best fridge set up ?

[Dzl]

Will you pair please talk about the same thing
A dorm fridge is an upright fridge just like your house fridge freezer
A chest fridge opens at the top ,hence like a treasure chest.

I think you are confused, we are talking about the same thing, we are comparing between the two.

Also please stop destroying a valuable thread with your bickering.

Yes, our dialogue was not as constructive as I hoped and has ceased being fruitful as we simply don't see eye to eye (that said, this thread has been dead and buried for 2 months, so I'm not sure our exchange is 'destroying' anything). And most of our disagreement was substantive and on topic but did get a bit overheated. I agree, its not constructive to continue the exchange at this point.

Whats on your mind? What would you like to see discussed more? Help us re-rail the derailed conversation.

 

[pat.kane]

Whats on your mind? What would you like to see discussed more? Help us re-rail the derailed conversation.

Wow, that speaks highly of your emotional intelligence. Thank you.

Though I didn't necessarily care for all of the back-and-forth, I did get meaningful info out of the discussion from both of you.

I will be converting a step van into a RV so my takeaway was I would probably be better off investing in a full roof of solar and AC fridge than spending that money on an expensive DC fridge. The question then becomes which AC fridge? I'm not looking for that answer here as I don't even know how big I want my fridge to be. What I will comment on though is I've looked at a lot of mini fridges at the box stores and many use almost as much energy as the large fridges. It makes you wonder if that's true.

 

[Dzl]

What I will comment on though is I've looked at a lot of mini fridges at the box stores and many use almost as much energy as the large fridges. It makes you wonder if that's true.

From what I've heard, yes its true, a large fridge will use more energy than a small fridge, but powr consumption won't increase proportionally to volume. In other words a 6 cubic foot fridge will consume more power than a 2 cubic foot fridge but it won't consume anywhere near three times as much power even though it is three times the volume. Put simply large fridges are more efficient in the sense of watts/volume. As I understand it, If you have the space and the need for a larger fridge, it won't 'cost' that much more to power.

I will be converting a step van into a RV so my takeaway was I would probably be better off investing in a full roof of solar and AC fridge than spending that money on an expensive DC fridge. The question then becomes which AC fridge?

This is a reasonable takeaway. There is one other option too (also AC) which is using a chest freezer adding an external thermostat for use a fridge. This might be a middle ground between efficiency and cost for a medium sized unit. I don't know a lot about this option, but a lot of people have been taking this route recently and I think chest freezers are pretty cheap. People claim they are quite efficient when used as a fridge because they have very substantial insulation compared to cheap fridges. I believe some forum members here have gone that route, but I can't speak to that option personally.

 

[BiduleOhm]

From what I've heard, yes its true, a large fridge will use more energy than a small fridge, but powr consumption won't increase proportionally to volume. In other words a 6 cubic foot fridge will consume more power than a 2 cubic foot fridge but it won't consume anywhere near three times as much power even though it is three times the volume. Put simply large fridges are more efficient in the sense of watts/volume. As I understand it, If you have the space and the need for a larger fridge, it won't 'cost' that much more to power.

That's because it's dependent on the area, not the volume, and the area increases slower than the volume when you increase the dimensions.

 

[Sgt Raven]

That's because it's dependent on the area, not the volume, and the area increases slower than the volume when you increase the dimensions.

It is also dependent on how full each fridge is.... A full fridge works better than almost empty one. The Mass of cold items inside it stays colder and there is less change when you open/close it.

ETA: Also a chest style fridge or freezer looses less cold each time it is opened. A upright style dumps all the cold air inside it when opened. Where a chest style doesn't. Remember heat rises, so the cold stays in a chest style.

 

[Ped]

I will be converting a step van into a RV so my takeaway was I would probably be better off investing in a full roof of solar and AC fridge than spending that money on an expensive DC fridge. The question then becomes which AC fridge?

Why a full roof? We used absurdly, over-the-top high consumption numbers for 120v (3-5x) and ridiculously low consumption numbers for 12v (trucker fridge states average 2.5x higher energy usage for their units) and still only needed 200w of solar difference.

As to which fridge, whatever will fit in you RV. Youre probably not going to find radical differences in energy consumption between brands. Id look at energy star ratings and try to get the lowest but if it wont fit in the rv compartment thats fine too. You will want to avoid ones with exposed evaporator coils which I think most are not anymore.

 

[Dzl]

You need to re-read the last page. The example was at an absurd 100% duty cycle, meaning the fridge runs non stop 24/7, you would only need a nominal 200w more solar. No fridge ever runs anywhere near 100%. Think more like 10-30%.

I'm pretty sure the 'invest in a full roof of solar' statement, wasn't meant to imply a roof full of solar was needed to compensate for an AC fridge. I think they just mean, put the savings on a fridge towards more solar.

As to duty cycle, from what I've seen, I agree that 10-35ish % is normal, but up to 50-60% is not uncommon in summer extremes. This probably depends on the fridges logic (as well as whether it is a fridge or fridge/freezer), many DC units are designed for environments with large temperature fluctuations, whereas it may be that fridges designed for fridge-only indoor use, may not exceed a certain duty cycle but would struggle to maintain temperature in extreme temperatures (but this is just speculation).

 

[Ped]

Ahh ok. From what ive seen most DC native units have a compressor run time around 10 minutes. Does this concur with your research? I know mine and others have reported usually around half that.

 

[pat.kane]

Why a full roof?

Dzl explained it better than I did. Dollars saved on fridge become dollars invested in solar generation.

 

[Sgt Raven]

For me I don't see a Dorm Fridge standing up to off road use in my 4x4 pickup and I think things will stay in place better in a top load fridge/freezer. Plus my dual zone can be used all fridge, all freezer or half/half.... Add in all the cold air won't spill out every time I open the door.

 

[Dzl]

For me I don't see a Dorm Fridge standing up to off road use in my 4x4 pickup and I think things will stay in place better in a top load fridge/freezer. Plus my dual zone can be used all fridge, all freezer or half/half.... Add in all the cold air won't spill out every time I open the door.

These are all the reasons I value the purpose built, 12/24/120 chest style fridge freezers as well. They are the only units designed to be used in harsh environments (that I am aware of). They are designed to handle vibration, shocks, temperature extremes, dust, steep off-angles, and off-grid and/or unreliable power. From simple design decisions like horizontal (chest style) design, robust secure latching mechanisms, mechanical vibration dampening, efficient variable speed DC compressors, to more advanced features like programmable thermostats and low voltage cutoff.

That said, many of these benefits become important in offroad and/or marine applications, your average motorhome won't necessarily benefit from the rugged design, and you could buy and break a few cheap dorm fridges and still spend less than a purpose built dc chest style fridge.

 

[WSix]

Somewhere in my video meandering, I saw where someone had taken a dorm fridge, and modded the motor assembly by orentating it on its side which allowed them to run the fridge as a chest type cooler with the door opening upward.

 

[Dzl]

Somewhere in my video meandering, I saw where someone had taken a dorm fridge, and modded the motor assembly by orientating it on its side which allowed them to run the fridge as a chest type cooler with the door opening upward.

Yeah I've seen a similar video. There are a handful of cool videos out there of people modding old dorm fridges, I came across one of this guy modding his dorm fridge to try to get maximum efficiency, I think he improved it about 40% with some pretty basic techniques, and another of a guy modding his fridge to run direct from DC, then there are the many videos of people modding a chest freezer to run as a fridge.

 

[WSix]

I have seen a chest freezer done as well. (on line).
It really gives a lot o diversity as how to use it.

