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Old 12-04-2017, 18:27   #16
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Re: Fan on AB compressor

7. Condenser Cooling and process heat disposal Fan or fans.

Performance and energy efficiency of any refrigeration unit depends on the condenser’s Cooling Medium temperature. Refrigerators are generally designed for optimum standard day air temperature of 68 to 70˚F. Most small 12 volt boat refrigeration units have long capillary tube, refrigerant expansion devices that control refrigerant at a specific volume of refrigerant flow. If the condenser’s cooling medium varies above or below the manufacturer’s design temperature, a system’s optimum performance will change. The reason performance changes when the cooling medium temperature changes is that the refrigerant’s high pressure increases and as temperature increases it draws more current.

Home condenser cooling medium temperature do not change much inside a home where creature comfort is maintained but when installed in a boat ambient air temperatures do change.

The key to gaining the best performance from small 12/24 volt refrigerators or icebox conversion units is how correctly it is installed in your boat. Using cabin air directly into intake side of condenser cooling coil and using a fan to dispose of process heated air to an open area so that it can not re-circulate again is what I mean by correct installation. Some manufacturers elect not to use positive displacement fan shrouds to insure all fan air capacity flows through the condenser coil. These units should be avoided if they are to be installed in a closed space. If you want peak performance on an already installed unit, look at ways to better direct air over the condenser coil. Standard designs for condenser fan capacity on condensing units powered by Danfoss BD compressors are to use four inch muffin fans with a cfm capacity of around 60 cfm.

Twelve condenser fans are also available in 80, 100, and 130 cfm. The problems with replacing a small capacity fan with a larger capacity one is that they are noisier and higher cfm fans are 5/8 inch thicker than the original. The larger 100 and 130 cfm fans can be connected to Danfoss BD2.5 and BD 3 modules direct because they draw less than one amp. If a fan draws more than ˝ amp it cannot be powered from the BD35 or BD50 compressor modules direct and a relay is required. For tropical climates, my designed units all had 80 cfm fans. The best thing about these little air cooled units is high refrigerant pressure performance can be maintained in cool climates by blocking a portion of condenser coil. Danfoss BD35 and BD50 compressor module condenser fans are always 12 volt even when module and compressor are running on 24 volts.
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Old 13-04-2017, 07:01   #17
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Re: Fan on AB compressor

Great information Richard, as usual .

This paper also explains the interaction of pressure and temperature and how it applies to refrigerant flow inside a capillary tube .

http://icemeister.net/backroom/wp-co...ed-Version.pdf

As you can see , there is a performance trade off as temperatures rise . Capillary tube based refrigeration systems are, as you said, better suited inside a home were the ambient temperatures are far better controlled.

This is the reason so many manufactures see water cooling as the most stable way to control condensing temperatures , but that has its own set of maintenance nightmares as this forum will attest to with hundreds of posts from people with failed systems.

We build DC systems they use a completely different way of controlling refrigerant flow. No water cooling , no capillary tubes .

Regards John.
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Old 21-04-2017, 07:05   #18
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Re: Fan on AB compressor

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Originally Posted by ColdEh Marine View Post
Great information Richard, as usual .

This paper also explains the interaction of pressure and temperature and how it applies to refrigerant flow inside a capillary tube .

http://icemeister.net/backroom/wp-co...ed-Version.pdf

As you can see , there is a performance trade off as temperatures rise . Capillary tube based refrigeration systems are, as you said, better suited inside a home were the ambient temperatures are far better controlled.

This is the reason so many manufactures see water cooling as the most stable way to control condensing temperatures , but that has its own set of maintenance nightmares as this forum will attest to with hundreds of posts from people with failed systems.

We build DC systems they use a completely different way of controlling refrigerant flow. No water cooling , no capillary tubes .

Regards John.
John, can you tell us how you would apply this link (Theory of the cap tube as a refrigerant control) when applied to Danfoss BD 200 to 800 Btu compressor. systems.
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Old 04-04-2018, 04:46   #19
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Re: Fan on AB compressor

Hi everyone, and thank you Richard and John for sharing your accumulated wisdom on refrigeration, especially this useful info on fans to cool the condensor. Our Frigoboat setup with BD50F has a noisy Bi-Sonic fan (rated at 43Db, drawing 0.38A and moving 80cfm) which is in a housing coupled to the condensor so it can suck the heated air out of the tiny compartment housing the compressor and condensor under the ~ 70L fridge and ~ 60L freezer. There's no air intake into this compartment other than the grilles around the edges of the fan housing! So my sound engineer partner (who is very sensitive to discordant noise) and I (sensitive to the risk of overheating our compressor) are thinking of installing 2 fans which are far quieter - 25Db - though only move 64cfm. They draw 0.22A each. The idea being that one draws air in to said tiny compartment from the floor of the cabin next door and the other replaces the noisy fan which sucks it out. Unfortunately the intake will have to be at right angles to the exhaust. I'd love to hear your ideas on whether we should drill that 120mm dia hole to install an air intake fan - it's not my boat or I'd have already done it!
Another option we discussed is replacing the grilles with 2x90mm intake fans (which would fit) but my problem there is that they'd be bringing in the air which has just been exhausted. Or would we set them to extract as well? We're also wondering if 64cfm in and out = 128cfm in reality or is it just 64cfm? And are thinking if we used the 2 x 90mm fans should they be wired to run from a separate power supply (always on) as the total draw would be >0.5A? Or a relay?
We cruise above 35 south and into the tropics. Currently north of Brisbane.
Hope you can help, our local fridge mechanic isn't boat/12v savvy. Regards, Fiona
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Old 04-04-2018, 05:54   #20
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Re: Fan on AB compressor

