Can we run ac w/out dc battery hooked up??

[lynxranch]

Hi,
I have a 1977 International Land Yacht Soverign and would like to know if we can run just 120 Volt AC Power without the 12v batteries being connected????
I plugged in the 120V AC power without the battery and the DC fuse panel started humming very loud. Is this a problem?
As of now, everything is un plugged.
Also on this model, rear bath, middle twin beds, can anyone tell me where the univolt is located. I could not find it.
Thanks a million for anyones help since I am totally new at this camper business.
Joe - Lynx Ranch

[HowieE]

The humming you heard was the convertor/inverter, depending on which your trailer has, running without a battery load.

Yes you can run the AC without a battery but you should disconnect the convertor/inverter from the AC to keep it from humming.

[TG Twinkie]

HowieE: I don't think they are asking about the Air Conditioner. They are asking about the 120 volt power.
Yes you can run it, but if you turn off the converter you will not have any 12 volt DC power for lights etc. Apparently you have an old Univolt converter and that is what is humming. They are famous for the humming sound. They are also famous for boiling batteries dry.

[Aage]

Originally Posted by lynxranch

Hi,
I have a 1977 International Land Yacht Soverign and would like to know if we can run just 120 Volt AC Power without the 12v batteries being connected????
I plugged in the 120V AC power without the battery and the DC fuse panel started humming very loud. Is this a problem?
As of now, everything is un plugged.
Also on this model, rear bath, middle twin beds, can anyone tell me where the univolt is located. I could not find it.
Thanks a million for anyones help since I am totally new at this camper business.
Joe - Lynx Ranch

Howdy and welcome to Airforums.com, Joe! You're already getting answers to your questions. Keep asking!

I believe your '77 is similar to my '74 in that the DC fuse panel and the Univolt (factory-supplied 120V to 12V converter) is located in the curb-side closet.

Get on your knees in front of the closet and look in on the bottom right-hand side. If yours is like mine, there is a little door that will pull open to reveal the 12V fuse panel. That fuse panel is connected to the front of the Univolt!

ps: the hum is due to the fact that the original Univolt has seen better days, and the laminations in the main transformer it has are loose. That's why they hum. We ran our Univolt for over a year with no battery, but it did in the fuse panel, so I won't say that it's recommended. Also, with no battery, your fail-safe for an accidental disconnection while underway will not operate.

Good idea to get a battery, especially if you plan on travelling. But get it AFTER you replace the Univolt: it will boil a battery dry, due to its out-of-date circuitry.

Get a new one, you'll be glad you did. And while you're at it, put in a nice new 12V fuse panel, too!

[CanoeStream]

I have read that the circuitry is not balanced properly to plug in without a battery in the circuit. Not sure about all the ramifications...

The AC requires 120V -- right. But it requires a minimum of 20A -- if no other significant loads are operating at the time. You are safer with a full 30A circuit (like most campgrounds). Your standard household 3 prong outlet is 15 amps -- totally insufficient to run any RV AC unit. 15A, 20A & 30A outlets have unique and individual prong patterns.

[HowieE]

Originally Posted by TG Twinkie

HowieE: I don't think they are asking about the Air Conditioner. They are asking about the 120 volt power.
Yes you can run it, but if you turn off the converter you will not have any 12 volt DC power for lights etc. Apparently you have an old Univolt converter and that is what is humming. They are famous for the humming sound. They are also famous for boiling batteries dry.

Interesting point about the question relating to ac power as apposed to Air Conditioning.

Both our comments are correct it just remains which issue he was questioning.

[davidz71]

My '77 Excella 500 had a front entertainment center with the univolt in the lower center section below the fuse panel. It actually was below floor level.