Dometic fridge electrical question - Fiberglass RV


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Old 08-21-2019, 01:00 PM   #1
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Dometic fridge electrical question

I have a 1.9 c.f., 3-way, dometic fridge. The specs indicate that on DC the fridge draws 10.5 amps to support a 125 watt heater. Would I be correct to assume that this would be the condition at the maximum cooling setting (#7 on this model) and that when the control is reduced to a lower cooling setting (ie higher fridge temp) the heating element operates at a lower wattage and the amperage draw is reduced? I'm just not sure how the innards of the DC system work and the manual is no help here.

I ask because my initial experiments with running the fridge on dc while driving appear to work without draining the battery but I've only tried with the fridge dialed down to about #3 and am curious about the impact of asking it to work harder on a hot day.

Thanks for your insights.
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Old 08-21-2019, 01:39 PM   #2
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If thats a 2193 there is no temp adjustment for DC operation. AC operation has the numerical adjust and gas operation is low, medium, and high.
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Old 08-21-2019, 02:03 PM   #3
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Many thank Raz. It is a 2193. The manual's illustration referred to the knob as the "electric thermostat" and I jumped to the conclusion that it meant AC or DC. Reading the fine print later in the text I see that you are of course correct. DC is either on or off. Thanks for the prompt and clear response.
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Old 08-21-2019, 03:00 PM   #4
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Keep in mind that if you've been camping and your trailer battery depleted, and if you run the fridge on DC while moving to your next camp, your trailer battery will still be depleted when you arrive. Just not enough power delivered to run the fridge on DC and to recharge the trailer battery.
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Old 08-21-2019, 03:12 PM   #5
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Many thank Raz. It is a 2193. The manual's illustration referred to the knob as the "electric thermostat" and I jumped to the conclusion that it meant AC or DC. Reading the fine print later in the text I see that you are of course correct. DC is either on or off. Thanks for the prompt and clear response.
david
Glad to help out. If yours is like mine, it is very easy to toggle that switch on, which will make short work of your battery while you sleep. I pulled the fuse after the first time it happened. I still think it was the dog that did it.
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Old 08-21-2019, 03:13 PM   #6
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Keep in mind that if you've been camping and your trailer battery depleted, and if you run the fridge on DC while moving to your next camp, your trailer battery will still be depleted when you arrive. Just not enough power delivered to run the fridge on DC and to recharge the trailer battery.
That depends on the amps available on a particular tow vehicle. My Ram will keep up and runs fine on DC, while towing. Some won't, some will. But it's not an absolute rule.

Still, I'd rather just run mine on propane all the time, unless I have a shore tie.
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Old 08-21-2019, 03:18 PM   #7
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That depends on the amps available on a particular tow vehicle. My Ram will keep up and runs fine on DC, while towing. Some won't, some will. But it's not an absolute rule.

Still, I'd rather just run mine on propane all the time, unless I have a shore tie.

Which depends on the wiring from the tow. Apparently 12 gauge is standard. I had to pay extra for 10 gauge, and then decided not to get a three-way fridge ( AC and propane only ).
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Old 08-21-2019, 04:22 PM   #8
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Thanks all for a great discussion. Very good caution Glenn - one we definitely will keep in mind and limit any 12v use accordingly. Raspy, as I said, my wiring seems to keep up but Iím not sure what gauge it is. I didnít know enough when it was installed to request 10 gauge. Can one determine the gauge looking at it where it is connected in the TV? The installer fused it for 10 amps. I have tried using propane when traveling but the flame always blows out.
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Old 08-21-2019, 04:39 PM   #9
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10 gauge could be fused up to 30 amps. 12 gauge up to 20 amps. 14 gauge up to 15 amps.

10 looks noticeably larger than 12, So if you had a known #12 or #10 to compare it too, you could determine what it is. Or find the diameter of the actual conductor and measure it. Some wire has the gauge printed on it, but not all do.

My propane flame used to blow out on another trailer I had. I was able to make a little metal shield out of sheet metal that fixed it. You might try that.
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Old 08-21-2019, 04:44 PM   #10
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Thanks Raspy. Soundslike the fusing doesn't tell me much. I'll get some known wire and compare. I think there may have been a thread on the forum some time ago about a baffle to protect the flame. I'll see if I can chase it down.
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Old 08-21-2019, 04:44 PM   #11
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..Can one determine the gauge looking at it where it is connected in the TV? ....
Some wire is labeled.. you can try to read any writing on the wire wherever it is visible. But if it works for you I would not worry about it.

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..I'll get some known wire and compare. ..
The problem is the insulation might be thick or it might be thin, so its hard to guess the thickness of the wire inside. I've got some stuff off ebay that was supposed to be a thicker gauge and it was thick cable, but when I cut it I saw the wire was thin and the insulation thick so it was not as advertised.
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Old 08-21-2019, 07:34 PM   #12
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Fridge Power Check

With shore power disconnected or converter turned off for at least half an hour, a charged battery should measure at least 12.5volts with a meter. With the tow vehicle connected and running, trailer battery voltage should rise to at least 13.5V. With the tow vehicle still running, turn on the fridge 12V power. If the battery voltage drops below 12.5V, it is possibly discharging and certainly won't be charging while driving.

Our propane flame blows out while driving. With an adequately wired inverter in the tow vehicle, I run 115VAC back to the trailer for the fridge. The trailer battery still charges through the seven pin connector. I turn off the converter in the trailer to avoid an "infinite loop."

It works for us.
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Old 08-21-2019, 08:09 PM   #13
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Originally Posted by Lynn Eberhardt View Post
...
Our propane flame blows out while driving. With an adequately wired inverter in the tow vehicle, I run 115VAC back to the trailer for the fridge. The trailer battery still charges through the seven pin connector. I turn off the converter in the trailer to avoid an "infinite loop."
The "infinite loop" comment confused me but after thinking about it, I assume you run the tug's inverter to the trailer's shore power connection somehow, therefore the converter would run unless it was turned off. Turning off the converter is the right thing to do in that case, since it would be a charging source in parallel with the tug's charge line, which would not be problem when the tug is running, except for the singular fact that it might overload the inverter.

However, if the tug was off and the inverter in the tug was still on, then the tug's battery would be powering the converter if it was on, which would be charging the trailer battery AND the tug battery (unless it was isolated with a diode or isolator) and that would not work so well to say the least. It would basically be trying to charge a battery from the same battery, with the associated losses in the inverter and wiring.

But if you ran the tug's inverter to the fridge and ONLY the fridge, then it would not be a concern except it would still discharge the tug's battery if the inverter ran too long with the tug not running.

But maybe the inverter would shut off when the voltage dropped too far or does not run at all with the tug ignition off.

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It works for us.
Indeed... that is what counts.
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Old 08-21-2019, 08:32 PM   #14
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My solution for charging the trailer battery in the new trailer, is to take advantage of the Anderson plug at the tongue, with it's heavy wiring to the battery, that comes with the trailer. I will run heavy wires from the tug's battery to the rear and install a matching Anderson plug. This will send some serious amps to the trailer battery separately from the 7 pin plug. It's nice while driving, but will also be nice while camped and just needing to top off the bats. I've been doing essentially the same thing with jumper cables while parked and it charges very well.

I've already been leaving the generator at home, and now it seems unlikely to ever go with us.

I still like running the fridge on propane, unless we are plugged in, but I could be convinced to run on DC if we'll be on the road all day and wish to save a bit of propane. There will be no shortage of DC power for that use.
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