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Topic: Hot weather and the 'frig while in motion (Read 3 times) previous topic - next topic
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Hot weather and the 'frig while in motion
Yahoo Message Number: 147356
John said " A Dometic tech thought it was negative pressure inside the  motorhome" ; between the magnetic seals and the door latches I can't believe air  leakage would even be a consideration. Maybe he meant the airflow alongside the  motorhome could be pulling warm air out of the louvered door vents (sucking air  from the roof, into the roof vent) and disrupting normal convection flow.  That direction of flow would still cool the 'frig unless it was just enough to  cause stagnation around the cooling coils. I've seen Volkswagen Beetles with air  scoops just below the rear window to aid air cooling. I wonder if a temporary  double stick tape air scoop might force extra air into the side vent of a 'frig  without blowing out the burner flame.
Several times I've seen people having 'frig cooling issues in  high temperature situations, and the problem was rust particles filling up the  burner. There is a wire screen across the surface of the burner to spread the  flame, and rust particles fall down below it and distort/decrease the flame.  Vacuuming the rust out or blowing it out with compressed air (or both at once)  seems to help a lot. Minor cases aren't always very visible, but  cleaning should be done every year or so. I think the rust filters down  even when the 'frig isn't running. With the 'frig running on gas while driving,  air buffeting might distort the shape of the flame to reduce its effectiveness,  without actually blowing it out. It might actually blow out now and then if the  control board relights the flame. (OK Andy, no 'pilot' light per se in the  refrigerator). Hope this was helpful, RonB and 'Bluebelle' a  '99TKB
RonB (Bostick) living in San Diego
Original owner of "Bluebelle" a '99 TKB
Re: Hot weather and the 'frig while in motion
Reply #1 –
Yahoo Message Number: 147363
John said " A Dometic tech thought it was negative pressure inside the  motorhome" ; between the magnetic seals and the door latches I can't believe air  leakage would even be a consideration.
  • Except that's exactly what the Dometic tech told me.....inside negative pressure may be pulling the reefer door "open" and causing cold air to escape and warm moist outside air to be pulled in via the drain hose. I later found out this "tech" was actually Dometic's head tech guy...the guy they send out in the field when they have real problems. He suggested testing this theory by having a passenger "push" against the reefer door as we drove down the road and to plug the drain hose with a cotton ball. Doesn't give me a lot of confidence in Dometic.
Monday after the 4th of July was typical. We were camping 45 miles north of where we live. Reefer read 38 on two thermometers, one wireless, the other a Taylor brand, when I left. Outside temps were high 80's and muggy as Midwest summers always are. By the time I arrived home less than an hour later, both thermometers were reading 58-59F. So why would the air temp rise 20 degrees in an hour? If the gas shut off, the reefer is a two way, not a three way, then the reefer in essence becomes a cooler and the contents, or "thermal mass" as Andy mentioned, should result in the inside reefer temps slowly rising, but not 20F in an hour. Others have suggested an outside downdraft over the cooling coils on the back of the unit, but then again, why isn't the cooler affect being seen? The only logical explanation that I've come up with is the unit is somehow drawing in outside hot/moist air faster than it can cool it.

As far as a Norcold Vs. a Dometic is concerned, the current unit is a Dometic RM2620. The rough opening dimensions are [HxWxD] 51 31/32 H x 22 23/32 x 24 9/16 - http://www.dometic.com/enus/Americas/USA/RV-Products/refrigerators/Refrigerator-Product-Display/?productdataid=71039

The Norcold N641, now the NX641, requires a rough opening of 52 7/8 x 23 1/2 x 24 - http://www.dometic.com/enus/Americas/USA/RV-Products/refrigerators/Refrigerator-Product-Display/?productdataid=71039

Now somebody out there is going to say "Ah, you can get that inch of height real easy."  Well, before you say that, remember that the reefer from at least 1991 forward in the TK 22 footer sits essentially over the hot water heater. So you aren't going down to get that inch. So the only place to get the inch is up.....BUT...the reefer sits right next to the A/C, which protrudes about 2" down from the ceiling. I remember finding an N641 and measuring not only the rough opening part but the doors and found out if you could shoe horn in the N641, you wouldn't be able to open the freezer door because it would hit the A/C unit. If the reefer had remained where the wardrobe is now in the TK, the swamper wouldn't have mattered because it was far enough back to allow the freezer door to open at least 90 degrees.

So, if anybody has any ideas on how to solve this problem, man I want to hear from you. My next option, like I mentioned in an earlier posting, is to get a hot/humid day and drive down the road with a shower extension rod "pushed" against the door to see what happens to the inside temp. Makes not sense, but nothing else has either.

John 1994 22' TK Chug
Re: Hot weather and the 'frig while in motion
Reply #2 –
Yahoo Message Number: 147391
"that's exactly what the Dometic tech told me.....inside negative pressure may be pulling the reefer door 'open' "

To me, that seems extremely unlikely. The negative pressure required to pull that door open against the magnetic seals and mechanical latches would be enough to pop your ears rather painfully. I don't see how that could ever occur.

I agree that a 20° F. increase in one hour is extraordinary. Even if you simply shut off the fridge for an hour, you'd be unlikely to see that much of an increase... unless perhaps the sun was beating on that side of the rig. Even so, it seems unlikely. I agree that it sounds like an air leak of some kind.

I understand about the air conditioner-clearance issue. I was lucky that both my T/K and midbath don't have that problem, but in the rigs that do, there's probably no workaround.

By the way, for what it's worth: with an outside temperature of 78°, my Norcold's freezer is now at -6.4° F., and it's 35.8° in the fridge. That's with the thermostat set to 6 on a scale of 1 to 9.

Andy Baird

Travels with Andy
Andy Baird
2021 Ford Ranger towing 2019 Airstream 19CB
Previously: 1985 LD Twin/King "Gertie"; 2003 LD Midbath "Skylark"
Re: Hot weather and the 'frig while in motion
Reply #3 –
Yahoo Message Number: 147392
By the way, for what it's worth: with an outside temperature of 78°, my Norcold's freezer is now at -6.4° F., and it's 35.8° in the fridge. That's with the thermostat set to 6 on a scale of 1 to 9.

Ahhhhhhhhhhh

John A Wozniak  Sent from iPhone Please excuse any typos
Re: Hot weather and the 'frig while in motion
Reply #4 –
Yahoo Message Number: 147393
Yes one of the variables of draft speed is chimney length but what folks often miss is wind speed.   The chimney length sets up a temp differential thereby pulling air in one or the other direction.  But and this is a large but there must be good air circulation.  If you have a air tight system nothing can move.  It may seem counter intuitive but maybe you frig is to air tight to allow for removal of heat.

Glen
personal fine art photo stuff
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It's all good .......
2014 Twin King