Cooling Super Maramu Refrigeration Units


Paul Stascavage
 

I thought I would throw this out to the group and see what those more knowledgeable than myself had to say.

I recently had to replace a bad fan on the aft salon refrigeration chest.  The fan I was replacing was installed to draw air from the salon, over the condenser, and into the compartment where the compressor and electronics are housed (sucking cooler air over the condenser).

When I looked at the forward unit in the salon, the fan was mounted the opposite way. That unit draws air from the compartment where the unit is installed, and blows it over the condenser and out into the salon (blowing warmer air over the condenser).  Additionally, this fan was the same brand and model sold by Coastal Climate Control (a US Frigoboat Distributor) which made me wonder if this was the original fan with the original Amel installation (blowing air out).

The Frigoboat installation  instructions seem to imply that the original set up is to blow air from the installed compartment and out (to the salon in our case):

“These units are designed to be mounted with compressor right way up on a horizontal surface in areas where they will not be susceptible to physical or water damage, but accessible for service. They require good ventilation, preferably expelling the heated air to another location by attaching a flexible duct of not more than 6' in length to the duct ring on the unit. A duct kit is available for Capri 35 and Capri 50 models. Do not add any filter type material anywhere in the air flow.

If air is required to be drawn into the unit from another area, the fan may be reversed by removing the housing and re-mounting the fan in the opposite orientation. Reversing the fan leads does not make the fan run in reverse, and the incorrect polarity will result in the fan not operating.

There should be adequate ventilation to allow cool air to enter the condenser, and precautions made to prevent the heated expelled air from being drawn back in. The temperature of the air entering the condenser determines the efficiency of the system. Re-circulating the heated air back into the condenser in a sealed or poorly ventilated cabinet will result in poor system performance. Poor system performance will also result from air being drawn in from a heated space, i.e. an engine room.”

Google searches seem to imply that these fans do a better job blowing than they do sucking, so the question is, what is better?  Blowing a lot of warmer air over the condenser and out into the salon or sucking less’ but cooler air over the condenser and into the installation compartment where all the heat is generated?

I tested the forward fridge unit with the fan installed both ways and the unit ran for basically the same amount of time regardless of fan direction, although the cabin temperature was only 74 degrees Fahrenheit.  I imagine things might be different at higher temperatures (which I plan to check).

My feeling is that the better mode of operation is to introduce cooler air over the condenser and into the installation area.  I believe this would be the more effective way to both cool the condenser efficiently and cool the area where the heat is being generated (compressor definitely felt cooler to the touch drawing air in rather that blowing it out).  Additionally, having the fan blow from the installation compartment and into the salon means that the dust is going to collect on the compartment face of the condenser.  To me, that translates to a situation whereby the condenser is rarely getting cleaned as you would have to gain access the area, remove the fan, and get the vacuum at it (another project for the list).

With the fan drawing air into the condenser, you can easily inspect the condenser from the salon and give it a cleaning whenever the vacuum is out to clean the floor.

As I said, I plan to do some more testing when we get to warmer climates, but I am curios to find out how others currently have their fans installed and any thoughts on which way is indeed best for our installations?

Incidentally, our galley fridge is also set up to draw air from the galley, over the condenser, and then towards the compressor.

Thank you in advance for any and all replies.

All the best,

Paul Stascavage
SM #466 - s/v Rita Kathryn
Preparing to depart for Brunswick, GA

www.RitaKathryn.com


Bill Kinney
 

Paul,

I think you are worried about differences that, while theoretically true, matter little in the real world.  In my experience, the temperature of the air under the settee is trivially different than the air in the cabin.  The amount of air moved by the fan is also so slightly different in the two directions that it doesn't really matter.

Far more important is to keep the condenser clean and free of dust and dirt.  Even a light coating of dirt will have a far bigger impact on heat transfer.

Bill Kinney
SM160, Harmonie
Annapolis, MD, USA (heading south in 24 to 48 hours....)


Jose Venegas
 

Paul,
The proper way is to blow air into the condenser. Not only it improves the heat transfer by blowing cooler air into the condenser but , more importantly, it filters the air before it is blown into it
José
Ipanema SM2k 278
Red frog Panama

Enviado desde mi iPhone


Michael & Robyn
 

Hi Paul,

we replaced all fans of our frigoboat fridges with:
epm-pabst fans 4412FGL: DC Fan, 12V, 120x120x25mm, 55.3CFM, 1.3W, 26dBA, Wire Leads
and added screens epm-pabst LZ60  to prevent the dust get into the fan itself, because that is what killed our pantry fridge fan.
We bought em here:
https://www.alliedelec.com/product/ebm-papst/4412fgl/70105044/?keyword=70105044
https://www.alliedelec.com/product/ebm-papst/lz60/70105471/?keyword=70105471
be careful which way you mount the screen to the fan so the blades don't scrape (ask me why I know...).
These fans are so much quieter and provide at least the same amount of airflow.

