Run fridge on 110v (inverter) while driving?

[DHart]

We don't have our Airstream yet, but I was wondering... with the 1000w inverter in the new Airstreams, do the batteries get charged by the tow vehicle's electrical connection while the Airstream is being towed?

And, given that battery charging while driving, would the 1000w inverter be able to run the fridge on 110v, inverted from the batteries that are being charged while the trailer is being towed?

In other words, rather than consume propane to run the fridge while in travel, wouldn't the fridge run off the inverter, from the batteries being charged while driving the TV?

[wahoonc]

Unless something has drastically changed; the answer is no. The fridge will most likely drain the batteries faster than the tow vehicle can recharge them. However there are several variables.

Aaron

[Skater]

Originally Posted by wahoonc

Unless something has drastically changed; the answer is no. The fridge will most likely drain the batteries faster than the tow vehicle can recharge them. However there are several variables.

Yeah, this is the answer. The charge line doesn't contribute much, while the fridge draws quite a bit on electric mode, plus losses in the inverter. I've done it, but even with 3 batteries and a large solar system, my batteries were pretty run down by the time we got to the site, and we only did it for a few hours. (We were going through a tunnel where we had to shut off the propane, and it was a blazing hot day, so I tried that solution.)

[idroba]

The 120 volt heating element in the refrigerator takes about 300 watts depending on the size of the refrigerator. The inverter is about 90% efficient in converting from 12 volts, so you would then have an input of about 330 watts. At 12 volts 330 watts is around 28 amps.

The charge from the tow vehicle through the cord can be as low as 6 amps, and I have never seen mine larger than 12 amps with new vehicles and virtually perfect electrical plugs. So, any difference comes from the RV battery.

Trust me, it will not hold up long with that rate of discharge. (about 20 amps).

BTW, the heating element in an absorption refrigerator such as RV's use is on a great deal of the time, especially in warmer weather. That is, it really averages close to maximum 300 watts in most situations.

RV refrigerators are very inefficient operated on 120 volt power. While a modern large household compressor refrigerator may average less than 100 watts an hour, the much smaller RV refrigerators I have measured come in over 250 watts an hour.

Bottom line, use propane to power the refrigerator while towing.

[ckottum]

Our fridge is always on propane when traveling, has never failed us and doesn't use much propane. Freezer and fridge sections work perfectly in this mode.

cheryl

[dames7]

Can someone tell me how much propane will I use to run the frig. on a 8 hour drive, I have a 2015 25ft Flying Cloud.

[Skater]

Originally Posted by dames7

Can someone tell me how much propane will I use to run the frig. on a 8 hour drive, I have a 2015 25ft Flying Cloud.

Probably not even enough to measure. A single 30 lb propane tank will run the fridge for weeks, if not months. Of course there's some variation in usage depending on how much the fridge has to work to stay cool (you'll use less in cold weather than warm, for example). But I wouldn't even worry about the amount of usage you're describing. We had ours running for an entire weekend on propane, along with some furnace and water heater usage, and we still used only used a couple pounds of propane.

[wrhjr3]

The answer, with relatively simple modifications, is yes. I've towed my Avion with Dometic 3 way for 30,000+ miles using the 12v heaters. There are only a couple of amps difference in the requirements. The answer is a #8 charge line in the vehicle so that the vehicle can supply the necessary current. Nearly all vehicles are set up with a wimpy charge setup. It was a delight not to have to screw around with propane all the time. Unfortunately, the 12 volt heaters are a little lower wattage than the 110 volt heaters, So, the cooling effect is only adequate. You can't load up with warm stuff and expect the fridge to cool down very well. On the other hand, the refrigerators are designed to run with the 110 volt heaters. If the charge supply is properly set up, it'll work fine.

It is true that absorption refrigerators are energy inefficient. But it works.

There can be much more to the whole quandary, but that's the simple answer.

Roland Hyatt

[whippet201]

Originally Posted by Skater

Yeah, this is the answer. The charge line doesn't contribute much, while the fridge draws quite a bit on electric mode, plus losses in the inverter. I've done it, but even with 3 batteries and a large solar system, my batteries were pretty run down by the time we got to the site, and we only did it for a few hours. (We were going through a tunnel where we had to shut off the propane, and it was a blazing hot day, so I tried that solution.)

How big is your inverter? I have a 345 watt fridge, a 2000 watt inverter, 2 100 watt solar panels and 2 deep cycle batteries. Am I wrong in thinking this would work while driving? Thank you for any information. This is my first time posting and I have had my AS since November. Loving it!!

[spclkaz]

I just run mine on propane going down the road... no muss, no fuss...

[AnnArborBob]

Be aware that regardless of your battery or solar capacity, power via umbilical to the tow vehicle and the power draw of the fridge, the standard Airstream supplied inverter is not wired to provide 110 AC to the fridge, only to three or four designated "inverter outlets." If you want to run your fridge off the batteries and inverter while underway, you will need to change the factory setup to provide inverter power to the fridge 110 AC outlet which is located behind the access panel on the outside of the trailer.

We run the fridge on propane while underway and have never had a problem or the impression that it drains the propane tanks quickly. We are on the road all the time and only fill the propane tanks once or twice during the summer (more in the winter.)

[idroba]

Originally Posted by dames7

Can someone tell me how much propane will I use to run the frig. on a 8 hour drive, I have a 2015 25ft Flying Cloud.

