Refer fans for improved cooling...what are the best options?

[Baja_Man]

I have a Norcold N843 8cf refer with ice maker. It works well. However, when ambient temps get up to 95-105F, it struggles to stay cold. It will only cool to 46F when ambient temps are at 100F and side of RV with refer is directly facing sun.

So, since I can't control weather, and can't always predict how my RV will be parked when visiting campgrounds (facing sun), I want to ensure that my refer has all the things it needs to stay as cold as possible.

I've read about two types of fans installed to assist with cooling...

1. A fan on the evaporator (inside refer) to move the cool air around on the inside of refer and prevent frost build up on evaporator fins

2. Fans on rear on refer between the back side of refer and exterior RV side. These are used to assist with moving hot air up and out of roof vent.

The rear fans can be difficult to install if choosing to mount above coils since access is only through exterior vent lid (without removing refer).

Questions...

REAR FANS:

1. Where should rear fans be placed for most effective outcome? Above coils, on coils, below coils, etc?

2. Which fans have been proven to be most effective...computer fans, Valterra type of fan, etc?

3. Should fans be thermostatically controlled or manually with a on/off switch, or both?

4. How should these fans be wired? 12V power and ground from refer wiring OR separate 12V and ground wiring pulled from somewhere else?


INSIDE FANS:

1. should these fans be the hard wired ones that are wired to inside light OR the D battery operated type, or is there something else?

2. Are inside fans necessary or can good results be had with only the rear fans

Any other tips, suggestions or ???

Thanks!

[BoonHauler]

GordonThree wrote:

BoonHauler wrote:
Anyone using a thermostatically controlled switch to turn the fan/s on and off?

Any links? How are you controlling the fans/s?

There are simple 12v thermostat modules on ebay and ama zon ... the poster using the fixed thermostatic cut-out switch found a great solution too, can't beat that for simplicity.


I'll be using one of these, a multi purpose module I designed myself



It's a WiFi connected DC switch, that also supports data collection. So I can monitor temperatures, adjust the on/off settings, using my cell phone. It has two outputs, so in theory I could use number one on fans for summer cooling, and number two on a relay and 40 watt light bulb for winter heating.

Thanks for posting.

So with your set-up do you have an upper and lower limit (set point or do you have a simple on above set point, off below set point?

I'd have to think the later would be susceptible to cycling.

[GordonThree]

BoonHauler wrote:
Anyone using a thermostatically controlled switch to turn the fan/s on and off?

Any links? How are you controlling the fans/s?

There are simple 12v thermostat modules on ebay and ama zon ... the poster using the fixed thermostatic cut-out switch found a great solution too, can't beat that for simplicity.


I'll be using one of these, a multi purpose module I designed myself



It's a WiFi connected DC switch, that also supports data collection. So I can monitor temperatures, adjust the on/off settings, using my cell phone. It has two outputs, so in theory I could use number one on fans for summer cooling, and number two on a relay and 40 watt light bulb for winter heating.

[nickdarr]

We use a shade that we set up to cover the fridge area when the sun is directly facing it. It does not cover the entire roof area, but it does cover the side of the TT. We have done this in Death Valley and Arizona, New Mexico, and Texas. It made a huge difference from before we used it. We are in our TT now in 100 degree daytime heat and fridge maintains the fridge at the bottom of our thermometer's safe zone set at 3. We have not needed an exterior fan, but do use a fan in the fridge.

[TechWriter]

BoonHauler wrote:
Anyone using a thermostatically controlled switch to turn the fan/s on and off?

Any links? How are you controlling the fans/s?

www.coolerguys.com

[beemerphile1]

Baja Man wrote:

beemerphile1 wrote:
I would suggest that before you go messing with fans you should insure the refrigerator is installed correctly. Your manual will have very explicit directions about spacing and clearances, these directions are often ignored by the RV manufacturer.

Sometimes adding baffles or closing off a dead air space above the refrigerator is all that is needed to optimize function.

beemer....

I agree with the installation info. I reviewed the install manual and it states that there should be 1" max space behind refer. This is basically almost kissing the coils.

My space is more like 6". I'm sure this added space has the effect of more hot air hanging around coils, which means longer times for air to rise and exit roof vent and also equals more hot air warming coils.

Less space means less hot air around coils, air rises quicker as there is less of it, and ultimately cooler coil.

Is this logic about right?

Also, can I decrease the space down to 1" without removing the refer?

If so, how? Can I glue blocks foam against RV sidewall until I reach the 1" gap between the new wall of foam and refer?

Thoughts?

You are on the right path. The design is for air to circulate by convection (hot air rises). The air needs to move thru the coils rather than past them to get a good air current going.

I used some sheet metal and bent baffles to close the space. Others have used Reflectix. Foam blocks sounds like it would work also.

You may be able to do it without removing the refrigerator, it is impossible to know without seeing the installation. My refrigerator wasn't difficult to remove but they do come in some very large sizes which are unwieldly.

