Large Solar Panels on a FWC

[Bwht4x4]

Wow, Bill I didn't know that a 3-way cooler uses the 12v or 110v to heat the gas in the system. I thought on 12v or 110v it was running an inefficient compressor. Based on this and the need to be level how does one drive down a hilly/mountainous road and still keep the refrig running?

 

[Kispiox]

Let me say that my opinion on refer efficiency is less than scientific. There are many models. Each of us also operate in different ambient temperature zones. My 3way is the larger Dometic that FWC is building into their Hawks. My experience is coastal Pacific Nortwest NoCA to SE Alaska. I have no desert 100 plus degree experience. When I first got my camper, I used DC when driving. I complained about the inability to freeze solid to a fellow camper and he said to travel with propane and that's what I have been doing ever since with great performance.

When I re-provision underway, I load up the freezer while on propane all the time. I experience virtually no difference with propane vs AC in terms of efficiency. However, my opinion is not based upon charting box temps vs. ambient temps or anything scientific. All I know is that with DC the pop cycles are mushy and almost falling off the stick and meat is not hard as a rock. With both AC and propane the unit appears to perform excellent and about the same. By same I mean frozen through quickly and hard as a rock. I have left Northern BC with the freezer full of frozen Salmon and enjoyed Salmon dinners once or twice a week for a couple of months while being on propane 85% of the time.

It would be interesting for a refrigeration expert to weigh in here. I would like to know more about the technical efficiencies of the three options. .

 

[billharr]

Wow, Bill I din't know that a 3-way cooler uses the 12v or 110v to heat the gas in the system. I thought on 12v or 110v it was running an inefficient compressor. Based on this and the need to be level how does one drive down a hilly/mountainous road and still keep the refrig running?

You get enough movement going down the road to prevent a vapor lock in the system. A vapor lock is what stops the gas from circulating if the unit is not level.

 

[Kispiox]

You do realize that a 3 way fridge (absorption cooling) needs to be level to work no mater if on propane, 12v or 110 volt. All are just heating the gas in the system.

Yea, I know that's what the directions say. This one is subjective on my part. However, I think that DC is less sensitive than propane. I find the check light will come on with propane when out of level while without moving the truck, the DC will operate. I am not talking severely out of level. My thought was that a flame is going straight up where as the heat element encapsulates? That is a question? This is purely a guess and I may be entirely wrong. I'll defer to an expert and would be most interested.

 

[pvstoy]

The gas inside the tubes, and when leaked out smells like ammonia, is heated that causes a rise and fall and in a nut shell creates the cooling inside. It can be boiled by AC, DC, or propane. If your unit is not level to the extremes front and back the gases inside the tube get trapped to one side and ends the flow cycle (vapor lock). Extreme results over time in this state you burn it up and it becomes a brick. The side to side is more forgiving because the tubes are round and the cycle will still happen but at a reduced rate. When traveling down the road as mentioned by Bill, the constant rocking keeps the cycle going.

As I read once, if you feel comfortable standing inside then most likely the refrigerator is ok.

Propane boils the gases the best and gets the best cold transfer to the inside. AC heating unit is second. The DC unit draws a whole lot of amps and lacks really boiling the gases. It will get you by while traveling. Running on DC while traveling takes away amps that is needed to recharge you house battery. If you run DC when your battery is low just so you know you are not getting all the amps to the house battery that is needed. If you have a battery separator than the starting battery is going to be taken care of first. Then you wonder why is my house battery always down?

If you are always changing from propane to DC remember it will take a while to get each system up to operational for cooling. It is not like a light switch that is instant on when flipped.

These are things I understand, feel free to correct me, we are all here to learn and understand how our stuff works.

 

[Lighthawk]

If you are always changing from propane to DC remember it will take a while to get each system up to operational for cooling. It is not like a light switch that is instant on when flipped.

That matches our experience. We watched our remote temp sensor climb up a few degrees when we switched from propane to DC, then it started to drop down. But, it was not very effective.

As mentioned, if you pre-cool with AC or propane before heading out, you can use DC while driving. I only tried it to see how my 110w solar panel would perform. I can imagine a few scenarios where that might be useful, but generally we're still using propane for our cooling.

 

[Kispiox]

Thank you pvstoy.... Good job!. Cooling with heat is a mystery for most, including myself. Every time I sit down to read and understand it I only momentarily retain the concept. Age may be a factor?

