Propane refridge

[barnyard-TMO]

With the popularity of solar power is it still desirable to have a refridgerator that has propane feature? have to replace my refridge and wondering if 12v/110v is sufficient

 

[Shane826]

If you’re going just electric you don’t need an AC/DC fridge. Just get a 12V compressor style fridge and never look back.

 

[Bill]

Shane is exactly right. If you have plug-in AC power, then the TM's converter will supply all the 12VDC power you need. And if you are boondocking on solar power, your solar system will provide the 12VDC power you need for your refrig. You never need AC power for your refrig.

Again as Shane said, get a compressor-style refrig. I will add that you should NOT get side-tracked onto a 12-volt thermo-electric refrig, lured by its very low price. They are absolutely unsuitable for your primary refrigerator.

If you like, you can Search the Forum for "thermo-electric" to find the list of reasons.

Bill

 

[rickst29]

In my opinion, propane power is not needed (in a replacement)

Maost of the the "12 volt DC" refrigerators contain built-in converters. My own Dometic model switches to use 120-VAC automatically, when it detects that 120V power is present.

These 12 Volt DC capable refrigerators tend to be expensive, in comparison to dormitory-sized household units (120-VAC only). The first issue with a dormitory-style fridge/freezer is the high current (power requirement) needed to start the compressor. That's typically about seven times more than the labeled average running watts. A '400 watt' dormitory fridge therefore needs a converter capable of about 2,800 watts, consuming all of the "savings" on the fridge -- unless you also need that converter for other reasons. If you buy a smaller converter to drive such a refrigerator, you WILL burn out that converter.

Compressor-based refrigerators of both (12 volt DC specialty units AND household units) are both more efficient than the heater-based 'absorbtion' refrigerators widely used in RVs. When using battery, than need only about 1/4 as much power (in watt hours).

The second issue with those 'dormitory-style' is the wide range of outdoor temperatures which the TM fridge needs to handle. Most of them are designed for "indoor use only". So I recommend that you invest much more to buy a 12-VDC refrigerator instead, they're built using a special low voltage DC compressor. That Danfoss compressor (and its clones) also have extremely low "compressor start surge requirements", with no need for bigger wire size or battery capabilities.

Most of the fancy '12V compressor' refrigerators can also maintain safe and cold interior temperatures much better than the absorption refrigerators. (My original TM fridge couldn't stay cold when outdoor temps exceeded about 95 degrees, while my replacement "12V compressor unit" is widely used by tour operators in excursions to Uhru ('Ayer's Rock) in Australia - temps above 120 degrees are common). I've never had even the slightest problem with mine, although my highest outdoor temps have never exceed about 105.

 

[Shane826]

Rick- If I recall you have a Dometic CR1110 AC/DC fridge? That one is capable of switching on its own. The new 12V fridges are just 12VDC and rely on the camper’s converter to switch AC to DC when on shore power. You can get a 3.3cf 12V fridge in the $500 range.

Or, do what I’m working on… 4.5cf 120VAC fridge with a transfer switch and converter. Costs a little bit more (I’m in the $700 range total) but provides a bit more flexibility with the household outlets now able to be powered by the battery.

 

[rickst29]

Rick- If I recall you have a Dometic CR1110 AC/DC fridge? That one is capable of switching on its own. The new 12V fridges are just 12VDC and rely on the camper’s converter to switch AC to DC when on shore power. You can get a 3.3cf 12V fridge in the $500 range.

Or, do what I’m working on… 4.5cf 120VAC fridge with a transfer switch and converter. Costs a little bit more (I’m in the $700 range total) but provides a bit more flexibility with the household outlets now able to be powered by the battery.

Yes, I have that older and much more expensive Dometic. (I was probably the first TM Onwer to make that switch. At that time, the fridge was only listed by Dometic as "boating" product for yachts, it was not listed as a RV product at all.) Thanks for the info regarding the newer and cheaper 12V-only units.

Will your Converter be capable of 3000 watt peaks? You should not install a Converter with a lower rating.

Also make sure that your Converter does not 'bond' the AC-Neutral (White) and Safety Ground (Green) outputs for "shared use, higher efficiency" before reaching the Inverter's output electronics. That horrible "feature" is incompatible with GFCI circuits, and also subjects the batteries to a bit of 60-cycle noise on the DC ground plane.

