Adding cooling fans to the back of the fridge

**nadkaw1957** · 07-18-2018, 07:00 PM

Finally... after struggling to get the temp in my 2250's Dometic refrigerator to reach and maintain 39-40 degrees, I made some changes. I noticed that there was only one cooling fan in the back, and after googling it extensively, I found that it blew about 30 CFM across the coil. I also saw that there were holes in the crossbar to mount a second fan. So, I removed the single, inadequate fan and replaced it with two fans that blow 48 CFM each. In one upgrade, I more than tripled the airflow across the coil. I went out to look after work, and the temp was down to 35 degrees - and it's 102 degrees outside.

**TheLexx** · 07-18-2018, 09:07 PM

Do you have any pics of what you did? This sounds like an awesome mod!

**nadkaw1957** · 07-19-2018, 04:18 PM

I'm sorry, I don't. I can describe it for you, though. The first thing I had to do was cut out the baffle behind the upper vent so I could see and get to the original fan. I just used a utility knife - it's only 1/8" plywood. I left enough wood at each edge and the bottom so that I could screw a new piece of plywood to it to create the baffle again. I then removed the original fan from the aluminum cross brace. There are two screws holding it on. I snipped the power wires to the original fan - black = negative, red = positive. I installed the new fans onto the cross brace using the screws that came with them. They are self tapping and screw into the fan frame pretty easily. I connected the two new pairs of wires with the original wires (I used crimp connectors rather than just wire nuts). Finally, I replaced the baffle with a piece of 1/4" plywood I had in the shop. That was pretty much it.

**CFDWheeler** · 07-19-2018, 05:38 PM

Nice mod. Perhaps a dumb question, but this was all done through the vent on the outside of the trailer, correct?

**nadkaw1957** · 07-19-2018, 05:57 PM

Yes, the upper vent.

**Paul_Lori_Millie** · 02-17-2020, 03:00 AM

Originally Posted by nadkaw1957

Yes, the upper vent.

May I ask why the upper vent, as opposed to the lower? Positive Pressure Ventilation (pushing air through) is easier and more efficient than Negative Pressure Ventilation (pulling air through). After 15 years fighting fire, PPV is much better than NPV.... But it seems like everyone puts them on the top. Just curious.

**nadkaw1957** · 02-17-2020, 06:25 AM

Originally Posted by Paul_Lori_Millie

May I ask why the upper vent, as opposed to the lower? Positive Pressure Ventilation (pushing air through) is easier and more efficient than Negative Pressure Ventilation (pulling air through). After 15 years fighting fire, PPV is much better than NPV.... But it seems like everyone puts them on the top. Just curious.

The fans are actually located between the upper and lower vents in a "chimney" type of space. It's pulling air from the lower vent, but pushing it past the upper coils (where the heat is) and out the top vent. Unfortunately, the design (especially of the vent themselves) doesn't lend itself to great airflow.

**Paul_Lori_Millie** · 02-17-2020, 10:38 PM

Originally Posted by nadkaw1957

The fans are actually located between the upper and lower vents in a "chimney" type of space. It's pulling air from the lower vent, but pushing it past the upper coils (where the heat is) and out the top vent. Unfortunately, the design (especially of the vent themselves) doesn't lend itself to great airflow.

Exactly my point - in order for negative pressure ventilation to occur, there has to be a sealing of the area around the fan, meaning nothing can get by without going through the fan. Damned near impossible. In Positive Pressure, it's not required to have that sealing, thus it does not impede air flow, only improves..... Just wondering, because I've seen it both ways. I'm going to start at the bottom (I'm short

) and if I have to go to the top, I will... I bought 5 of them for $20.