High altitude Dometic fridge problems

[dznf0g]

Originally Posted by wulfraat

We live on the front range and camp in RMNP often. Have never had any issues with our appliances running on gas (fridge, water heater, range/stove top or furnace).

Well, your regulator must be adjusted correctly AND your mixture settings must be correct. Lucky you!

[switz]

Another example of the ever expanding tool box contents necessary to keep the Airstream running.....

Tools...More Tools....Yeah

[dznf0g]

A guy can never have too many tools

[carl2591]

not sure i understand the higher pressure for higher altitudes. seem to me with less air you would need less gas?

but then i see someone was having a problem with reefer not running or running poorly, and having low pressure at regulator when check..

seem like more gas would create a overrich burn with a lot of sooting.

confused ..

[dbj216]

I have not measured static or dynamic propane pressure downstream of my regulator in the Airstream. I've had some trouble getting my new Dometic 2510 fridge to ignite on gas.

At 8300 feet we have about 25% less air and a corresponding drop in air pressure. Packaging that includes air tends to expand once we haul it up here, for example chip snack bags. I installed a heater in my shop and it came with the "high altitude" kit including orifices to accommodate the atmospheric conditions here. I had trouble with my house "tankless" water heater sooting up. We discovered it was not set correctly for high altitudes when installed and thus burning rich.

I agree with carl2591 that less air may result in too rich settings. And that may result in poor ignition, like a flooded engine. Increasing propane delivery pressure seems counter intuitive to me. But people do it and it seems to resolve the problem. Besides, I wouldn't mind purchasing a manometer.

David

[carl2591]

http://www.rheem.com/docs/FetchDocum...7-ac5a6b665761

in this pdf by Rheem water heater corp show the orifice size increases when the altitude increases.. for example the chart show orifice size at sea level as a #10 and at 10,000 ft it decreases to a #19. (orifice size is smaller the larger the orifice number, weird.

So what this says is you should decrease the pressure vs increase it. guess i will have to wait till I get up there to find out.

[dbj216]

Thanks for your research Carl. It makes good sense to me. Less air, less fuel wanted. Gotta have the mixture right.

That said, maybe like high altitude aircraft with turbos or superchargers, is more gas pressure needed to maintain the same burner BTU rate with the smaller orifice?

David

[dznf0g]

Originally Posted by dbj216

Thanks for your research Carl. It makes good sense to me. Less air, less fuel wanted. Gotta have the mixture right.

That said, maybe like high altitude aircraft with turbos or superchargers, is more gas pressure needed to maintain the same burner BTU rate with the smaller orifice?

David

Exactly. The mixture is controlled, not by the pressure as much as by the sliding "vent" surrounding the orifice. If the pressure is low, you won't be able to get the mixture exactly right with the slider to get the nice hard blue flame.

[Burnside Bob]

We experienced a problem similar to the original poster’s, namely our Dometic RM3762 refrigerator worked during the day, but would stop overnight and would show the E-1 code. While I realize it has been 2 ½ years since anyone posted here late comers might find our experience useful.

We’ve never had a problem over the past 4 years, despite camping at elevations up to 10,400 feet and many below freezing nights. This trip we were at 5,000 feet and night time temps were in the high 30’s. Since this was the first trip of the season we ran the refer two days on LP prior to departure without issue. So when we awoke the first morning to the E1 code I figured the rig wasn’t level. Hitched the Phoenix up, cycled the refer off on—LP, cruised all loops of the campground, got her leveled up nice, and yeah the refer is cooling like the ice age is back.

That is until the next morning when we awoke to the E1 Code. Cycle off—on LP, works until next morning, new E1 code, repeat. Three nights, 3 E1 codes.

