Summertime + Fridge = 46°+

[ntsqd]

Sounds like the OE fan circuit could easily drive a "sugar cube" relay, which in turn is normally rated for 30A. Put both fans on the relay.

 

[craig333]

The fan I wired into my fridge is rated at 20ma. Its plenty big enough.

 

[PaulT]

Dawn,

Using your phone in selfie mode or a mirror, open the bottom vent and look towards the top vent inside the fridge compartment. You should see a pair of wires with terminals crimped on the ends in the center bottom of the upper vent area

In the area behind the lighting switch panel at entry (battery compartment on my Hawk), there should be a pair of wires (blue in my case) with terminals attached that will plug into a refer fan switch. I ordered one from FWC and it just snaps into the existing hole after removing the small cover plate.

Crimp on some appropriate terminals (male bullet connectors) to the fan. Mount the fan behind the fridge and plug the fan into the two wires.
This makes a manual fan, rather than an automated one but you're not limited to the power that the fridge can supply. A thermostat could be added between the fan wires in the fridge compartment and the fan wires, or a relay to switch the power when the fridge is running.
Ensure that the fan is mounted to blow out and that it actually blows out when running.













Paul

 

[JaSAn]

Yes, but if using a modern compressor fridge like a Dometic or Isotherm that uses either a BD35F or BD50F Danfoss compressor *and* tapping off the fridge's wiring, make sure to not exceed the fan output's rating of .5A sustained or 1A burst for 2 seconds or the compressor will turn off as per the the attached document in this link.

My refrigerator is on a dedicated circuit and the exhaust fan is on a circuit with my USB and ciggy plugs. Fan is controlled by a thermal switch (80° on) and if it runs continuously will draw 1/2 amp hours/day. So small I don't worry about it.

I agree that you need to do your homework if you add loads to the refrigerator circuit.

jim

 

[ntsqd]

FWIW Our t-stat switches are located next to the fans and the 80° unit would have the fans running all day, every day. Even when the air blowing out doesn't feel like it's 80° I think that is partly due to ours being a 3-way fridge that is usually running on propane. Wouldn't be a bother if they weren't so loud. I included a manual switch in the circuit to turn them off when the camper isn't in use, but I end up using it as a reality check (sanity check?) to keep the noise down when not necessary.

 

[Stalking Light]

I think I'll go the relay route and trigger it off the compressor fan circuit that way no worries about additional fan draw.

 

[Kodachrome]

I think I'll go the relay route and trigger it off the compressor fan circuit that way no worries about additional fan draw.

Thinking the same...

 

[hoyden]

Thanks for all the info and ideas!
I can do a lot of mechanical things, but electricity makes me nervous.
I sent Clint at AT (Adventure Trailers) an email, and he's going to help me out.
Yay campering people

 

[Stalking Light]

Thanks for all the info and ideas!
I can do a lot of mechanical things, but electricity makes me nervous.
I sent Clint at AT (Adventure Trailers) an email, and he's going to help me out.
Yay campering people

Clint's the man all right. Tell him I said hi.

 

[PaulT]

Thanks for all the info and ideas!
I can do a lot of mechanical things, but electricity makes me nervous.
I sent Clint at AT (Adventure Trailers) an email, and he's going to help me out.
Yay campering people

Makes you nervous? Why do you think Electrical Engineers are so weird?
They can't even see the raw material with which they do their work. .

They talk about a voltage drop on a wire going uphill.
They can move it from one wire to another without any connection between them.
They run a bunch of it into a chunk of metal stuck up in the sky and it magically disappears only to reappear in another chunk of metal stuck up in the air miles or even a world away.
They have to use imaginary numbers to discuss it.
Nobody else understands what they say.

Don't let it make you nervous. We software engineers have just learned to keep a respectful distance and let the EE's have at it.

No. Really. I appreciate those EE's. Just don't grok what they do.
Paul

 

[hoyden]

<snip> No. Really. I appreciate those EE's. Just don't grok what they do.
Paul

heehee! you said "grok"

Last year, I spent a few months staring at my 1975 Yamaha RD350 wiring diagram... never did really get it.
I can do basic stuff, and understand voltage drop, and not to put too small a wire in (sometimes bigger IS better)
Soldering is fun!

Many years ago, I had a stock RD and put a new battery in. I didn't realize the new battery was taller than the old one... when I closed the seat - with a metal pan - it shorted out and burned up half my harness! Der.

Now I'm gun shy and don't want to accidentally burn up my fridge.

 

[Alley-Kat]

I'm not an Electrical Engineer, however, let's see if my research has been successful.