With regard to DC, I gleaned this from the Dometic site which pretty much sums it up for us layman.

["The DC source is not a true cooling source, rather it is designed for maintaining a temperature while traveling."]

 

[Otis]

"As I read once, if you feel comfortable standing inside then most likely the refrigerator is ok."

I was given similar advice as pvstoy mentioned:
If the camper is level enough to sleep comfortably the refrigerator will be level enough to work well.

This has proven true for us, in fact often times using the propane, it is hard to keep from freezing stuff in the frig.

 

[Kispiox]

Pvstoy, Bill and others...
A couple of statements to be certain am of the correct understanding and a question that others may also want to know the answer to..

I'm understanding from what you say that the issue of being out of level is the same for all three energy sources. The fact that my warning light did not come on when switching to DC was probably because I just didn't give it enough time. If I do not have these statements correct please advise.

Okay, now my question.. Understanding that I normally travel in the propane mode, when I am faced with needing to park someplace out of spec with respect to being level for a short duration, should I turn the refer off or let it just do its own thing? It sounds like you say that we can damage the unit? If just left alone out of level for say an hour, is it cycling itself off, or is damage being done?

Please advise.

 

[JHanson]

Kispiox, I can confirm what others have said: If the camper is level enough for you to sleep comfortably, the fridge will work fine - or at least as fine as I've ever seen a three-way fridge work. We're much, much happier with the two-way in ours, with a proper compressor. But we live in Arizona, where the fridge gets worked hard.

As to PV panels, we're delighted with our two Global Solar semi-rigid panels, which adhere directly to the roof and create no drag at all. Much lighter than rigid panels as well (and also more expensive of course). Two hundred watts total gives us all the power we need.

 

[Riverrunner]

Okay, now my question.. Understanding that I normally travel in the propane mode, when I am faced with needing to park someplace out of spec with respect to being level for a short duration, should I turn the refer off or let it just do its own thing? It sounds like you say that we can damage the unit? If just left alone out of level for say an hour, is it cycling itself off, or is damage being done?

Please advise.

This is my second camper with a 3way and I've never had an issue parking somewhere where I'm way out of level side to side. If I'm out and about and that is all I have to park, I park. I've parked like this for a few hours. I'm I doing damage? Maybe, but a nice level parking place is not always available and I don't worry about it. When I set up camp, that's different I will level the rig. Sometimes I think we tend to overthink things. My 2 cents...

 

[Kispiox]

I sent an inquiry to Dometic, and followed up with a tel/con. Some of you may think I am over-analyzing, but I am frequently leaving my caper on uneven off-road ground while hiking in to fish various rivers. I would just like to know if I am damaging the unit by leaving it on with no manual shut-down. According to what I found out,.. I am. For those of you who would like to know what I found out read on.

According to the gentleman that I talked to, there is a tolerance of 3 degrees fore and aft, and 6 degrees side to side that the unit is designed to operate within. (Now, if nothing else we know our sleeping tolerances, but I have a few too many sometimes and I have a tendency to overlook this tolerance) If outside that tolerance, a restriction will occur and the ammonia fluid solution will over-heat resulting in a crystallization blockage. Evidently this crystallization can happen immediately, but usually is something that is cumulative and layers each time. Also the unit does not shut itself off. If done consistently over a period of time, like Pvstoy says, then you end up with a brick instead of a cooling unit that will need replaced.

When I asked about DC operation, he said that he needs to formally state that the specification is the same for all three operations. Off the record, he indicated there was not as much heat in DC mode and therefore the crystallization formation would not be as pronounced. However, in the out of level condition the free flow of the ammonia coolant exchange from liquid to gas is still not present so neither is the ability to cool. So, no better in DC mode and best to turn it off.

So, net of it is,... If you are going to consistently be parking on ground out of this specification, you need to manually shut down your refer, otherwise over time you have problems and it's cooling capacity will degrade. With this decrease in cooling capacity an increase in energy would be required, thus less efficiency.

This is my understanding of my conversation. Possibly I misunderstood. It is also possible that the individual that I talked to didn't really know, but it sounded good to me. So,... Shut it down if your sleep angle is exceeded, it won't turn itself off.

