A while back I wrote about refrigeration problems and that what seems like a refrigeration problem may actually be a battery problem.
Cruisers Jim and Barbara Shell left a comment on that post that one of the simplest things you can do to know how the refrigerator is doing is to have a thermometer in it. But instead of one of the ones marketed as a “refrigerator thermometer” where you have to open the refrigerator to check the temp, they recommended one with a wireless remote sensor, typically called an indoor/outdoor thermometer.
Another duh moment for me. We’ve had a thermometer with a wireless remote sensor for some time — I’d just never thought to use it in the refrig. And on Que Tal, we’d used an indoor/outdoor thermometer with a wired remote sensor (wireless weren’t reliable when I bought it 10 years ago) to monitor the temperature in the battery compartment.
Before writing about it here, I did some testing with the wireless one to make sure it’d work in the refrigerator. Yep, it’s perfect! Mine even works in a typical home refrigerator where the signal has to pass through the metal “box.”
A couple of notes and then links to thermometers I like. First, it seems that humidity sensors often give incorrect readings unless you buy very high end units. Since this typically adds $10 or more to the cost, why bother? The ones with barometers also tend to get poor marks unless you buy an expensive one.
Second, if you use lithium batteries in both the base unit and the remote sensor, you should get at least a year before having to change batteries. I’ve only changed the batteries once in using mine over four years.
The “indoor” temp on the display means the temp right where the base unit is. If you mount it in direct sunlight, you can get some amazing readings if you’re in a hot climate. Ours was on teak (which soaked up heat) in the companionway (full sun) and I once saw it hit 128° F.! “Outdoor” refers to wherever you put the remote unit.
Some indoor/outdoor thermometers have an “ice alert” that flashes or beeps. The ones that flash (using an LED) aren’t bad, but you really don’t want one that beeps if you’re going to use it in the refrigerator or freezer, as the ice alert will start sounding at about 38° F — in other words, constantly if the refrigerator is working properly. Not only it is annoying but it eats through batteries!
Command Strips work really well to mount both the base unit and remote sensor (don’t put it where it could end up sitting in water or where you’re likely to knock it loose). If you’re not familiar with these, read my article on them — I love them for securely mounting all sorts of things without making holes!
Finally, some units can have multiple remote sensors (sold separately, of course). So you could have separate ones for the refrigerator and freezer, or in the refrigerator and battery compartment, in addition to the “inside” temperature being the temperature wherever you mount the base unit.
Of course, the unit that I have is now “out of stock” — since it may become available again, you can view it here (Amazon US only). Should you get this one, be sure to read the review I left on Amazon to learn a few things about how it works that aren’t mentioned in the user’s guide.
So my alternate recommendations are (basic links are to Amazon US, Amazon Canada/UK shown where available) —
- Acu-Rite Wireless Indoor/Outdoor Thermometer. Simple basic unit that shows indoor and outdoor only — no additional info or extra remotes. Older reviews show problems with battery life but newer ones are much better. I’ve had two Acu-Rite units (the one shown in the photo at the top of this article and the wired one we had on Que Tal) and both have worked well, with good battery life. Available from Amazon.
- Oregon Scientific Indoor/Outdoor Thermometer (Amazon). This is a good choice if you need to monitor more than one remote location. The basic unit comes with one remote sensor, but you can one or two more and monitor up to three remote locations. My biggest gripe with this unit is that additional remotes cost almost as the base unit and remote, but it does work well. (Update: This products appears to no longer be available. This is a similar unit.
A note about units such as this one that include an atomic clock, which is great if you want really accurate time on the boat. If you’re outside the continental US, see the “official” coverage map from the National Institute of Standards and Technology for the atomic clock radio signal below (although I’ve heard that you can get the signal in most of Alaska and Hawaii, which are outside the coverage map) — there is no way to manually set an atomic clock, so if you’re outside the coverage area, the clock won’t work.
In addition to Amazon, you can buy similar units at many big box stores, including Walmart, and at Radio Shack. But be sure to check recent online reviews (discount any over a year old if newer ones show a different level of satisfaction).
Mount the base unit where you’ll see it easily — for us, it was right above the battery monitor, which we also checked several times a day. And then note what the typical temperature is (see my article, Making Your Mark) so that you’ll see not only big problems but also slow, creeping ones.
Keeping an eye on the temperature means that you may catch and solve a problem before you lose a refrigerator full of food. As Jim and Barbara related, “In 2006 while out cruising, we noticed a rising temperature and were able to replace the blown fuse before any thawing occurred.”