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It can really save money. My 21 year old 210/85L cool/freeze Bosch fridge failed, and it used 270 kWh/a (measured with an energy meter). And that one was for its time very efficient, 6 cm think walls of the cooling section. It needed one electronic repair on those 21 years. The replacement Liebherr, slightly larger inside, saves about 130 kWh/a . I fully expect it to last 20 years.

Depending on your electricity price, it might not be a good idea to keep an old fridge running.

Mat Nieuwenhoven

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What is kWh/a? Is that per year? The marginal cost of 130 kWh to me is ha rd to estimate as I'm on ToU metering so it varies from $0.08 per kWh to $0 .33 per kWh. The lower bound for the electricity savings would be $10.40 p er year. That's not very much. An average cost considering the time durat ion of the peak charges would be about twice that amount.

If I could find a reliable timing device I would have the fridge not run du ring the expensive peak times. The longest peak time is 4 hours and I full y expect the temperature to not increase significantly in that time. When

ld rise a lesser amount given the very good insulation they now have.

kWh/a is per year (annum), sorry. If you have an energy meter, measure your old fridge. I measured during two weeks in spring and again in autumn to estimate year use. A 30 years old fridge probably uses a lot of energy. I am on a constant price of 0.21eurocent (1 year contract), and the savings on electricity won't quite recoup the investment in the new fridge. But it had to be replaced anyway, and who knows what the price will do in the future, with ever more electirc cars.

Mat Nieuwenhoven

Ok, so I guessed right. So far my fridge is working ok. It used to keep t

C). Lately the fridge is warmer than 45 and my milk goes bad faster that I 'd like. This might be ice blocking air flow from the freezer to the fridg e or something. They use flaps to control the difference between the two c ompartments. I need to remove some covers and check it out. I expect it's not mice or the cats haven't been doing their jobs and they are all about patrolling for mice.

A new fridge won't help me debug logic either.

Your idea of leaving the fridge compressor off for 4 hours at a time should really be tested by logging the internal temperature during the 4 hour period. I'm a little bit skeptical of leaving a kitchen fridge turned off for that long, especially during the part of the day when people will be opening it. It might be a reasonable approach for a chest freezer that's rarely opened.

No, hot coffee does it for me :-)

Mat Nieuwenhoven

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?C). Lately the fridge is warmer than 45 and my milk goes bad faster that I'd like. This might be ice blocking air flow from the freezer to the frid ge or something. They use flaps to control the difference between the two c ompartments. I need to remove some covers and check it out. I expect it's n ot mice or the cats haven't been doing their jobs and they are all about pa trolling for mice.

How does your refrigerator control the temperatures of the two compartments when using a single compressor?

would sometimes freeze things in the bottom when the temperature was set be

Same way your furnace can heat different parts of the house to different temperatures, you use zones. You allow the chiller coils in the freezer to be able to run at different timing then the coils in the refrigerator.

This does require more complicated control systems then the simple loop with a diverter.

ents when using a single compressor?

I've never seen a fridge that bothers with that. They just direct airflow. Why add needless complexity and cost to a simple device that works well?

So your refrigerator has one compressor, but two sets of coils and a valve to change the flow of coolant and two thermostats? Yeah, that's a lot of m oney when designing a consumer item.

in the freezer. It was really packed tight. That was likely preventing ad equate airflow to the refrigerator part of the unit. I've eaten a lot of t he stores now and the air flow is restored.

I have my power monitor on the Tesla at the moment. Once it is done chargi ng later today I'll drag the fridge out and measure the wattage it uses.

I have not looked into it, but it does. The previous one (an 20+ years old Bosch) did it too. There is no air connection between freeze and cool department. Both the old and new fridge both have a digital display where you set freeze and cool temperatures independently. They must have some valve or other control thing for it. In fact, some fridges have even different temparature zones inside the cooler department.

