Energy efficient Fridges

[Shadow]

Maybe Volvo farmer can help me understand this.Were looking at getting the most efficient fridge other than the Sunfrost etc. I thought the bottom freezer ones were the real deal but now I find out they arent the most efficient ones but rather the top freezers are.How does that work? I thought heat rises, so the coldest parts should be the lowest, but apparently not.Were looking in the 18-19 cu,ft. range and are in the 445 kwh range. Can we do alot better than that? Thanks for any info

[nothing to lose]

Well my fridge is a top freezer, hot air may rise but also cold air settles and the cold air from the top freezer is what keeps the milk and soda's cold in the fridge

 It's mostly fan forced air blowing the cold freezer air down to the fridge for fast cooling, but I think some is convection if not opened much and thus it runs less often.

Kinda like the old ICE BOXES, ice in top.

A bottom freezer would not cool the fridge part by convection since there is no reason for cold air to rise. So the fan or entire system may run everytime the fridge gets a bit warm just to move some cold air.

The convection is not all that great though in mine, when the blower fan burned up stuff stayed cool in the fridge by convection but NOT cold. Milk would have spoiled alot faster but sodas were alot cooler than if sitting in the room on the floor.

 Mine has only one cooling unit in the rear of the freezer, keeps freezer plenty cold without a fan but not the fridge.

For awhile I had 2 12V computer fans running in mine with a SLA battery sitting beside the fridge. Worked good except the freezer frosted up alot more because of the wires running in the door and not sealing well. But it worked good till I found a correct used $1 fan from a scrap fridge, was $100 for a new fan!!!

[Volvo farmer]

Your observations are correct. I don't know why though. Nothing to Lose has a pretty good explanation. None of these fridges work right without that fan moving the cold air from the freezer compartment into the fridge. It seems less complicated to have the freezer on top because you don't have to duct cold air from the bottom, all the way up to the top of the refrigerator compartment.

You're right in the ballpark with that KWH/year figure. I think I've seen them about 5% better, maybe about 420KWH/year. If you Google "energy star refrigerator" You'll eventually find a site that rates most everything on the market and gives model numbers. Frigidaire makes some of the most efficient stuff last time I checked and there's a Kenmore product with very similar numbers. I think Frigidaire builds that unit for Sears.

[scottsAI]

Hello Shadow,

I thought heat rises, so the coldest parts should be the lowest...

Yes heat rises and cold sinks.

The cooling coils are in the freezer (second link is a nice picture:)

To cool the refrigerator, its heat needs to go up and the freezer coolness goes down. By regulating that relationship the proper temp can be kept. With freezer in the bottom need a fan to make it work.

The bottom freezers have pull out drawers, this mechanism is complex adds to cost, may offer places for heat loss or things to impact efficiency. Side by sides have large suffice areas for the freezer, thus efficiency suffers. Top is the place of choice, most development work has been on the top, so this is where I would expect the best.

Diagrams of various fridges:

http://www.repairclinic.com/0088_4_1.asp

Top Freezer: (from first link)

http://www.repairclinic.com/0100_2.asp

Good advice on:

http://michaelbluejay.com/electricity/refrigerators.html#energystar

My Fridge is like link 2, except heat discharges in rear. Whole back of Fridge gets warm, put a temp probe on top. 80'F. Have a cold air return in the wall behind Fridge. Cut a hole and blocked the air from coming up the back. Top now reads 70'F in 74'F room. I got my Kill-o-watt meter after I did this so have no idea how much energy it saved, math suggests 22%. Looks like most of the new fridges discharge the heat to the front, much better than to back.

The efficiency is greatly effected by two things. The compressor and insulation.

You can buy a nice Fridge and add more insulation. 4 x 8 sheet is like $12 (not blue or pink stuff, want the silver / black stuff). I measured my fridges insulation at 1.125" for refrigerator and 1.625" freezer, By doubling the thickness I would expect the cost to drop in half. Unfortunately I do not have room to do this. If I was willing to tear up my walls and cabinets then I could, not worth the cost. Make sure if you try this you understand how fridge is constructed and don't cover things you should not or it will not work, could even break it. Manual frost fridges are more delicately balanced, may not get the benefits or cause an imbalance between ref and freezer.

Looking over the super efficient units, their only claim to fame is the thicker insulation. Compressor does not seem to be any better. Yet cost 2-3x more than a normal unit, which is frost free!

I checked this by using a spread sheet, measured all the areas and expected heat loss, can match their numbers with thicker insulation for much less dollars. Might not look as good unless you can build in the unit! Built in units are offered today at huge cost adder, you don't have to pay their $ by doing it yourself.

I was very surprised the energy cost of the refrigerator compartment is almost the same as the freezer. Area is the difference. Hope this was helpful.

Have fun,

Scott.