 

[jha6av8r]

The reason you stated from your call to the manufacturer was why we went with a 2-way compressor fridge. I thought it was easier to deall with battery charging needs than it was to deal with level and regulating temperature.

 

[Bwht4x4]

Very interesting info and for me to go with a 2-way refrig and solar is even more of a no-brainer! I'd stress out way to much about the 3% thing and probably wouldn't sleep.

 

[MarkBC]

The reason you stated from your call to the manufacturer was why we went with a 2-way compressor fridge. I thought it was easier to deal with battery charging needs than it was to deal with level and regulating temperature.

Which brings us back to the actual topic of this thread -- "Large solar panels...".

There are long and vigorous threads already that include the 3-way-vs-compressor fridge topic.

 

[Bwht4x4]

Thanks Mark for getting this topic back to the point of large solar panels. I think I'm about sold on the 160 watt panel and a 15 amp Morningstar MPPT controller. This should power whatever 2 way refrig I buy and charge my batteries. My main concern was needing more solar wattage due to sitting in one spot for weeks at a time in the early fall to winter on a hunting trip. I think the 160 watt panel should do fine with this scenario. In the colder weather I could likely get by with turning the refrig off and putting everything back on ice since I generally have a couple of 150 quart ice chests with a few hundred pounds of ice on hand. This would save a ton of power, but means I have to go in and out of the camper to get food. Not that big of a deal!

 

[Kispiox]

Please accept my apologies. It didn't dawn on me that you guys were sizing your solar to run DC refrigeration, yea load it up. Probably can't get enough solar, batteries too. This old man isn't as experienced in the ways of the Internet as you young turks. You have nothing to learn from me. Sincerely, Sorry again. I'm out,.. get back to it.

 

[craig333]

Not to worry, we're pretty tolerant about threads going off and "wandering the west"

 

[Kispiox]

Thanks Mark for getting this topic back to the point of large solar panels. I think I'm about sold on the 160 watt panel and a 15 amp Morningstar MPPT controller. This should power whatever 2 way refrig I buy and charge my batteries. My main concern was needing more solar wattage due to sitting in one spot for weeks at a time in the early fall to winter on a hunting trip. I think the 160 watt panel should do fine with this scenario. In the colder weather I could likely get by with turning the refrig off and putting everything back on ice since I generally have a couple of 150 quart ice chests with a few hundred pounds of ice on hand. This would save a ton of power, but means I have to go in and out of the camper to get food. Not that big of a deal!

First, Craig333, thank you! You are a gentleman.

Second, w/re to the above Bwh4X4 quote.... In "colder weather" and even moderate conditions above and a shade below freezing, every storage compartment with an adjacent exterior surface becomes a refrigerator and is perfect for drinks, dairy, produce, yada, yada. They even stay cool during a slightly warm stint for a few hours mid day. Also, what I term the "root cellar" accessed from the turn the buckle doors, in real cold weather is a freezer. Be careful what you put in there if you don't want it frozen. Not to worry, you don't need to go outside. Also, when calculating your DC refer draw for cold conditions it will be reduced significantly because the demand won't be there. You won't need to turn it off because in "colder weather", it will not cycle itself on... very much. So adjust your demand math calculation with that in mind. And., you may want to consider not sizing your solar capacity for the extreme trip, but rather the average trip. Why? Because batteries like to be cycled, so for your average trips they won't be and that will shorten their life span. Solar capacity is one thing that bigger is not better. FWC does a good job of sizing and engineering their systems. Maybe I'm off topic again? Just trying to help. Okay I'm really gone now.

 

[pvstoy]

[SIZE=10.5pt]Even when it is that cold the demand may not be high for a DC refrigerator to cycle on and off, but if you need the dc to run the heater there is more demand on the system. [/SIZE]

[SIZE=10.5pt]I'm thinking that where you live (or traveling), time of year of available sun duration and what demands you have on the dc system is what it comes down to. Would you design for the worst case scenario, or you pick something in the middle and know that in the winter with short rate of return on high demands you may not get by without running the truck or bring a supplemental generator?[/SIZE]

[SIZE=10.5pt]So “size matters” and larger panels sounds like a better return on the worst case conditions. I suppose when and where you plan to take trips govern how much panel you need. Person in the pacific north west needs more panel watts than a person in Phoenix. I would like to do solar at some point but in the meantime all these post are great to get designs working in my head.[/SIZE]