Back home I downloaded the service manual which lists specific items to check on an E1 code, but, given how Airstreamers solved their problems other ways, the list is incomplete. Long story shorter, disassembled the LP burner assembly to find a glob of carbonized gunk on the end of the thermocouple. Removed this, vacuumed up the little rust and dust in the burner area, reassembled, fired unit up on LP and all is good 36 hours later. Night time temperatures here at home aren’t going into the 30’s for months, so we have to go some place high and cold ASAP for a good test. Yeah!!

The burner assembly uses the venturi principle to work—that is the propane is jetted thru a precision orifice. The velocity of the propane entrains air (the Venturi effect), the now mixed propane/air enters the combustion chamber where it burns merrily away, cooling our groceries. So Andy’s suggestion of increasing the propane static pressure should work. By increasing the propane pressure, the velocity of the propane out of the orifice is increased, which entrains more air into the combustion chamber. The posters commenting that higher altitude means less oxygen per volume of air are absolutely correct, but thanks to the Venturi Effect increasing the gas pressure gets more air to the fire.

Because the distance between the propane orifice and the entrance of the combustion chamber is fixed, it is not possible to mechanically adjust the propane/air mix into the chamber. Fiddling with the propane pressure is the only way to change the mix, and, for liability reasons, Dometic isn’t going to tell us about it. The user and service manuals for the RM3762/RM3962 do not mention high altitude operation. The inability to adjust the propane/air mix is, perhaps, why Dometic says their newest units are not designed to function above 5,000 feet elevation.

Ciao

[Ray Eklund]

Something must had been wrong with the Dometic in our 2014 25 foot Safari. It worked well at high elevations.

When the evening temperatures DROP below freezing, I do not recall the Dometic firing up. Probably was at temperature.

Sometimes we would hear the clicking before the pilot fired up when at lower elevations and warmer, but usually one click and it was operating.

I think that Andy is giving good advice. We had no trouble at nearly 10,000 feet elevation in Utah in the Manti-La Sals Mountains.

The Dometic refrigerator worked perfectly for us. We were not full timers but the shielding on the 2014 Dometic was much better than that on the 2006 smaller Dometic in our 23 footer. Simple system. When it is working, it works great. Ours worked great and no complaints.

If I had a problem with the Dometic... I am not bashful to report any bad experiences.

[carl2591]

anyone say how much to "increase gas pressure" to help with this problem?? you need a gas gauge to do this properly or is this a turn the regulator adjuster till it looks like it burns better?? are you going from 13" Water Column to say 14.5" ??

I would think if you spent a lot of time "up high" it might be better to get a new proper size orifice for the unit to have on hand. I have seen info on gas furnaces to reduce the size for proper high altitude operation.

http://www.reznorhvac.com/files/7084010.pdf

https://andersonforrester.com/conversion-chart/

[Burnside Bob]

Hi Carl:

Andy said to increase pressure to 14" water column. I don't know the source for his recommendation but given his long and intimate history with the Dometic refers installed in Airstreams he must have some guidance--IOW I don't think he is making this up.

There is a manometer port on the burner assembly, so if you have a manometer you can plug it in to see the gas pressure at the burner assembly. Personally, I'd be cautious about changing system pressure much as adjusting pressure to accommodate the refer may adversely affect performance of other gas devices, the water heater in particular. Plus who wants to be adjusting the gas pressure continuously as your camping altitude changes?

Since our refer had no soot or carbon build up the "stock" pressure setting is OK for the elevation range we've been camping at. This fall we hope to visit Utah and NM so we'll be in higher and colder venues. So far I've had no further E-1 faults at my barely-above-sea-level location.

* * * * * * * * * *

Ray, you are a lucky guy!! Your experience with your Dometic seems about what we've experienced. Our 10,400 ft camping experience was 2 nights boondocking in the Snowy Range before meeting up at the Wyoming Territorial Prison.

May everyone's refreshments be pleasantly cold!!

[dznf0g]

The 11" figure is a dynamic spec. That is with water heater, furnace and fridge on gas and burning. Can't turn on the stove, as that's where the pressure gauge is installed. Adjust to 11" with everything on and you'll find static pressure at 14" with everything off.

