Auxiliary refrigerators and coolers

On the refrig. issue we have purchased an Edgestar AC/DC model that can cool to -5degrees F. So you can use it as a refrig or freezer.
Not cheap, but well made and works well. You can find them on line.
Still a bit of a pain to get to the TM refrig., but this expands capacity and access.
As far as TM's go for a number of years, I went to one of the largest RV shows in the country (Hershey, Pa.) and looked at everything under the sun. And when I factored in I could pull a 2720 with my existing minivan, store it in my garage and has much more room than my previous VW Westphalia Camper etc. I am very pleased after 2 years of use. Just need more time to go places....

[Bill]

Originally Posted by moaboy

On the refrig. issue we have purchased an Edgestar AC/DC model that can cool to -5degrees F. So you can use it as a refrig or freezer. Not cheap, but well made and works well. You can find them on line.

That's a nice unit, and the price has come down a lot. I paid almost twice that amount for our same-size Engel frig/freezer six or eight years ago. It has worked flawlessly for all that time, which is great, especially considering that we also use it as an adjunct freezer in the garage during holidays when we're expecting a lot of company. An additional advantage is that it can run all night in the tow vehicle, on the tow vehicle's 12-volt plug, without killing the battery. We tried that (once!) with a thermo-electric cooler, and had to beg a jump-start next morning.

Bill

Originally Posted by Bill

An additional advantage is that it can run all night in the tow vehicle, on the tow vehicle's 12-volt plug, without killing the battery. We tried that (once!) with a thermo-electric cooler, and had to beg a jump-start next morning.

Same thing happened to us with our thermoelectric cooler. But I always thought thermoelectric was more efficient than compressor driven frigs, no?

The Edgestars are compressor driven and can really remove heat, but I never thought you would want to leave one plugged into your car battery over night.

[Bill]

Thermo coolers are terribly INefficient. That's why they see use in only a few specialized applications where a compressor won't work for some reason. (They are also fairly cheap in small sizes.) By contrast, compressors are quite efficient. From Wikipedia,

"Thermoelectric junctions are generally only around 5–10% as efficient as the ideal refrigerator (Carnot cycle), compared with 40–60% achieved by conventional compression cycle systems (reverse Rankine systems using compression/expansion). Due to the relatively low efficiency, thermoelectric cooling is generally only used in environments where the solid state nature (no moving parts, maintenance-free) outweighs pure efficiency."

In addition, a thermo cooler can develop only a fairly small temperature differential, hot side to cold side. I think the Coleman-type units that many of us own advertise 40 degree differential. In other words, if it is 95 degrees out, the best you can do inside the cooler is 55 degrees, and then only if you have perfect insulation. A compressor unit can generate a much larger temperature differential.

The compressor units that Moaboy and I mentioned have a thermostat. They reach a set temperature, and then cycle on and off to maintain it - just like a household refrig. An RV-market thermo cooler has no thermostat. ON is ON, and it is ON 100% of the time.

A Coleman 40-quart thermo-cooler draws a bit over 5 amps from the 12-volt supply, and as noted, it draws it 100% of the time. If you let it run for overnight, say 12 hours, it pulls 60 amp-hours from the battery. For a typical 75-AH battery, that is the kiss of death, and explains why we needed a jumpstart in the morning.

A compressor cooler draws about 2.5 amps from the 12-volt supply - and again as noted, it draws this only when the compressor is running. On an overnight stay, this may total about 3 hours of run time, which amounts to less than 8 AH from the battery, which is why we got away with it. Incidentally, I agree with you about not leaving it running from the tow vehicle battery on purpose - that was a mistake I made at the end of a very long day.

Make no mistake, a thermo cooler can be a great thing if used within its limitations. I had one for years, and loved it because it was so much better than nothing. And the $70 price tag of a 40-quart thermo unit is very attractive when compared to the $400 tag on an Edgestar, or the $700 tag on an Engel. In this case, it is true that you get what you pay for.

Bill

[ShrimpBurrito]

Originally Posted by Bill

That's a nice unit, and the price has come down a lot. I paid almost twice that amount for our same-size Engel frig/freezer six or eight years ago. It has worked flawlessly for all that time, which is great, especially considering that we also use it as an adjunct freezer in the garage during holidays when we're expecting a lot of company.

I did a little research on them, Bill, and the Engels are still the same as what you probably paid. The 43-qt one is ~$800 here:

http://www.compactappliance.com/MT45...rtable_Coolers

...and the 43-qt Edgestar is ~$450.

http://www.compactappliance.com/FP43...rtable_Coolers

One difference I noticed between the 2 is the current draw. The Engel specs say it draws 2.5A, and the Edgestar 5.4A. That's a huge difference. But they may have different compressors....I don't know much about such beasts, but I'm not sure the Engel uses a Danfoss compressor, which may draw more current but don't have to run as long.

