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Old 10-11-2016, 08:12 PM   #1
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Refrigerator fan

We have an 11 cubic foot 110 volt household refrigerator on board that we will be replacing soon. I would like to add a couple 12 volt PC fans to exhaust the hot air from the back. Is there an easy way to have the fans come on and off with the refrigerator?
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Old 10-11-2016, 08:17 PM   #2
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All you need is a Thermal switch $16 on ebay
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Old 10-11-2016, 11:57 PM   #3
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What kind of fridge? If it's a Nova Cool it should already have an output terminal on the controller that will drive up to 0.5A at 12VDC.

Actually any fridge with a Danfoss compressor should have that terminal.

Do NOT use two fans. Use one fan that is large enough to do the job. I made the two fan mistake years ago and the two set up an unholy racket. Each fan individually was dead quiet but the two together sounded like a tiny jet engine. Harmonics drove me to go for the single larger fan. I used a single 4" fan that draws about 0.18 A, well within the Danfoss ability.

Runs only when the fridge operates.

Before I forget again use a diode to snub any voltage spike from the fan. Failure to do that could damage the output over time. a 1N4007 should do the trick.
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Old 10-12-2016, 03:26 AM   #4
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Quote:
Originally Posted by C lectric View Post
What kind of fridge? If it's a Nova Cool it should already have an output terminal on the controller that will drive up to 0.5A at 12VDC.

Actually any fridge with a Danfoss compressor should have that terminal.

Do NOT use two fans. Use one fan that is large enough to do the job. I made the two fan mistake years ago and the two set up an unholy racket. Each fan individually was dead quiet but the two together sounded like a tiny jet engine. Harmonics drove me to go for the single larger fan. I used a single 4" fan that draws about 0.18 A, well within the Danfoss ability.

Runs only when the fridge operates.

Before I forget again use a diode to snub any voltage spike from the fan. Failure to do that could damage the output over time. a 1N4007 should do the trick.
Been there too....just use 1 fan
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Old 10-12-2016, 07:33 AM   #5
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You can add a relay that triggers a fan when the compressor goes on. Relays and computer fans are available in 110 VAC or 12 VDC. We added fans on our 12 volt system using Bosch style relays (less than $10). We took the trigger voltage from the compressor and used the power in source for the fan power/voltage. The fans we installed put us over the current draw limit to power them from the compressor it self. That's why we used relays. There's lots of info on the internet. Here's one example.

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Old 10-13-2016, 12:51 AM   #6
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Yes, a relay can be used if the fan you wish to drive draws more current than the fridge output can handle. Most relays of the nature shown will use about 40-60 milliamps or 0.04A - 0.06A. I would still use that diode across the relay's power terminals.

However, a 4" computer type fan should be plenty for just pulling the heat away from the back of the fridge, at least most fridges, ventilating the compartment.
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Old 10-13-2016, 01:24 PM   #7
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Thanks for the replies. The refrigerator in the boat now is a General Electric. Due to the limited space it looks like the replacement will also be a GE. I wasn't aware of 110V computer fans, but that might be the way to go. Larry M, I'm very familiar with the Bosch relays, having been a Porsche technician for 40 years. The number system for the wiring is burned into my brain. I will look at the refrigerator wiring diagram and figure out where to get the signal from. Thanks again.
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Old 10-14-2016, 07:39 PM   #8
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All you need is a Thermal switch $16 on ebay
That sounds like the beginning of a good idea but you should really explain it.
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