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Refrigerator Venting

Discussion in 'Alternative Energy' started by crashsite, Jan 6, 2008.

  1. crashsite

    crashsite Banned

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    This one isn't so much the generation of alternate energy as energy management in the home (or institutions).

    I've had running disagreements with the architectural community for a long time. They are extremely "building code" oriented and, Frank Lloyd Wright aside, don't seem too inclined to "experiment" much. The result is that we have houses being built today that don't include technology much beyond the 1920s.

    In my kitchen is a refrigerator, nestled into a nook between the dishwasher and pantry. I don't know how it manages to work as well as it does since the heat exchanger is backed up to a blind wall in that nook (with cabinets that overhang the top of the fridge!).

    I suppose, in the winter, it's okay since whatever heat load the fridge adds, just sums to the other heat sources in the house. But, in the summer, it doesn't seem like a very good solution.

    Houses really need to be designed (in combination with refrigerators) such that the fridge expels its heat into a plenum that has a airflow gating system such that in winter the warm air is returned to the house while in summer that heat vents, via the plenum, to the outside.

    Am I the only sane one on this issue or am I missing some major concept in physics?
     
  2. felis

    felis New Member

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    The only heat that you'd be able to add this way is the heat generated by the refrigerator itself. Imagine opening refrigerator door and leaving it this way for a while - your kitchen will heat up, but just a little, since even old refrigerators were quite effective.
     
  3. Hero999

    Hero999 Banned

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    We have our fridges up against a blind wall and they seem to work alright.

    Where do you live?

    We don't have very hot summers in the UK so I suppose that's why we don't have this sort of problem.

    Perhaps you should consider moving your fridge to an out house or garrage where you can leave plenty of room for ventillation.
     
  4. dave

    Dave New Member

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  5. HarveyH42

    HarveyH42 Banned

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    :) Google 'Outhouse'... :D
     
  6. crashsite

    crashsite Banned

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    Well, it just seems like a solution waiting some famous "expert" to figure it out and get the credit for the idea.

    I'm sure, "outhouse" has a less colorful connotation in other parts of the world than here in the US. But, putting that aside, the idea of having to run out to some out building to fetch refrigerated food (while perhaps a good diet plan), does not appeal to me.

    I live in Oregon (pretty colse to the 45th parallel). In fact, I used to live in Salem and the 45th parallel runs right through the north end of the town.
     
    Last edited: Jan 7, 2008
  7. Pommie

    Pommie Well-Known Member Most Helpful Member

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    But, if the fridge was vented then your kitchen would cool down which is desirable in a hot climate. I think the reason that refrigerators aren't vented is because the amount of energy we are talking about saving is not worth the additional building costs. Far better to spend the money on better overall insulation.

    Mike.
     
  8. 3v0

    3v0 Coop Build Coordinator Forum Supporter

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    Outdoor appliances are somewhat common in areas with mild winters. I have a refrigerator on my covered rear deck. In the summer it does not add to the air conditioning load and in the winter it seldom runs. I do not have the ice maker hooked up.
     
  9. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    Word of warning! - don't do that with a fridge/freezer that has a single compressor. They use a single thermostat in the fridge section, and because it's in a cold environment it never turns ON, and the freezer part thaws.

    It's common here to have them in garages, and come the winter the freezer thaws out! :p
     
  10. 3v0

    3v0 Coop Build Coordinator Forum Supporter

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    Good Advice.
    This a large unit with two thermostats.
     
  11. HarveyH42

    HarveyH42 Banned

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    I grew up in Sandy, Oregon. Small town on the side of Mount Hood. Moved down to Florida about 20 years ago. Miss the moutains and the green, not so much the rain and the cold weather.
     
  12. Super_voip

    Super_voip New Member

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    I've always wondered why a fan wasn't placed in parallel with the compressor motor similar to the commercial units. The energy transfer fridge to air would have to many times greater.
     
  13. crashsite

    crashsite Banned

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    Parallel?

    I'm not sure what you mean by, "parallel". While the fan blows the cold air from the evaporation coils to the area to be cooled, all the compressor does is squeeze the coolant. You don't want to remove any of that heat until the coolant reaches the epansion section.
     
  14. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    I think he means to more rapidly remove the heat from the radiator at the rear, just as you would with a fan cooled heatsink.

