Chest freezer-to-fridge conversion - which temp. controlled switch to buy?

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Chest freezer-to-fridge conversion - which temp. controlled switch to buy?

(14 posts) (8 voices)

Started 7 years ago by goosewisperer
Latest reply from rockabye

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goosewisperer
Member

I'm hoping someone can give me some pointers on choosing a temperature controlled switch to buy for a chest freezer-to-fridge conversion.

I came across this article https://damnthematrix.wordpress.com/2009/09/06/heres-a-really-cool-idea/ which suggests this little unit out of china for only $15 http://www.ebay.com.au/itm/220-240V-Temperature-Temp-Thermostat-switch-relay-incubation-control-Controller-/400520293591?pt=AU_B_I_Electrical_Test_Equipment&hash=item5d40deacd7&clk_rvr_id=805153062051&rmvSB=true

Then there is the one from MtBest preassembled (I'm not great with a soldering iron) for $150 http://mtbest.net/freezer-to-fridge-thermostat.html ...more details on the design here http://www.builditsolar.com/Projects/Conservation/chest_fridge2.pdf

So I'm obviously tempted to go with the $15 one, but on the other hand it seems like the MtBest guy has gone to a lot of trouble to test and select components for his unit which are long lasting and efficient, something I have no idea whether the Chinese one is likely to come close to.

Does anyone have any thoughts on this?

Posted Sunday 29 Mar 2015 @ 8:28:14 am from IP #
Whitrock
Member

I converted an old fridge to a salami making cabinet using the ebay one with a humidity controller much the same.
works a treat.
Cheers

Posted Sunday 29 Mar 2015 @ 9:14:53 am from IP #
David
Member

I've used one similar to that one but went colder than that however, legally your supposed to have an electrician wire for you as it's 230VAC. #justsaying

Apart from that if the probe is located correctly (important) then it will work very nicely, you need to decide what the temp on off points are going to be, it can be as tight as just + - 1C ideally don't make wider than + - 2C. typical temp would be 4C. so on at 5C off at 3C for instance, for fridge.

Posted Sunday 29 Mar 2015 @ 9:40:32 am from IP #
goosewisperer
Member

David said:
I've used one similar to that one but went colder than that however, legally your supposed to have an electrician wire for you as it's 230VAC. #justsaying

Apart from that if the probe is located correctly (important) then it will work very nicely, you need to decide what the temp on off points are going to be, it can be as tight as just + - 1C ideally don't make wider than + - 2C. typical temp would be 4C. so on at 5C off at 3C for instance, for fridge.

Great!
Just so I'm clear - you're referring to the $15 ebay one right, rather than the $150 model?

Posted Monday 30 Mar 2015 @ 8:42:08 am from IP #
David
Member

The ones I used were remarkably similar but were about $30 dollars a piece at the time.

Posted Monday 30 Mar 2015 @ 10:38:27 am from IP #
cravenhaven
Member

After reading the article on the mt best thermostat it is clear that his design was focused on using as little mains power as possible, and providing a simple and accurate device. The chinese one will have no such ambition, so your decision depends on your requirement. If you want to minimise the power usage then the mt best unit will be superior (maybe you can find a friend to build it for you).
The other consideration is that the mt best unit does not include a temperature display and he states in his article that he uses a separate display unit to monitor the temperature in the fridge. Again your requirement might influence your decision on this point.
Allan

Posted Monday 30 Mar 2015 @ 10:34:36 pm from IP #
goosewisperer
Member

cravenhaven said:
After reading the article on the mt best thermostat it is clear that his design was focused on using as little mains power as possible, and providing a simple and accurate device. The chinese one will have no such ambition, so your decision depends on your requirement. If you want to minimise the power usage then the mt best unit will be superior (maybe you can find a friend to build it for you).
The other consideration is that the mt best unit does not include a temperature display and he states in his article that he uses a separate display unit to monitor the temperature in the fridge. Again your requirement might influence your decision on this point.
Allan

This is a good point, which I hadn't considered - the ebay one draws 3W which equates to 72 watt hours a day. The temperature display is not essential for me, so I will give the idea of tracking down a friend to build it some further thought.

Thanks!

Posted Monday 30 Mar 2015 @ 10:54:28 pm from IP #
David
Member

goosewisperer said:
This is a good point, which I hadn't considered - the ebay one draws 3W which equates to 72 watt hours a day. The temperature display is not essential for me, so I will give the idea of tracking down a friend to build it some further thought.

Thanks!

If power is that critical then, an analogue thermostat like the following one is an option. http://www.ebay.com.au/itm/2-Pin-WPF-20-Terminals-Freezer-Refrigerator-Thermostat-with-65cm-Metal-Cord-/171157343738?pt=LH_DefaultDomain_15&hash=item27d9c5cdfa>

Use a battery powered display for monitoring or setting up.

Posted Monday 30 Mar 2015 @ 11:14:59 pm from IP #
franks
Member

electronic temp controllers, solid state relay switching & thermistor temp sensor, very flexible & low idle power

Posted Wednesday 1 Apr 2015 @ 12:09:17 am from IP #
dreuky
Member

I'm not into playing with electrical "stuff" don't have the knowledge too scared to try. So my question is could you achieve the same by just monitoring the temp and turning the freezer off and on manually. I ask because we have a working chest freezer, a fridge that is seriously dying and don't want to buy a new fridge until we move out of our rental place and into our new home in a couple of months

Posted Thursday 2 Apr 2015 @ 11:19:25 pm from IP #
axess
Member

Hi dreuky,

What about buying the fridge now that you plan to use in you new home and just taking it with you?

Posted Friday 3 Apr 2015 @ 6:29:23 am from IP #
David
Member

dreuky said:
So my question is could you achieve the same by just monitoring the temp and turning the freezer off and on manually.

I've produced electronic temp controllers that plug-in between the GPO and the freezer in the past. All you have to do then is put the probe in-side and it turns the power on and off too maintain the temp. Should work with any functional freezer.

Manually turning a freezer on and off, I think your going to windup with stuff that's frozen when you may not want it to be, or if you can figure out how long it needs to on for and how long it needs to be off I guess you could use a timer, I suspect that will come unstuck as outside temps are not constant.

Posted Friday 3 Apr 2015 @ 7:13:47 am from IP #
dreuky
Member

Axess, our rental place has steps upto a really narrow door so our dying fridge is standing in the carport not something I really want to do with a new fridge

Posted Saturday 4 Apr 2015 @ 10:07:10 pm from IP #
rockabye
Member

I have both and the prior answers regarding standby power use are valid. The problem is that if you are running on solar power the inverter has to be on 24/7 for the low cost chinese type to operate. Hence your standby power use is considerable more than the 72W/h per day due to poor inverter inefficiency at low power levels.

If you are on mains power the waste is limited to the 72W/h per day which is around 7kWh per quarter or $2.10 roughly at current prices.

The price difference between the two is significant so the cheaper unit is probably the way to go on mains but the dearer Mt Best design is better if you are on solar. However if you have to pay someone to make your housing and wire it in the cost saving may soon disappear. ** ONCE AGAIN this is very DANGEROUS for an untrained person to do so if you don't know what you are doing get it done by a trained person.

The other significant benefit worth mentioning is that the Chinese models have a built in temperature display.

Posted Tuesday 28 Apr 2015 @ 2:03:19 am from IP #

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