Fridge circulation fan question
- Thread starter Ssil2000
- Start date
Hi @Ssil2000,
hmm, really interesting!
What is that a thermostat for? Usually the thermostat is a fluidy type thingy in a semi-flexible tube, but I cannot see it in this photo. A basic three-way fridge doesn't need power so it can run on gas. Also what is the other cable doing there?
What brand and model fridge is this? Seems like it might be an AES model. But I thought they all had interior lights since you always have to have a 12V feed to them to operate.
I would be inclined to not assume anything about what the wires going to the thermostat are used for. A normal electrical thermostat is a semiconductor or other temperature sensitive resistor. So you feed a fixed small current into it and then measure the voltage to determine the temperature. If that is the case with your setup, there is no 12V there to tap into.
Two basic options. Buy the self-contained unit that uses two D cells.
Buy a small 12V computer / cooling fan and mount it under the fin on the left hand side (or whichever side frosts up first) and run two thin wires out through the drain hole in the drip tray below the cooling fins.
There are several threads on the forum discussing these options. @Boots in Action (and many others) know this topic very well.
regards
Mike
hmm, really interesting!
What is that a thermostat for? Usually the thermostat is a fluidy type thingy in a semi-flexible tube, but I cannot see it in this photo. A basic three-way fridge doesn't need power so it can run on gas. Also what is the other cable doing there?
What brand and model fridge is this? Seems like it might be an AES model. But I thought they all had interior lights since you always have to have a 12V feed to them to operate.
I would be inclined to not assume anything about what the wires going to the thermostat are used for. A normal electrical thermostat is a semiconductor or other temperature sensitive resistor. So you feed a fixed small current into it and then measure the voltage to determine the temperature. If that is the case with your setup, there is no 12V there to tap into.
Two basic options. Buy the self-contained unit that uses two D cells.
Buy a small 12V computer / cooling fan and mount it under the fin on the left hand side (or whichever side frosts up first) and run two thin wires out through the drain hole in the drip tray below the cooling fins.
There are several threads on the forum discussing these options. @Boots in Action (and many others) know this topic very well.
regards
Mike
It’s a thetford n3185 I checked the wire with a multimeter and it’s live
When I unplugged it the front display stopped working so i assumed it had something to do with temp sensor but maybe it’s not?
As for the light there’s 2 little led lights that are outside the fridge bit wierd
As for running it through the drain hose it’s very small I’m a bit worried it’s too skinny I’ll play with it tomorrow
When I unplugged it the front display stopped working so i assumed it had something to do with temp sensor but maybe it’s not?
As for the light there’s 2 little led lights that are outside the fridge bit wierd
As for running it through the drain hose it’s very small I’m a bit worried it’s too skinny I’ll play with it tomorrow
Hi @Ssil2000,
I assume there are only two wires going to the sensor. If so, they cannot be both a 12V source (+ve and -ve) and a feedback for temperature. You would need at least three wires.
The fan draws 3/5 of 5/8 of almost nothing. So the wires can be very thin. You won't have any problem threading them through. The thinnest hook up wire they sell at Jaycar should be more than ample.
A Thetford N3185 is an AES fridge so it needs a permanent 12V supply to drive its electronic control panel. So it may well have an electronic thermostat and not the basic copper tube thingy.
cheers
Mike
Hi @mikerezny, you are correct about the normal temperature sender/control. It needs no electricity and consists of a thin capillary tube containing a gas/fluid. As temperature rises, the gas/fluid expands and MECHANICALLY pushes a contact onto a live connector. This starts compressor or connects power to heater in Absorption fridges. As temperature drops, the expanded (warm ) gas/fluid in hollow tube contracts and reduces pressure on movable contact and cuts circuit. Do any of our Absorption fridges have electronic temperature controls as standard as yet?? I know that most of the latest domestic 240 volt type have sensing units which connect to a control board to adjust individual settings according to what is required in freezer and and the fridge part.
@Ssil2000 , a small computer fan inside the fridge draws between 100 and 150 milliamps ( a very small amount!!) and you can have an inline switch to isolate it when not required. I think someone on this forum has a variable sensor to control automatically when fan runs which would be very handy.
Hi @Boots in Action,
I did find an online manual for a fridge similar to a Thetford N3185 which is an AES fridge. I looked briefly at the circuit diagram and there seemed to be two wires going from the control board to what seemed to be a thermostat. But then I got sidetracked and didn't follow it up any further.
cheers
Mike
So I gather the internal fan should be going when the fridge is switched on.
I have installed a thermostat for the external fan which is powered from the switch on the front of the fridge.
Should the internal fan be wired to the same switched supply but before the thermostat?
I have installed a thermostat for the external fan which is powered from the switch on the front of the fridge.
Should the internal fan be wired to the same switched supply but before the thermostat?