We choose to blow air outwards of the cabinets in the hopes that there is less dust coming from the bilge area.
If you would choose to blow air towards the condenser it would be easier to clean the dust off the screens with a vacuum occasionally.  If I would have to redo the fridges I would go for it.
I agree with Bill K. that the direction doesn't really matter much from an air temperature perspective. The dirt on the condenser fins is the bigger issue.

kind regards
--
Michael & Robyn

SY RIPPLE SM2K # 417
currently BLM Brunswick GA


Mike Longcor (SV Trilogy)
 

Hi Paul,

Our fridge/freezers pull cool air in from under the saloon table. The dust collects in a place you can easily clean and the warm air in the cabinet vents up and out behind the seat backs in the corner. It's worked well for us over the years.

As Michael and Robin point out, there are lots of inexpensive cooling fan options (used for computers, etc.). Definitely worth getting a spare or two.

Cheers,
Mike Longcor
SV Trilogy SM23
NZ


On Sat, Oct 30, 2021, 3:46 PM Paul Stascavage via groups.io <pstas2003=yahoo.com@groups.io> wrote:
I thought I would throw this out to the group and see what those more knowledgeable than myself had to say.

I recently had to replace a bad fan on the aft salon refrigeration chest.  The fan I was replacing was installed to draw air from the salon, over the condenser, and into the compartment where the compressor and electronics are housed (sucking cooler air over the condenser).

When I looked at the forward unit in the salon, the fan was mounted the opposite way. That unit draws air from the compartment where the unit is installed, and blows it over the condenser and out into the salon (blowing warmer air over the condenser).  Additionally, this fan was the same brand and model sold by Coastal Climate Control (a US Frigoboat Distributor) which made me wonder if this was the original fan with the original Amel installation (blowing air out).

The Frigoboat installation  instructions seem to imply that the original set up is to blow air from the installed compartment and out (to the salon in our case):

“These units are designed to be mounted with compressor right way up on a horizontal surface in areas where they will not be susceptible to physical or water damage, but accessible for service. They require good ventilation, preferably expelling the heated air to another location by attaching a flexible duct of not more than 6' in length to the duct ring on the unit. A duct kit is available for Capri 35 and Capri 50 models. Do not add any filter type material anywhere in the air flow.

If air is required to be drawn into the unit from another area, the fan may be reversed by removing the housing and re-mounting the fan in the opposite orientation. Reversing the fan leads does not make the fan run in reverse, and the incorrect polarity will result in the fan not operating.

There should be adequate ventilation to allow cool air to enter the condenser, and precautions made to prevent the heated expelled air from being drawn back in. The temperature of the air entering the condenser determines the efficiency of the system. Re-circulating the heated air back into the condenser in a sealed or poorly ventilated cabinet will result in poor system performance. Poor system performance will also result from air being drawn in from a heated space, i.e. an engine room.”

Google searches seem to imply that these fans do a better job blowing than they do sucking, so the question is, what is better?  Blowing a lot of warmer air over the condenser and out into the salon or sucking less’ but cooler air over the condenser and into the installation compartment where all the heat is generated?

I tested the forward fridge unit with the fan installed both ways and the unit ran for basically the same amount of time regardless of fan direction, although the cabin temperature was only 74 degrees Fahrenheit.  I imagine things might be different at higher temperatures (which I plan to check).

My feeling is that the better mode of operation is to introduce cooler air over the condenser and into the installation area.  I believe this would be the more effective way to both cool the condenser efficiently and cool the area where the heat is being generated (compressor definitely felt cooler to the touch drawing air in rather that blowing it out).  Additionally, having the fan blow from the installation compartment and into the salon means that the dust is going to collect on the compartment face of the condenser.  To me, that translates to a situation whereby the condenser is rarely getting cleaned as you would have to gain access the area, remove the fan, and get the vacuum at it (another project for the list).

With the fan drawing air into the condenser, you can easily inspect the condenser from the salon and give it a cleaning whenever the vacuum is out to clean the floor.

As I said, I plan to do some more testing when we get to warmer climates, but I am curios to find out how others currently have their fans installed and any thoughts on which way is indeed best for our installations?

Incidentally, our galley fridge is also set up to draw air from the galley, over the condenser, and then towards the compressor.

Thank you in advance for any and all replies.

All the best,

Paul Stascavage
SM #466 - s/v Rita Kathryn
Preparing to depart for Brunswick, GA

www.RitaKathryn.com


rossirossix4
 

We placed cut-t0-size spun furnace filter material over the inlet.  Low resistance and easy to clean with water.   Air flow is very good.  Avaiable in most hardware stores.  We also replaced AC filters with same material.  Lots of flow and no dust on fans or fins.  Just make sure they are low resistance. 

Bob and Suzanne       KAIMI SM429