Results 1 to 14 of 14
  1. #1
    PaDave's Avatar
    PaDave Guest

    A Newbie with a theoretical question.



    This is an impressive forum.
    I'm the worst kind, a bit of tech background (half a lifetime doing car crash research), lots of time (retired, non-golfer) and building our low energy house.
    The house in southern Australia, is designed around passive solar and cross flow ventilation principles. Large concrete slab and internal masonry walls provide thermal mass.
    Cooling during 4-5 months of 28C-32C averages with peaks of 38C-42C, without air-con is the challenge. Winter temp averages lows of 5C-7C. Frost is most uncommon, once in 10 years.
    A new kitchen is about to be designed, and will include a new fridge/freezer of about 400L/200Lcapacity.
    Here's the question! Is it practicable to modify a new domestic fridge to place the condenser unit remote from the kitchen (outside), to reduce the heat output into the living space during summer months. The distance from fridge to desired condenser location would be 7m lateral and 1.5m lower.
    This would not be DYI, money would change hands for the job. How much heat reduction could be expected from such a process?
    Weather or not it would be economical is another question, for another forum.



  2. #2
    Join Date
    Aug 2007
    Location
    Sydney
    Age
    51
    Posts
    1,094
    Rep Power
    23

    Re: A Newbie with a theoretical question.

    Hi PaDave and welcome to our forum.
    Yes it is possible and no it would not be economical for these reasons. The extra pipe run would require more power to push the refrigerant around, the condenser circuit is also used to heat certain areas of the fridge to help prevent condensation. Also the cost of the modification at a glance would have a many years payback period.
    I have two ideas to reduce the internal heat load. One; is to use an old fashioned cool box/cupboard on south side of house for vegetables etc - this would reduce the size the fridge you need. You could even use ice in the box for those extra hot days. Two; if you use cross flow ventilation you could place the exhaust air very near the condenser of the fridge thus reducing the amount of heat build up in the house.
    Other heat reduction thoughts are to place the hot water cylinder outside or high and to reduce the size you cold use a heat exchanger from the shower waste pipe to the hot water supply.
    There are some new technologies from fisher and pykle which are supposed to be super efficient for domestic fridges.

  3. #3
    Join Date
    Aug 2009
    Location
    New Zealand
    Age
    59
    Posts
    2,556
    Rep Power
    26

    Re: A Newbie with a theoretical question.

    Quote Originally Posted by PaDave View Post
    This is an impressive forum.
    I'm the worst kind, a bit of tech background (half a lifetime doing car crash research), lots of time (retired, non-golfer) and building our low energy house.
    The house in southern Australia, is designed around passive solar and cross flow ventilation principles. Large concrete slab and internal masonry walls provide thermal mass.
    Cooling during 4-5 months of 28C-32C averages with peaks of 38C-42C, without air-con is the challenge. Winter temp averages lows of 5C-7C. Frost is most uncommon, once in 10 years.
    A new kitchen is about to be designed, and will include a new fridge/freezer of about 400L/200Lcapacity.
    Here's the question! Is it practicable to modify a new domestic fridge to place the condenser unit remote from the kitchen (outside), to reduce the heat output into the living space during summer months. The distance from fridge to desired condenser location would be 7m lateral and 1.5m lower.
    This would not be DYI, money would change hands for the job. How much heat reduction could be expected from such a process?
    Weather or not it would be economical is another question, for another forum.
    Total energy adding to the Klitchen when running will be in the region of 100watts (heating and cooling cancel each other out), by removing the cond unit, you are likely to remove approx 200 watts of heat from the kitchen, total heat rejected approx 300watts. You then have way up these losses in summer (good) verses the heat lost in winter (bad)
    Also by increasing the pipe run, efficiency is lost by the refrigeration unit, so longer run periods are to be expected. A water cooled condensor would be better (for the refrigeration and rejection), you could use this to pre heat your water. Can be come complex.

  4. #4
    Join Date
    Oct 2006
    Location
    England
    Posts
    1,847
    Rep Power
    21

    Re: A Newbie with a theoretical question.

    Quote Originally Posted by mad fridgie View Post
    A water cooled condensor would be better (for the refrigeration and rejection), you could use this to pre heat your water. Can be come complex.

    I agree with the water cooled solution.

    You could then use the waste heat to pre heat any water you have in the building...

    taz.

    .

  5. #5
    Join Date
    Nov 2003
    Location
    NSW, Australia
    Age
    40
    Posts
    243
    Rep Power
    21

    Re: A Newbie with a theoretical question.

    might take a while to heat up 300 plus litres of water at 2~300w. not really practical to remote condense a domestic fridge the way you want, if you look around someone will do it for you and money will change hands, but its not what you want.
    "Old fridgies never die, they just run out of gas!"

  6. #6
    Join Date
    Jan 2008
    Location
    India
    Age
    70
    Posts
    171
    Rep Power
    17

    Re: A Newbie with a theoretical question.

    Fridge condenser is on the body of the fridge itself and it is on two sides and thus exposing it outside has to be planned right in the begining. Further fridge compressor will work for few hours depending on the product load and opening and closing.Thus the fridge heat although can be taken to outside it is not economical as the facilities required may cost more than the saving.

  7. #7
    Join Date
    Feb 2009
    Location
    Australia
    Posts
    273
    Rep Power
    16

    Re: A Newbie with a theoretical question.

