  This meant the only significant length of wire I had between the breaker and my RV was the 100 ft. extension cord, not the extension cord and an unknown length of house wiring that could have easily been another 50-100 ft. or longer all by itself.

At that point, it was just a matter of practicing load management and watching the voltage inside the rig, making sure it didn't drop below what was safe for the A/C.  I kept the A/C set at it's minimum temperature so the compressor ran continuously so I didn't have to worry about hot starts, and I made sure I wasn't pulling too much other current if the A/C did have to restart.

So yes, it is do-able if you watch what you're doing.

I have run two different RVs, independently, off of a ground faulted outlet on my deck for weeks at a time. That outlet is daisy chained through and at the end of five other outlets all wired with 14. I used a 100 foot number 14 extension cord with a 15 foot number 10 extension cord in the middle and adapted to the 50 amp cord at the MH.

I ran one air conditioner, watched TV (86 watts) and read the manuals of my new rig so I probably even had on at least one light and that was in August. My rig shuts off at 109 volts and the Viseo probably before that.

Thank you, everyone for help.  I am plugging into a 15/20 amp outlet that looks like this -| | .  The trailer is 20 ft from outlet that is located right below the breaker box.  I will get a pigtail and I think I should be OK.

Like where my RV is parked right now is a 15 Amp outlet place inside a large boulder. I've ran the A/C while plugged into the outlet (30A to 15A Dog Bone) also I ran A/C on a 100 foot 14 AWG extension cord as well. No issues.

I've had overheating difficulties with those "hockey puck" style 30/20 adapters on more than one occasion.  They don't seem to hold up under a sustained 12-14 amp load (which is about what one a/c is). The ones with a short length of wire between the make and female ends seem to work much better.

With the caveat that the a/c must be the ONLY thing operating, it will work. But most people forget the background loads, e.g. the battery charger, clocks, and sometimes even the fridge (or at least its ice maker).

bhamlyn said:

Thank you, everyone for help.  I am plugging into a 15/20 amp outlet that looks like this -| | .  The trailer is 20 ft from outlet that is located right below the breaker box.  I will get a pigtail and I think I should be OK.

Click to expand...

That's a 20A outlet so if the breaker is also 20A you will be fine.  Just use an extension no longer than necessary, at least 14ga.

I think the biggest mistake people make when plugging into a home outlet is they use a light duty extension cord.  You need a hevey duty 12 gage cord that an Handel the current..  Also make shoure the plug is clean .

I think the biggest mistake people make when plugging into a home outlet is they use a light duty extension cord.

Click to expand...

And that's the truth!

robertusa123 said:

I think the biggest mistake people make when plugging into a home outlet is they use a light duty extension cord. 

Click to expand...

Which is fine for just keeping the battery maintained but not for high current flow activities like A/C operation.

The first 3 year of my RV I stored it anywhere on the lawn and just ran a extension cord out for the converter to keep the batteries charged up. I avoided using the A/C knowing the run which was over 100 feet at times and light duty extension cords. But now with my new storage location I can plug the RV directly into 15 Amp socket.

http://www.calculator.net/voltage-drop-calculator.html

Quillback 424 said:

I have run two different RVs, independently, off of a ground faulted outlet on my deck for weeks at a time. That outlet is daisy chained through and at the end of five other outlets all wired with 14. I used a 100 foot number 14 extension cord with a 15 foot number 10 extension cord in the middle and adapted to the 50 amp cord at the MH.

I ran one air conditioner, watched TV (86 watts) and read the manuals of my new rig so I probably even had on at least one light and that was in August. My rig shuts off at 109 volts and the Viseo probably before that.

Click to expand...

I tried to run 2 (2002) and (2008) both diesel pushers  motor homes off a GFI protected outlet (at separate times) and the GFI blows.I then took out the GFI and the systems would power up however I have to set the factory built in PM level at like 10-15 amps.If Iam running the converter and say run the large hydraulic slide out or in, the PM shuts down the converter for a short time.If I try and run something out of a plug in that draws say 10 amps  it will not do so.PM shuts her down so  In my case the AC is out of the question.
that is why I don't  understand how people here say they run their converter,TV,sound system and AC all off a 15 amp circuit and through 100 ft cord
there is no way that will work no way(all at same time) .I also ran a small c through a short cord on another occasion (friend visting/different outlet) and AC would run but if it started hot it poped the standard breaker. The voltage at my house is super good.Gauge reads 124 volts @small load)  where am I going wrong here
Is this deal happening in my unit because of the large converter and the PM system is too sensitive ? After removing the GFI I found out on a forum all u have to do is shut down any opposing GFI protected circuits in the MH as GFI to GFI will not work? I never reinstalled the GFI but what more than one electrical person told me this??

Ok I removed the "don't believe" because apparently it offends some posters.its was not intended to offend it was a figure of speech I sometimes use when iam trying to figure out a certain situation where one person or 2 say it works fine and yet when I try the same thing using different senerios it wont work for me
I actually out of frustration went out and shut down my converter all breakers off except one roof AC.As soon as the AC trys to start a big warning on EMS says
voltage too low warning may go to invert. the voltage measure about 122 today as its warm out.that is why I don't see how? not only did one person run the AC they ran the converter,the Tv and the stereo deal all at the same time and in hot weather and through a small 100ft cord to boot
that's what iam trying to understand what is the difference here. why it works on a old old unit and not on a much newer more complex unit