Using Dometic refrigerator on 12 volts

[Glenn Baglo]

I am familiar with restrictions on propane-powered vehicles entering parking garages here and probably everywhere.

[Jann Todd]

Originally Posted by Glenn Baglo

I am familiar with restrictions on propane-powered vehicles entering parking garages here and probably everywhere.

I have been Googling to find the cities and can't find any now. Maybe since the newer safety valves OPD were put on them the cities are ok now. There's a lot of good articles by professionals on running with propane fridges on and the consences is there's a very minute danger. All say it is ok with the new OPD valves but do what you want to. The biggest danger is going into gas stations with them on. We have a policy to stop and turn off the fridge before entering the fuel area. Then we pull away from the pump area to restart the fridge. It's not a time consuming thing since you probably only fuel once a day at the most. If fueling early in the day we'll shut it off just before pulling out and turn it on after fueling. Never off for more than an hour.

[Raz]

I don't run my fridge on propane while driving down the road because it's a risk I prefer not to take. It's my understanding the flow restrictor on a twenty pound tank limits to 5 psi. The output of the regulator on my trailer I believe is 1/2 psi. If true, a ruptured line will continue to supply gas despite the safety device. But what concerns me more is the use of hydrogen gas as a component in the refrigerant. With no moving parts these fridges often fail through metal fatigue, most likely caused by vibration. The smell of ammonia is the tip off. But if the hydrogen encounters an open flame, an explosion occurs. Do a search for "RV refrigerator explosion", lots of stories, law suits etc. Interesting that Norcold is producing absorption refrigerators that use helium in place of the hydrogen.


When I encounter a guy smoking a cigarette while he's pumping gas, I drive away. He's been doing it that way for years. So what? Been driving for years with the fridge running on propane. I have the same reaction. I really don't care what others do, I just don't what them to take me with them. Raz

[Raz]

And it's an egg. .

http://rvlife.com/rv-propane-system-explode/

[rbryan]

There we go. Out of context. What part of normally operating (normally maintained) is hard to understand? Anything neglected and allowed to deteriorate can fail. Defective or poorly maintained fuel systems and appliances catch fire or explode at campgrounds too. Nope, lets show them under a gas station canopy. That's scarier.

Cars catch fire. Houses too. Anything that is defective and has a flammable material and ignition source associated with it can catch fire. By some of the logic expressed here, one should abandon their propane systems altogether after they've been bouncing down the road for a few years.

[cmartin748]

Sometimes the answers to a simple question on here are like drinking from a fire hose. Lots of good info tho. I take the good and leave the bad.

[gordon2]

Originally Posted by Raz

And it's an egg. .

RV Propane System Safety Tips And Precautions

I find no mention in the article or in the 17 minute video about the cause of the fire. The article does mention a different case in which a gas pump spewed gasoline which got into the fridge vent on a conversion van and ignited. An excerpt from that article:

Binder said the latch that holds the nozzle’s handle in the closed position was already pushed into place when he prepared to pump. Fuel spilled from the nozzle when he selected his grade, pushing the nozzle free and spilling gas on his RV and the ground.
Houma Fire Inspector Mike Millet said he was able to recreate how Binder explained the gas spill, and said it was possible. But Millet noted that’s a first for the department and he’s unsure if that’s how the fire started.
“It is possible what he said happened,” he said. “It was a freak accident. Nobody in the Fire Department has seen that happen before.“
Tom Freeman, the gas station’s owner, said he doubts Binder’s account.

But what made this incident worse was that propane fed the fire from the line. Apparently the firefighters could not get to the tank valve for some time. It did not explode however.

So we now have one semi-verified case of a fire cased in part by a running absorption fridge at a gas pump. And yes, you should turn off the fridge before approaching a fuel filling station. That is just common sense.

