Thread Tools Search this Thread Display Modes
Old 06-03-2014, 11:29 AM   #15
Wise Elder
Jammer's Avatar
2010 30' Classic
Vintage Kin Owner
South of the river , Minnesota
Join Date: Dec 2009
Posts: 4,023
Originally Posted by J. Morgan View Post
Damn, must most every thread be a war of wills?
Maybe, but this thread appears to me to be a discussion of facts together with sharing opinions, at least some of which are based on personal experience or expertise.


I would run propane going down the road, but that isn't what the op asked.

He asked whether it is possible.
He asked, "Thoughts?"

And since it is pretty much consensus that a 12 volt element is marginally sized, meant for maintenance, I don't see why its "control " couldn't simply be a toggle switch.
The 12 volt element in 3-way fridges has a reputation for being suitable only for "maintenance" because most RV 12 volt systems will not deliver adequate power to the fridge. Since 3-way fridges do not regulate the DC voltage, they must be designed to withstand around 13.5 volts which is what they typically see in a well-executed motorhome installation while the engine is running.

Installations that use undersize wire or that have loose connections at any point will only deliver 11-12 volts to the fridge. This includes most trailer installations, in large measure because of the resistance in the charge line circuit to the tow vehicle alternator. Heat produced is proportional to the square of the voltage. At 12 volts you get 80% of the heat you get at 13.5 volts. At 11 volts you get 66%. 80% of the rated heat will give you little cooling. 66% will give you none at all.

This is why 3-way fridges have a reputation for failing to cool properly on 12 volts.

But if the fridge is properly wired, and the charge circuit works the way it's supposed to, and you start with fully charged batteries in the trailer, then yes, you could get 13.5 volts at the fridge. And it will cool just the way it would on gas or electric. With just a switch , on a cool, cloudy day, you're not only going to freeze the lettuce, you're going to freeze the beer.

There also has to be an interlock so that two power sources aren't on at once, or the boiler will overheat, and may crack and leak.

Originally Posted by J. Morgan View Post
By the way, there is a 7.1 cuft Norcold on eBay, so apparently three ways are not exclusive to tiny trailers with tiny refrigerators.
As I noted upthread, they were once common in motorhomes.

Most tow vehicles have alternators that produce well over 100 amps. On GM vehicles the trailer hot line is fused at 30 or 40 amps.
Try drawing 30 or 40 amps from the connector and see what voltage you get.

In my Sovereign I run a 10cu ft residential fridge on an inverter, my tow vehicle keeps up with and gains on the draw going down the road.

There is more than one way to approach an issue.
It is rare for charge line circuits to work that well, though not unheard of. Mine is not stock and will deliver 40-50 amps. Also, inverters typically have the ability to compensate for input voltage swings within a reasonable range.

To learn to see below the surface, you must adjust your altitude
Jammer is offline   Reply With Quote
Old 06-03-2014, 11:42 AM   #16
Agent 86
J. Morgan's Avatar
1972 31' Sovereign
1975 31' Excella 500
Currently Looking...
Benton , Arkansas
Join Date: Mar 2013
Posts: 4,361
Images: 11
I guess one of my points was that if my tow vehicle will run my fridge that has an actual compressor, and recharge my batteries going down the road through the stock tv wiring, which it does, I think that probably the tow vehicle will run the heating element in the fridge.

Wiring with proper gauge wire was discussed, I even posted a chart, and yea, it would be important.

From what I have read about the three ways, I can't say for sure, but I don't think that there is a lot of risk in the low power element freezing things in the fridge.

The fact that I am opinionated does not presuppose that I am wrong......

J. Morgan is offline   Reply With Quote
Old 06-03-2014, 12:50 PM   #17
Rivet Master
Smartstream's Avatar

1982 28' Airstream 280
Port Angeles , Washington
Join Date: Aug 2008
Posts: 1,191
If anyone is interested I will add a comment about my method. I have the old fridge, manual start, in my moho. I run exclusively on propane. It's propane consumption is next to nothing and changing to electricity at a park and relighting the propane is just more hassle than it is worth. Unless I am staying for a week or more I just leave it on propane. It has never blown out on the highway.
Cheers, Dan

"Socialist governments traditionally do make a financial mess. They always run out of other people's money. It's quite a characteristic of them."
~ Margaret Thatcher ~
Smartstream is offline   Reply With Quote
Old 06-03-2014, 01:29 PM   #18
Rivet Master
Jim Foster's Avatar
1965 17' Caravel
1983 27' Excella
Walnut Grove/Laguna Woods , California
Join Date: Jun 2004
Posts: 1,599
Send a message via Yahoo to Jim Foster
Another option might be to plug the fridge into a 12v/110v inverter when going down the road. With a strong alternator, a good 12v battery setup and the proper inverter, it should work just fine.
Past President, El Camino Real Unit WBCCI#6620
Street Rod Builder (see avatar)
Kite flier (check out links below)
Jim Foster is offline   Reply With Quote
Old 06-03-2014, 04:37 PM   #19
Agent 86
J. Morgan's Avatar
1972 31' Sovereign
1975 31' Excella 500
Currently Looking...
Benton , Arkansas
Join Date: Mar 2013
Posts: 4,361
Images: 11
Good point Jim. That would be easier.

The fact that I am opinionated does not presuppose that I am wrong......

J. Morgan is offline   Reply With Quote

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
Making dinette into a bed ArchieGates 2011 - 2015 International 20 12-06-2015 06:50 PM
Way to bring top of door into shape? SkooterPop Windows, Doors, Locks & Vents 0 11-13-2013 08:41 PM
Making 2 twin beds into a king bed in a trade wind Maggiefoss Cabinets, Counter Tops & Furnishings 3 04-24-2012 08:10 PM
Water getting into fresh tank the wrong way grantb4 Fresh Water Systems 21 03-21-2012 08:25 AM
What is 2 way vs 3 way fridge? Astrodokk Refrigerators 12 06-01-2005 03:33 PM

Virginia Campgrounds

Reviews provided by

Our Communities

Our communities encompass many different hobbies and interests, but each one is built on friendly, intelligent membership.

» More about our Communities

Automotive Communities

Our Automotive communities encompass many different makes and models. From U.S. domestics to European Saloons.

» More about our Automotive Communities

Marine Communities

Our Marine websites focus on Cruising and Sailing Vessels, including forums and the largest cruising Wiki project on the web today.

» More about our Marine Communities

Copyright 2002-2015 Social Knowledge, LLC All Rights Reserved.

All times are GMT -6. The time now is 04:43 PM.

Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2016, Jelsoft Enterprises Ltd.

Airstream is a registered trademark of Airstream Inc. All rights reserved. Airstream trademark used under license to Social Knowledge LLC.