Replacement Refrigerator

Good Day all,

We recently purchased our TM, the original refrigerator had been replaced with a small home unit, strictly 120VAC. I have wired in an inverter so I could run it when we are traveling. Seems to work ok in the yard, will know more when we travel at the end of the month. The refrigerator draws 1 amp AC when running. I bought a 300 watt (peak 600 watt) inverter from Northern for $30. The wiring was a little tricky since I wanted to be able to change over from inverter to AC power without having to open the side cover.
The wires for the inverter were run directly from the battery (because the converter cannot handle the startup amp draw), thru the battery box bottom vent hole, then thru the refrigerator intake vent hole. I made up two short extension cords, which both run back out the vent hole. One is from the inverter, the other from the refrigerator AC outlet. I also ran the refrigerator cord out thru the vent.
From outside thr TM I can change the refrigerator from one power source to the other.
I added an AC muffin fan which directs air to the compressor whenever the TM is connected to AC.

I haven't been able to figure out how to include a pic in this post, but can email anyone the pics if desired.

I would love to see some pics of that mod having the same situation myself using a small dorm type fridge in mine. My email is [email protected] Please put TM in the subject line so's I don't accidentally delete it. I was thinking about doing the very same thing eventually with mine once I had time, just hadn't had a chance yet to give it much thought!

Thanks,
Happytrails......

[Bill]

Careful of connecting your inverter directly to the battery! This can kill the battery charger section of the converter. I suggest you go back and review a thread in General Discussion called Damaging the Converter. It relates to a fellow who hooked up an electric jack directly to the battery, and killed his converter. After some discussion, the consensus seemed to be that he should have hooked it to the non-charger section of the converter.

I've forgotten the details, but ISTR that the battery charging section is good for only 10 amps, and fails quickly if you put more load on it than that, as might happen if your battery is undercharged at the moment the load comes on. By contrast, the non-charging section of the converter has much more capacity, and is much more forgiving of overload. Not all of it is coming together in my brain at the moment, but you might want to check it out ...

Bill

Today I had to take the lower outside panel off to access that outlet to plug a carbon monoxide/propane gas detector to (It has a battery backup for dry camping btw). But while I was in there, I noticed the two wires (12v) that connected to the old fridge. I had totally forgotten about them. Would it be ok to hook the inverter up to those two wires, and maybe include a switch run to the outside so I don't ALWAYS have power going to the inverter, just while using it? Would this damage my converter by hooking into the 12v system at that junction? When I removed the old fridge, I simply cut the old wires, and capped them off with wire nuts, and taped them for good measure. DancinC, you should have the same two wires, a white one (hot) and a black one (ground) that come off that bundle of wires to the left of that compartment if you take off the lower access panel behind your fridge. They should be capped off much the same way. But I'd mainly be using it while in travelling mode, would this setup mess up my vehicle's charging system in any way as well?

I'm also tossing around the idea of using the gas line that went to my old fridge and route it through the lower vent and putting on a gas grill connection to be able to hook a gas grill up on the street side of the unit. Anyone with any thoughts on this idea as well?

[Bill]

Happy -

Re the refrig on the inverter - you SHOULD be OK here. The refrig circuit is fused for 15 amps DC, so presumably you are looking at #12 or bigger wire, which can carry 15 amps. I think you said your refrig needs 100 watts AC, so even allowing for some inefficiency, the inverter shouldn't draw more than 10 or 12 amps when the refrig is running. (Have you considered the turn-on transient? Can your inverter handle it?) In addition, the refrig circuit is connected to the 30-amp general-usage part of the converter, not the fussy 10-amp battery-charge-and-electronics-circuits part, so it shouldn't hurt your converter.

Re the propane grill connector - my expertise is less here. But it would seem OK, obviously assuming you put the connector inside the opening where it can't be smacked by the odd tree branch or car door in the parking lot. I'm not sure you'll enjoy running your propane grill right there between the sewer hose, water hose, and electric cord ... but to each his own. If I felt the need of a grill hookup (and sometimes I do), I would put it up on the tongue by the regulator.

