Checking our refrigerator’s insulation
Sadly, some friends of ours are currently dealing with some refrigeration woes. In trying to fix their problem, I saw that, among other things, they invested some time and money to improve the insulation of their top-loading refrigeration box. I don’t believe that their efforts completely solved the problem, but reading about the process inspired me to do a little experiment to see how well insulated our front-loading fridge actually is.
As refrigeration is generally the highest consumer of electricity on a sailboat, I know that some people routinely turn off their fridge overnight, knowing that the door won’t be opened. How much does the temperature change overnight when doing this? I wanted to see.
Not having an external temperature display for our fridge (I was smart enough to install one on ZTC), each of the past two days I took temperature measurements when the fridge was at its coldest (when the door hadn’t been opened for some time), and then also in the morning after turning off the compressor overnight. Note that I didn’t take the first measurement right before I turned off the compressor because I didn’t want to open the door and let the accumulated cold air escape.
Before: 5? C
After: 7? C
The first day I tried the experiment it seemed to me that the temperature didn’t change at all. The images below are from last night where you can see that the temperature went up 2? without the compressor running.
If you’re considering turning off your fridge overnight, I think it would be worthwhile conducting this experiment yourself.
Note: There appears to be a bit more condensation in the second photo, but the truth is that both times I removed the thermometer from the fridge it was covered in frost. I had to wipe it off and quickly take the photo before the temperature started to rise. Apparently I just didn’t do quite as good a job wiping it off in the second shot. As I said, an external temperature display would make this process so much easier!
I was shocked at the top loader frig on Kens Boat. I thought it would be more like an RV. It was efficient and effective. It passed the repeated beer tests. And no one had spoiled food. Yet it was clumsy using it.
Top loaders are reportedly better for keeping the cold air from escaping, but they are much more difficult to get things out of. It’s a trade off. We’re pretty happy with the fridge on this boat.
Why not just adjust the freezer thermostat setting up slightly for the same result? The compressor only runs when it needs to.
Exactly David. That’s what T-stats do. Also, top loaders hold temp better when open because cold air sinks. I agree they tend to be more difficult to load/unload. However, we were on a Salina 48 a couple years ago that had an awesome top loader. Wish I could remember what kind it was.
If you see the starting temperature (pic 1), you’ll see that it is 5?. I don’t want it any higher than that. The issue is not the thermostat, or the compressor, it’s the insulation.
I see your point now Mike. I misread your post. My bad.
No worries. I welcome the comments.
FYI bought a wireless thermometer at Walmart for $12. just placed the sender in the fridge. Works great on our topload and has min/max feature
Yes, those things are not pricy at all.
For your St. lucia file
http://www.cruisersforum.com/forums/f108/somtimes-its-better-not-to-rescue-a-boat-166488.html?utm_source=feedburner&utm_medium=email&utm_campaign=Feed%3A+cruisersforumnews+%28Cruisers+Forum+-+Emails%29
Wow!
Mike – we have a Technautics Cool Blue system (holding plate) in our top loading fridge. The box is insulated with 8-12″ of foam insulation, and the lids are pre-made. We also have a freezer, but that is a separate installation. Insulation is one area that loses heat, but another easy one is the gasket. Try the “dollar bill” test. This is where you insert a US dollar bill, close the lid and try to pull out the bill. Work the bill all around the gasket to see if there are any bad spots. I use a SCAD Sensistat Energy Controller and this gives me great visibility and control over the temperature. I prefer degrees Fahrenheit over Celsius for the apparent increased precision. The fridge hovers between 28F and 36F. Inside are two sliding baskets, 4 plastic baskets on the bottom, an aluminum drink container and 3 computer muffin fans for “cold” circulation. When defrosting (about every 6 weeks), Diane shuts down the fridge at about 2pm in the afternoon, cleans it out at 7am the next morning, and then restarts it 10 minutes later. The temperature then is about 40F, not much more. You need to install a temperature gauge like you did on ZTC.
I am very aware of the importance of the gaskets in keeping the cold air in. After failing the dollar bill test, we ended up sourcing new ones for the leopard’s fridge and freezer (front loading) and I replaced them both. I’m pretty happy with how our fridge is working these days. It functions much better than the one on the leopard ever did.
You have to be mindful about the safe temperature for food. In household fridges it is recommended to be 0-4C or 35-40F. I suspect our front opening fridge is 4 about the middle, and colder at the bottom, and definitely a little warmer at the top. I position food accordingly. We have a separate top opening freezer unit which is a little power hungry and as both units are only 12 volt we do turn off the freezer at night when we are short of power after a number of cloudy days.
That was exactly my purpose in doing this experiment, to see how high the temp would rise. I know people turn off their fridges at night without being aware of just how much the inside temp changes.