Extra fan for fridge unit.

Vara

Vara

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The compressor unit for my cool box is in a locker under the sink, this is vented top and bottom but the locker does warm up when it's running.

I want to mount a computer fan behind the top vent, piggy backed to the power feed for the compressor mounted fan, will this cause problems in terms of overloading.
 
Vara said:
The compressor unit for my cool box is in a locker under the sink, this is vented top and bottom but the locker does warm up when it's running.

I want to mount a computer fan behind the top vent, piggy backed to the power feed for the compressor mounted fan, will this cause problems in terms of overloading.
Click to expand...

No, computer fans are very low current and similar ideas are available commercially and used by motorhome owners to improve the efficiency of their fridges by doing the same job.
 
b
Vara said:
The compressor unit for my cool box is in a locker under the sink, this is vented top and bottom but the locker does warm up when it's running.

I want to mount a computer fan behind the top vent, piggy backed to the power feed for the compressor mounted fan, will this cause problems in terms of overloading.
Click to expand...
No, thats what I did a few months ago on my Bene. I put it at the bottom of the locker to suck cool air in.
S
 
Vara said:
The compressor unit for my cool box is in a locker under the sink, this is vented top and bottom but the locker does warm up when it's running.

I want to mount a computer fan behind the top vent, piggy backed to the power feed for the compressor mounted fan, will this cause problems in terms of overloading.
Click to expand...
I have done the exact same thing 2 yrs ago one in the bottom vent would help as well. i might just add another
 
I doubt very much that it will cause a problem.

Computer fans use around 0.5 A max, and depending upon which one you get / what size, possibly quite a bit less (maybe 0.25A).

I recently did exactly the same thing and ventilated the back space behind the fridge with a thermostatically controlled compter fan.
Fan from Maplins - £5
Temp controlled switch from ebay - £3
Small toggle switch from Maplins (on-off-on) - about £2
Speed controller for fan (it was way too fast at first) from ebay £5
Plastic grille £2

All cheap bits, but I'm really pleased with the installation.
I set my temp controlled switch to come on if the temp behind the fridge gets above 27 deg C.
 
It's much easier just to wire the computer fan(s) in to the compressor supply. They then come on whenever the compressor is running.
 
Vara said:
The compressor unit for my cool box is in a locker under the sink, this is vented top and bottom but the locker does warm up when it's running.

I want to mount a computer fan behind the top vent, piggy backed to the power feed for the compressor mounted fan, will this cause problems in terms of overloading.
Click to expand...

Didnt do so for me.
 
pvb said:
It's much easier just to wire the computer fan(s) in to the compressor supply. They then come on whenever the compressor is running.
Click to expand...

I'm just about to put a computer fan to assist getting rid of the heat in the locker. I was going down the same line of thought as Trundlebug with a Temp controlled switch, as I thought there was little point in running the fan when not required in cooler weather and it would continue to remove the hot air after the compressor had switched off. I agree it would be simpler to connect in parallel to the compressor supply, but for a few extra pounds it would be more efficient.
 
FulmarJeddo said:
I'm just about to put a computer fan to assist getting rid of the heat in the locker. I was going down the same line of thought as Trundlebug with a Temp controlled switch, as I thought there was little point in running the fan when not required in cooler weather and it would continue to remove the hot air after the compressor had switched off. I agree it would be simpler to connect in parallel to the compressor supply, but for a few extra pounds it would be more efficient.
Click to expand...

If you connect it to the supply to the compressor, rather than the supply to the fridge unit, it will only run when the compressor is running. Computer fans use so little power it doesn't really matter if it runs in cold weather.
 
Computer fans work well, but cheap ones can be noisy. Get the biggest quietest fan you can find, probably online.

John
 
As far as I can see from a quick look at specs, a fridge compressor fan of, say, 120mm might take ca. 0.5A for a nominal flow rate of ca. 100CFM. A small computer fan of, say 80-90mm might take as little as 0.1A, but produce a nominal flow rate of ca. 35CFM.

Taken along with the opinion here http://mil-embedded.com/articles/thinking-inside-box-boosting-effectiveness-air-cooling/ that fitting a second fan (implicitly, of the same size) in a PC enclosure would not double air flow but give only a maximum 40% increase, I wonder if fitting a small PC fan might be disappointing. And fitting a fan of comparable size to the compressor fan might well not produce an increase in flow proportional to the increase in power consumption. Not reasons against fitting a second fan of course, but worth bearing in mind when sizing one?

