Freezers

eth0

How long will the average freezer last without power before the food starts to thaw? (assuming door stays closed all the time)

also what is the minimum you'd have to run it for every day to keep the stuff any bit frozen, say you remove a few things from it once every day. I could probably run one off batteries +inverter or a generator but obfiously one wouldn't want to pour too much energy into keeping the thing going. Really just until its empty

bonniebede

24 hra wirth the door kept closed.

Check out solar freezers if you want to runone off a battery, they have extra thick insulation.

Doc Ruby

Maximum 2-3 days, the bits in the middle and bottom will last longer. I guess if you foil wrapped each piece, and wrapped the freezer itself in something, you might get over a week out of it.

I've never seen a time operational to time extension on useful food life study done before, that would be interesting.

Grizzly 45

Make sure your DC inverter will handle the power spike of the motor starting up.

eth0

Grizzly 45 wrote: »

Make sure your DC inverter will handle the power spike of the motor starting up.

It can for the big freezer but not the small one for some reason. I don't like to run the freezer off them because it puts out a dirty modified sine wave. ITs actually criminal that they can use the term "sine wave" to describe what comes out of that yoke

fodda

Whats a sine wave and cant you run a freezer off a small generator?

eth0

fodda wrote: »

Whats a sine wave and cant you run a freezer off a small generator?

A sinewave is a nice smooth aestethically pleasing waveform; something that doesn't come out of all but the most expensive inverters

Freezers use a small bit of electricity over a long period of time so its preferable to use the battery. obviously if you had a generator you'd have it connected so the freezer would be going whenever you were using the generator for something else

fodda

Couldnt you have the generator on 2 - 3 - 4 times a day to keep the freezer cold enough in emergencies?

eth0

fodda wrote: »

Couldnt you have the generator on 2 - 3 - 4 times a day to keep the freezer cold enough in emergencies?

probably if i run out of batteries. but how long would it have to stay on for without thawing the food

waterfordham

Thats a very interesting question.
I've just checked on my own small chest freezer. It cycles on for a few minutes about 10 times every hour. I've also got about 6 Litres of frozen water bottles in there.

I've got both batteries, a pure sine-wave inverter and two Generators. I know I can run the central heating and the chest freezer simultaneously on the 800w unit.

I have no idea if it would work, but now that you mention it I think I would leave everything alone for a few hours, then start the jenny, turn the freezer to it's coldest setting, and let it run until everything is back at the coldest temperature. Check it again maybe 6-12 hours later. TBH I've no idea how long it would take, and I really only have enough petrol for about 10-12 hours of runtime depending on load. I'd have to organise to have several things ready to run before starting the 3kw gas jenny.

Interesting question, anyone else got any thoughts on strategies?

fodda

Where do you get these batteries and sine wave inverter and what kinds?

Why cant you just run your fridge and freezer straight off your genny say every 2 hours just to knock the temp back down?

waterfordham

fodda wrote: »

Where do you get these batteries and sine wave inverter and what kinds?

Why cant you just run your fridge and freezer straight off your genny say every 2 hours just to knock the temp back down?

Deep cycle batteries can be got at any battery wholesaler. Pure Sine wave inverters, ebay or anyplace that does boat supplies, but its an expensive way to do it.

There's no reason you can't run them straight from the jenny every 2 hours, but how long are you planning to run the jenny, and for how long are you going to do that? Will you get up every two hours at night etc?

Hence my question about strategies

fodda

waterfordham wrote: »

Deep cycle batteries can be got at any battery wholesaler. Pure Sine wave inverters, ebay or anyplace that does boat supplies, but its an expensive way to do it.

There's no reason you can't run them straight from the jenny every 2 hours, but how long are you planning to run the jenny, and for how long are you going to do that? Will you get up every two hours at night etc?

Hence my question about strategies

I understand, but if a freezer is ok for up to 24 hours before food thaws out surely a boost from a genny say every 8 hours? will put the temp back down in to deep freeze again?.........just a thought.

Doc Ruby

I wonder would covering it in a couple of duvets like a tea cosy help extend the freezing at all, the insulation should work both ways. Some more good ideas here:

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.

-- ..-, 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, 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 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)
July 06, 1999.

Tigger

if you want leccy:
hen you need big batteries and wind gennys
or a big store of oil and diesel gennys

growing rape to run on a modded indirect diesel engine genny is the way i'd go
combined with wind and big batteries

but a freezer is always a luxery cans and preserves replaced with cans and jars is how you'd do it if serious

canning and jaring food is easier than it sounds

the skills thatr we've lost in the last few (30) years are massive
boil it till its clean then put in in an anerobic state and bobs yer late aunts hubby

http://www.preservefood.com/canning/howto2.shtml