Using a DC to AC inverter to power fridge while towing

[MRO2009]

Howdy fellow hybrid owners,

I searched through the forums, but didn't really see this sort of question answered by anyone. So I tried to calculate this out using some formula's such as Ohm's Law and such.

First off, I have a Dometic fridge in my HTT, Model: DM2652RBX which has the following power requirements: 120V 60Hz 2.7 Amp. And what I was wondering is if I can power an inverter from 12v DC which will in turn power my fridge while I am towing (my model does not support 12v DC as a power source). I can either use 120v AC, or Propane and a very small amount of 12v DC (for the control panel).

So using Ohm's Law, I can calcuate the Wattage needed to power the Unit. Ohm's Law says: V x I = W
So plugging in my values, I get the following: 120V x 2.7A = 324W

So it looks like a 400W inverter (or greater) will do the trick.
Which seems like a much safer option while towing and it will be
pulling power from the TV's alternator and HTT's battery.

However... After reviewing an online calculator which estimates the power draw on the 12v DC side, I see that it will need around 30A for a 2.7 amp AC load. So what I am curious of can the tow vehicle's connection support 30+ Amps DC? From what I was able to find on Google, the TV's trailer connection is fused at 30 amps. Which doesn't leave much wiggle-room, if I try to power the inverter from the TV. I am curious if other folks are doing something similar with their rigs, or if the general consensus is just run the fridge off of propane while towing since the power draw of the inverter is too high to run off of the TV?

Thanks,
Mike

[time2roll]

Yes the 'automatic' setting takes care of everything.

[MRO2009]

I decided to try running the fridge on propane while traveling on my last trip and it worked flawlessly. Plus it was way easier than trying to hook up an inverter directly to the fridge. Thanks to the folks that pointed out the obvious solution. :S

[slavco]

MRO2009 wrote:
Howdy fellow hybrid owners,

I searched through the forums, but didn't really see this sort of question answered by anyone. So I tried to calculate this out using some formula's such as Ohm's Law and such.

First off, I have a Dometic fridge in my HTT, Model: DM2652RBX which has the following power requirements: 120V 60Hz 2.7 Amp. And what I was wondering is if I can power an inverter from 12v DC which will in turn power my fridge while I am towing (my model does not support 12v DC as a power source). I can either use 120v AC, or Propane and a very small amount of 12v DC (for the control panel).

So using Ohm's Law, I can calcuate the Wattage needed to power the Unit. Ohm's Law says: V x I = W
So plugging in my values, I get the following: 120V x 2.7A = 324W

So it looks like a 400W inverter (or greater) will do the trick.
Which seems like a much safer option while towing and it will be
pulling power from the TV's alternator and HTT's battery.

However... After reviewing an online calculator which estimates the power draw on the 12v DC side, I see that it will need around 30A for a 2.7 amp AC load. So what I am curious of can the tow vehicle's connection support 30+ Amps DC? From what I was able to find on Google, the TV's trailer connection is fused at 30 amps. Which doesn't leave much wiggle-room, if I try to power the inverter from the TV. I am curious if other folks are doing something similar with their rigs, or if the general consensus is just run the fridge off of propane while towing since the power draw of the inverter is too high to run off of the TV?

Thanks,
Mike

I would just run it off propane and save yourself the headache and trouble. I usually plug the fridge into house power 24hrs before a trip to get it cooled down and then switch to propane right before we leave. It has worked flawlessly every time, even in heavy rain and wind. The power supplied by your TV will be sufficient to power the panel and igniter while towing. Also, the amount of propane used for cooling the fridge is negligible, so you're not really saving yourself anything by trying to hook up an inverter.

Just my $0.02 🙂

[Sandia_Man]

One of the first mods we did on our new rig was to install a large inverter, tried what you are asking about a couple of times and found that in our case we did not get enough charge from the alternator via the 7 pin cord to keep up with the roughly 325 watts the fridge required when in AC mode.

We noticed TT batteries were taking a hit while underway arriving to our destination with less than fully charged batteries. No biggie as we normally just set fridge to auto mode which of course switches to propane when traveling down the road. Our fridge cools better on propane anyway.

[pianotuna]

Place the inverter in the tow vehicle and run a 120 volt cord to the RV.

#8 wire from the chassis battery to the inverter. #16 light cable to the fridge, with plugs as needed.

[time2roll]

NO. The OEM wire to the trailer will not support 30 amps. More like 5 to 10 amps. You could go to great lengths to make it work but why?

Run the fridge on propane while in transit same as a million RVs do every day.

[sch911]

Most of us just use propane while underway. You should too.

[SidecarFlip]

Simple answer is of course, when fueling, shut of the fridge (on propane) if you have a gasser because fumes are an issue. Diesel not so much but still adviseable.

A fridge on propane going down the road actually works better because the thermo-siphon action works well with moving around.

[MRO2009]

I wasn't quite sure if running the fridge on propane while towing was really safe. With our old pop-up camper that was never really needed because we couldn't access the fridge while towing anyways, so it just sat empty until we got to the campground and plugged in or ran it off propane. I did try Googling that question and I got conflicting answers. So I thought that maybe running an inverter would be a good compromise. But of course I would have to redirect the fridge's power to the inverter, or 'back-feed' power from the inverter to the fridge (which is a really bad idea). So this solution starts to get really ugly fast! I agree with KD4UPL's comment about the actual power that you can get to the TT from the TV. I'm sure the wires were not designed to carry a sustained 30A load. So it sounds like propane is the best option. Thanks!

[SidecarFlip]

No brainer for me. Propane.

[KD4UPL]

You will have to upgrade the tiny wire in your TV and TT's wiring harness to actually get 30 amps back there. Even then, you will still not have enough. You will have other loads in the TT like the radio, LP leak detector, etc. drawing additional power. If your batteries were down at all from camping there won't be anything left to charge them.
There's no reason not to run it on propane, that's the normal way of doing things. It's designed for that. It will likely cool better and you don't have to change or buy anything.

[Bionic_Man]

Why not just run it on propane?