Some refrigerators also have a huge dead air space at the top of the cabinet which also holds heat and prevents convection from doing its job.

[popeyemth]

Here's my solution:
Fridge Fans

[BoonHauler]

Anyone using a thermostatically controlled switch to turn the fan/s on and off?

Any links? How are you controlling the fans/s?

[Baja_Man]

can these fans be used to more air out the side vent and not the upper roof vent? My unit has a roof vent as it NOT installed in a slide.

Which is preferred...move air up and out.....OR move air out side? Seems as if air is moved out side there is no opportunity for fresh air to enter and cool coils?

[Baja_Man]

beemerphile1 wrote:
I would suggest that before you go messing with fans you should insure the refrigerator is installed correctly. Your manual will have very explicit directions about spacing and clearances, these directions are often ignored by the RV manufacturer.

Sometimes adding baffles or closing off a dead air space above the refrigerator is all that is needed to optimize function.

beemer....

I agree with the installation info. I reviewed the install manual and it states that there should be 1" max space behind refer. This is basically almost kissing the coils.

My space is more like 6". I'm sure this added space has the effect of more hot air hanging around coils, which means longer times for air to rise and exit roof vent and also equals more hot air warming coils.

Less space means less hot air around coils, air rises quicker as there is less of it, and ultimately cooler coil.

Is this logic about right?

Also, can I decrease the space down to 1" without removing the refer?

If so, how? Can I glue blocks foam against RV sidewall until I reach the 1" gap between the new wall of foam and refer?

Thoughts?

[GordonThree]

landyacht318 wrote:

I have one 120Mm delta fan which is ridiculously powerful at 252CFM and at about 50 watts, but it cannot be slowed below about 35 watts via PWM or voltage control, or it just shuts down. Much too loud and powerful for normal use, and its impeller will easily chop off a fingertip.

Nidec and Delta both make some awesome fans.

If you're ever in the market for a do-over on a speed controlled fan, the 4-pin "PWM" type are very easy to drive with a microcontroller or 555 timer circuit. You don't chop the supply voltage, as that messes up the brushless controller.

The 4th wire is a pwm input (3rd wire being a hall-effect switch open-drain for tachometer). You feed it a ~100hz pwm signal to vary the speed, or connect it to ground for minimum speed. The brushless controller will sync with the pwm input and resist stalling, vs pwm of the main dc input.

[landyacht318]

Fans vary widely in how much air they move for noise made and current sconsumed.

I like the variable speed fans for all these reasons.

While speed control can be added to any fan I like the Silverstone fm121 for the dual ball bearings and the provided speed controller whose potentiometer one can mount remotely.

The fm121 cam move 110CFM at highest speed and as low as 32CFM very quietly.

Larger computer fans can move a lot more air for even less noise.

The silverstone AP182 moves ~70 CFM for only 0.05 amps on lowest speed, and on highest speed is good for a concentrated 170CFM, but this fan does not like highest speeds and battery charging voltages, the hub will get stinky plastic hot.

Noctua make some very good fans and have 'industrial' versions of their fans which spin a bit faster and are rated against dust and moisture ingress.

I am not sure how much an absorption fridge benefits from huge volumes of air moved by a fan, compared to much lesser volumes as I use a compressor fridge.

I use the Noctua NF-f12 120Mm fan on its condenser pushing air, and fridge duty cycle improved instantly. The noctua fan being ~53CFM and the provided fan being 72CFM. The pushing of air through the resistance of the condenser and the Noctuas design allow better heat removal and shorter run times than the original fan sucking air through condenser. Also the Noctua draws only 0.05 amps compared to the 0.12 amps of the provided fan.

There are many hundreds of computer fans available in all different sizes and rpm ranges. Noctua is pretty much top of the line in my opinion, but they do not offer the blazing RPMS available from fans like Delta.

I have one 120Mm delta fan which is ridiculously powerful at 252CFM and at about 50 watts, but it cannot be slowed below about 35 watts via PWM or voltage control, or it just shuts down. Much too loud and powerful for normal use, and its impeller will easily chop off a fingertip.

[GordonThree]

Baja Man wrote:
I, too, thought about the fans used to push air out the side vent, but....
My research on the subject indicates that the air should be moved up and out of the roof vent. Fans installed so that they move/push air upwards. Heat rises so this makes sense.

Thoughts?

Not all installs use a roof vent. My fridge has two side vents. I'm sure some hot air is able to bypass the upper vent and accumulate above the ceiling.

[Baja_Man]

I, too, thought about the fans used to push air out the side vent, but....
My research on the subject indicates that the air should be moved up and out of the roof vent. Fans installed so that they move/push air upwards. Heat rises so this makes sense.

Thoughts?

[beemerphile1]

I would suggest that before you go messing with fans you should insure the refrigerator is installed correctly. Your manual will have very explicit directions about spacing and clearances, these directions are often ignored by the RV manufacturer.

Sometimes adding baffles or closing off a dead air space above the refrigerator is all that is needed to optimize function.

[MrWizard]

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