#101567  by Neddy
 Tue Oct 20, 2015 8:01 am
I guess I am questioning Grant's definition of "working perfectly". It could simply be that the fridge got
reasonably cold and the compressor eventually turned off. What we really want to know is the duty cycle.
How long is the compressor off and how long does it run for when it turns on again?

By way of example, at its "middle" thermostat setting, our Danfoss-powered fridge cycles On for 3 minutes
then Off for 7 minutes. This setting maintains the freezer at -6°C and the fridge at 4°C.
If Grant's fridge is running at, say, 15 minutes On/7 minutes Off, this would be symptomatic of it being low on gas.
Such a duty cycle would of course significantly increase the overall power consumption of the fridge and would explain the apparent shortage of House battery power.

Neville.

PS. Questions for Grant. Does your fridge have an electric cooling fan? Is it still working as it should?
Has the cooling air supply to the fridge been obstructed in any way? (Just checking!)
 #101570  by Teardrop
 Tue Oct 20, 2015 9:37 am
Check the fridge door seals as well.

Also, when you say it runs okay on 230 volt, do you mean it cycles on and off normally, or do you mean it just seems to operate normally but still could be running constantly (but seeming okay) because it has unlimited power to draw from?

Dene
 #101623  by yachty
 Thu Oct 22, 2015 5:04 am
I think you should be looking at 12v cable size, if working fine on 240v (I am guessing this is a Weaco fridge with direct 240v connection) then it would suggest the cable size is over heating or not allowing good current. Two things over looked on 12v fridge installs is Cable size (a min size cable should be 4mm sq if short run but 6mm sq if over about 2metres) and venting the compressor still needs to cool.

I would also look at my reg for solar panel as 2x 250 watt panels should be way to much energy to full your batteries, i think your 12v issue with fridge is all related to 12v wiring, a good charger/reg should be more than able to keep up with fridge power use unless you are using a lot of 12v ie through inverters etc
 #101637  by RaymonD
 Thu Oct 22, 2015 1:56 pm
reading the original post, the at home running was via a battery charger and ok., in the field on solar, continual running, but turning back thermostat setting it stops, but does it restart and operate correctly on the lower thermostat setting ??
The continual running is indicative of low gas, surely.
Low voltage should cause the low voltage protection to operate and stop the compressor ??
 #101640  by mattn
 Thu Oct 22, 2015 2:27 pm
The consensus is its most likely to be a problem with the amount of cooling being less than needed. Most likely cause is low gas. Other causes are motor shot and unable to run at full speed, or cold escaping the fridge. It is very unlikely the root cause of the problem is power supply to the fridge and low voltage, although fixing these (if an issue) may create the impression the problem is fixed.

The Off/On cycling when the thermostat is turned down, and slightly improved performance of the compressor when on mains indicates the cooling is "nearly but not quite" enough. Its likely a slow degradation in cooling performance has occurred (over months or even years), with a corresponding increase in duty cycle, that only been noticed now the duty cycle has reached 100%.

Next would be an experiment to confirm the hypothesis. Put a thermometer in the fridge, turn the thermostat as low as it will go and record how cold the fridge gets...... Turn the thermostat up a notch and record that. Repeat till done (5 or 10 samples would be enough). A plot of fridge temperature vs thermostat setting will show a trend. Is the line is flat and never drops below a certain temperature then follows the thermostat, flat - regardless of thermostat, or follows the thermostat? If you have a way to log the motor duty cycle, that would be valuable information to add to the graph.
 #101662  by yachty
 Fri Oct 23, 2015 4:57 am
In Landlubers second post he states fridge works fine when plugged into mains Waeco fridges that are built in build stage would normally have a 240v connection and a 12v connection (the fact the batteries are getting charged most likely has nothing to do with fridge running while on 240v) these fridges very rarely prosent compressor trouble or degassing, that is the reason i would be looking at the 12v wiring
 #101671  by Shilo
 Fri Oct 23, 2015 7:32 am
+2
I have a very small & old Waeco 12v. When I first tried it I plugged it straight into a normal 12v socket in the jeeps dash and went Ok but never great. When I used an extension lead on it it would run constantly struggling to start. After increasing the wire size and leading power directly from the battery it worked so well it froze everything inside until I turned it down.

They require a large amperage to start up but once started continue to run on lower amps. If there is too much resistance from thin wiring then it will keep trying to start and sound like it is never shutting off.
Last edited by Mark on Fri Oct 23, 2015 9:01 am, edited 1 time in total. Reason: Redundant quote of immediately prior post.
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