rvupgradestore.com Composet Products Fridge Defend
RV Life Magazine RV Park Reviews RV Trip Wizard

Author Topic: Rv fridge exhaust fan question  (Read 1396 times)

GARYJ

  • ---
  • Posts: 54
  • 2007 Mallard 18ck
Rv fridge exhaust fan question
« on: October 28, 2019, 11:04:26 PM »
Mine is a 2007 Mallard travel trailer with a two door dometic fridge
Itís working just fine but Iíve been watching many YouTube videos about installing an exhaust fan to help discarding warm air and helping itís performance
Does it really work? Is it really worth the effort?
Thanks for your advices

Lou Schneider

  • Global Moderator
  • ---
  • *
  • Posts: 10035
Re: Rv fridge exhaust fan question
« Reply #1 on: October 29, 2019, 12:05:50 AM »
Usually external fans only make a difference in high temperatures, above about 90 or 100 degrees unless there's another factor limiting the airflow over the refrigerator's rear coils.

The way the system is supposed to work is the hot tubing on the rear of the refrigerator sets up a chimney effect and convection carries waste heat out of the roof vent while sucking in cooler air from the bottom vent.

When the ambient air temperature is high enough, there's no longer enough temperature difference between the outside air and the hot tubing to maintain the convection flow.  The chimney effect breaks down and heat is no longer carried away from the cooling unit.  This is where a small fan blowing upward behind the refrigerator can help, restoring the airflow to carry the heat away from the refrigerator.
« Last Edit: October 29, 2019, 12:14:33 AM by Lou Schneider »

John From Detroit

  • ---
  • Posts: 23625
  • ^My New Home^
    • Diabetics Forum
Re: Rv fridge exhaust fan question
« Reply #2 on: October 29, 2019, 06:32:59 AM »
When replacing my 14+ cooling unit that faild (I put fans on it oh about 12 years ago) my RV tech showed me the downside of those fans.

Have you ever notice how fans tend to get crudded up. Same for air conditioner condensers.. Same for the heat exchanger when you have fans blowing on it.....

I may again put fans on but now I know how to clean the heat exchanger

(The crud blocks or reduces air flow)
Nothing adds excitement like something that is none of your business
My Home is where I park it.

lynnmor

  • ---
  • Posts: 1465
Re: Rv fridge exhaust fan question
« Reply #3 on: October 29, 2019, 09:43:42 AM »
Usually a fan is required if the fridge is installed in a slide and the vents exhaust thru the side.  The chimney effect is poor unless the air exhausts thru the roof.

Gary RV_Wizard

  • Forum Staff
  • ---
  • *
  • Posts: 70306
  • RVer Emeritus
Re: Rv fridge exhaust fan question
« Reply #4 on: October 29, 2019, 04:54:06 PM »
If the fridge is cooling fine in the places & temperatures you normally travel, I wouldn't install a fan. As others have explained, they are useful when the rear of the fridge area does not have adequate normal convection ventilation and thereby struggles to cool.  You stated you don't have that problem, so there is nothing to be gained.
Gary
--------------
Gary Brinck
Summers: Black Mountain, NC
Home: Ocala National Forest, FL

mudisfun

  • ---
  • Posts: 16
Re: Rv fridge exhaust fan question
« Reply #5 on: October 31, 2019, 12:33:32 PM »
I placed two 5 inch fans at the top of the chimney to help with air flow over the fins... just two 5 inch computer fans which have a 95 degree F normally open bi-metal thermostat inline. When the temp in the chimney reaches 95F, the fans kick on increasing air flow and helping dissipate heat. When the interior temp drops, they kick off until needed again.

Total amp draw is something like .75 between the two.

Gary RV_Wizard

  • Forum Staff
  • ---
  • *
  • Posts: 70306
  • RVer Emeritus
Re: Rv fridge exhaust fan question
« Reply #6 on: October 31, 2019, 03:34:28 PM »
I doubt if that 95 degree thermostat ever opens while the fridge is on - the flue temperatures will probably always be 100+.   For example, Norcold fridges that have factory-installed fans switch on at 135 and off again when it drops to 115.
Gary
--------------
Gary Brinck
Summers: Black Mountain, NC
Home: Ocala National Forest, FL

mudisfun

  • ---
  • Posts: 16
Re: Rv fridge exhaust fan question
« Reply #7 on: January 08, 2020, 01:04:16 PM »
When camping near my house, the fans stayed off for most of the time, but the outside temp was in the mid 60's. When traveling in the summer, they kicked on for most of the trip since the outside temp was exceeding 100 degrees on its own.

