Beneteau 323 refrigerator improvement

[wrbeglin]

The compressor on the 323 came from the factory poorly vented. It's location under the sink came with one vent, and it was below the shelf the compressor was mounted on. See the pictures attached. I cut a 3-1/2 hole on the aft side of the compartment, which allows fresh air to be drawn in by the compressor fan. On the discharge side of the condensor, I cut a hole in the shelf and then cut a std. 3" pvc elbow to fit and taped it to the discharge duct. It's made a huge improvement as the compartment now stays at ambient temperature vs. the large heat build up previously.

 

[Ron20324]

You could continue the PVC duct to blow it out the forward vent, though the boat in motion and/or with the hatches open would tend to blow air IN the front vent- like a wind scoop. I placed that aft vent as high up as I could, so fan or not, convection(?) naturally draws colder air in the lower front, and as it heats, it wafts out the higher aft vent. Also, some insulation under the cabinet will keep hot air from drifting under it and around the fridge box.

Try: http://www.beneteau323owners.net/

 

[Mike B]

I've done something simlilair on our 43 plus also clean the dust out of the fins on a regular basis. It's amazing how much air dust blocks. Good air flow is a must for maximum cooling.

 

[Gunni]

That install doesn't sound right, the duct shown looks like the INTAKE duct for the evaporator coil. The fan pushes cool intake air over the coil and out past the compressor. In any case, ducting the intake to the low cabin makes a huge difference but like Mike notes these things suck up a lot of dust and that will send the compressor into a fault shutdown. A patch of furnace filter on the intake screen, easily reached, will save you a lot of maintenance.

 

[wrbeglin]

The air flow is from left to right in the pictures. The fan draws air from the aft end of the boat through the new vent and blows it over the compressor first then past the condensor coil. After I took the picture I did install a small piece of filter material over the vent. Maybe Beneteau should have installed the compressor 180 so that air flow was from front to back, but honestly most of the time I'm sailing I have the hatches closed to keep splashed water out and prevent the jib sheets from getting caught on the hatches when tacking. Even with air flowing through, there is not enough pressure differential to force air through this space. The duct I installed very nicely directs the warm discharge air from the compressor unit down towards the the large orignally installed vent.

 

[wrbeglin]

You could continue the PVC duct to blow it out the forward vent, though the boat in motion and/or with the hatches open would tend to blow air IN the front vent- like a wind scoop. I placed that aft vent as high up as I could, so fan or not, convection(?) naturally draws colder air in the lower front, and as it heats, it wafts out the higher aft vent. Also, some insulation under the cabinet will keep hot air from drifting under it and around the fridge box.

Try: [URL="http://www.beneteau323owners.net/"]http://www.beneteau323owners.net/[/URL]

I like your idea of continuing the PVC and actually have a 4" el that I toyed around with installing for just that purpose. Decided to try it like this first so i'd have a base fr comparison. Also plan to leave a space between it and the vent grill so that even when the compressor isn't running there will be some convection flow through the cabinet. From experience on this boat an others, I know the keys are correct freon charge, good batteries, clean coils and not dating a women that leaves it open like her frig at home !

 

[Mike B]

If you're still not happy with the air flow you can always install a small fan available for use in a PC or other electronic device. They're cheap, quiet and move a fair amount of air. Not much energy draw either.

 

[wrbeglin]

The air flow with my set up is great. I was out in 25 mph winds the other day and 85 degrees and was very peased with the fridge. The only place I'd install an auxillary fan would be in the box itself. Several boats do this, I have a friend with a Bavaria and it has a small interanl (PC type) fan inside the box and it makes for a nice improvement and much more consistent temperatures throughout. Thanks for your thoughts.

 

[Gunni]

"The duct I installed very nicely directs the warm discharge air from the compressor unit down towards the the large orignally installed vent."