It’s theoretical reasoning I admit - I once considered locating the compressor internally, but decided for efficiency to put it in the cockpit locker - but is it way off beam?
 
Hydrozoan said:
As far as I can see from a quick look at specs, a fridge compressor fan of, say, 120mm might take ca. 0.5A for a nominal flow rate of ca. 100CFM. A small computer fan of, say 80-90mm might take as little as 0.1A, but produce a nominal flow rate of ca. 35CFM.

Taken along with the opinion here http://mil-embedded.com/articles/thinking-inside-box-boosting-effectiveness-air-cooling/ that fitting a second fan (implicitly, of the same size) in a PC enclosure would not double air flow but give only a maximum 40% increase, I wonder if fitting a small PC fan might be disappointing. And fitting a fan of comparable size to the compressor fan might well not produce an increase in flow proportional to the increase in power consumption. Not reasons against fitting a second fan of course, but worth bearing in mind when sizing one?

It’s theoretical reasoning I admit - I once considered locating the compressor internally, but decided for efficiency to put it in the cockpit locker - but is it way off beam?
Click to expand...

I fitted a couple of 80mm brushless computer fans to ventilate the fridge compressor locker on a friend's mobo. Chose them from Maplins, based on getting a mix of low current and low noise. They made a significant difference - reducing compressor run time.
 
How does ducting fit into the equation?

I'm thinking of freeing up a locker by moving my compressor into a void outboard of the battery locker. There aren't any adjacent free surfaces to put vents in, but I could run something like tumble-drier ducting to places where there are.

Should I just duct the input, or just the output, or both? If I just ducted the output, the incoming air would be drawn over the batteries and past the mains charger, which might be beneficial for them but presumably less efficient for the fridge. Or vice versa with a powered input, I guess. The batteries are AGM so hopefully hydrogen shouldn't be an issue!

The compressor itself has a fan on one end - not sure whether it sucks or blows. So should I attach ducting closely to it, using the existing fan to suck or blow through the ducting, or give the ducting its own fan and just have it blow air in the general direction of the compressor? Or one

Hmm. I think I'm answering my own question here (see http://en.wikipedia.org/wiki/Rubber_duck_debugging ). I should set up an intake duct with its own fan, and point it closely at (but not fully attached to) the fridge compressor. That will then be working in a more favourable environment than just sitting in a passively vented locker. The raised pressure at that end of the void (thanks to the powered intake) will cause a general flow out past the batteries and mains charger, which won't care about the slight heat increase from the fridge (batteries are sometimes mounted in engine bays). By not actually attaching ducting directly to anything, I shouldn't create any unforseen problems.

Now I just need to investigate whether the couplings on the refrigerant pipes are the self-sealing reusable type, so I can disconnect them to move the compressor.

Pete
 
pvb said:
I fitted a couple of 80mm brushless computer fans to ventilate the fridge compressor locker on a friend's mobo. Chose them from Maplins, based on getting a mix of low current and low noise. They made a significant difference - reducing compressor run time.
Click to expand...

Thanks, it's interesting to hear real evidence of significant improvement, albeit with two fans. The PC enclosure example is not a close analogy, I admit.
 
ianj99 said:
No, computer fans are very low current and similar ideas are available commercially and used by motorhome owners to improve the efficiency of their fridges by doing the same job.
Click to expand...

Totally agree. Also, if you can make sure that the fan on the compressor is blowing OUT of the locker and no in to it. Sadly, most production boats allow the hot air from the heat exchanger to be blown back into the structure of the boat around the insulation which does no good at all, instead of evacuating it into the accommodation or even externally where it can do no harm.

Max
 
Totally agree with Max K; did this on my own boat to stop all the warm air accumulating under the fridge box. Had to remove the fan and refit 180 degrees around ( 4 screws) as fan was unidirectional ( reversing wiring did not change direction). Seems to make quite a difference in the running time too.
 
Vara said:
The compressor unit for my cool box is in a locker under the sink, this is vented top and bottom but the locker does warm up when it's running.

I want to mount a computer fan behind the top vent, piggy backed to the power feed for the compressor mounted fan, will this cause problems in terms of overloading.
Click to expand...

I have done exactly that. No problem and I use less power because the cooling is better.
 
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