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Author Topic: Anyone's Dometic RM7030 Frige really work on gas?  (Read 6345 times)
TexasBorderDude
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« Reply #30 on: December 06, 2007, 07:36:21 AM »

Texasborderdude: Read the the other replies again. Your refrigerator uses a boiler to boil the refrigerant. More heat equals more boiling and more cooling. Nothing to do with control boards, voltages or batteries. When it is working properly, the gas flame produces more heat than the electric element. Your problem is simply not enough heat (do you have a blue flame?), or it is not large enough, or it is not in the right place.

Stan:  Thanks for the input.  Got it! Please read me again; the battery situation is separate, I understand... just want to save a trip.  The flame is blue, heats the exhaust flue about the same to the touch as the elec element.  I'll see if I can get a picture of the flame.  Just how do I relocate the place for the flame?... as it seems that's all that's left. Grin  Thanks to all, I do remember that I'm the one asking for help!



ps.  The coils were cool to the touch on gas; switched back to elec and they're heating up!  I agreee "it's simple"... butt nothing simple is ever easy!!!!

pps.  Was able to post a picture of the flame.
« Last Edit: December 06, 2007, 08:25:59 AM by TexasBorderDude » Logged

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« Reply #31 on: December 06, 2007, 09:10:10 AM »

Your FLUE baffles are missing.... They hold the heat in the tube when using gas mode so that the heat has time to absorb into the boiler.

Should either be a restricting chimney baffle at the top of the burner tube or a flat zig-zag strip that hangs down in the chimney tube with a metal rod attached.

The other way is a cover (shroud) over the burner section that restricts air flow up into the burner tube. ( The burner gets it's air from outside the shroud )

I had the same problem with an RM2801 until I slowed the air flow down.

It would work with the shroud on but not work well with it off.

Just a thought.....
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TexasBorderDude
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« Reply #32 on: December 06, 2007, 10:12:39 AM »

Your FLUE baffles are missing.... They hold the heat in the tube when using gas mode so that the heat has time to absorb into the boiler.

Should either be a restricting chimney baffle at the top of the burner tube or a flat zig-zag strip that hangs down in the chimney tube with a metal rod attached.

The other way is a cover (shroud) over the burner section that restricts air flow up into the burner tube. ( The burner gets it's air from outside the shroud )

I had the same problem with an RM2801 until I slowed the air flow down.

It would work with the shroud on but not work well with it off.

Just a thought.....



Thanks Dr... I found http://gasrefrigeration.net/dom_techdata/7030_7732SM.PDF and it looks like the flue is the problem.  Gotta wait til I unload the fridge and then pull it out from the inside.  (Only an access panel on the outside, butt can't get the flue off the back) Then I can clean it and check for the flue baffle.

Appreciate all the help!
« Last Edit: December 06, 2007, 10:42:32 AM by TexasBorderDude » Logged

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« Reply #33 on: December 06, 2007, 12:21:40 PM »

Doyle - there used to be a good refer guy at RV Mobile Medic, who just happens to be next Interstate Batteries - coincidence ? - I think not - I have not used them in a long while as there is nothing RV in my bus - but call and see if they have anyone - # is 813-935-3268 - HTH

P.S. - I never heard from you?
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« Reply #34 on: December 06, 2007, 02:20:45 PM »

Have not read the other posts, ssoooss again if I duplicate.....sorry.  When we had our solar cabin/homestead we had to run a small dedicated 12 vdc muffin suction fan above the propane burner inside the exhaust stack during hot weather to get the reefer to make and hold ice cubes.  Made a tremendous difference in efficiency and propane comsumption.  We also found the beginnings of a substancial wasps nest in the vent pipe.  Smiley Smiley Smiley
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Stan
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« Reply #35 on: December 06, 2007, 05:46:35 PM »

Texasborderdude: I just went back and read all your posts again. You say that you think the refrigerator is seven or eight years old. I presume that this means that you did not buy it new. Did it ever work correctly  on gas after you bought it?

When someone posts a question about their refrigerator not working, it is assumed that all the pieces are there, that it is installed correctly and was working fine until now. If all of these facts are not true, then it is almost impossible to guess what might be wrong.
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« Reply #36 on: December 06, 2007, 11:14:43 PM »

From what little I have seen and what less I know.....you are missing the entire bottom assembly of that refer.  The burner should be contained within a sheet metal shroud that has a little door like hinged sliding thing.  That "thing" restricts the flow of air going up the chimney.  Before you go to the trouble of pulling the refer, get a pictorial diagram of the thing from the dometic manual and verify this.  Missing parts from the mfr at the time of mfr?Huh?  Dometic might give you what you need.  A refer guy probably has the item siting on an old carcass "out back".  You will be able to install that with the refer installed.  I removed mine once to do a thorough cleaning.  Sheet metal screws held all together......  Even I can do "Phillips".