    PaDave,
    I think you would be better off putting effort into solar electricity while the government is still willing to pay for 90% of it.I have 1500 watts on my roof and is well worth it.During a normal sunny day i get 1300watts per hour free from the big fella upstaires and the excess is put back into the grid and i get paid 2 1/2 times the cost i get charged,,,,,
    Lawrie
    Lawrie
    Remember we are here for a good time, not a long time.
    Trust me i'm a Fridgy.

  8. #8
    PaDave's Avatar
    PaDave Guest

    Re: A Newbie with a theoretical question.

    Many thanks for your replys. You have convinced me. I'll get on and finish the build. There is so much to know about everything, one life-time won't be long enough.

  9. #9
    Join Date
    Jul 2010
    Location
    NTH.QLD Australia
    Age
    62
    Posts
    1,762
    Rep Power
    32

    Re: A Newbie with a theoretical question.

    Quote Originally Posted by lawrence1 View Post
    PaDave,
    I think you would be better off putting effort into solar electricity while the government is still willing to pay for 90% of it.I have 1500 watts on my roof and is well worth it.During a normal sunny day i get 1300watts per hour free from the big fella upstaires and the excess is put back into the grid and i get paid 2 1/2 times the cost i get charged,,,,,
    Lawrie
    Lawrie
    Hi Lawrie, good to see you're into conservation. I want to do the same but have to replace the old roof first. Put up solar hot water 10 years ago and it's paid off. Seriously considering micro-hydro from gutter runoff with the amount of rain i get/year here.
    To the optimist, the glass is half full. To the pessimist, the glass is half empty.

  10. #10
    Join Date
    Feb 2009
    Location
    Australia
    Posts
    273
    Rep Power
    16

    Re: A Newbie with a theoretical question.

    mikeref.
    my brother has put 3000watts solar on his roof and his last bill was a cheque for $25
    Remember we are here for a good time, not a long time.
    Trust me i'm a Fridgy.

  11. #11
    Join Date
    Aug 2007
    Location
    Sydney
    Age
    51
    Posts
    1,094
    Rep Power
    23

    Re: A Newbie with a theoretical question.

    Dudes
    In Aus and NZ I can highly recommend the ATA Alternative Technology Magazine it is a wealth of info on this subject. As for the big rebates on PV cells and payment from the electricity suppliers - I'm sorry but it is being scaled down (here in NSW at least). Some of us city slickers got a little jealous and just imagine if everybody did it - just a thought we might all be better off. Not to worry there is new technology on the way I think Titanium Oxide cells being developed in Brisbane.
    When I grow up I want self sufficiency too.
    Last edited by Tesla; 20-01-2011 at 01:52 PM. Reason: Almost forgot about NZ

  12. #12
    Join Date
    Jul 2010
    Location
    NTH.QLD Australia
    Age
    62
    Posts
    1,762
    Rep Power
    32

    Re: A Newbie with a theoretical question.

    Quote Originally Posted by lawrence1 View Post
    mikeref.
    my brother has put 3000watts solar on his roof and his last bill was a cheque for $25
    Lawrie, depends where you live will make a big difference with solar. Two weeks without rain here is considered a drought,(local saying). Have small pv setup for lighting and 12/24 volt fridges that come in for repairs. When solar cells become more efficient for low light, i'll commit to a 3kw. Local sparkie has a 10kw, 3 phase grid feed, but most times i go past his place, its raining or overcast.. Mike
    To the optimist, the glass is half full. To the pessimist, the glass is half empty.

  13. #13
    Join Date
    Feb 2009
    Location
    Australia
    Posts
    273
    Rep Power
    16

    Re: A Newbie with a theoretical question.

    Mikeref,
    you gotta be kidding 10kw 3 phase,,,,,that equates to according to my calc's 54 panels at 185watts each.i have 8 panels for 1.5kw system.He must have a strong roof as well.
    Lawrie
    Remember we are here for a good time, not a long time.
    Trust me i'm a Fridgy.

  14. #14
    Join Date
    Jul 2010
    Location
    NTH.QLD Australia
    Age
    62
    Posts
    1,762
    Rep Power
    32

    Re: A Newbie with a theoretical question.

    Quote Originally Posted by lawrence1 View Post
    Mikeref,
    you gotta be kidding 10kw 3 phase,,,,,that equates to according to my calc's 54 panels at 185watts each.i have 8 panels for 1.5kw system.He must have a strong roof as well.
    Lawrie
    Just about there.. 58 pannels on a new home, spread over house and large garage. Nice to have a few dollars for something like this hey?
    To the optimist, the glass is half full. To the pessimist, the glass is half empty.

Similar Threads

  1. Newbie question about performance curve
    By ali_g in forum Technical Discussions
    Replies: 3
    Last Post: 04-12-2010, 07:51 PM
  2. Newbie Question - SH Pressure
    By keepmecool in forum Fundamentals
    Replies: 6
    Last Post: 12-08-2009, 08:24 PM
  3. Newbie Question - SH Pressure
    By keepmecool in forum New to RE
    Replies: 4
    Last Post: 12-08-2009, 05:50 PM
  4. Newbie Question (and also, check out my refrigeration hack)
    By dustball in forum Trouble Shooting
    Replies: 14
    Last Post: 25-07-2009, 11:33 PM
  5. Newbie with a question
    By AcidSlasher in forum Fundamentals
    Replies: 4
    Last Post: 07-03-2006, 12:20 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •