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19-01-2011, 02:26 AM #1
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.
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19-01-2011, 03:12 AM #2
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.
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19-01-2011, 03:26 AM #3
Re: A Newbie with a theoretical question.
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.
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19-01-2011, 08:22 AM #4
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19-01-2011, 08:52 AM #5
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!"
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19-01-2011, 09:13 AM #6
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.
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19-01-2011, 11:01 AM #7
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
LawrieRemember we are here for a good time, not a long time.
Trust me i'm a Fridgy.
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19-01-2011, 09:15 PM #8
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.
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20-01-2011, 07:03 AM #9
Re: A Newbie with a theoretical question.
To the optimist, the glass is half full. To the pessimist, the glass is half empty.
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20-01-2011, 07:19 AM #10
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 $25Remember we are here for a good time, not a long time.
Trust me i'm a Fridgy.
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20-01-2011, 12:51 PM #11
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 12:52 PM. Reason: Almost forgot about NZ
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20-01-2011, 10:57 PM #12
Re: A Newbie with a theoretical question.
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.
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21-01-2011, 06:32 AM #13
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.
LawrieRemember we are here for a good time, not a long time.
Trust me i'm a Fridgy.
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21-01-2011, 07:16 AM #14
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