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

Author Topic: Refrigerator Overheat due to Wind Conditions  (Read 4725 times)

Paul+Mao

  • ---
  • Posts: 7
    • ARPrvSafe
Refrigerator Overheat due to Wind Conditions
« on: December 19, 2013, 01:51:21 PM »
The below message was sent to me by a Monaco owner that has a Norcold 1200 refrigerator.  He is a Mechanical Engineer and started monitoring his boiler temperature  with the ARP control.  I told this gentleman that the largest issue with my Dometic DM3663 boiler temperature, besides off-level operation, was wind direction resulting in stagnation in the cooling unit compartment for my camper.  Cooling fans help, but they can not over power mother nature.  With years of test data, just shutting off the heat source for a brief period will generally correct the overheat situation.  Wind overheating can occur both while parked, as in the testimony below, or when driving.

**********************************************************************************

The ARP devise has triggered 3 times in the last month. The boiler normally runs at 190c give or take a degree. I have the trigger point set to 200 so if it gets to 201 it turns off.

Turns out , as Paul Unmack had told me, air stagnation can be the enemy. All it takes is a sustained light to moderate breeze from the right direction and the air stops flowing thru the flu.

Obviously, I have not been able to pin down the exact direction or magnitude. I just know it happened the other day when it was kind of breezy.

I usually leave the refer in the diagnostic mode so the fin temp shows on the panel. When I walk by I know everything is working right.

When the ARP cuts the juice and turns it back on the display defaults to the single decimal point normal mode so I know the power has cycled.

Took me a day or two to figure that out, so when I looked at the stored data, sure enough it had triggered 3 times.... not all in one day because the decimal point showed up more than once over a couple days before I figured out that power had been cycled.

The ARP records the number of triggers and the max temp encountered.. which is my set point plus 1, 200c+1= 201c

I find this a great benefit for the absorption unit that was not emphasized I think or just went past my senses... .what my coach susceptible to air stagnation.. who me?

Think about it... just the right breeze can be killing the refer. I think this applies to all absorption units. This is just as bad as off level operation, and pretty much out of our control. You can level the coach and avoid un-level operation, but you cant control the wind.

Frank I know it doesnít really apply to you since you have the residential, but I thought you would find it interesting. I think I could set the trip point a little higher as I think Paul told me the boil point of the solution is like 230c. If the fluid gets to that, the irreversible precipitation and crystallization of the sodium chromate starts taking place. That needs to be avoided and is why CUís end up in a junk pile.

A lot more data needs to be acquired and anecdotally or empirically analyzed. But Iím satisfied at the moment that the device is yielding yet another benefit. Paul also has a version which will control a fan for the absorption coil stack to control stagnation. That may be in a beta phase... not sure. But turning it off when it needs to be off is the important thing.
Happy <:)> Camper
<:()()()()<><
Fish for Dinner
2003 F350 Ford
Lance Legend 945
Slide In Camper
Dry Camping 54 Years

Paul+Mao

  • ---
  • Posts: 7
    • ARPrvSafe
Re: Refrigerator Overheat due to Wind Conditions
« Reply #1 on: December 19, 2013, 04:50:41 PM »
What is wind stagnation?

Wind stagnation is when the wind currents around your RV result in a no cooling air flow situation in your cooling unit compartment.  Thus, your cooling unit can not get rid of the heat as it should.

How/Why does this happen?

Chimney Effect:  Have you ever tried to make a fire in a fire place, and the smoke just fills the room?  This is because the wind is causing higher pressure on the top of the chimney, and the house has lower pressure.  Solution, change your chimney cap or put a longer chimney to get the top of the chimney away from the wind currents that are directly around the roof.  This works for a house/cabin but not so easy for an RV.
« Last Edit: December 19, 2013, 04:52:24 PM by Paul+Mao »
Happy <:)> Camper
<:()()()()<><
Fish for Dinner
2003 F350 Ford
Lance Legend 945
Slide In Camper
Dry Camping 54 Years