 

[maciekp]

Hi Iam uk based Solar novice i have a XLWB 2013 Transit running 4 x 100w renogy mono going to renogy DC 2 DC / MPPT combined with 1x 200AH lucas AGM battery adding another in the near future. In my van I Would like as big a fridge as i can get but a 12v 3 way fridge is expensive £600 for a small dometic crx 50 top reviews good name. So before i bite the bullet and get one i want to look at all options be it a lesser named 12v fridge but bigger or i have been looking at Mains chest freezer to fridge conversion using an external thermostat costing around £150 to £200. Has anyone got any advice or experiance with this sort of set up i won't be full time in the van just long weekends wild camping mainly and if i go the chest freezer option and it doesn't work i can always use it at home so i wont be out of pocket to much so any advice on how much power difference there maybe is my system to small has anyone done it or are there bigger better value 12v 3 way fridges out there. Thanks in advance hope you all have enough info be grateful for your help Cheers

Buy normal 230 or 110V fridge. Connect to inverter. Inverter switch connect with relay to fridge thermostat . Fridge will turn on inverter when required. You will get best efficiency for lowest price. Alternative solution is inverter with eco mode but they are not always compatible with some fridges ...

 

[Ped]

In 2020 its generally cheaper to produce than to conserve.

 

[Dzl]

In 2020 its generally cheaper to produce than to conserve.

Generally speaking, I think you are mostly right.
Given limited space, most people in this subforum (vehicle mounted systems) will probably need to maximize both to a degree.

Buy normal 230 or 110V fridge. Connect to inverter. Inverter switch connect with relay to fridge thermostat . Fridge will turn on inverter when required. You will get best efficiency for lowest price. Alternative solution is inverter with eco mode but they are not always compatible with some fridges ...

This is a viable option worth considering but its not really the:

Best efficiency for the lowest price

Its a compromise between lowest price and highest efficiency

• A cheap dorm fridge will be somewhat cheaper (save money not buying a dedicated inveter + relay)
• A DC compressor fridge will be somewhat more efficient (no inverter conversion losses)

Still its a viable option, especially if you happen to have an extra inverter lying around. The biggest improvement I've seen for dorm fridge efficiency is adding extra insulation on the back and sides. Combine that, with your inverter trick, and you'd probably have a pretty cheap, pretty efficient little setup.

 

[Sgt Raven]

Generally speaking, I think you are mostly right.
Given limited space, most people in this subforum (vehicle mounted systems) will probably need to maximize both to a degree.



This is a viable option worth considering but its not really the:

Its a compromise between lowest price and highest efficiency

• A cheap dorm fridge will be somewhat cheaper (save money not buying a dedicated inveter + relay)
• A DC compressor fridge will be somewhat more efficient (no inverter conversion losses)

Still its a viable option, especially if you happen to have an extra inverter lying around. The biggest improvement I've seen for dorm fridge efficiency is adding extra insulation on the back and sides. Combine that, with your inverter trick, and you'd probably have a pretty cheap, pretty efficient little setup.

Exactly, on a Vehicle mounted system, you have to factor in the space to mount panels. Without overhanging the sides/ends, I have 49" X 90" on my roof. Also I'm limited to <45V panels with my DC-DC/MPPT. So far with those parameters, the best I've found is a LG 370W 40V panel at 40" X 67"s.

 

[Ped]

Space is limiting but were generally talking about 20-40w of solar area discrepancies an inverter consumes. Less than 10% most vehicles space capabilities. If you're that up against the wall in headroom of solar production youre going to need alternative power sources either way.

 

[Dzl]

Exactly, on a Vehicle mounted system, you have to factor in the space to mount panels. Without overhanging the sides/ends, I have 49" X 90" on my roof. Also I'm limited to <45V panels with my DC-DC/MPPT. So far with those parameters, the best I've found is a LG 370W 40V panel at 40" X 67"s.

When designing small vehicle systems (or marine systems) I think it makes sense to think in terms of costs not cost.

• Cost in $$$
• Cost in roof space
• Cost in weight
• Cost in autonomy
• Cost in xyz

Almost every design decision has a tradeoff, efficiency (often) has a cost in $$$ but is often 'free' in terms of these other costs.