Alternative Technology Assn Forums

1. 

   SteveJ
   Member

   I have just re-read the section in Michael Mobbs' book (Sustainable House) regarding venting the fridge to reduce running temps and improving efficiency, I am a little confused as to why a passive system is better than making use of a low wattage fan? I would think that the lower the compressor temp the better? I run a small fan to push the air through my composting toilet and it uses virtually no power and I was thinking of doing the same in my fridge ventilation, as I think there would be an efficiency gain? Any thoughts on this, any links to good info on designing the venting systems? We are replacing our fridge soonish to one of the efficient models, any thoughts about brands etc.?

   Cheers
   Steve

   Posted Thursday 2 Jun 2011 @ 9:38:53 am from IP #
2. 

   cw nsw
   Member

   Steve, a few here have posted in various threads about our Electrolux fridges - part of the 'Eco' range using the R600a refrigerant - very low electricity usage etc & environmentally friendly.

   you might like to check out the link below

   http://www.electrolux.com.au/Products/Product-listing/?categoryId=698390f5-bbb3-4087-81e4-97d2c5bf3bec

   (I've got an ETM4200 (420L) 349kWh pa unit - great fridge)

   Posted Thursday 2 Jun 2011 @ 10:25:32 am from IP #
3. 

   Eamon
   Member

   Steve, I have to say if the fridge is one which evaporates of exces moisture then i have to fully support you using a low watt fan to remove the moisture out of the house and in turn cool the rear of the fridge down, making it more efficient. One of the biggest breakdown issues with fridges is the void space surrounding it is too small left by kitchen fitters and in turn, the fridge over works and breaks down. Using an forced fan would enhance the circulation and in turn keep temps down. I would however make sure the fan was high level and drawing the air upwards or externally (cooler air).

   Posted Thursday 2 Jun 2011 @ 11:03:55 am from IP #
4. 

   Catopsilia
   Member

   Steve, we share our living space with our fridge. To preserve the food by keeping it cool, the refrigerator gives off heat just as a person does. For a given amount of food preservation, an efficient fridge gives off less heat than an inefficient one, but it still gives off heat.
   During a cool winter, a fridge vented into a room will help to keep the room warm. Venting it outdoors will simply waste heat. Although an inefficient fridge vented into a room will keep it even warmer, this is probably an expensive form of heating.
   During a hot summer, the heat given off by a fridge conflicts with measures to keep the house cool. If possible, the fridge, except for its door, should be in an enclosure vented outdoors, not into the room. Vents should be both high and low, to encourage circulation. A fan would help, but adds complication and expense. The fridge, cooled by hot outdoor air, would actually draw more power than if cooled by cooler indoor air. However, the indoor air is cooler only because of measures taken to cool it, almost certainly at some cost.
   I read of a person (perhaps in this forum) who put the fridge in a shed, so that it would not be adding to the heat in the house in summer.

   Posted Thursday 2 Jun 2011 @ 11:23:57 am from IP #
5. 

   SteveJ
   Member

   Thanks very much for the input, it helps a lot. I had planned to have a switchable vent to direct heated air in or out side depending on season. Our fridge is located in large (4400 x 1800) walk in pantry on the south side of the house, the air will be drawn form under the house (cool air in) and expeled out the top wall or back into the house. Would increasing the insulation of the fridge assist? The pantry is insulated like a cool room already so is further insulating the fridge overkill? We currently run a 1 Kw PV system and this exceeds our needs at the current time (with the FIT) we use about 4.5 Kw day much of which is refridgeration, so cuttting fridge costs means high % savings. Has anyone else got such venting in place? Thanks again for your thoughts.

   Posted Thursday 2 Jun 2011 @ 12:05:46 pm from IP #
6. 

   Russell Moore
   Member

   Maybe we need a fridge vent that can be opened into the house in winter, and closed off and directed outside in summer? What SteveJ already had that idea, wow you have to be quick here!

   Posted Thursday 2 Jun 2011 @ 12:06:36 pm from IP #
7. 