From those that are talking about powering the OEM and AUX fridge fans via a sugar cube relay, I had to refresh my memory of a single pole single throw relay and what terminal connections are connected to which wires and what goes on inside the relay.

This is what I found. Maybe this will help others to also understand.

And, if I understand it all, then here is the original wiring to the OEM fan and the new wiring with a sugar cube SPST relay to the OEM and AUX fans. (Danfoss BD35/50F compressor fridge)

So, correct me if I'm wrong...

The circuit that used to power the OEM fan is now only powering/triggering the sugar cube relay, reducing the load on the fridge electronic unit.

The "+12 VDC" on the right side of the sugar cube relay is a new electrical source, not connected to the fridge's electronic unit, maybe connected to the 12 VDC line before the fridge, or even a seperate direct line from the battery (which would work - either?, or be better?).


Corrections?


What I don't know is which sugar cube relay will work.
I'm not an Electrical Engineer.

I can see that the fridge electronic unit will do 0.5 amps continously when the fan is activated, and I can add up the amps my OEM and AUX fan will use, however, the sugar cube characteristics I've looked up online just don't have any meaning for me.

Does anyone have a web link to a sugar cube relay, along with a way to mount or hold the sugar cube relay?
Or, can anyone give the characteristics of a sugar cube relay that will work and I can search for that either online, or at my local electronics supply store.

 

[PaulT]

You could always use an industrial rated solid state relay to do the job such as this one from Mouser electronics. I'm sure you can find a mechanical relay to do the job for less but these are easy to mount to the floor of the compartment and are reliable. I would recommend a fuse in the circuit to the battery.

Paul

 

[Alley-Kat]

Thanks.
I like solid state stuff.

Let's check my understanding...
I'd just like to understand it all.

Control Voltage Range -> 3.5 VDC to 32 VDC so our 12 VDC is within range.
Load Voltage Rating -> 3.5 VDC to 32 VDC, so our 12 VDC is within range.
Load Current Rating -> 3 amps, so the fans should not exceed 3 amps when added together (yes or no?).

How do I read this...
Input Current -> 2.2 mA to 25 mA, (same as 0.0022 amps to 0.25 amps).
Is this the minimum current range that the relay needs to trigger or activate, and 0.5 amps is higher, however, OK?
Or, is it the range of current values that the relay will work within, as in, more or less amps and the relay doesn't work, 0.5 amps is too much.

Thanks.
Just trying to learn...

 

[K7MDL]

The input current is detailed in the SSR datasheet graphs. It is linear relationship to the input voltage since the input impedance (resistance if you like) is constant. So looking at the chart, 13V is about 7-8ma. 32V would draw about 25ma. Your control circuit is more than capable of driving that SSR device.

The rest you have is correct. You can tap off the fridge power source at the fuse panel or anywhere downstream the fridge power cable (perhaps at the fridge terminals?) as long as you use a separate fuse to power the fans via your SSR - size the wire to carry more current than your fans will draw, and the size the fuse to protect the fans (thus protecting the wire).

If you look at mechanical relays, most will draw more current than the SSR example but all of them will work fine as an alternative to the SSR. The SSR is easy to connect to and mount as mentioned. Most mechanical relays need more work/cost to connect to them.

 

[PaulT]

What Mike said.

The nice thing is that mounting the SSR is as easy as driving a wood screw or two into the bottom of the fridge cabinet.

Paul

 

[Alley-Kat]

OK, thanks PaulT & K7MDL.

I appreciate the help.

 

[Kodachrome]

OK, I just got done installing my second fan, a 140mm 20MA one and I just tapped into the existing fan wiring and it is fine, the stock fan is only 14MA so at 34MA the total is well under .5A.

So there you go, the stock fan gives you about 30MA or so to safely play with if there is no need for a margin of error.

 

[longhorn1]

Is the blue and black wire what everyone is talking about? This is the view of my 2014 Grandby from the bottom vent. What is the fan everyone is installing? I'm assuming that the blue is the power and the black the ground and that the fan will have 2 wires. Can you connect a second fan to the first to run in tandum?

In Paul T's post he said he ordered a switch from FWC. Is the blue wire plugged in at the fuse box or is it in need of being plugged in as Paul's photo shows



I hear something running on my Dometic 80 compressor fridge, but I don't see any fan on the outside so I question whether FWC installed one.

I'm not a do-it-yourself person and especially when it comes to electrical. I like the idea of using the switch. There is an unused switch marked Refer switch.

In summary, what brand of computer fans, what type of plug fits the plugs on the wires, can I tape a second fan into the first, and is there a wire that needs to be plugged into the panel?

Thanks, jd

 

[gaylon]

Did you solve this? My refer fan came installed with a switch, but it would be easy to retro one in. Keep on campering