 

[Bill]

Just adding an FYI. We bought a 44-qt Engel MT44 compressor unit in about 2002. Scary expensive, but we were about to do extended TM traveling through the desert southwest, and nothing similar was available at the time. It had a single compartment, any temp setting from 0* to about 50*. Auto-select 12VDC / 115VAC.

Wonderful unit, maintained 0* when the TM's interior temp hit 110*. When we got home, we ran it 24/7 as an aux frig in the garage for years. Finally began to malfunction in about 2015. Engel Customer Service phone call diagnosed a power supply problem, they sent out a new unit, I installed it - up and running to this day.

Engel's Sawafuji "swing motor" compressor, like the now-famous Danfoss compressor, is very efficient. Ours draws 2.6 amps @ 12VDC when running, and at 95* ambient, it holds 5* inside temp with 47% run time, so average current is about 1.2 amps. I tried to measure a turn-on surge, and it didn't have one. For 5* freezer temp at 95* ambient, I think that is outstanding.

If I sound like I am shilling for the Engel, it is because I love ours. Today, both the Danfoss and Sawafuji compressors have entered the realm of legend (look them up), and today you can choose from a number of refrig/freezers that use one or the other. Either will be an excellent choice. If you want a rugged reliable unit for extended use - as opposed to the occasional picnic - I would recommend spending some extra bucks to get either one.

Bill

 

[kjfatl]

I picked a compressor frig that runs at 110V or 12V. It uses 110V if available and falls back to 12V when necessary. I was concerned that a continual load on the 12V inverter would reduce the life of the inverter unnecessarily. In the long-term I will probably get a larger solar panel for the top of the camper that can keep the frig going when AC power is disconnected for an extended period of time.

 

[Wavery]

My 120V 4.5cu ft dorm fridge used about 500W for about 2 seconds at start up. It ran 90W when the fridge was cooling down and 35W after the fridge was cold. I ran it off of my 2000W inverter with no issue at all and it would probably have run on a 500W inverter just fine.

At the time that I installed my fridge the 12V fridges were quite expensive. Although I would probably opt for the 120V dorm fridge anyway. Power consumption was never an issue.

My thought with preferring the 120V dorm fridge is, if the fridge goes out on a long trip, getting a replacement in a timely manner, in God knows where, would be next to impossible. That would leave me with no fridge for the duration of the trip or stuck is some town, waiting for a new fridge to be delivered (somewhere?). 120V dorm fridges can be found in most any town, anywhere in the US and I would be out another $200 as apposed to $1200 (after I got home).

As some people know, it is quite a rough ride inside of the TM when going down the highway. Things often fall apart or screws come out. The compressors inside all of the compressor fridges are mounted on rubber mounts and the refrigerant lines are solid copper lines. Those lines are subject to a lot of shock loading and the possibility of a line cracking is high (in my opinion) over time and miles on the road.

 

[Shane826]

^ Yeah what he said. ^

 

[lederhos]

I’ll second Waverly’s comment. Got my dorm fridge on sale for $100 shipped free from Walmart. Doubled my refrigeration space (had to removed radio I never used), but I have a large lithium battery, a LOT of solar and a very efficient inverter

 

[barnyard-TMO]

110 volt refridge

Wavery -I like your idea about 110volt refridge. Is 1000 watt inverter suffficient? pure sine wave?

 

[Wavery]

Wavery -I like your idea about 110volt refridge. Is 1000 watt inverter suffficient? pure sine wave?

A 1000W inverter would work just fine. Just don't plan on running much of anything else that's 110V. If you are going to all the trouble of installing an inverter, I'd recommend a 2,000W so that you can run a coffee pot or microwave. If you don't use those, you're golden.

Just be sure to use the proper sized pure copper wire (depending on the distance) from the batteries to the inverter and a 100A Mega Fuse in the line.

What batteries are you using and do you have solar?