Bill

Well that's good to know Bill about the hookup, and yes, I'm sure my inverter can handle it, it's a 600w, and I can hook the wires from the old fridge directly to it via screw mounts although I'll probably put a switch in between so's it won't always be running, just when I need it to that runs to the outside.


Lol, I didn't even think about the hookups in relation to the grill......maybe I can run a line up to the toungue through the vent hole that's right there, or just run something directly off the regulator.

Happytrails........

Hello all,

I didn't receive any tech data on my converter, I am trying to obtain some. I will find and read the thread on converter damage.

But in my case I think it is a mute point. I only run the refrigerator on the inverter when I am not connected to shore power. At least it worked well this past weekend on our trip. But then again my battery was fully charged. Had no trouble with my van keeping the TM battery up during travel.

I did try at first to use the existing 12V wires in the compartment for the old refrigerator, but blew the circuit fuse when it tried to start. The fuses in my converter are all 15amp, did not want to change up until I have better info on the converter.

Currently after I unplug the refrigerator from the inverter I pull the inline fuse to turn the inverter off. I am thinking about adding a switch, but one which will handle the rating of the fuse, 35 amps, is not inexpensive.

So far the install seems to work well. It was quite a rainy holiday here in Virginia, and the AC plugs under the floor did not seem to get wet or dirty from the travel.

Take care,
Dan

DancinC, interesting......I'm wondering if I'd run into the same problem as well. My fridge draws 185w I think, so the 600w inverter should handle it, but not sure how many amps it draws.

Happytrails.......

[Bill]

Bill / Happy -

I hate to be a wet blanket, but yes, you are headed for trouble.

The function of an inverter is to take current in from a 12 volt source, and send it out at 120 volts. Your refrigerator needs 185 watts, so the inverter must provide about 1.55 amps at its output [120 volts x 1.55 amps = 185 wattts]. Since watts is watts, the converter will need to take in 15.5 amps at 12 volts (12 volts x 15.5 amps = 185 watts]. But this is true ONLY if your inverter is 100% efficient, meaning IF it could do the conversion perfectly. Unfortunately, NOTHING is 100% efficient - the inverter will waste some power, so it needs to take in a little extra to make up for this waste. If we assume it is 90% efficient (a very optimistic number), then only 90% of the input current gets changed to 120 volts. So it really needs 17 amps, not the 15.5 amps we calculated earlier. The extra 1.5 amps is what is wasted.

Now consider this. At the TM converter, the wires to the refrigerator are protected by a 15 amp fuse. When you plug in your inverter and turn on the refrigerator, this fuse will probably blow. It is tempting to put in a bigger fuse, but you can't do this because the wiring can handle only 15 amps. If you increase the fuse, it will overload the wires.

And we haven't even talked about the turn-on transient yet.

My suggestion is that you set up your refrigerator, your inverter, and a spare battery on the floor of the garage or someplace, get an accurate ammeter, and MEASURE the current going from the battery to the inverter. Measure both the starting current and the running current. This should tell you what is going to happen in the final installation.

My guess is that you will see an overload, and the only answer is to run a new pair of wires to the refrigerator cubby - not a big deal for someone of your skills and intimate (!) knowledge of your TM. Let us know how it comes out. But please, don't try to cheat on this. Fried wires and a trailer fire are not something any of us wants to experience.

Bill

Well, I was thinking of maybe installing a spare battery just for odds and ends like this. (As well as a backup battery). And yes, the very LAST thing I would do is replace a fuse with a higher rated fuse. I would have to hook it up for charging off the tow vehicle while dry camping when there's nothing connected to it of course, but at least it wouldn't threaten anything in my converter. A couple of knife switches perhaps would be easy to install to reroute power from my main battery and disconnect anything connected to it. A battery case is fairly inexpensive, and I can vent it into the main battery vent. Does this sound like a viable solution Bill?

[glow=red,2,300]Happytrails........[/glow]