Measuring Propane Pressure at Fridge

[George Johnson]

Since I have plans to be camping at high altitude soon, I thought I'd buy a manometer and learn to "tune" my fridge for best performance at altitude. In general, the process seems simple enough. However, I have come up with a question my local RV service shop couldn't answer. I seem to be spending too much time thinking about this while awaiting the arrival of my new toy.

With the manometer connected to the port upstream of the fridge burner, and with the stove top burners operating to represent an approximate 50% usage capacity of the propane system, should the fridge be in operation, or should it be off and the reading be taken while the fridge line is in a static condition? Does it even make a difference?

If you have had any experience with this, an inquiring, and ignorant, mind would like to know.

[Iowa Dave]

The fridge uses so little propane compared to the burner on the furnace and one or two in the stove that you will not see a noticeable change in the manometer reading. Now the water heater kicked in, that will make a noticeable change. Thats a pretty small orifice on the refrigerator compared to what the ones are on the other appliances. That’s what we noticed when we adjusted the regulator on a 21 foot Escape a couple months ago. Hope this helps.
Iowa Dave

[rubicon327]

George: The fridge BTU's are insignificant but it's a practical matter of gas valve versus test port placement. You have the Dometic RM 2510 so you need to have the fridge running to make your measurement because the gas shutoff valve integral to the fridge is upstream of the pressure test port. So with fridge off you can hook up your manometer and then turn the fridge on and do your pressure test. (As an aside I believe that some newer fridges like the RM8551 have the test port upstream of the gas valve so you would get a representative pressure regardless of whether the fridge was on or not. The downside with this design is you would definitely want tanks closed when hooking up the manometer as the entire propane system wants to empty when you hook up to the test port.)

To help determine 50% load you may find this old post of mine helpful:
https://www.escapeforum.org/forums/f...tml#post260752

FWIW the BTUH input of the RM 2510 is only 1,080.

[fudge_brownie]

Last September I had refrigerator alarms during the nighttime at 9,000 feet and cold temperatures. As has been pointed out on related posts and based on my readings on the internet this issue seems to be sporadic. Some refrigerators balk at elevations, others keep working.

In my efforts to stop the alarms I spent two weeks playing with column inches, going as low as 9. I could not stop the alarms. I finally resorted to turning the unit off at night. The down side was my ice cream melted, refrigerator keep its contents at proper temps.

While doing this I was unable to access the manometer port on the refrigerator plumbing. The access bolt would not loosen and I was unwilling to force it. All my adjustments were done at the port on the propane regulator.

I had already replaced the propane regulator. Again, Dometic warns their units are only operable to 5,000 feet.

[George Johnson]

Thanks to all of you for sharing your insights on the operation of our Dometic fridges. I'm learning a lot. The pandemic has me doing a lot of stuff I would probably ignore in more normal times. Adversity is opportunity, I suppose.

I don't know if the following comments are germane to this thread, but my overall purpose has been to improve the efficiency and stability of the fridge. I have added insulation to all the open spaces around the fridge in addition to making and installing a sheet metal deflector plate to direct rising hot air out the top vent with as little turbulence as possible. I've also sealed the gaps around the back of the fridge with aluminum tape to isolate the back of the fridge from the rest of the unit. None of these are new ideas as they came from reading old threads on the forum.

One interesting thing I found on my own was that when looking at the louvered vent covers on the outside of the trailer (I got to do that a lot with this project), is that there seems to be relatively little actual open air space available in the louvered covers. To check this out, I did some rough measurements and calculations and determined that the lower vent on my '09 19 has approximately 60.0 square inches of open vent space and the upper vent has approximately 57.75 square inches. Taking the square root of these numbers tells me that the lower vent has an effective square vent hole of 7.75 inches and the upper one is about 7.60 inches.

Not only does that seem to be a rather small vent area for all the heated plumbing at the back of the fridge, but at least theoretically the smaller vent area at the top could restrict the free flow of hot air out the top. Has anyone made or looked for vents with more open ventilation space that could replace the stock vents?

I'll sure be glad when this pandemic is over and I can get back to more normal things like wondering where my next meal is coming from...

[rubicon327]

Originally Posted by George Johnson

None of these are new ideas as they came from reading old threads on the forum.

Have you seen this thread? Skip to the last two posts for my summary and three year follow-up. Our RM 2510 now works fantastic with only an occasional cleaning of the jet and burner.
https://www.escapeforum.org/forums/f...est-11296.html

[George Johnson]

Rubicon327, yes I have seen your very informative thread. I hold you responsible for all the trouble I have caused myself in trying to improve my fridge! I'm looking forward to a nice, stable fridge--vastly better than the little unit I had in my previous A-Liner.