Hi Fiona .

Always, the more air flow the better and if you can assure that the airflow to the condenser is fresh at all times or brought into the condenser from a different place, not to use any exhausted heated air . Systems designed like the one you have are very sensitive to condensing temperatures.

The fans your are looking at are .22 amps each , or .44 amps total , if you use these fans you will be approaching the limit of the fan driver circuit in the compressor controller , you may want to use a relay. Or you could just wire the fan that draws the air into the compartment to your ships power and have it run 24/7.

Or you could get two of these fans that take 0.1 of an amp and wire them both on the controller . These are the fans we use , they are expensive but the best on the market. Move a lot of air and are very quiet.

https://noctua.at/en/products/produc...strialppc-2000



Another solution is to mount a snap relay on top of the compressor and have it run the compartment fan when the compressor reaches a certain temperature like this below.



Hope this helps .

Regards John.
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Old 04-04-2018, 15:03   #21
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Re: Fan on AB compressor

Quote:
Originally Posted by ColdEh Marine View Post
Hi Fiona .

Always, the more air flow the better and if you can assure that the airflow to the condenser is fresh at all times or brought into the condenser from a different place, not to use any exhausted heated air . Systems designed like the one you have are very sensitive to condensing temperatures.

The fans your are looking at are .22 amps each , or .44 amps total , if you use these fans you will be approaching the limit of the fan driver circuit in the compressor controller , you may want to use a relay. Or you could just wire the fan that draws the air into the compartment to your ships power and have it run 24/7.

Or you could get two of these fans that take 0.1 of an amp and wire them both on the controller . These are the fans we use , they are expensive but the best on the market. Move a lot of air and are very quiet.

https://noctua.at/en/products/produc...strialppc-2000



Another solution is to mount a snap relay on top of the compressor and have it run the compartment fan when the compressor reaches a certain temperature like this below.



Hope this helps .

Regards John.
Hey John thankyou for your speedy reply and all the design ideas. With the help of your post I've talked the skipper into cutting a hole (yay!) and have ordered two Noctua fans, one for intake and one for exhaust. Huge thanks ☺
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Old 05-04-2018, 05:27   #22
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Re: Fan on AB compressor

My pleasure

Happy to help.

Regards John
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Old 05-04-2018, 08:40   #23
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Re: Fan on AB compressor

Quote:
Originally Posted by ColdEh Marine View Post
My pleasure

Happy to help.

Regards John
Hi John,

Just coincidentally I have been planning to replace the very noisy Bi-Sonic fan on my fridge so have been following this thread closely. Based on other research I was focusing on the Noctua fans so it was good to see an endorsement from a pro.

I was looking at two models, the NF-S12A FLX and NF-A14 industrialPPC-2000 that you mentioned. I have a Frigoboat, air cooled (obviously) Capri BD50 system. You say you use two of the 2000 fans. Is one going to be adequate? They are rated a little lower air flow than the Bi-Sonic, 120 m3/hr vs 135 m3/hr if I recall.

Thanks
Skip
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Old 05-04-2018, 09:03   #24
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Re: Fan on AB compressor

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Originally Posted by skipmac View Post
Hi John,

Just coincidentally I have been planning to replace the very noisy Bi-Sonic fan on my fridge so have been following this thread closely. Based on other research I was focusing on the Noctua fans so it was good to see an endorsement from a pro.

I was looking at two models, the NF-S12A FLX and NF-A14 industrialPPC-2000 that you mentioned. I have a Frigoboat, air cooled (obviously) Capri BD50 system. You say you use two of the 2000 fans. Is one going to be adequate? They are rated a little lower air flow than the Bi-Sonic, 120 m3/hr vs 135 m3/hr if I recall.

Thanks
Skip
Hey Skip.

Yes, I recommended two of them for the previous poster . They can use one directly as replacement on the condenser and the second as a compartment fan . They both can be wired on the Danfoss controller because of there extremely low amp draw , these fans are very sophisticated compared to your basic computer fan . The ones we use are even water proof! The way I see it if they can keep out water they will keep out dust as well and that is what kills a fan over time . So we opt for the top of the line IP67 rating .


