Will this setup work for fridge fan?

[tjwoods1]

I decided to replace the fridge fan on my Bambi sport 16. That fan system hanged down and blows air out the side ( there is no top vent). My RV service person replaced my fan with two nocturas per my request, but has the facing up. He insists that is better. Is that right? I would presume Airstream had a reason for hanging it the way they did. Does it matter the way my service guy did it?
New Fans

Original:

[rmkrum]

Fans laying flat may live longer. Less strain on bearings. Better airflow with them together like that.


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[cwf]

Well, we mounted horizontal on ours but we have roof vent.

Seems as
Long as the fans move the air over the fins and "out" they should do fine.

[Jukeboxfun]

I don't think it will hurt to try, looks interesting. I've tried a couple of different things with fans and I am still not satisfied.

[lewster]

I have found that fans work much better when they pull the air rather than push it across the condenser. That requires placing them on the top side vent or roof vent for maximum efficiency.

Your placement will work, just not optimally.

BTW, I place these fans on 20-30 units a year........ most are Airstreams.

[J. Morgan]

Originally Posted by lewster

I have found that fans work much better when they pull the air rather than push it.......

That I accept as fact.

I read somewhere that pushing air with a fan causes a loss of about 1/3 of the cfm when compared with the same fan pulling air.

[kamadeca]

Isn't one side of the fan pushing air and other pulling air - just asking?

[nrgtrakr]

Originally Posted by kamadeca

Isn't one side of the fan pushing air and other pulling air - just asking?

Yes ...

There is more to push vs pull as more efficient than meets the eye. It has to do with the specific application. In this case I'm with Lew.

A potentially ridiculous case of push being more efficient is a turbo charger where the exhaust gas pushes a fan which in turn pushes combustion matter. Imagine trying to pull that ...

A questionable example of which is which, push vs pull, the central heat/air in a home. Is the fan blowing the air out to various locations, or pulling it from various locations? Or both ...

[tjwoods1]

Lester,
When you say you have found that the fans work much better when they pull the air rather than push it across the condenser, is that what happens when they are hung the way Airstream had installed them? Are they pulling air that way? (Like I mentioned, the 16' Sport has no top vent, it vents out the side only)

[TouringDan]

Originally Posted by lewster

I have found that fans work much better when they pull the air rather than push it across the condenser. That requires placing them on the top side vent or roof vent for maximum efficiency.

Keeping the fridge cool in the summer is a problem, especially when we are traveling all day. It may start out at 32 degrees in the morning but by the end of the day traveling is in the high 40's.

I am going to try to install 2 or 3 computer fans in the chimney at the top and see how this helps fridge performance.

Thanks for your helpful comment Lew.

Dan

[lewster]

Originally Posted by tjwoods1

Lester,
When you say you have found that the fans work much better when they pull the air rather than push it across the condenser, is that what happens when they are hung the way Airstream had installed them? Are they pulling air that way? (Like I mentioned, the 16' Sport has no top vent, it vents out the side only)

Nope. If you really want maximum efficiency from your fridge fans and only have side vents, attach the fans to the upper vent door.

This location pulls air across the condenser to moderate it's temperature, which is the whole reason for the fans.

Oh, and BTW, it's 'LEWSTER' :-))


Lew Farber
RVIA/RVDA Nationally Certified Master Tech
Master Tech Energy Systems, Inc.
AM Solar Certified Installation Center
Lifeline Batteries**Magnum Inverters
541-490-6357

[SeeMore]

I mounted my fans under the fins but close enough that the pull or push efficiency difference should not be an issue.

http://www.airforums.com/forums/f425...ml#post1320168

My trailer has the roof opening which is a better chimney cavity than the side ported. I also have a larger exhaust fan mounted at the opening wired to a manual switch for truly hot days. I have only turned on the upper fan twice since the pictured mod was complete. Those were 110°+ days in the desert.

The pictured fans keep my reefer cold on the number 1 setting whenever its under 95°.

[tjwoods1]

Attach to the door like this?

[lewster]

There ya go!

[BearScream]

Originally Posted by tjwoods1

Attach to the door like this?Attachment 244896

More efficient [nod to Lewster] and seems simpler than fabricating a bracket on the interior structure to hold the pair of fans. When a AS servicer claimed my fan was inoperative, I ordered twp Silenx replacements -- but removing and checking the old fan with a 12v supply showed the fan was OK. I suspected the thermostat was frozen open so the fan never works (the symptom) regardless of the switch.