 

[barnyard-TMO]

110 volt fridge

kinda entry level and large learning curve. Just bought 07 2720 w/ trashed refridge. just purchased 4.4 cu, ft. unit 110volt Have 100watt panel and ep ever controller,2 6v golf cart batteries from years ago. Question: better to have inverter close to batteries w/ long110v cord or inverter close to refridge and long 12v wires? Thanks for input

 

[Wavery]

kinda entry level and large learning curve. Just bought 07 2720 w/ trashed refridge. just purchased 4.4 cu, ft. unit 110volt Have 100watt panel and ep ever controller,2 6v golf cart batteries from years ago. Question: better to have inverter close to batteries w/ long110v cord or inverter close to refridge and long 12v wires? Thanks for input

Put the inverter as close to the batteries as possible. DO NOT use the battery cables that came with the inverter. 90% chance that they are copper coated aluminum (CCA) and that's not good. You want to have pure copper battery cables and they should be the proper size, depending on the size of the PURE SINE WAVE inverter (Don't buy a modified sine wave inverter) and length of the cable. You can run a long wire to your fridge or just wire the positive wire from the inverter into the fridge circuit breaker and the negative wire into the ground busbar in your power center. If you do that, you can just use the 110V outlet that is already inside your fridge cabinet, behind the fridge.

If your batteries are over 3-years-old, don't plan on them performing very well. If over 5-years-old, you may want to replace them with a 100AH lithium battery (or 2).

 

[barnyard-TMO]

110 v refridge

with the 110 volt refridge is it necessary to keep the cooling fan behind unit?

 

[Bill]

with the 110 volt refridge is it necessary to keep the cooling fan behind unit?

The short answer is that it may not be strictly necessary, but it is probably a good idea to keep it.

Why? All refrigerators create some heat as they cool the food area, and the refrigerator MUST get rid of that heat in order to function. Compressor refrigerators create much less heat than absorption (3-way) refrigerators, but the heat still should not be trapped and allowed to build up.

So in regard to your question, some compressor refrigerators have an array of vertical cooling tubes (usually colored black) on the back. They remove the heat by letting air circulate from the floor, up the back of the unit and over the tubes, over the top, and out into the room. Others have an array of horizontal cooling tubes at the bottom, just above the floor. They have a small fan to blow air from the back near the floor, across the coils, and out into the room.

Either way - but especially with the vertical tube arrangement - if venting is not good, the heated air will tend to collect in the area behind the refrig. I would consider it a good idea, though perhaps not strictly necessary for a small refrig, to exhaust this air outside.

Bill

 

[Bill]

A couple small points to consider.

1. In the summer, you may not want the refrigerator's waste heat to be exhausted into the room, so blowing it outside with the exhaust fan might be welcome. But in a colder season, you might welcome it inside. Then you turn off the exhaust fan, and keep that warm air inside.

2. As noted above, a refrigerator MUST get rid of the heat that it generates. That is part of the physics of refrigeration. If the heat is allowed to build up, then the refrigeration mechanism must work harder (longer) to overcome it. This means that the refrig uses more electric power. If you are boondocking, using the small amount of power to run the fan may be worth it.

Bill

 

[Wavery]

with the 110 volt refridge is it necessary to keep the cooling fan behind unit?

The short answer is "No" you do not need to keep the cooling fan if you install a compressor fridge.

The long answer is:
I think that you might be asking this question because the old exhaust outlet may be prevention you from pushing the new fridge all the way back into the cabinet.

I was faced with that and my wife was happy with having the fridge stick out the 1.5 inches from the cabinet. If she wanted the fridge totally flush, I would have removed that vent hose flange and rearranged it to be out of the way.

In reality, that exhaust vent was really made for the heat that was developed for the old fridge to operate. With the old ammonia fridge, the burner (either propane or electric) had to get quite hot to boil the ammonia to make the fridge work. There is no "Heating" element in the compressor fridge and the amount of heat that needs to be exhausted (if any) is minimal and occurs naturally through the vented panels behind the fridge.

Think about the fridge in your home. There is no vent for that fridge. Back in the 1940s and into the 50s a lot of homes had propane/ammonia fridges in them (if they could afford it). Those fridges had to have exhaust vents through the roof, just like a gas water heater.

 

[rickst29]

I picked a compressor frig that runs at 110V or 12V. It uses 110V if available and falls back to 12V when necessary. I was concerned that a continual load on the 12V inverter would reduce the life of the inverter unnecessarily. In the long-term I will probably get a larger solar panel for the top of the camper that can keep the frig going when AC power is disconnected for an extended period of time.

Your fridge, like mine probably RUNS on "12v". These convertible types contain contains a small power converter, from 120-VAC to 12 Volts DC, with a sensor which switches to use the "converted AC power" whenever AC is present.

Much smaller than the main RV converter, this converter only needs to supply about 70-90 watts.