   SteveJ
   Member

   Russel we posted at the same time Onto it already...

   Posted Thursday 2 Jun 2011 @ 12:08:33 pm from IP #
8. 

   Catopsilia
   Member

   Schemes for isolating a fridge from the living space in summer also apply to hot water storages. Special vented enclosures, switched according to the season, are actually quite expensive, unless you do it yourself, and discount the labour cost.

   Posted Thursday 2 Jun 2011 @ 1:25:33 pm from IP #
9. 

   Jeffbloggs
   Member

   Hey SteveJ
   Venting the refrigeration is generally a good idea, but take heed of Cat's advice. The more efficient the refrigerator the less heat it will produce in the room, and the less effective additional ventilation will be. Convective ventilation from top to bottom will work better in the winter, but taking hot air in summer to cool your fridge is not a good idea.

   Have you ever considered using a modified chest freezer instead? They can be modded for $100 by simply changing the thermostat to run at fridge temperatures aka:
   http://mtbest.net/chest_fridge.html

   Generally the more you insulate your fridge/freezer the better it is, that is if the door seals are up to the job. Because of the top opening design a chest freezer loses less cold (better said gains less heat!) when you open it than the normal convection from a vertical open fridge door. Plus it already comes with much thicker insulation standard.

   Think of your fridge as a rusty water tank, the less water (heat) it "leaks" the less water you will use. Plug up the holes with insulation. Seeing that you already have it in a large pantry already, then why not dedicate one side of the room for it and "build it in" with insulation. If you insulate it properly it will not really need the passive/active summer/winter ventilation at all. That is of course if the compressor used is relatively efficient as well.

   Another trick is to over dimension the chest freezer/fridge, and place large water bottles as a thermal store in the bottom eg 100 litres or so, (add some salt of glycol to lower the freezing point if needed) and then set it to run more/only in the cooler night time period. (possibly taking advantage of your low tariff TOU meter?) That way the water store acts as a buffer to keep the fridge temperature low. You might need to experiment a bit with the timing, temp etc but we've used this design a few times; they are notorious as battery killers!

   Let us know if you want to know more. Refrigeration accounts for 10% of electricity consumption in most houses...but I don't think it is that much in yours at 4.5kWh a day! How good is your current fridge, the consumption seems fairly low already, or do you like romantic evenings with candles a lot?
   Regards
   JB

   Posted Thursday 2 Jun 2011 @ 1:33:11 pm from IP #
10. 

    SteveJ
    Member

    Yer good point. Our hot water system (the boiler for it) is enclosed under the house to help heat our composting dunny (Rotoloo). The composting toilet is on the southern sub floor and locating the solar HWS boiler next to it (under the bathroom), was a cheap and easy way to speed up the poo breakdown.

    Posted Thursday 2 Jun 2011 @ 1:38:15 pm from IP #
11. 

    rockabye
    Member

    Talking to my friend yesterday who fitted a 'mt best' kit to a cheap 150 litre chest freezer and it is working well using about 80kWh pa or 220Wh/day according to the powermate energy monitor.

    Posted Thursday 2 Jun 2011 @ 7:20:21 pm from IP #
12. 

    Johnnojack
    Member

    When I built my house I built my fridge alcove with a full width vent to the ceiling space. Did this by packing out the studs on the upper half of the back wall and fitting 2 halves of wall lining. The top half is further forward than the bottom one leaving a gap between. The fridge is very power hungry and uses 3kw out of our 7/day. I was going to raise it up on blocks to provide a bigger gap beneath it, but by removing the kick panel below the door it did the same job. Think our power use has dropped a bit as a result. I once insulated the sides but power use went up, think this cut ventilation. No it doesnt have evap built in, it has grill on the back. Yes a new fridge would be better that is a big investment.

    Posted Monday 6 Jun 2011 @ 2:14:26 am from IP #
13. 

    SteveJ
    Member

    Thanks JJ, intresting reading, I like the practical experience stuff.

    Posted Monday 6 Jun 2011 @ 4:48:53 am from IP #

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