Makes me feel the fridge is more efficient, not sure this is true, but in my head I feel better.

coxid

  • ---
  • Posts: 107
Re: Rv fridge exhaust fan question
« Reply #8 on: January 13, 2020, 05:41:01 PM »
Here is a temporary fix for a occasional excessive out door heat/refer problem. Temporarily remove the outside Refer access cover, do only if the backside of the Refer is in the shade. If not in the shade move to another site or rig a temporary shade.
2017 GMC 3500 4X4 Denali Duramax Short Bed
2019 Outdoor timber Ridge 24RKS

8Muddypaws

  • ---
  • Posts: 3021
Re: Rv fridge exhaust fan question
« Reply #9 on: January 13, 2020, 07:51:01 PM »
One thing the fans help with in any weather is when you first turn the refer on.  My 4 door Norcold cools down in about half the time it used to.

135F N/O thermostat on the same fin as Norcolds controlling 4 120mm muffin fans.
Retired computer professional
Musician, songwriter,  mediocre guitar player.
2006 Bounder 34H, 2008 CR-V Toad

John From Detroit

  • ---
  • Posts: 23625
  • ^My New Home^
    • Diabetics Forum
Re: Rv fridge exhaust fan question
« Reply #10 on: January 14, 2020, 06:28:07 AM »
Here is an observation.. DO you run a fan in the house (Regular room/window/stand fan) Notice how the cage and blades get Cruded up and need to be cleaned from time to time.

I had two computer fans blowing up on my Fridge and when we pulled the cooling unit there was a "mat" of fibers on the bottom of the heat exchanger outside from the fans blowing on them...    Not too bad (considering the first fan was installed 14 years prior) but there non the less.

I will put fans inside the fridge though those made a big difference in icing of the fins.
Nothing adds excitement like something that is none of your business
My Home is where I park it.

8Muddypaws

  • ---
  • Posts: 3021
Re: Rv fridge exhaust fan question
« Reply #11 on: January 14, 2020, 12:02:32 PM »
 how do you clean the heat exchanger?

We stay in some places that get pretty warm so it seems to be worth a little bit of extra effort to have a reliably cold refrigerator.
Retired computer professional
Musician, songwriter,  mediocre guitar player.
2006 Bounder 34H, 2008 CR-V Toad

John From Detroit

  • ---
  • Posts: 23625
  • ^My New Home^
    • Diabetics Forum
Re: Rv fridge exhaust fan question
« Reply #12 on: January 14, 2020, 04:11:07 PM »
I was afraid you'd ask that.. The best way involves removal of the fridge. but I suspect if you "pop the top" (remove the top cover) and the bottom cover (Side panel) and blow down with Compressed air.. it might work

IF it's in a slide out removal of the outside access panels and again blow down with an air jet. (Unless you can see a better way)
Nothing adds excitement like something that is none of your business
My Home is where I park it.

Lou Schneider

  • Global Moderator
  • ---
  • *
  • Posts: 10035
Re: Rv fridge exhaust fan question
« Reply #13 on: January 14, 2020, 04:40:13 PM »
Most of the time you don't have to fully remove the fridge, just do everything like you were going to remove it and then slide it forward a couple of inches ...  just far enough for you to reach up behind it with a dust brush.

8Muddypaws

  • ---
  • Posts: 3021
Re: Rv fridge exhaust fan question
« Reply #14 on: January 14, 2020, 06:32:34 PM »
I think Iíll peek up there with my bore scope first.
Retired computer professional
Musician, songwriter,  mediocre guitar player.
2006 Bounder 34H, 2008 CR-V Toad

Gary RV_Wizard

  • Forum Staff
  • ---
  • *
  • Posts: 70306
  • RVer Emeritus
Re: Rv fridge exhaust fan question
« Reply #15 on: January 14, 2020, 09:07:35 PM »
There are three "heat exchangers", the condensor at the top of the stack where the boiler riser tube dumps ammonia vapor into it, and two evaporators, one each for freezer and fridge. The condensor sheds heat so that the ammonia vapor condenses to a liquid, while the other two extract heat from the interior to make the liquid ammonia go back to gaseous state (evaporate).  The evaporators, which do the actual cooling, are closed and don't need cleaning.  No air flowig through or over those.   The condensor usually doesn't need cleaning in the usual sense, but it is in a semi-exposed area where critters could build nests. I suppose in environments with lots of blowing dust it could also get just plain dirty. If you want to be sure, remove the upper vent (roof or upper sidewall) and vacuum or use compressed air.  If something is stuck to it, e.g. mud dauber nests, you might have to scrape it away (carefully - don't poke any holes!).
Gary
--------------
Gary Brinck
Summers: Black Mountain, NC
Home: Ocala National Forest, FL