Some ways to run a fridge on solar energy

[acdoctor]

My 10 cf 120 volt fridge in the RV developed a leak in the evaporator.
I replaced it with a 12 volt inverter model. It uses about 0.5 kw per day. It also allows me to turn off the inverter. Now I only turn the growatt on when I need it.
New fridge cost about 3 times the price of a 120 volt model but I can only fit 2 kw of panels on the roof.

 

[Checkthisout]

My 10 cf 120 volt fridge in the RV developed a leak in the evaporator.
I replaced it with a 12 volt inverter model. It uses about 0.5 kw per day. It also allows me to turn off the inverter. Now I only turn the growatt on when I need it.
New fridge cost about 3 times the price of a 120 volt model but I can only fit 2 kw of panels on the roof.

Which one did you get and does it auto defrost etc?

Lots of RV's are just going to residential fridges. I assume they can be either ac or dc

You can run them while driving (not that we didn't run the propane one while driving), they cost less, are way cheaper to install, have more room and auto defrost. Auto defrost is important for efficiency and convenience..at least that's how I feel.

 

[Tomthumb62]

Which one did you get and does it auto defrost etc?

Lots of RV's are just going to residential fridges. I assume they can be either ac or dc

You can run them while driving (not that we didn't run the propane one while driving), they cost less, are way cheaper to install, have more room and auto defrost. Auto defrost is important for efficiency and convenience..at least that's how I feel.

Yes we went with an AC fridge. Compressor uses 800W for 1-2 seconds on startup and 65-75W typical the rest of the time.

The thing many people overlook is the idle draw of their inverter. Some pull 45-100W. Our 2000W 12v Renogy inverter uses 24W. I'm looking at an AIMS 1500W inverter-charger that uses 11W idle and has an eco idle switch that only uses 8W.

24W constant draw is 576Wh a day! Our tiny trailer solar system struggles to keep up with powering the fridge, inverter and other stuff like lights, pump. So only using 8W is 192Wh a day, which is 3x less! Only problem is having to sell the Renogy inverter to justify the $$$ of the AIMS device.

 

[acdoctor]

Which one did you get and does it auto defrost etc?

Lots of RV's are just going to residential fridges. I assume they can be either ac or dc

You can run them while driving (not that we didn't run the propane one while driving), they cost less, are way cheaper to install, have more room and auto defrost. Auto defrost is important for efficiency and convenience..at least that's how I feel.

It’s a Everchill from Recpro. It does have 120 watt automatic defrost. Freezer seems to max out at 0 deg F. Just like any fridge it draws higher watts while cooling down from room temperature.

 

[Checkthisout]

Yes we went with an AC fridge. Compressor uses 800W for 1-2 seconds on startup and 65-75W typical the rest of the time.

The thing many people overlook is the idle draw of their inverter. Some pull 45-100W. Our 2000W 12v Renogy inverter uses 24W. I'm looking at an AIMS 1500W inverter-charger that uses 11W idle and has an eco idle switch that only uses 8W.

24W constant draw is 576Wh a day! Our tiny trailer solar system struggles to keep up with powering the fridge, inverter and other stuff like lights, pump. So only using 8W is 192Wh a day, which is 3x less! Only problem is having to sell the Renogy inverter to justify the $$$ of the AIMS device.

If you already have a converter (rv battery charger) just get a normal aims 2000 watt psw inverter.

The aims inverter chargers are kinda spendy and I don't believe they offer any special features like victron multipluses such as surge using both gen and battery juice etc.

You might also just look at an even more tiny inverter strictly for the fridge.

Have you done any advanced electrical investigation and seen if your ac fridge actually has a DC compressor and what voltage it requires?

 

[Tomthumb62]

If you already have a converter (rv battery charger) just get a normal aims 2000 watt psw inverter.

Might just do that. Except we need a better charging system for our AGM batteries. Current method is very bulky and my wife doesn't like tripping over large AC chargers, lol.

The aims inverter chargers are kinda spendy and I don't believe they offer any special features like victron multipluses such as surge using both gen and battery juice etc.

Good to know. Wasn't really planning on it, not quite in the budget for an RV. Getting a little obsessed with this stuff for how little we use it!

You might also just look at an even more tiny inverter strictly for the fridge.

Not a bad idea either. A 700W inverter would suffice, since the fridge only pulls 800W for 1-2 seconds. When it's first plugged in, it pulls 500-600W for about 5-10 seconds, then shuts off.

Have you done any advanced electrical investigation and seen if your ac fridge actually has a DC compressor and what voltage it requires?

No, I haven't. You saying it might be possible to directly wire our fridge's compressor to the battery (fused of course)? Or perhaps with some small voltage converter? That would be awesome!

 

[Checkthisout]

Might just do that. Except we need a better charging system for our AGM batteries. Current method is very bulky and my wife doesn't like tripping over large AC chargers, lol.

Good to know. Wasn't really planning on it, not quite in the budget for an RV. Getting a little obsessed with this stuff for how little we use it!

Not a bad idea either. A 700W inverter would suffice, since the fridge only pulls 800W for 1-2 seconds. When it's first plugged in, it pulls 500-600W for about 5-10 seconds, then shuts off.

No, I haven't. You saying it might be possible to directly wire our fridge's compressor to the battery (fused of course)? Or perhaps with some small voltage converter? That would be awesome!

Maybe. Or you could use the thermostat (if manual) to turn the inverter on and off. That sort of thing. When fridge calls for cold, inverter switches on etc.

That requires tinkering though.