[Ray Eklund]

Originally Posted by Burnside Bob

Hi Carl:


Ray, you are a lucky guy!! Your experience with your Dometic seems about what we've experienced. Our 10,400 ft camping experience was 2 nights boondocking in the Snowy Range before meeting up at the Wyoming Territorial Prison.

May everyone's refreshments be pleasantly cold!!

******
August 27, 2016 after the Wyoming Adventure we cut through to catch some thin air ourselves. A great Boondocking Off the Grid camping site just west of the Medicine Bow Peak and north on a well groomed gravel road. No Dometic issues at over 10,000 feet.

Anyone wanting to test your Dometic... this is the spot. Lots of fly fishing in the area... also mosquitos if YOU are 'in season'.

Nancy likes the freezer in the 25 foot International to be close to 0 set on three, four or five depending on the outdoor temperature. She changes it around depending if we are in the Red Desert of Wyoming or the Snowy Range. That is her department.

[CDONA]

I did notice when living in Flagstaff (7 k feet) for 2 1/2 years, my freezer would thaw a bit when outside temps were around zero, well below freezing.
I attributed this to the heat exchanger failing to work, when the outside air was colder than the inside of the freezer.
The fix would be storing food in a cooler left outside.

[Burnside Bob]

Good Observation CDONA. From Page 9 of the Dometic RM3762/3962 Service Manual:

Low Ambient Control
In colder weather, the temperature inside the absorption
refrigerator lower box tends to hold the temperature inside
for a very much longer period of time, with very long periods
in between ON/OFF cycling of the heat source; this
is OK for any food product inside the refrigerator cabinet,
but is not OK for the freezer compartment (if it happens to
have perishable product inside). Because of the long time
in between cycling ON/OFF, there is a chance that the
temperature may rise above freezing in the freezer compartment,
resulting in food spoilage. This is why we have
a low ambient control. If it so happens that the temperature
in the refrigerator has satisfied the thermostat setting,
and the CUT-OUT threshold has been reached, the
refrigerator cycles OFF. If the temperature remains at
lower than the CUT-IN threshold for 35 minutes or longer,
the LAC output will be activated; this output, typically, is
connected to the interior lamp situated inside the refrigerator
compartment. The warmth generated by the lamp
slowly raises the temperature inside the refrigerator cabinet
to the CUT-IN threshold; when CUT-IN is achieved,
the refrigerator cycles back ON again. At this point, the
LAC output is de-activated, and the interior lamp turns
OFF. The refrigerator will now assume normal operation,
and will continue to cool until thermostat is satisfied once
more. If it should so happen that CUT-IN is not achieved
again within 35 minutes, the LAC process will be initiated
once more (and any time thereafter) as required.

For this to work your refrigerator lamp must be a functioning incandescent bulb. I was wondering why the Dometic was starting when it was so darn cold both in and out of the trailer. Now I know.

The land whereof Ray Eklund speaks:

[CDONA]

I may be in for it, I did replace the 10 amp fridge light with LED last month.
Who knew that the inside light came on with the door closed?

[carl2591]

I know right.. replaced mine as well with LED..guess the trick in high places is to reinstall the Old light or remember to open the door every so often.

[dznf0g]

Originally Posted by carl2591

I know right.. replaced mine as well with LED..guess the trick in high places is to reinstall the Old light or remember to open the door every so often.

Hmmm, my older fridge is dumber than that. Mine is a manual LAC switch. On =light on. Off= light off. No automatic time out, time in stuff. I, too, installed led. I just monitor temps in cold weather and add more warm beer, and "dispose" of the very cold beer. [emoji41]

[CDONA]

My LED is flickering now, last legs, I did try the door light switch last nite, wouldn't stop the flickering. This morning it did.
Got to go shopping for a real bulb, and defrost again.