Gary RV_Wizard

  • Forum Staff
  • ---
  • *
  • Posts: 65346
  • RVer Emeritus
Re: Refrigerator Overheat due to Wind Conditions
« Reply #2 on: December 19, 2013, 06:53:58 PM »
I've been suspicious that I am getting some "wind stagnation" while driving. The fridge doesn't seem to cool as well when underway, and wind effect seems a real possibility.
Gary
--------------
Gary Brinck
Summers: Black Mountain, NC
Home: Ocala National Forest, FL

Jeff

  • Forum Staff
  • ---
  • *
  • Posts: 9003
Re: Refrigerator Overheat due to Wind Conditions
« Reply #3 on: December 19, 2013, 07:32:05 PM »
I've been suspicious that I am getting some "wind stagnation" while driving. The fridge doesn't seem to cool as well when underway, and wind effect seems a real possibility.

Gary have you checked the integrity of the seal at the top of the fridge vent? Our 1200 was warming up to the high 40s while driving until it was sealed properly.

Gary RV_Wizard

  • Forum Staff
  • ---
  • *
  • Posts: 65346
  • RVer Emeritus
Re: Refrigerator Overheat due to Wind Conditions
« Reply #4 on: December 20, 2013, 10:33:28 AM »
Not sure which seal you mean, Jeff. The one around the fridge box itself?  There is no seal at the top vent, since it is intentionally open.

If you mean the seals around the back edges of the box itself, they appear ok but I can't get a decent look at the top edge. I'm thinking to remove the roof vent cover and see if I can get a better view from there. My recollection from the last time I had the roof vent cover off is that I still couldn't see in very well.

Another possibility is that I created the problem a few years ago when I raised the roof vent cover 0.5" to allow hot air to exit better. That worked fine - I can now feel a nice hot air current coming out when parked, but I'm wondering if the vent cover is acting as an air scoop when on the highway? I may lower it again, or at least lower the front end back to its original height.

My fridge rises from 32-34 to the 38-40 range when driving at interstate speeds.  Not really a problem but clearly something is happening as I drive. I'll be using the ARP monitoring package to investigate further once we hit the road gain.
Gary
--------------
Gary Brinck
Summers: Black Mountain, NC
Home: Ocala National Forest, FL

Molaker

  • ---
  • Posts: 6021
  • We don't camp. We tour.
    • Pumpkin and Us
Re: Refrigerator Overheat due to Wind Conditions
« Reply #5 on: December 20, 2013, 11:02:29 AM »
Just a thought.  Most RVs have the lower (intake?) vent on the side.  I can picture a pocket of negative pressure developing at hwy speeds, perhaps caused by an awning arm or some other obtrusion in front of the vent.
Tom & Joyce and Ditto the "don't tell her she's a dog" Westie
U.S. Navy (Ret)
2014 Winnebago ERA 70X 24' class B Sprinter chassis

Paul+Mao

  • ---
  • Posts: 7
    • ARPrvSafe
Re: Refrigerator Overheat due to Wind Conditions
« Reply #6 on: December 20, 2013, 11:10:46 AM »
Jeff,

Good comment, when removing the roof vent, look to see if there is an empty space above the refrigerator?  All empty spaces should be filled with fiberglass insulation to prevent heat from reaching the outside walls of the refrigerator.  Also, this empty space results in changes of air flow which could cause problems with the chimney effect.

My assumption is that the RV builders left this space above my refrigerator empty so that a larger refrigerator could be put in?

Insulation is always good in the empty spaces unless the insulation falls out and prevents air flow.  I believe that this was an issue with one coach builder.
Happy <:)> Camper
<:()()()()<><
Fish for Dinner
2003 F350 Ford
Lance Legend 945
Slide In Camper
Dry Camping 54 Years

Jim Godward

  • ---
  • Posts: 5835
Re: Refrigerator Overheat due to Wind Conditions
« Reply #7 on: December 20, 2013, 11:14:05 AM »
Gary,

My thought would be to add a barrier to the front of the roof vent.  I would think that it would then act like the vent covers that rotate with the wind.  Another thought would be to have a vent cover like the ones we put on the roof vents so they can be open when it rains.