Never, because cool and freeze are completely independent, even though they must share the same motor, at least on my model, a Liebherr CP4813. The energy differences between modern fridges can run in the hundreds of kWhs per year, according to a consumer test here; energy use was a selection criteria for us.

Mat Nieuwenhoven

nts when using a single compressor?

Being able to set independent temperatures does not mean there are two coil s with valves. It is much more likely to have a controlled damper to modul ate the amount of cold air from the freezer entering the refrigerator. My refrigerator has a fan, but I can't say for sure where it blows, freezer o nly or freezer and refrigerator.

e would sometimes freeze things in the bottom when the temperature was set

Sorry, I can't follow your reasoning. If you set the refrigerator temperat

scale? Or does your refrigerator not keep things at the set temperature?

Well, a lot of european refrigerators do have two compressors. I know mine does. There's no air connection between freezer and refrigerator and there are two completely separate thermostats.

Maybe they had two compressors. I thought most Bosch ones did.

That has to be an expensive refrigerator. Two of everything makes for a lo t of works. I can't see the need. With the thermostat in the refrigerator and the evaporator around the freezer, the unit will run until the refrige rator is cold and by then the freezer will be adequately cold. That can be adjusted by adjusting the air flow between the two. I can't see adding a second compressor to take the place of an air damper.

You don't actually need a second compressor. You just need a seperate cooler coil to cool the refrigerator compartment, and control valves to select which cooling coils are being feed by the compressor based on the demands.

lot of works. I can't see the need. With the thermostat in the refrigerato r and the evaporator around the freezer, the unit will run until the refrig erator is cold and by then the freezer will be adequately cold. That can be adjusted by adjusting the air flow between the two. I can't see adding a s econd compressor to take the place of an air damper.

That's not the issue. The issue is there is added cost with little gain. Someone mentioned a unit with multiple freezer compartments. It would be a very specialized use to need multiple freezer compartments in a single ref rigerator. None of that makes any sense to me.

There is the gain: you can keep the fridge slightly above freezing and the freeze side well frozen if there are two cooling systems. A single-compressor unit relies on suitable thermal leak out of the fridge side to keep the temperature difference between the compartments.

I did not see a second compressor. There was one at the back, with on top a kind of dish that caught the condensation runoff from the cooler department via a hole, had to clean it once. The compressor was at the level of the highest freeze drawer, which was shorter than the other two. There must have been some valves controlling when a compartment got cooling. The control was fully electronic on a single PCB board. I never heard different noises too, I think if there are two compressors that at some times you'de hear both instead of one. My current fridge also has a single compressor.

I'm not sure that "a lot of european refrigerators" have two compressors. Maybe the side-by-side fridges, they consume much more energy.

Mat Nieuwenhoven

They really do have a single compressor, control is fully electronic, and whatever they use for separate control must make it worthwhile, they seem to use less energy judging from the brochures. Only the cheapest fridges have a single mechanical control on the cooler compartment. Seperate controls also mean that freezing in a large numer of goods doesn't affect the cool compartment's temperature.

I don't know what you'd call expensive, ours was less than 800 euro's.

Mat Nieuwenhoven

Like I wrote above, there is _no_ connection between freeze and cool compartments. Not on our old and not on our current fridge. Both are combined freeze/cool fridges with the 3-drawer freeze section at the bottom. The cooler section has its coil after the back wall of the compartment, you can feel it getting colder if it's running. I wonder too if a controlled air movement damper is not more expensive than two on-off valves for freeze/cool coils, plus less prone to error.

Ah, I missed the minus sign, sorry. Yes it would freeze up, if I could do that, but the fridge won't allow me. I never tried it on the old one (also digitally controlled), but the current one allows selection only from +1 to +9 C for the cooler compartment. The freeze section is adjustable from -26 to -16 C.

Control seems to be accurate too. If I measure the white back wall of the cooler compartment with an infrared thermometer, it is within 0.1 C of the set 4 degrees centigrade. On white painted metal the measurement should be fairly accurate.

Mat Nieuwenhoven