 

[Tomthumb62]

Maybe. Or you could use the thermostat (if manual) to turn the inverter on and off. That sort of thing. When fridge calls for cold, inverter switches on etc.

That requires tinkering though.

Thanks a good idea. Would require opening up the inverter to wire that in. Have to check to see if I'm out of warranty yet lol.

Only issue with that is when the fridge is first plugged in, it always draws about 600W for about 10 seconds. If that happened several times a day, it might negate the savings of just having the inverter run 24/7. I think a smaller inverter (or at least with a lower idle draw) is the best bet overall.

 

[sunsurfer]

Indeed.

But do you really want to be one of the first folks to put a butane-based refrigerator in a kitchen near a stove?

I'd be happy with it for an outdoor fridge but I'm not all warm and fuzzy thinking about using one in a kitchen.

legally in the USA, I think it is just an ounce or so max allowed. I prefer hydrocarbon refrigerants. They are super efficient and move oil very well through the system. Every custom system I have built has been either propane(R290) or butane(R600a). They work very well. If you design it right, you can go with very small charges. Not enough to do any thing with a leak.

They have been used all over the world for many years without problems. The USA like usual is behind. Our problem is the big lobby forcing us into DOW chemical patented refrigerants that we all pay for at a premium $$$$.

 

[efficientPV]

When looking up fridges, I have noticed several comments that say the R600 refrigerators are not to be used in garages. Lawyers are over sensitive to some car driving into them.

 

[alfsauve]

When looking up fridges, I have noticed several comments that say the R600 refrigerators are not to be used in garages. Lawyers are over sensitive to some car driving into them.

The manufacturers are concerned about the temperatures and dirt issues. Garages tend not to have HVAC and leantoward extreme cold during the winter and heat during the summer. I'm in GA and keep my garage door closed except to enter/exit. I've never had a problem.

 

[Checkthisout]

Has anybody bought a DC compressor and swapped it into their standard fridge?

 

[CoolWill]

DC fridges are stupid expensive and very rare compared to standard AC household units. For the price difference it would seem that taking the hit in efficiency using an inverter for a regular fridge is worth it. If you're a prepper type, it also makes sense to use readily available equipment in case the SHTF. DC refrigerators are just flashy toys for people with money to burn.

 

[Checkthisout]

DC fridges are stupid expensive and very rare compared to standard AC household units. For the price difference it would seem that taking the hit in efficiency using an inverter for a regular fridge is worth it. If you're a prepper type, it also makes sense to use readily available equipment in case the SHTF. DC refrigerators are just flashy toys for people with money to burn.

I'm proposing taking an old fridge or free fridge off craigslist and swapping in this:

If dc fridges are $2000.00 or whatever, why not get the size fridge you like and pop this puppy in there?

Cooling capacity-wise, do DC compressors draw less juice than their ac counterparts and if so, how much? Also, let's ignore inverter draw and just examine the fridges themselves when answering this question.

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[Nevadablue]

So, the maximum that compressor can handle is a bit over 5 cubic feet. It costs more than half what a 21 cubic foot refrigerator costs. The real fridge runs on 50 watts or so. If you don’t want an inverter, I suppose that may be a reasonable choice, but for most people, it doesn’t seem to make sense. My cheap Reliable inverter is rated at 30 watts idle. I am not sure what it pulls when working. But, it sure seems more reasonable to have a real fridge.

 

[Checkthisout]

So, the maximum that compressor can handle is a bit over 5 cubic feet. It costs more than half what a 21 cubic foot refrigerator costs. The real fridge runs on 50 watts or so. If you don’t want an inverter, I suppose that may be a reasonable choice, but for most people, it doesn’t seem to make sense. My cheap Reliable inverter is rated at 30 watts idle. I am not sure what it pulls when working. But, it sure seems more reasonable to have a real fridge.

Ok. What size compressor is needed? Just engaging in fat-chewing here.

My 3k, 6k surge inverter runs 12 watts idle. My fridge shows 120 watt draw via its power measuring smart switch but a 78 watt draw with power factor correction.

Would I save about 50 watts if the compressor ran on straight dc?

 

[Nevadablue]

I just looked at the spec on the compressor. I didn’t quickly find the current draw, but the size was scaled for ‘small’. Nothing wrong with that, but the cost/benefit doesn’t add up IMO.

Here is the spec sheet for that compressor. It appears that it pulls from 50 to over 100 watts. For 5 cubic feet.

 

[Checkthisout]

So, the maximum that compressor can handle is a bit over 5 cubic feet. It costs more than half what a 21 cubic foot refrigerator costs. The real fridge runs on 50 watts or so. If you don’t want an inverter, I suppose that may be a reasonable choice, but for most people, it doesn’t seem to make sense. My cheap Reliable inverter is rated at 30 watts idle. I am not sure what it pulls when working. But, it sure seems more reasonable to have a real fridge.

Saya it does 647 Btuh, that translates to about 14 cubic feet.

 

[Nevadablue]

The spec says ‘up to 150 liters of box’ so that is 5.25 or so cubic feet.

 

[Checkthisout]

I just looked at the spec on the compressor. I didn’t quickly find the current draw, but the size was scaled for ‘small’. Nothing wrong with that, but the cost/benefit doesn’t add up IMO.

Here is the spec sheet for that compressor. It appears that it pulls from 50 to over 100 watts. For 5 cubic feet.

View attachment 116845

Where are you coming up with 5 cubic feet?

The calcs I ran say 837 btuh for 16 cubic feet. This compressor does ~640.