After it flows across your cooling radiator. OK, lets take a step back. The refrigeration unit pumps heat from your cold box out to the condenser (radiator) where the refrigerant heat is dissipated in the air flow and refrigerant is sent to the compressor where more heat is created in the gas compression, only to have that heat flow across your condenser. Venting the space is great, but your engine is essentially in front of your radiator, greatly increasing the load. Not sure why you have a filter on the vent side, you need it on the intake side where the dust comes in. What is the manufacturer of this system?

 

[wrbeglin]

In the refrigeration systems, compressors are designed to compress the refrigerant gas. This hot, high pressure gas then passes through the condenser and condenses into a liquid, releasing heat equal to the latent heat of condensation, which also equals the enthalpy or latent heat of vaporization of the refrigerant. This is why the temperature differential of the Freon across the condenser does not change significantly even though there has been significant heat removed from it. The real change is that while it is still under high pressure, it now exists as a liquid. There is also some benefit in the air passing over the compressor as excessive retained heat is the enemy of the compressor motor. If it's located downstream of the condensor there is less benefit. Comparisons to automotive engines really don't apply as in a car radiator, there is no change of state (gas/liquid) involved. In addition the total surface area of the condenser fins are significantly more than the smooth surface area of the compressor housing so the temperature differential across the condenser coils still remains quite high. Essentially the condensor will do it's job either way.

Also note that after the refrigerant exits the condenser, it goes to the expansion valve in the refrigerator box, just ahead of the evaporator, not back to the compressor. This compressed liquid absorbs heat in the evaporator equal to it’s latent heat of evaporation times the mass flow rate. It then returns to the compressor to begin the cycle again.

In the evaporator in the refrig box, the heat of vaporization, i.e. the heat absorbed when the 'cooler’ compressed liquid is run through the expansion valve is about 170 times the amount of heat absorbed when the temperature of either the pure liquid or gas is raised 1 degree. The key is this change of state process.

So while it can be debated whether or not the compressor is up or downstream of the condenser, the net impact is relatively insignificant. The real key is total air flow and the correct Freon charge in the system to most efficiently utilize the change of state of the Freon.

Sorry this was a bit long.

 

[Gunni]

Yeah, I've just never seen this kind of set up. The Adler Barbour system for instance is exactly opposite - the condenser is upstream of the compressor. Air is fan-drawn from the outside directly to the condenser, then across the compressor. And the only problem I've ever experienced with them is dust clogging the condenser fins causing a loss of cooling efficiency. The compressor runs continuously trying to cool the box and eventually goes to fault mode (shutdown).

 

[wrbeglin]

Interesting, I sent off a quick note to Frigiboat, the Danish company that makes my unit and asked them about this, why one way vs. the other etc. Will be interesting to hear their response/justification for one way vs. the other.

 

[Gunni]

Ah Frigiboat! They like to configure their refrigeration units with a keel cooler, which eliminates the fan condenser.

 

[Ron20324]

Interesting, I sent off a quick note to Frigiboat, the Danish company that makes my unit and asked them about this, why one way vs. the other etc. Will be interesting to hear their response/justification for one way vs. the other.

Probably was a left-hand unit, but meant to be in a starboard galley?

 

[wrbeglin]

Frigiboat responded a few days ago, i'm just now catching up. They did have the airflow over the compressor first then the condensor fins for the reason I expected. It helps keep the compressor cool and if you study thermodynamics, any heat removed from either the compressor of the refrigerant contributes to the total cooling. they also stated the fan could be reversed, but in their experience have found the set up as is to be the most beneficial.

 

[sheetmusic21396]

I was able to duct my coil out the wall behind the sink which allows cool air from the existing factory vent to rise as it is heated and expelled thru the cabinet wall above the refrigeration unit

 

[wrbeglin]

Great idea. Either way we've both made a major improvement. I've seen a tremendous improvement in efficiency. This was one of the few bad design decisions on an otherwise very well thought out boat.

 

[Ron20324]

I was able to duct my coil out the wall behind the sink which allows cool air from the existing factory vent to rise as it is heated and expelled thru the cabinet wall above the refrigeration unit

And use the heat for the cabin warmth- for what it's worth.