But my take away from this entire thread, and many like it, is that people generally fail to put risk into perspective. I have no doubt that the risk from running an absorption fridge on the highway is exponential less that that from being hurt or killed in a traffic collision, or even the risk from accidentally eating spoiled food because your RV fridge was too warm. If the outside temperature is over 70 f or so, my fridge warms up in a few hours to levels that will cause spoilage given enough time. Frankly, if I thought the risk from running my absorption fridge for a few hours on my longer road trips was too much, then I would in fact stay home, because the risk from a traffic collision is many times higher and by logic, I would be more concerned about that.

The warning labels on gas pumps warn of the danger of static electricity also. It would take just the right conditions to allow enough gasoline vapor to accumulate but if the conditions exist, a static spark could ignite it. One of the admonishments is to not get back into your vehicle because that could cause a static spark. But in cold dry winter, when static is more likely, who is going to follow that advice? No – the benefit of a warm vehicle when its 10 below outweighs the very slight risk.

So we all do risk assessment and decide if the benefit is sufficient for the degree of risk. Traveling to a prime campground is actually a fairly risky endeavor, but the reward is also significant. If there is no benefit, then no risk should be taken. Since there is no benefit to leaving a fridge on while fueling up, but there is a small risk, the propane should always be shut off. As for the risk / reward of using propane while traveling.. the debate will no doubt continue.

[rbryan]

Excellent post Gordon, and well thought out. Putting any risk into it's proper perspective is key. One of the signs you posted is a prime example of bogus information and assumptions which have no scientific basis - the one about cell phone use while refueling. That theory has been completely debunked. There was even a Mythbusters episode about it.

[John in Santa Cruz]

do realize, that even if you're not using propane, the absorption fridge STILL has ammonia and hydrogen in it, its just being heated electrically.

[Jim er]

The heating elements for a Dometic frig when running, measure at about 150W. At 110V it only takes ~1.4A to run the frig when it needs cooling. At 12V, it takes about 12.5A and the reason any battery is quickly discharged at that huge a drain rate. If your frig is already at temp, then it will only demand 12V when it gets above a set temp and turns off when it reaches the set lower temp. On a warm day, you can expect 12V demand to be 90% on or more. If running solar, then usually the solar will catch the battery back up during the off periods.

I personally run on propane while traveling. My later model Dometic frig switches automatically to 110 when plugged in and back to propane when not plugged in.

I do believe the people who say there is a fire risk when using propane while traveling. The odds of it happening as far as I am concerned, are slim and none. Not having to worry about food spoilage and ice cream melting, priceless.

Consider the gas station warning signs: no smoking and turn your engine off. Then a car rolls in besides you and guess what, his engine is running and he could be smoking with a window open. How many times has that caused a fire?

I worry about the big stuff, not about running my frig on propane.

[Alex Adams]

I made the conscious decision, based on some of the issues I have read about an absorption fridge and the extra propane plumbing, to go with a 12 volt compressor style fridge. I found a Nova Kool R3000 2.5 Cu ft Marine fridge that only draws 2.2 amps at 12v DC when running. I will be putting it in during phase 2 of the upgrades to my 13' Boler. It's a little taller than the Ice box that came with the trailer so I will lose the silverware drawer.

[John in Santa Cruz]

I violate the cell phone thing all the time, as I'm tracking my fuel consumption with Fuelly.

[GaryM]

Your tow vehicle will not charge the battery via your 4 pin connector. I would have a 7 pin connector installed with at least 10 gauge wire for the charging wire so that enough current will be supplied to the camper battery to charge it while running the fridge. The Dometic fridge does not have a compressor. It's a gas absorption system. From experience, if you get a 7 pin connector installed in your TV, but do not get at lease 10 gauge wire on the charging circuit, your camper batter will last 4 - 5 hours while traveling.

[Richard S.]

Originally Posted by Ziggy

The majority of TV's can't charge the battery and run the fridge while towing. A few can. It depends on the size of your alternator and the wiring to the trailer. It's safe and legal to run your fridge on propane the road. There are a very few well marked tunnels where you need to turn it off as well as all ferries. Many RV refrigerators don't even have a 12V option. I have the same fridge in my Casita and always run it on propane. In a poll on the Casita Facebook page with 221 respondents, 69 said they run the fridge on the road on 12V and 152 said they use propane. Any formula to determine how long you can run your fridge while towing would have to take into account the output pf your alternator and the voltage drop over the wires between the alternator and the battery for your particular TV and trailer.

