"My question is with fridges like this is if you adjust the freezer temperature to lower like that, won't that lower the temperature of the fridge too to a temperature too low? "

"Don't you really need a fridge with dual compressors or dual evaporators to really adjust the temperatures of the fridge and freezer separately and precisely without one affecting the other?"

The answer to both questions is NO!!!!!!

The way (at least of a well designed) single compressor and single evaporator system works is a follows:

There are temperature sensors, (Thermistors) in both the fridge and freezer compartments.

The fridge sensor, upon seeing a higher that set temperature, will cause a flap to open between the freezer and fridge compartments and also turn on a fan that blows the air from the freezer compartment into the fridge compartment. Once it sees "set temp" in the fridge it closes down that flap and turns the fan off.

If it took enough cold air from the freezer, such that the freezer is now above it's "set temperature", then the system starts up the compressor to cool down the freezer.

This is your "Basic, No frills Fridge" and how they work.
Since both the freezer and the fridge have their own temp sensors either the freezer compartment or the fridge compartment can be set at their own "Independent temps".

Such a system can recover from rising temps in the fridge (caused by repeated opening of the fridge door), faster than a dual compressor or dual evaporator system, as it opens the flap I mentioned and really cranks up the fan between the fridge & freezer compartments. A dual compressor system will have to crank up the compressor in the fridge section and that takes longer to cool the fridge, than just "Dumping frozen air into the fridge from the freezer"

As this post is long enough (LOL) I will make another post about how the fancier stuff, (Like my Jenn-air) works.

"To me at least", this dual compressor stuff is just "Sales Hype" trying to convince us why we should pay outrageous prices for fridges, (Not to mention the price of parts/service) to keep them going!

Gary

This post was edited by dodge59 on Mon, Jul 7, 14 at 10:21

There are advantages to dual compressor and evaporator fridges. The fridge I ended up getting has dual evaporators. It is not the main reason I bought the fridge, but it is a nice bonus. Fresh food does last longer. So shoot me. I don't really take advantage of it like some people would, because I try to match my shopping to my consumption so that I don't have stuff sitting in my fridge for months. Some people want the redundancy of 2 compressors, or they want 2 evaporators without the added valving complexity needed to make them work with one compressor, they like the look of Sub-Zero and they can afford the price premium for it. Nothing wrong with that. Just because you don't find a feature important doesn't mean you need to bash something that is important to some other people as a "sales gimmick".

Note the "To Me at Least".

To other folks it may not be, but it will always be to me.

The (again to me) "Sales Hype" about the dual evaporator or dual compressor systems is it keeps the 2 compartments (fridge and freezer) separated from each other. They like to mention "Off Taste Ice cubes" or some such ~~~~~~~whatever!

Recall the freezer air is blown into the fridge not the other way around (Fridge air blown into the freezer), and in my 72 years here on terra firma, and always having single compressor/single evaporator fridges, I have yet to encounter an "Off taste Ice cube", but then I may not have the "Golden Palate" that some folks do?

As far as keeping food fresher longer, much of that has to do with the better insulation, better door seals, and probably the most important, being able to keep the fridge temp much more stable than older models did, and also the recovery time in getting the fridge back down to set temp after the door is opened.

Gary

OK, back to your original question, marvelousmarvin.
Consumer reports tested many SxS fridges for "temperature Performance".

Consumer Reports"
"Temperature performance:
This combines results of tests measuring the accuracy of initial temperature settings along with how well a model 1) kept optimum temperatures in the refrigerator and freezer at the same time; 2) kept temperatures even throughout each compartment; 3) kept temperatures constant despite changes in room temperatures; and 4) maintained set temperatures even with very high room temperatures."

Here are 4 Fridges that received "Excellent Ratings" by using the "Criteria Above".

Kitchenaid KitchenAid KSF26C6X[YY]

DCS RX215PJX1

Fagor FQ9925XUS

Samsung RSG257AA[WP

Now as far as dual evaporators go, I posted, maybe a couple years ago, that I thought if was a "Kewl" and ingenious idea, alto as I mentioned not a must have for me, as I have no complaints in my many years of experience with single compressor/single evaporator fridges~~~~~~But in the interest of "Full Disclosure", here is what "some experts say" about the Dual Evaporator Fridges, and I must admit that most of the fridges with excellent temperature performance were Dual evaporator fridges!

"Dual evaporators. Air freshness claims have become a noisy part of refrigerator marketing. You'll hear about charcoal filters, ion air purifiers, ethylene absorption packets, and other devices that promise to keep your food fresh. These claims are difficult to measure, but we can tell you one thing that definitely works: dual evaporators, which we've found maintain higher humidity levels in the fresh food section, while also keeping freezer odors from finding their way into the refrigerator.
Models with this feature:
Samsung RF266AE[WP], $1,700 (CR Best Buy).
KitchenAid KSF26C6X[YY], $1,950."

Another thing I found in my studies is that the fridges with the digital controls and readouts of the temperatures have the best Fridge Temp Performance.

Other things that the experts "Deem Important"
The ability to set different temperatures for the different compartments in the fridge~~~~Chrisper, Meat Compartment~~~~etc.

That's the one thing I really like about my 2006 JA Fridge.
I can set the meat compartment for 31 F, the veggie/fruit bin @ 34 F and the main fridge at 37 F, and they all have digital readouts.

Some of the newer fridges have that, (the ability to set different compartments in the fridge at different temps), and it fact, one very expensive fridge gets "dinged" because they don't offer that!
Anyway, probably all you ever wanted to know about Fridges and "Then Some"~~~ya thinks?

Yeah I agree with you nobody NEEDS dual evaporators. The simple damper system works fine. Heck, the basic system in most top mounts where there's only ONE thermostat in the fridge and no damper at all works fine! And yeah you don't need dual evaporators to get tasteless ice cubes. But in my experience, no matter the fridge, you WILL get off-tasting ice cubes if you let them sit in there for too long. I ended up disabling the ice maker on mine because I just didn't go through ice fast enough, and there was no way to adjust it to make smaller batches.

Another follow up question:

If the freezer temp is too high and you have to adjust it with the thermostat to get it low enough, does this mean that this putting a strain on the compressor and that it'll break down sooner vs another fridge where you don't need to do that?

Are you talking about a brand new Fridge, Marvin?
One that has digital controls and readouts to display both temp settings and the actual temp,
or one where you have a knob with numbers like (1, 2, 3~~~~)

An older fridge, where you have to adjust the control to a lower setting than you used to, in order to get the freezer cool enough, may have seal leaks around the door, problems with the auto defrost, or possibly dirty condenser, and at the very least it would use more electricity than it should,, but as you mentioned, it is at the very least putting a strain on the compressor, and if it's one of the newer style compressors, (Linear or Variable Speed), then it is putting a strain on the circuit board that drives the compressor.

Gary

Marvelousmarvin, you're overthinking this! You won't significantly reduce the life of the compressor by adjusting the temperature in the fridge or freezer. Further, calibration can vary per unit. Just because Reviewed.com had to adjust the temperature, doesn't mean you will. I challenge you to find a refrigerator that has NO complaints online.