Amount of Power

Will the factory 80 wt solar panels provide enough power to operate the refrigerator without running down the batteries, assuming no additional power from the TV, no additional battery drain, and a 'normal' sunny day? To maybe make the question easier, how long would you estimate the refrigerator would stay operate and stay cold if the TV were parked and not connected to shore power? You would be correct in assuming that I was absent for the electricity unit in science class!

Hi, sorry I can't answer your question directly concerning solar power, but I can tell you that your fridge will run great on propane while not connected to shore power and not use much fuel. We don't have solar on the trailer, so hopefully someone else can respond to this question.

[Bill]

Scott -

The answer is No. The refrigerator draws about 120 watts from the 12-volt system. So if you have a single 80-watt panel, you are behind right from the start.

In addition, the refrigerator draws 120 watts continuously, 24 hours a day. Under the best of conditions (and "the best of conditions" is a rare occurrence), a panel produces 80 watts for only 4 or 5 hours a day.

The refrigerator will kill your battery in a hurry, and a solar panel will delay that death by only a small amount. Follow Brigitte and Steve's recommendaton, and use propane. A tank lasts a long long time.

Bill

I appreciate the info. I was more concerned with parking the TM when we spend the afternoon at a museum or some such diversion. It is pretty inconvenient to set up and change power, and as I learned from another thread the trailer needs to be set up when on propane to discipate heat. When set up I will always use alternate energy other than 12v.

The fridge will likely hold quite a bit of cold while parked for a few hours. What I do is run the fridge on 12 volts when towing. If I was going to stop for several hours I would unplug the TM from the TV and disconnect the TM batteries via the switch that I added.

Milk would certainly survive all day with no power to the fridge, but I am not sure about ice cream.

[Bill]

You have a good question, so let me elaborate a bit on the answers.

First, as I noted, a single 80-watt panel won't cut it. But there is no reason why you can't mount two 80-watt panels. If I recall correctly, RockyMtnRay actually mounted three panels on his TM, though one was smaller than 80 watts.

Second, if you are taking part in a "diversion" in the middle of the day, and if the panels are in full sun, then you can get full power from the panels. If you have a pair of panels, then they will run the refrig just fine.

Third, solar panels generate full power only during the hours when full sun strikes the panels at nearly a right angle. In other words, sun overhead. These hours are roughly 10 AM to 2 PM. In the earlier morning hours, or the later afternoon hours, the angle of the sun is too shallow, and panel output drops off drastically.

Fourth, solar panels do not generate any useful amount of power when the sky is overcast. Even thin clouds reduce the output very substantially.

Fifth, if a panel is shaded at all (tree branch, building shadow, etc), then its output drops to near zero. You'd think that if 10% of a panel is shaded, but the other 90% is still in the sun, then you would get 90% of the expected power output. Not so, for various technical reasons. What most people don't realize is that if even 5% of the panel is shaded, then output drops by about 95%. This means that when you begin your diversion, you have to park your TM in the sun - and you need to park it in a location that will remain in the sun for the next several hours.

Finally, I've seen the warnings about not running the refrig on propane when the TM is closed. I'm not sure I buy it. Think of it this way. The refrig mechanism uses a heat source to generate the cold for the box. There are three different heaters in the back of the refrig (propane, DC power, or AC power), and you choose which one you want to use at any given time. The manufacturer intends to make the refrig perform about the same regardless of which heat source you choose, so the three heaters all generate about the same amount of heat. [Notice I didn't say EXACTLY the same.] Regardless of which heat source you choose, you MUST get rid of the excess heat, and that is the purpose of the little fan. If you leave the fan off, the heat buildup may, in fact, scorch the stuff in the back of the refrig. But the propane heater isn't more likely to do it than either of the electric heaters. Conclusion? Even if you run the refrig on DC power, you still must turn on the little fan.

Your best bet might be to make sure that at the beginning of your diversion, the refrig is full of cold stuff, and the freezer portion has lots of frozen stuff (blue ice packs are great). Then power down your refrig during the diversion, and think of it as a cooler. Since it is acting as a cooler, it is important to park your TM in the shade. Direct sun, of course, will heat up the interior of the TM and cause the cooler to warm up faster.

Hope this helps.

Bill

Once a year I take my TM to work and leave from there. Since my TM will be sitting in the parking lot for the entire day, I can't count on the fridge to stay cold all by itself. So I pop it open and put the fridge on propane until I leave.

I suppose if it was only for 4 hours or less I would just turn it off with the external battery disconnect and unplug the TV. More that 4 hours and I would put it on propane. It doesn't take long to switch, but it is annoying to pop it open.

I just don't feel comfortable driving down California freeways in rush hour traffic on a Friday night with propane appliances running when there is an acceptable alternative that is only a modest amount of extra effort to use.

Do be aware that in some places you will have to turn the propane off before going through a tunnel. This seems to be mostly on the east coast and not the west coast.

One other thing to keep in mind. The two-way fridge my dad had would not cool properly if it was not close to level. I am not sure that applies to the TM fridge, but maybe somebody can let us know.

You're correct. That type of refer needs to be pretty level, or needs to be shaken as when it's being towed. There is no compressor to move the refrigerant as there is in a home refer, so for good circulation of the refrigerant, it needs to be close to level. Leveling the trailer should be enough to keep the refer working.

[Bill]

The refrig needs to be more-or-less level, but unlike refrigerators in the past, there is no need to obsess over it. The Dometic manuals, for example, say that "The vehicle needs to be leveled only so it is comfortable to live in (no noticeable sloping of floor or walls)." This is quite an improvement over units 20 years ago, when even a slight slope would decrease the cooling of the refrig, or even stop it. I remember my father failing to obsess over his RV refrig, and the effect that it had.

Bill