    I would imagine it's not done for cost, for noise, and for efficiency - it would cost more to run using active cooling rather than passive.
     
  15. crashsite

    crashsite Banned

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    Yes, I misspoke. You do want to remove the heat....not the pressure. Don't mind me. Brain farts are a pretty normal part of my life.
     
  16. Oznog

    Oznog Active Member

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    I had that same thought a long time ago.

    Well first off a fridge doesn't take all that much power and shouldn't be really be such a load on the house's A/C. In fact, your TV set or computer takes a lot more, so you might as well be asking why not vent these outside.

    You're missing one point- any air taken from the inside and blown outside requires an equal volume of hot/wet outside air to be sucked into the house which usually results in an even higher cooling load for the A/C. It might come in around door seals or some other place but it MUST come in!

    So you could pull in outside air, run it past the condensor or PC power supply, and vent it back out. Well, couple of probs there- one, these appliances don't work as well with hot air. PC power supplies tend to have shorter lives if run on 95F air. Fridge compressors don't last as long and in fact a fridge will have to draw significantly more power to stay cool in 95F than 70F air. This may end up being less efficient when you add the A/C and fridge consumption together. But all it takes is one premature compressor failure and having saved $2/mo in electricity seems kinda trivial.

    So consider the enormous problem of keeping insects, birds, dust, and rats from getting in, sealing against rain, and having to make ugly holes in the siding is a very high expense. Wow, that's a design feature that could cost hundreds or thousands and totally ties down where the fridge can be in the kitchen design too unless you're running hoses around.
     
  17. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    I suggest you check the relative consumptions, fridges are reasonably high, far more so than a TV or computer - modern, energy efficient ones, obviously take less than older ones though.

    But you're also completely missing the point, TV's and computers are doing something with the energy, with only a fairly small amount lost as heat. A fridge is a heat pump, it's pumping heat out of the food and in to the room - and an efficient heat pump will provide considerably more heat than the energy it consumes.
     
  18. crashsite

    crashsite Banned

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    You do make some very good points, Oznog.
     
  19. Roff

    Roff Well-Known Member

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    Some good points, Gonzo. I looked up a 25 cu. ft. Kenmore fridge just for the hell of it, and they rate it at 721 kilowatt Hrs per year. That averages out to about 82 watts, 24 hours a day. Not a very significant heat load, as you pointed out.
     
  20. mneary

    mneary New Member

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    You can consider a refrigerator located inside an air-conditioned area to be part of a two-stage heat pump. The refrigerator could be optimized to operate at a constant temperature differential.
     
  21. Oznog

    Oznog Active Member

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    Right. So a fridge may consume 80W average and remove another 100W average from the fridge (really I have no idea, it's a Wild Ass Guess).


    Now a desktop PC and monitor can consume 250W and put out 250W of heat to warm the room. A big screen TV can produce heat near that too. So one could wonder why not vent that heat to the outside too.


    There's a subtle difference here too. A fridge cooling the condensor with 70F air require less power to produce the same cooling effect than one working off 90F outside air. A PC or TV however won't require more power if cooled by 90F outside air. However, they DO have a shorter Mean Time Between Failure at higher temp.

    So you'd need specific numbers on how much energy is used by the A/C system to remove that 180W of heat generated by the fridge.
    You can also evaluate the case for taking inside room air, using it to cool the condensor, and venting the warmed air outside rather than try to reuse it. All the cubic feet of air vented out this way have to be drawn in from the outside and cooled by the A/C to replenish the air inside the house. This is counterproductive for sure if the rejected air is still cooler than the outside air temp.

    Actually there's another case. Where the coolant exits the compressor, it's very hot. We could run outside air past one condensor, maybe getting the coolant down to 100F with 90F outside air. Then use a SECOND condensor cooled with 70F inside air to get the coolant temp down to 80F, which has significantly more cooling power than coolant at 100F for the same electrical input to the compressor. So we maintain the compressor's efficiency while rejecting the lion's share of the heat outside. A downside is that longer coolant lines and more condensor passages present additional restrictions to the coolant flow and the compressor will have to do more pumping work to make it flow quickly.

    Well you can figure nobody's gonna rip a hole in the side of the house and route huge hoses out to shave a fraction of a % of the A/C bill. But for battery-driven RV systems and space stations hell yeah it's something to look at. And for building large-scale cooling systems this sort of issue can become quite significant to consider.
     

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