For this newbie trying to fix a fan problem...

In your photo, there is a device mounted below and wired to the fans on the vent door. What is it?
Also the wiring does not seem to go to the thermostat. Are you bypassing it and operating manually?
Lewster, how would you check the thermostat operation?

Thanks.

[Alphonse]

Originally Posted by tjwoods1

Attach to the door like this?Attachment 244896

Blowing out the vent helps avoid recirculation (thereby more efficient). Mounting the fans in free space, hoping the momentum of the air flow will carry it out, is less efficient. Mounting in free space will cause some recirculation of the flow and affects the flow across the fridge coils.

As Lew has pointed out before, put them where they are pulling air up through the cavity behind the fridge and blowing out a vent, on top or the side as your layout allows.

[lewster]

Originally Posted by BearScream

More efficient [nod to Lewster] and seems simpler than fabricating a bracket on the interior structure to hold the pair of fans. When a AS servicer claimed my fan was inoperative, I ordered twp Silenx replacements -- but removing and checking the old fan with a 12v supply showed the fan was OK. I suspected the thermostat was frozen open so the fan never works (the symptom) regardless of the switch.

For this newbie trying to fix a fan problem...

In your photo, there is a device mounted below and wired to the fans on the vent door. What is it?
Also the wiring does not seem to go to the thermostat. Are you bypassing it and operating manually?
Lewster, how would you check the thermostat operation?

Thanks.

Most of the thermostats used for fridge fan circuits, regardless of the manufacturer, are essentially worthless. They seem to fail at exactly the point when most needed!!

I have found it far easier (and more reliable) to use a simple lighted SPST switch placed somewhere in the interior for easy access that controls fan operation.

My 19CCD had such a switch right at the entry door. On when needed....off when not. Works every time!

[tjwoods1]

The photo that accompanies my post "attached like this" is not mine. I found it and showed it to see if that was was setup Lewster was referring to. Therefore I can't comment on the schematics. Sorry.

[dalecamp`]

I've had similar problems on my 1982 Avion 34V and found a thread on a forum on RV net. RV.Net Open Roads Forum: Propane vs Electric Use with NO Fans/Fans Test Results
It details temps during cool down using a fan to vent air in the top of the fridge on elect and on LPG with and without the fan. Based on this article I installed 2 fans below the top vent in my 1982 Avion 34V by removing the back of the compartment above my fridge, a Dometic RM 2080 that replaced a RM100 last year. Poor cooling has been an issue with the new fridge. Sometime temps in the 30s, mostly in the 40s. If traveling like TouringDan the temps will rise into the high 40s and low 50s. I filled the Dead space on one side of my fridge that was 2 inches with Corning rigid foam insulation called Foamular available from Home Depot. The other side was inaccessible without pulling the fridge but only a 1/2 inch dead space. The fridge cooled down adequately during the night. Temps now are 33 in the fridge part of the box and 14 in the freezer. The temps in the cavity above the fridge are in the mid to high 90s with the new fans running and 115 without the fan running. So the fans do vent the hot air. Temperature outside the trailer is 92 at noon, expected to be 100 by 4pm. Traveling with the fridge on LPG is always an issue. On a 5000 mile trip last month to the UP of Michigan the temp would always be in the mid to high 40s to the low 50s at the end of the day while driving. I will see next month, during a trip to Colorado from Texas, if the vents will help while traveling, hopefully they will.

I've made numerous contacts with Dometic Customer Service and they stated the following: "The refrigerator area should be a substance temperature of 38-43 degrees and the freezer 0-14. "
I also talked to an independent Dometic service person in Indiana during our trip, and he said dead space is problem. That is why I filled the dead space best I could with the rigid foam insulation stacked in the area space next to the fridge.

That is my 2 cents worth.

[greghoro]

I have no roof chimney and went with a trio of computer cooling fans (Scythe Gentle Typhoon D1225C12B3AP-13 120mm Silent Case Fan) fastened to a bracket permanently attached to the inside of the top outlet door opening blowing outward. The fans sit about 1/2" from the cooling fins and the bracket has been trimmed to not impede air flow through the fans.

I suppose I could increase efficiency by filling in the space between the fans.




Greg