I doubt that you can put much of charge in your battery while towing. Your highest voltage is at the towing vehicle battery and drops down through the 20 some feet of wire and connectors. You would need a DC to DC converter to raise the voltage to the trailer to around 15 volts to get a good charge. I tried charging my 12V. Marine CPAP battery from the cigar lighter with no success. I had to resort to a 120v AC inverter and a Die Hard 120 AC marine battery charger. It's clumsy, but it worked and I can breathe at night.

[GaryM]

Originally Posted by Richard S.

I doubt that you can put much of charge in your battery while towing. Your highest voltage is at the towing vehicle battery and drops down through the 20 some feet of wire and connectors. You would need a DC to DC converter to raise the voltage to the trailer to around 15 volts to get a good charge. I tried charging my 12V. Marine CPAP battery from the cigar lighter with no success. I had to resort to a 120v AC inverter and a Die Hard 120 AC marine battery charger. It's clumsy, but it worked and I can breathe at night.

Modern automobiles, especially SUVs and pickup trucks have no problem providing enough voltage to run a small Dometic fridge on 12 volts while traveling. The limiting factor is the gauge of the charging wire running from the TV to the camper. I had a 2009 Ford Escape that had a factory 4-pin trailer connector. I had a 7-pin connector installed, using a 10 gauge charging wire. I towed the camper with the 3-way Dometic fridge running on 12 volts for ove 60,000 miles with no problems. I traded for a 2015 Ford Explorer which had a factory tow package with a 7-pin connector, but only used 14 gauge wire to supply current to the camper battery. After towing the camper for 4-5 hours with the fridge running on 12 volts, the battery in the camper would no longer run the fridge. The culprit was the 14 gauge wire, not the alternator.

[John in Santa Cruz]

my Casita, i measured the voltage drop with the fridge on DC, and also with just the Tacoma charging the battery. with the ~12 amp load of the fridge, I was only seeing like 12V at the Casita's battery, and 13V at the 7-blade connector, yet the Tacoma's battery was getting the full 14.4V of the alternator. with the fridge off, the casita battery was seeing 13.8V which is plenty to charge it and keep it charged.

to run the fridge off my Tacoma, I would have had to upgrade BOTH the factory wiring in the Tacoma, AND the wiring from the trailer pigtail back to its DC converter and battery.

btw, at least in 2008, the Tacoma's factory towing package not only included the hitch and engine+transmission coolers, it also included a bigger 130A alternator.

[GaryM]

Originally Posted by John in Santa Cruz

my Casita, i measured the voltage drop with the fridge on DC, and also with just the Tacoma charging the battery. with the ~12 amp load of the fridge, I was only seeing like 12V at the Casita's battery, and 13V at the 7-blade connector, yet the Tacoma's battery was getting the full 14.4V of the alternator. with the fridge off, the casita battery was seeing 13.8V which is plenty to charge it and keep it charged.

to run the fridge off my Tacoma, I would have had to upgrade BOTH the factory wiring in the Tacoma, AND the wiring from the trailer pigtail back to its DC converter and battery.

btw, at least in 2008, the Tacoma's factory towing package not only included the hitch and engine+transmission coolers, it also included a bigger 130A alternator.

Increasing the size of the wire running back to the Bargman connector would provide enough current to charge the battery and run the fridge. I've seen it done many times.

[stevebaz]

Did you recheck the voltage with the engine revved up off idle? A 130 amp alternator only puts out that amperage with alternator at full speed. Another thing to try is check the power with the headlights on so the system sees a greater need to charge.

[jon carpenter]

WOW, a lot of explosive posts here. Lets focus on what the OP had asked. (And yes I do drive with the frig on LP except in tunnels.)

jon

[jon carpenter]

oops, 'explosive' may have been the incorrect word. sorry.