vyv_cox
Well-Known Member
I would wire it in with the external fan at first and see if it makes a difference. Think of something else if necessary later.
danfoss fridge, internal fan operation?
- Thread starter Cactus Sailing
- Start date
rogerthebodger
Well-Known Member
Early I posted to connect the fan to + and to F on the Danfoss connection panel.
This is how my fridge works and has worked for the last 7 years.
On my previous boat I had a heat exchanger with sea water pumped through for cooling the same as Vyv had on one of his.
If the current draw is to big for the Danfoss electronics you can control the fan/pump with a 12VCD relay driven by the + and F connection.
Small computer fans do not need a relay water pumps do.
Daverw
Well-Known Member
Evaporator fan should run all the time, some switch off when door opened. The evaporator is cased in so little natural convection for air circulation so temps would be very poor and evaporator would freeze up
superheat6k
Well-Known Member
+ 1 for running the fan all the time.
Its job is to circulate the cold air around the fridge and past the evaporator plate and it's thermostat. The compressor's job is to cool the evaporator plate as demanded by the stat. If the fan does not run then the air circulation ceases and the stat can pick up the wrong temperature of the cold evaporator, but not the rest of the fridge.
Cactus Sailing
Well-Known Member
the internal fan would only run when the compressor was on, (and for a short while afterwards) is this correct operation? of course it would work but is it correct?
Is this from the manual or knowledge, every boat I have chartered over the past 10 years the fridge fan has intermittently run hence why I'm sceptical about just putting 12v on it permanently which will also use more battery. (albeit very small @ 0.15amps)
GHA
Well-Known Member
As the coldplate warms so rapidly after the compressor turns off why not? If the air has been mixed while the compressor was running what are you going to mix?
Without a load of data logging and thermostats placed around the fridge it's all guesswork anyway, and if the beer is cold who cares?
rogerthebodger
Well-Known Member
I did mine from a but of both but mainly knowledge from my previous boat. The connections + and F are the + is permanent 12VCD but the F connection is only connecting the negative of the fan to the supply negative when the compressor is running. So the Danfoss controller switched the negative and not the 12VCD positive supply.
One think to in my case the temperature bulb of my fridge thermostat is connected to the cooling plate and not the ambient inside the fridge.
GHA. the beer may be cold in the bottom of the fridge but the meat for the sarmis in on the top shelf will go off very quickly where we are in the summer.
GHA
Well-Known Member
Forget the meat then, just drink beer
I've only a little fridge anyway so don't have such a problem, anyway the comment as regarding an internal fan connected to F & + so it just runs when the compressor does, seems little point having it with a separate thermometer but without some work logging difficult to say anything for sure.
rogerthebodger
Well-Known Member
Forget the meat then, just drink beer
I've only a little fridge anyway so don't have such a problem, anyway the comment as regarding an internal fan connected to F & + so it just runs when the compressor does, seems little point having it with a separate thermometer but without some work logging difficult to say anything for sure.
The stuff that is caller beer here is the cold tasteless stuff. I prefer my beer still alive and kicking and not too cold. One thing I do miss from the UK.
BTW I also use the + and F terminals to workout the fridge duty cycle using to resetable timers one on the supply terminal and one on the fan terminals.
GHA
Well-Known Member
The stuff that is caller beer here is the cold tasteless stuff. I prefer my beer still alive and kicking and not too cold. One thing I do miss from the UK.
BTW I also use the + and F terminals to workout the fridge duty cycle using to resetable timers one on the supply terminal and one on the fan terminals.
Good idea
When my thermostat broke a while ago it was cheaper to make a new one using an arduino, since this pic was taked the software has been updated to record duty cycle as well. Interesting to watch the duty cycle go up when the warm beers are added
And just how much it will increase on a warm day.
Daverw
Well-Known Member
I'm a refrigeration engineer as superheat6k i suspect is as well, it's not normal to cycle the evaporator fan as you are try to keep the air temp profile inside as close as possible, if you turn the fan off the cold air will just drop to the bottom, warmer air rise to the top and most likely turn the thermostat back on sooner than it needs to. The small current from the fan over run by the larger current if the compressor. If you logged this over a few days you are likely to be using more power. The idea is to use the stored contents as a thermal load to even out short running which is not as efficient as more power is used to start the refrigeration cycle each time.
Don't assume that anything we have in our boats is either efficient or best practice out in the real world
Don't assume that anything we have in our boats is either efficient or best practice out in the real world
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rogerthebodger
Well-Known Member
Good idea
When my thermostat broke a while ago it was cheaper to make a new one using an arduino, since this pic was taked the software has been updated to record duty cycle as well. Interesting to watch the duty cycle go up when the warm beers are added
And just how much it will increase on a warm day.
That also a good Idea. When I needed to workout the duty cycle I was not un to speed on the current microcontrollers only the old 8031. so just used two resettable timers
I have started to play with the arduino nano and brushing up on my C programming.
I would be interested in any technical details of your set if possible.
superheat6k
Well-Known Member
If you are concerned at the minuscule power drawn by a computer fan the you could consider a separate stat with its sensor phial situated in the top of the fridge, so if the top area becomes warm the fans then runs, but the system will not work effectively if linked to the compressor for the reasons Daverw explains. In my view this extra stat is something of an overkill.
In a commercial fridge the compressor operation is completely autonomous to the evaporator fan control, indeed most commercial systems will have a condensing unit (Compressor / Condenser combination) running numerous evaporators, and the same is true of most multi split office air-conditioners. As the OP has explained his evaporator is partially boxed in, the air flow will not be effective once the compressor stops, if the fan also stops.
In a commercial fridge the compressor operation is completely autonomous to the evaporator fan control, indeed most commercial systems will have a condensing unit (Compressor / Condenser combination) running numerous evaporators, and the same is true of most multi split office air-conditioners. As the OP has explained his evaporator is partially boxed in, the air flow will not be effective once the compressor stops, if the fan also stops.