Yes to first and second lines. For the last line, that would work, but you then have BOTH fans controlled by SAME switch which means you are unable to isolate the external fan without shutting down the internal one. Better to have separate switches if possible, but depends on what has to be done to wire same.
Hi @RickB,
now that is an interesting question.
I haven't installed an internal fan yet.
There seem to be three main reasons people put them in:
1: the bottom part of the fridge gets too cold and freezes the lettuce and other things.
2: frost builds up on the cooling fins and prevents the fridge operating efficiently.
3: put more airflow over the cooling fins.
So, running the fan whenever the fridge is in use would be the go.
But, if you can, try to avoid having the fan running when you open the door, as this will just be ensuring better circulation of the outside warm air with the cool fridge air.
I got around the first by putting in a 'crisper' tray. Never had anything frozen in the fridge area.
I have, sometimes, a small amount of ice buildup in the left-hand end of the cooling fins. But, even after two weeks it hasn't been much.
Take note that fans dissipate heat. So, take careful note of the current draw and thus the power dissipation. 100mA at 14V is 1.4W burning away inside an absorption fridge is probably as much as you would want.
cheers
Mike
Not quite as bad as that @mikerezny . If voltage is as high as 14 volts, battery would be in a fully charged condition and if continued to stay at that voltage , it would not be a worry on current draw. As an example, I have 2 fans inside my fridge (see previous postings) and 2 fans in my outside portable 3 way fridge. Total draw at 13 volts comes in at approx 0.75 A. (which are not controlled as yet except by manual switch!!) and the external fans X 2 each draw 0.250 A but are thermo controlled. Should not be too much of a worry for @RickB if he has suitable recharging means. Just had 5 overcast days in the Connondales again, and although total daily use for all electrical usages was as high as 37 ah on some days, my MPPT controller was able to cover this amount on 4 out of the 5 days with at least this amount and I only have the one 120 ah battery. Info taken from data provided by controller.
Yes @RickB . A micro switch on the door is the way to go to switch off the internal fans when door is opened. Too much work and difficulty to fit switch for this "black duck". That is why I have a separate switch for my internal fans. All manual but just as good if you have the switch readily available. If you can do a micro switch without difficulty (not removing fridge and able to thread suitable wiring, go for it!! And let me know too as I will incorporate same for my set up. By the way, I do not like drilling little holes into the innards of my fridge. I used velcro to attach fans to walls in both fridges. See previous postings and pictures of set up. Hope this helps. Cheers.
Small micro switch would be the way to go, depending on what the temp setting is for your external fan it may run all the time, I have a 70 deg switch and my fridge is a large 2 door similar to yours I imagine and it virtually runs all the time where as the smaller units will shut off from time to time......My fridge has an internal light so a little relay does the job of shutting the fan down when door opened, it works but still haven't fitted it yet..............velcro and double sided tape only way.
Hi @Boots in Action,
I wasn't worried about the current drain of the internal fans on the battery. I WAS worried about the heat generated by the fans INSIDE the fridge.
Basically, most of the energy used by the fans will end up as HEAT inside the fridge. How would you feel about leaving a 5W interior light burning continuously inside your fridge on a 40C day? Well, at least that would be one way of solving the problem of freezing lettuce.
If it was me, I would want the internal fans to generate less than or about 1W of heat. So less than 100ma would be my choice.
cheers
Mike
bit off topic, but my acurite fridge temp sensors arrived, perfect timing really as it was hot yesterday and hotter today
so this test is with an empty fridge on setting 4(of 5)
while the sun was on the door side of van and temp around 30 the fridge held 2 degrees and freezer -15/-16 once the heat of the day hit late in the day i saw a 7-8 degree variance in temperatures both in freezer and fridge. this is also with the fans off (fridge has 3 fan setting built in, off 1 or 2)
today i have turned the fan to 2, we will see if this will improve the cooling or not as today will get close to 40 in the shade.
once i finish the test empty i will run the test again under load to see if that will help keep temp down or make it worse...
photo attached to show the variance.
so this test is with an empty fridge on setting 4(of 5)
while the sun was on the door side of van and temp around 30 the fridge held 2 degrees and freezer -15/-16 once the heat of the day hit late in the day i saw a 7-8 degree variance in temperatures both in freezer and fridge. this is also with the fans off (fridge has 3 fan setting built in, off 1 or 2)
today i have turned the fan to 2, we will see if this will improve the cooling or not as today will get close to 40 in the shade.
once i finish the test empty i will run the test again under load to see if that will help keep temp down or make it worse...
photo attached to show the variance.
Attachments
Hi @Ssil2000 , that will be a harsh test in 40C temp. I will be very interested in your results. Cheers
Sorry @RickB , I replied a couple of days ago but it didn't get here, stupid phone, I meant to say micro switch not relay, just stuck on so the lever actuates it...