Just a couple of ideas off the top of my head.  I need to think about this.
Jim
Jim & Pat Godward
AC7PO & KD7ZDM
Hillsboro, Oregon

Paul+Mao

  • ---
  • Posts: 7
    • ARPrvSafe
Re: Refrigerator Overheat due to Wind Conditions
« Reply #8 on: December 20, 2013, 11:22:41 AM »
Just a thought.  Most RVs have the lower (intake?) vent on the side.  I can picture a pocket of negative pressure developing at hwy speeds, perhaps caused by an awning arm or some other obtrusion in front of the vent.

Tom, I have been aware of the wind problem for years on my Lance camper.  The issue always occurred camping at the same place in a river valley with steep walls.  At first I assumed it was unique to the local terrain.  Then, I came to find it happened other places, so I assumed it was the air conditioner on the roof next to the refrigerator roof vent.  I removed the air conditioner, I still developed the problem while driving.  Thus, the features of the RV combined with where the vents are placed along with the wind or highway speed all come into play (anyone have a wind tunnel?).   I could post a temperature curve of my boiler while driving if so desired?  Let me know if a temperature curve is appropriate and useful?
Happy <:)> Camper
<:()()()()<><
Fish for Dinner
2003 F350 Ford
Lance Legend 945
Slide In Camper
Dry Camping 54 Years

Jeff

  • Forum Staff
  • ---
  • *
  • Posts: 9003
Re: Refrigerator Overheat due to Wind Conditions
« Reply #9 on: December 20, 2013, 12:20:39 PM »
Gary
.
If I understood my tech correctly there is a seal or baffle that separates the air coming up from the coils from entering the inside area around the top of refrigerator and surrounding the box with warm air, especially in the summertime.

Paul+Mao

  • ---
  • Posts: 7
    • ARPrvSafe
Re: Refrigerator Overheat due to Wind Conditions
« Reply #10 on: December 20, 2013, 01:46:22 PM »
Gary
.
If I understood my tech correctly there is a seal or baffle that separates the air coming up from the coils from entering the inside area around the top of refrigerator and surrounding the box with warm air, especially in the summertime.

Please look at the Norcold installation manual.  They show a baffle at or around the level of the absorber coils.  All this baffle does is restrict the air flow past the absorber coils.  This baffle has two purposes:
 
1) It forces the air to flow over the absorber coils rather than around the absorber coils.  A well placed fan can do the same thing.  Please reference the theory of operation of the absorber coils on my YouTubes or web-site to further understand the importance of air flow over the absorber coils.

2) This baffle forms kind of a venture effect.  The absorber coils generate some heat, while the flue and condenser generate a lot of heat.  Thus, as Jeff said, this baffle should be in place, but I have only seen it in a few Norcold 1200 installs.  In addition, this baffle catches debris that drops down, thereby chocking the air flow.

My preference is a well placed blower (not a muffin fan) on the absorber to create forced air flow rather than just relying on convection.  My testing, the greatest improvement in efficiency is to cool the absorber coils directly.   
Happy <:)> Camper
<:()()()()<><
Fish for Dinner
2003 F350 Ford
Lance Legend 945
Slide In Camper
Dry Camping 54 Years

Gary RV_Wizard

  • Forum Staff
  • ---
  • *
  • Posts: 65346
  • RVer Emeritus
Re: Refrigerator Overheat due to Wind Conditions
« Reply #11 on: December 21, 2013, 12:30:31 PM »
Quote
If I understood my tech correctly there is a seal or baffle that separates the air coming up from the coils from entering the inside area around the top of refrigerator and surrounding the box with warm air

You understood him correctly. The box edges should be sealed to prevent warm air from surrounding the fridge and many installations require a baffle as well. This is outlined in the Norcold 1200 Install manual. The more recent versions have detailed instructions about that, whereas my recollection of the older ones is that they had only the specs for min and max clearances and something about sealing around the back of the box. I assume that there have been numerous problems reported that turned out to be installation issues. I know that a friend's 2007 Phaeton came from the factory with a large gap at the top and no baffles and they had very erratic cooling for a couple years until they finally got to a knowledgeable tech who spotted the problem. Only took him an hour or so to fix it too, and Tiffin paid for it even though well out of warranty.
Gary
--------------
Gary Brinck
Summers: Black Mountain, NC
Home: Ocala National Forest, FL