[cpaharley2008]

Just remember you should probably cover the interior of those covers with bug screening to prevent wasp nests forming while not in use........

[George Johnson]

You make a good point, Jim, while at the same time the screens contribute to the restriction of cooling air circulation. There always seem to be unintended consequences. Thanks for the reminder.

[a602pmcc]

Originally Posted by George Johnson

Thanks to all of you for sharing your insights on the operation of our Dometic fridges. I'm learning a lot. The pandemic has me doing a lot of stuff I would probably ignore in more normal times. Adversity is opportunity, I suppose.

I don't know if the following comments are germane to this thread, but my overall purpose has been to improve the efficiency and stability of the fridge. I have added insulation to all the open spaces around the fridge in addition to making and installing a sheet metal deflector plate to direct rising hot air out the top vent with as little turbulence as possible. I've also sealed the gaps around the back of the fridge with aluminum tape to isolate the back of the fridge from the rest of the unit. None of these are new ideas as they came from reading old threads on the forum.

One interesting thing I found on my own was that when looking at the louvered vent covers on the outside of the trailer (I got to do that a lot with this project), is that there seems to be relatively little actual open air space available in the louvered covers. To check this out, I did some rough measurements and calculations and determined that the lower vent on my '09 19 has approximately 60.0 square inches of open vent space and the upper vent has approximately 57.75 square inches. Taking the square root of these numbers tells me that the lower vent has an effective square vent hole of 7.75 inches and the upper one is about 7.60 inches.

Not only does that seem to be a rather small vent area for all the heated plumbing at the back of the fridge, but at least theoretically the smaller vent area at the top could restrict the free flow of hot air out the top. Has anyone made or looked for vents with more open ventilation space that could replace the stock vents?

I'll sure be glad when this pandemic is over and I can get back to more normal things like wondering where my next meal is coming from...

Hi George,

Chris R addressed the issue of the size of the refrigerator vent installed by Escape (among other issues) and his replacement with a larger vent in a previous thread. See https://www.escapeforum.org/forums/f...ade-20473.html

I am replacing my Dometic RMD 8555 refrigerator, and as part of that process plan to undertake many of the improvements to the cavity that Chris and others have done. Haven't yet decided on adding the larger vent. May wait and see how the new one performs before making that decision. The existing one is smaller than specified by Dometic for both the old and the new fridge, so enlarging it is definitely under consideration for me.

Good luck,

Paul

[rotorbudd]

Originally Posted by George Johnson

Thanks to all of you for sharing your insights on the operation of our Dometic fridges. I'm learning a lot. The pandemic has me doing a lot of stuff I would probably ignore in more normal times. Adversity is opportunity, I suppose.

I don't know if the following comments are germane to this thread, but my overall purpose has been to improve the efficiency and stability of the fridge. I have added insulation to all the open spaces around the fridge in addition to making and installing a sheet metal deflector plate to direct rising hot air out the top vent with as little turbulence as possible. I've also sealed the gaps around the back of the fridge with aluminum tape to isolate the back of the fridge from the rest of the unit. None of these are new ideas as they came from reading old threads on the forum.

One interesting thing I found on my own was that when looking at the louvered vent covers on the outside of the trailer (I got to do that a lot with this project), is that there seems to be relatively little actual open air space available in the louvered covers. To check this out, I did some rough measurements and calculations and determined that the lower vent on my '09 19 has approximately 60.0 square inches of open vent space and the upper vent has approximately 57.75 square inches. Taking the square root of these numbers tells me that the lower vent has an effective square vent hole of 7.75 inches and the upper one is about 7.60 inches.

Not only does that seem to be a rather small vent area for all the heated plumbing at the back of the fridge, but at least theoretically the smaller vent area at the top could restrict the free flow of hot air out the top. Has anyone made or looked for vents with more open ventilation space that could replace the stock vents?

I'll sure be glad when this pandemic is over and I can get back to more normal things like wondering where my next meal is coming from...

I always open the locks and let the door hang open from a 5 in. wire when camped in high temps (think Big Bend heat).
This seems to help quite a bit with fridge temps.

[Chris R]

can't get this to quote?

this link should work. https://www.escapeforum.org/forums/f...ade-20473.html

[Centex]

Originally Posted by Chris R

can't get this to quote?

this link should work. https://www.escapeforum.org/forums/f...ade-20473.html

Thanks, Chris