Dave

[Bill]

Dave -

Good research. I didn't notice the amps difference between the two.

The Engel website has added a lot of techie information since I bought mine. You can now see just how much current the compressor will draw, for a whole range of ambient and inside-the-box temps. And 2.5 amps is the max - nice for a solar boondocker.

You mentioned compressors. For what it is worth, most compressors are rotary - there is an electric motor, which is coupled to a piston(s) (think of the engine of your car), or a set of vanes of some kind (think of a windmill). A rotary compressor has several moving parts, all of which decrease the efficiency of the unit because of the friction involved. This probably accounts for the increased current. And of course, more moving parts increases the failure rate, so goes the advertising hype. While I am sure it is true, I suspect that the failure rate is so low that it doesn't really matter. The Edgestar most likely has a rotary compressor, though they don't say so.

The Engel has a different kind of compressor. They call it a Swing Motor (which I find unhelpful). A cylindrical slug of magnetized steel (a piston) is free to slide back and forth within a piece of non-magnetic pipe. Wrapped around the outside the pipe is a coil of wire. When a pulse of current is applied to the coil, the piston shoots in one direction within the pipe, and rebounds at the end. As the piston returns past center, a pulse of current with opposite polarity is applied to the coil, and the piston is shot along the other direction, and again rebounds at the end. The cycle repeats, with the piston shooting back and forth in the pipe many times per second. At the end of each stroke, the momentum of the piston compresses a pocket of refrigerant gas.
Two big advantages:
1. Only one moving part (the piston).
2. No startup current surge - it draws only normal running current as it starts.
Disadvantage:
The control circuitry to sense the position of the piston, and pulse the coil at exactly the right time, is more complex than a simple on-off switch for a motor.

I had a half-hour conversation with the lead engineer at the Engel facility in Florida a while back. They are very proud of that compressor, and he told me that they have never had a single failure of the compressor. You can take that for whatever it is worth, but I bet it is at least close to true. The primary market for the Engel cooler is in mission-critical applications where failure has a very high consequence - mobile medical applications in the outback of Australia. Hence the high cost, I suppose.

So there it is. That's way more than you wanted to know, right? At the bottom line, I'm not sure that I would pay the extra cost of an Engel if I were doing it today. My applications (cooling beer, keeping meat frozen) just aren't that critical.

As a final note, a couple years ago we had a long discussion about portable air conditioners for the TM. It got bogged down and died over the issue of one air-flow hose vs dual hose. There didn't seem to be many dual-hose units around. I just noticed that Edgestar makes some dual hose units.

Bill

[ShrimpBurrito]

Thanks for the explanation, Bill. That "swing motor" sounds pretty neat. I too read that there was a very low failure rate among the Engels, but I don't know how that rate compares to other manufacturers. I did come across this guy's analysis:

http://home.iprimus.com.au/rfh/portablefridges.html

It can be a little hard to follow at times, but I think it is comprehensive. In any event, he researched repair costs for several brands, and they were all very high -- at least 1/2 of the total fridge cost, especially that Engel control board you mentioned. An interesting read.

Dave

I considered (briefly) the Engel before I bought the Edgestar. One advantage as I understand it of their fancy compressor is that it will work even when the unit is not level. Since I try to keep my TV and TM as level as possible (yuk, yuk) this was not a big factor. My understanding is that the company that manufactures the Edgestar looked at the Engel and their goal was to make a good, solid unit but at less cost. Since I am not -at least to date- transporting any organ transplants etc. the less expensive unit works for me. btw, I did leave mine plugged in all night just to see if my minivan would start the next day and it did no problem. Only time will tell how good a unit it really is.

[Virginia Deacon]

We use one of the newer Igloo coolers, to keep pop and suds cold. It will still have ice in it after three days. We use the 'fridge in the TrailManor for eggs, meat, and other perishables. Works for us!

Looking forward to the upcoming season; there are a lot of TrailManor rallies coming up!

[OneMoBear]

We are considering buying this: http://www.compactappliance.com/CRF1...efault,pd.html

We don't think we need the ac/dc option but when we are on the Oregon coast for a month with the nearest grocery store almost 15 miles away, we think we're going to need the additional freezer space. We also like the idea that it can be used as a fridge or freezer for the holiday season.

This seems to be the best price because the price gets pretty darn close to $200 with shipping from most other merchants.

Anyone see any red flags?

Malinda