Sorry back to your question. You could go to one of these .


https://noctua.at/en/products/produc...alppc-3000-pwm

They will move more air but will be a bit noisier .

Also you have to remember the way these fans are rated , some of them move more air on paper in open air but have a problem moving it under any head pressure . The Noctua will outperform most fans when you press it to move air though a condenser . We tested dozens of fans before we settled on the Noctua.



You have to consider were you exhausting your condenser air as well. You may be better served by doing the same thing as the previous poster and use two smaller fans . .

Regards John.
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Old 05-04-2018, 09:29   #25
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Re: Fan on AB compressor

Hi John,

Thanks for the reply. Maybe a little more info on my setup. The compressor/condenser is installed under the floor in my main cabin. It's a pretty large area, roughly 2' high, 6' long, 6' wide at the top following the hull curve to the bottom. Also open in a few spots (around the keel stepped mast, bottom of the cabinets in the head, gaps around the settees, etc.) so not too worried about heat buildup in the area. Should I be? Also is the coolest spot on the boat in really hot weather.

I'm thinking about installing the 2000 in the shroud to replace the Bi-Sonic and maybe a second, possibly the ULN model, sitting over or next to the compressor?

Skip



Quote:
Originally Posted by ColdEh Marine View Post
Hey Skip.

Yes, I recommended two of them for the previous poster . They can use one directly as replacement on the condenser and the second as a compartment fan . They both can be wired on the Danfoss controller because of there extremely low amp draw , these fans are very sophisticated compared to your basic computer fan . The ones we use are even water proof! The way I see it if they can keep out water they will keep out dust as well and that is what kills a fan over time . So we opt for the top of the line IP67 rating .


Sorry back to your question. You could go to one of these .


https://noctua.at/en/products/produc...alppc-3000-pwm

They will move more air but will be a bit noisier .

Also you have to remember the way these fans are rated , some of them move more air on paper in open air but have a problem moving it under any head pressure . The Noctua will outperform most fans when you press it to move air though a condenser . We tested dozens of fans before we settled on the Noctua.



You have to consider were you exhausting your condenser air as well. You may be better served by doing the same thing as the previous poster and use two smaller fans . .

Regards John.
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Old 05-04-2018, 09:53   #26
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Re: Fan on AB compressor

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Hi John,

Thanks for the reply. Maybe a little more info on my setup. The compressor/condenser is installed under the floor in my main cabin. It's a pretty large area, roughly 2' high, 6' long, 6' wide at the top following the hull curve to the bottom. Also open in a few spots (around the keel stepped mast, bottom of the cabinets in the head, gaps around the settees, etc.) so not too worried about heat buildup in the area. Should I be? Also is the coolest spot on the boat in really hot weather.

I'm thinking about installing the 2000 in the shroud to replace the Bi-Sonic and maybe a second, possibly the ULN model, sitting over or next to the compressor?

Skip
Sounds like you have a good setup for heat dissipation , I really wouldn't worry about heat building up in that area.

As for fan choice the NF A P S fans are very quiet but suffer when used with any head pressure. At least this is what we found when we tried to use them to move air though a condenser . Your Bi-Sonic fan states slightly more air flow then the NF-F 2000 fan in free air but I know they are noisy and power hogs . I wouldn't be to concerned about the difference. The blade design on the Noctua fans work well under pressure and they are quiet . If you want lots of air flow get a 3000 but they are a little noisier but quieter then your sonic .


If you think your compressor temperatures are a little high with the sonic go for the 3000 . That should get lots of air over your compressor and keep it simple , but your idea of the satellite UL fan over the compressor would work as well.

Regards John.
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Old 06-04-2018, 15:23   #27
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Re: Fan on AB compressor

John,
I notice the Noctua fans you recommend are either 3 pin or 4 pin wire leads. Is it correct to assume for 12 volt install to replace condenser fan on a AB cold machine you just use the red to positive and black to negative and you will get max RPM ?

If so are the unused wire(s) on the fan typically used to reduce fan speed when hooked up to speed control in a computer cooling setup ?

Than you for the insights on the fan questions !
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Old 07-04-2018, 10:52   #28
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Re: Fan on AB compressor

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John,
I notice the Noctua fans you recommend are either 3 pin or 4 pin wire leads. Is it correct to assume for 12 volt install to replace condenser fan on a AB cold machine you just use the red to positive and black to negative and you will get max RPM ?

If so are the unused wire(s) on the fan typically used to reduce fan speed when hooked up to speed control in a computer cooling setup ?

Than you for the insights on the fan questions !

Here you go . Just use the + and - and the fan runs at full speed .

Regards John

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Old 07-04-2018, 12:43   #29
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Re: Fan on AB compressor

You can contact Donna at "R parts" , they have them in stock .

RPARTS.COM - Refrigerator Thermostat


Any idea where, on the actual thermostat, are the part numbers? I have a couple now I've been fooling around with and can't find any identifying numbers that match what's on RParts.....?
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