HTH

John
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TexasBorderDude
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« Reply #37 on: December 07, 2007, 05:52:07 AM »

Texasborderdude: I just went back and read all your posts again. You say that you think the refrigerator is seven or eight years old. I presume that this means that you did not buy it new. Did it ever work correctly  on gas after you bought it?

Thanks Stan, yer right!  I bought the coach from the fellow that converted it.  He bought the unit new from Dometic and installed it.  As far as I can tell it is complete, installed correctly and has always worked well on elec. (never on gas.... I've owned it since Feb. 07)
When someone posts a question about their refrigerator not working, it is assumed that all the pieces are there, that it is installed correctly and was working fine until now. If all of these facts are not true, then it is almost impossible to guess what might be wrong.

I hope I've not violated any protocol with you for not having owned it from day 1.

.....you are missing the entire bottom assembly of that refer.  The burner should be contained within a sheet metal shroud that has a little door like hinged sliding thing.  That "thing" restricts the flow of air going up the chimney.
John

John, good catch... I removed the cover to get a picture of the flame.  With that in place, doesn't cool on gas.  Thanx.
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« Reply #38 on: December 07, 2007, 06:53:42 AM »

Texasborderdude: Nothing wrong with buying used equipment but it creates it own set of problems when it doesn't work. You probably don't know if the gas system ever worked for the original owner. If not, there may be a manufacturing defect that is impossible to correct. If it worked originally, someone may have serviced it and in the process made some change that is not obvious to you, and certainly not obvious to people who have not seen the unit.

As almost everyone has emphasized, RV refrigerators run on heat under the boiler. The gas burner puts out a lot more heat than the electric element. I have no idea why you are not getting this heat to the right place.

On the older model units with a pilot light, the main burner seldom came on in moderate ambient temperature. The pilot light provided enough heat to keep the freezer frozen.
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TexasBorderDude
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« Reply #39 on: December 07, 2007, 07:05:55 AM »

Stan, thanks for your continued input.  It's got me stumped too!  It's almost gotten to be a personal challenge and I'm going to ice up my ice chest, unload the fridge and pull the thing out and check the flue.  The service manual indicates tests of the upper and lower circuit boards if it cools on elec but not gas; but also sez the flue should be cleaned anually.  With the fridge out, I'm going to see if I can rig the flue so I can access it without removing the unit.  Thanks again, and I'll post the results.

dg
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« Reply #40 on: December 07, 2007, 07:16:55 AM »

Hey texasborderdude,
Think you may be able to look down the flue and clean it thru the top vent cover.
The heat from the electric or gas in the flue must exit the top vent.
For mine it's amost a straight shot, but I pull the heat mixer insert and go down with an old speedometer cable I keep around.
Give it a try, lots easier than pulling the unit.
Frank
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makemineatwostroke
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« Reply #41 on: December 07, 2007, 07:21:39 AM »

Doyle, being around that bus a few times i can assure you it worked on gas because Brown would have drove the supplier nuts till it did and never did I know of him buying anything used for that bus.But you do need to call Dometic they had  problems with the eye level controls and the auto change over and had several recalls (on mine anyway)
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« Reply #42 on: December 07, 2007, 09:43:12 PM »

I've seen a number of these Dometics that were marked 1500 BTU input. Just for drill, I divided the 1500 by the number of BTU per watt hour (1500 / 3.413), which equals 440 watts. On the unit that I checked, the heating element was 440 watts of AC. The DC element was only in the couple hundred watt range.

It seems to me that AC and gas ought to cool about equally, since the heat input is supposed to be the same. The paperwork says that the DC is only for holding, not for cooling the unit.

If someone was to run the refrigerator on AC from golf cart batteries, then the batteries would have to provide 500 watts to the inverter, or more. Since golf cart batteries only hold 1 1/3 KWH each, and since they shouldn't be discharged all the way, I would figure they would be good for about 2/3 KWH, in practice.

If the refrigerator was running about half the time to keep cold, that would mean that a pair of golf cart batteries would be good for about 5 hours of normal operation, if there were no other loads. To go a full 24 hours would take 5 pairs of golf cart batteries. That would add up to 650 pounds of batteries.

The same day should take only about a pound of propane, if it was run on gas. If I fouled up the calulations on this, someone please correct me!

Tom Caffrey
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TexasBorderDude
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« Reply #43 on: December 12, 2007, 03:23:42 PM »

New gas pressure regulator doubled the gas pressure output.  Will advise if this solved the problem.  (Got some heat in the coils, but can't tell just yet on the cooling efficiency.)

dg
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« Reply #44 on: December 12, 2007, 06:49:36 PM »

I'd suggest placing the malt beverages in an iced cooler.  Better than waiting for the fridge to cool down. 
Your Dometic will take an hour to feel cool on the walls, and overnight to get cold.   
If you haven't had it turned completely off for a while, you may have forgotten just how long absorption fridges take to cool down to ice-cream maintaining temps.   

Hope it works!  JR
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