I am going to use wind gens. to charge batts. for electric. I have an inverter that can power everything I need except my well. I will pull the plug on my 2 refrigerators and 1 of my freezers, but want to use one chest freezer for ice, cold water, and temp food storage. I know that compared to super high efficiency models that nearly all freezers are power hogs. My question is - how much more efficient does a chest freezer become if 4 inches of styrofoam insulation is added to all sides less the exposed motor area? Does this increase the efficiency enough to be equal to the expensive high efficiency models or does it have more to do with the efficiency of the motor.

Waiting with styrofoan, knife and adhesive in hand. Thank you.

-- daryl (rushmore@dailypost.com), July 06, 1999

Answers

daryl

You would do better with urethane foam board since it is roughly twice the insulation value per thickness as styrofoam (either as the white, pink or blue kind). Usually urethene foam board comes with foil backing on both sides.

You should find out where the heat disapation coils are on the unit. Ask a service person. These days they are using the back metal panel of the unit to dissipate the heat so you would not want to put any insulation on that metal panel.

It is important to consider the thickness that is worth applying. If you apply an inch of baord and this drops the energy used by half then to drop the energy use by half again you would have to put on 2 more inches not 1 inch. So 1" of styrofoam is usually R5 meaning it will reduce the transfer of heat by 80%. If you wish to reduce the remaining heat transfer by another 80% (a total of reduction = 96%) you would need to apply another TWO inches of styrofoam board (for a toal of 3") ( If you used urethane foam it would be 1.5"). After that its 4 ADDITIONAL inches to reduce that remaining 4% to 0.8%. So you can see that at a certain point it's uneconomical in space and $ to pursue that remaining few %.

Consider also that losses out the back and door and seal will reduce what you can save just by applying foam to the flat side surfaces..

One thing to consider would be to relaocate the fridge to a cool part of the house. This would reduce the demand for cooling to be performed and in general the closer you can keep your fridge to "room" temp the less E will be required. This also is somehwat exponetial. So if you are trying to cool by 5 degrees it will take you x amount of electricity, by 10 degrees 2x and by 20 dgrees 4x. If a frdige is in a 70n degree room it will use a heck of alot more power than if it is sitting in a 40 or 50 degree room.

Hope this helps. (I've been thinking this one over for quite a while now.

-- ..- (dit@dot.dash), July 06, 1999.

How about fridges and freezers outside in a open barn in a cold climate? Can you just unplug or should you leave them open? This is assuming the outside temp does not get above 30 degrees.

Of course, if we're unlucky enough to have a January or February thaw, we'll be repacking, waterproofing and putting in the creek.

-- sue (deco100@aol.com), July 06, 1999.

If your freezer is of the type which has the condenser coils against the outside of the cabinet, your idea will not work. The insulation will prevent the transfer of heat to the outside air. If the outside of your freezer gets warm when the compressor is running, better not insulate it. I think most models are made this way at present.

If you have the condensor as a plate or row of coils separate from the freezer, you will be ok adding insulation, but be careful not to hinder the air circulation around the condenser.

Another respondent asked about leaving the refrigerator door open if it's in an unheated barn in cold weather: the inside temperature will not normally exceed the ambient temperature unless there is some source of heat inside (like composting food). I think it would be fine to just keep it closed. At least it will keep the critters out.

gene

-- gene (ekbaker@essex1.com), July 06, 1999.

If ambient air temperature (in the shade) is assured to remain below 32F, and no solar radiation will raise the "room temperature" above freezing, then you can leave a closed old freezer or fridge exposed the ambient. But if the sun warms the "shed" or barn every afternnoon, then expect the interior and the interior air to get hotter (possibly above freezing) too. For example, the air temperature may be 20, but the sun will warm a closed car up higher than than on a bright day. Cloudy days - not a strong probability since most heat is reflected off the clouds.

If you already have the insulation sheets, ad them as long as you don't block air circulation around the coils - look underneath or in back for a grid of samll (1/8 inch or finer) black wires. Vacuum them too to improve efficiency and economy.

Keep the outdoor coolers used like this closed and locked - kids find them attractive and so they are a safety hazard in older models. The insulation does you no good sitting in the closet.

-- Robert A. Cook, PE (Kennesaw, GA) (cook.r@csaatl.com), July 06, 1999.

After the freezer's been running for a while, hold your hand on the outside. If it isn't really cool, then the insulation is good enough. If it is, then you're right - go ahead with more insulation, but not over the cooling area/coils.

-- Don Armstrong (darmst@yahoo.com.au), July 06, 1999.