I would like to occasionally run my new Scamp's Dometic A/C when plugged into standard household line voltage (20 amps) rather than the usually-recommended 30 amps. There are products such as SoftStartRV that you can install in the A/C to enable that. I read somewhere that some A/C manufacturers have begun including soft-start capability at the factory, but my queries to Dometic and SoftStartRV have gone unanswered.
Any advice?
I installed the soft start on my 2017 Scamp and it works well, but I also ran the A/C on both a 20 amp circuit and a Honda 2200 before the addition. If your outlet is really a 20 amp ( not 15) and the adapter is heavy duty it will work. Playing with the thermostat or running other things may cause problems.
I've also run the A/C with power connected to a 20A receptacle. Works fine, but don't run other stuff at the same time -- Except for things like a 12v led light that draws very little power -- Yep, 12v items actually increase 120vac current draw when the convertor is powered up.
Check your voltage at the trailer with the AC running. It should be at least 110. You could kill your AC if it falls below 108. If you need an extension cord, it should be 12 gauge and no longer than 50 feet. Those are more expensive, but cheaper than a new AC.
A volt meter and a receptacle tester, I've watched campground voltages drop to 99 volts.
Although I haven't done it on the Scamp yet, I've run AC units on three Airstreams and a newer Forest River off of 20 amp household outlets without a problerm. I was running a fairly short extension cord--25 foot max and heavy gauge wire, and wasn't running anything else in the trailers but the Fridge and the lights. Wouldn't want to plug in a microwave or anything though--it would probably pop the breaker. Like others have said, monitor the voltage just to be safe.
Dave
The circuit breaker in our Scamp 19, AC is 20 A. So a 20 A circuit should be ok.
2020 Scamp 19’ Deluxe, 2021 Nissan Frontier Pro4X
All, thanks for the guidance and suggestions. I'll monitor my voltage ( https://amzn.to/3ApaKRw ) to watch for dips, and if I add an extension cord I'll use a heavy gauge cord no longer than 25 feet.
FYI, I finally heard back from Dometic, in response to my query about whether it's OK to run the A/C on a 20 amp plugin. Their response seems to imply that soft-start isn't built into the A/C at the factory:
The A/C units definitely do not have a soft-start built-in from the factory, these are add-on devices. They only affect startup current, and are primarily aimed at using generators that can't handle the peak power of starting the motor for the A/C compressor.
The A/C is on a 20A breaker itself, and momentary higher startup current is already figured into the way circuit breakers trip. They are an inverse time delay type of device, meaning that they allow higher than the trip current for short periods -- The higher the excess current the shorter the allowed time.
The reason for preferring a 30A power source to the trailer is that the wiring would be sized larger than a 20A, and the voltage drop would be less for both running and starting the motor. Also, AC motors will actually draw more current when the voltage is low.
If I remember right, utilities get a 5% voltage tolerance and house wiring adds another 5% voltage drop limit. Combined, that's 108VAC minimum at a receptacle where I'd say no manufacturer could legitimately complain about low voltage issues to their device.
But reality is that devices often have to run on a bit lower voltage than that. Sometimes utilities have short term low voltage issues, plus we haven't added in voltage drop from extension cords, and house/campground wiring isn't always up to snuff either -- Hence ac0gv's observation of seeing as low as 99VAC inside the Scamp at a receptacle. I wouldn't run the A/C at 99V knowingly, but it certainly could happen. Campgrounds are probably the worst for wiring issues, and the voltage might look fine in the morning until all the A/C units start turning on. There are some pretty fancy devices which can be installed to protect (disconnect) during under-voltage, but for me they are more trouble than they're worth.
EDIT: I got curious at the under-voltage setting for RV electrical protection equipment. Per one of the manuals for a Progressive Industries Electrical Management System for RV's (at progressiveindustries.net), it disconnects the RV when park power voltage is less than 104VAC.