As I recall, the propane burner in most RV refrigerators of moderate size use is about 1200 btu per hour. There are 90,000 btu in a gal. of propane, so running full flame about 75 hours per gal. With some on and off, longer, but probably not twice the time. So, 75 to 150 hours per gal of propane.

So, with your 8 hour drive question, maybe 1/10 gal max.

[Jammer]

Originally Posted by dames7

Can someone tell me how much propane will I use to run the frig. on a 8 hour drive, I have a 2015 25ft Flying Cloud.

A typical larger fridge like that uses about 1/3 gallon of propane per day if the burner runs continuously.

The burners are about 1000 BTU/H. 81,000 BTU/H = 1 gallon, 81 hours = 1 gallon, about 1/3 gallon per day.

Smaller fridge or conditions allowing the burner to shut off some of the time will reduce the propane draw.

As noted upthread, the propane use by the fridge is negligible while traveling and camping. In nearly all cases the propane used by the water heater will be much greater. The propane use by the fridge only becomes a factor when deciding whether to leave the fridge running while in storage.

[Skater]

Originally Posted by whippet201

How big is your inverter? I have a 345 watt fridge, a 2000 watt inverter, 2 100 watt solar panels and 2 deep cycle batteries. Am I wrong in thinking this would work while driving? Thank you for any information. This is my first time posting and I have had my AS since November. Loving it!!

The inverter in ours is 1500 watts, so it's large enough to run everything but the A/C in the camper. But, it was installed after the camper was built, so it does attempt to power everything in the camper, if I let it. The factory ones will, as someone noted, only power certain outlets. That all depends on the wiring.

But that's not the issue we're explaining: A 345 watt fridge + 200 watts of solar (under optimum conditions, remember) still means your battery bank is going to be loaded with a 12 amp draw (145 watts/12 volts), plus inverter overhead, so your batteries won't hold out for more than a few hours (exact time depends on the capacity and age of your batteries, as well as the amount of sun your panels receive). For comparison...actually, I'm not sure anything on the 12 volt side draws that much current.

So, sure, you can do it, but not for very long, unless you do the charge line mod that wrhjr3 described, for example, but that will need to be able to supply about 30 amps of 12 volt power if you want the batteries to stay even. (30 amps + long run means some very heavy wire and a very good connector...and can your alternator support an additional 30 amp load? So that could turn into an expensive modification.) And if don't do the full 30 amp setup, and you run longer than expected, say, because of a traffic jam, then you run the risk of destroying your batteries by discharging them too much.

Meanwhile, you probably already carry around something that will power it for weeks without worry... propane. The only downside - against all of what I listed above - is that a few tunnels I've been in require you to turn it off. No big deal; stop, turn it off, then restart it after the tunnel at your next break - it'll be fine for a few hours.

Or just shut the fridge off entirely. Ours stays plenty cold throughout the day on all but the hottest days.

Edit: On re-read, I see wrhjr3 was describing a 3-way fridge. Had one in my B190, but I haven't seen one in any kind of modern trailer. So you'd have to replace the fridge to accomplish that solution.

[wrhjr3]

Well, as I pointed out ... there's much more to the story. In my motorhome, I took out the 3 way fridge. I installed a new Norcold 110/12 volt refrigerator. It's a tad smaller, at 7 cu. ft., but 2 door and it draws about 40 watts. It utilizes a VERY well respected Danfoss variable speed compressor cooling system. I installed solar panels that will much more than power that miniscule power drain.

I just put 250 watts of panels on my Avion. I think I will sell the 3 way and install the same super-efficient Norcold in there too.

1964 Airstream International Tradewind
1985 Avion 40R
1989 Monaco Crown Royale
1991 Dodge Cummins TV

[wrhjr3]

Typo........1985 Avion 30R

[BAB]

I installed a Magnum MSH inverter in my new Classic along with four Lifeline 6V batteries. Also 600 Watts of solar. In rewiring the main panel into the sub-panel (inverter circuits), I moved the 120V fridge wiring onto the sub-panel -- which means I can run the Dometic off the inverter rather than use propane. IF I'm traveling on a sunny day, the panels will keep the batteries well above the programmed low battery cutoff point (this is programmed into the inverter and keeps you from over-draining the batteries --- which could cause them to be damaged). I tried this set-up and it does work.....but for all practical purposes, it's a LOT easier to let the Dometic flip over to the propane. Then if we pull over in a rest stop and want to have a sandwich with toast, or use the microwave there's plenty of "juice" in the batteries to use the heavy power consumers.

[mandolindave]

Other better options.

Just run the fridge on propane while driving.

If for some reason you can't or won't. You can run the fridge on 110 for a few days before departure ( you really need to do that any way ) Then put frozen bottles of water in the fridge right before you leave, and don't open the fridge until you arrive at destination.

[boblind]

I installed a 10 gage wire from the TV batteries thru a fuse to an outlet on the back bumper, then I have a separate wire from a matching plug thru a 120 volt controlled relay to a 300 watt invertor powering my Dometic model 2452 120 volt refrigerator. This refrigerator uses less then 2 amps to keep it cold. 2 Amps x 120 volts is 240 watts, divide that by 12 equals 20 amps from the TV batteries.
If you have a 100 amp alternator on your TV, you should not have any issues keeping everything cold.
I have a homemade lashup that has been working just fine. Total cost including the wire about $300.00

[DHart]

A lot of great info here, thanks folks for your comments!