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Author Topic: Anyone's Dometic RM7030 Frige really work on gas?  (Read 6030 times)
DrivingMissLazy
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« Reply #15 on: December 05, 2007, 03:22:54 PM »

Is the unit fairly old or has it been sitting for a few years?

 have heard that in cases like yours where the flame is correct and it still does not cool that it needs to be removed and turned upside down for a few hours. I do not recall what this does, but something about the ammonia. Others may know more.

Richard
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« Reply #16 on: December 05, 2007, 03:30:32 PM »

Is the unit fairly old or has it been sitting for a few years?

 have heard that in cases like yours where the flame is correct and it still does not cool that it needs to be removed and turned upside down for a few hours. I do not recall what this does, but something about the ammonia. Others may know more.

Richard

I think it's about seven or eight years old.  I've been using it daily since June.  Do I remove the burner unit, the refigerator or turn the whole bus upside down?

dg
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« Reply #17 on: December 05, 2007, 06:11:42 PM »

The turning is upside down fix is for when it just doesn't work.  It is an attempt to clear a blockage.  If it working well on 120v, it is not blocked.  Are you saying that the flame is twice the size of a toothbrush meaning maybe 10 inches long!  If so, that is huge.  It should be a couple of inches at most.  If you mean twice the size of the brush part only, that would be about right.  The question than would be, does the flame stay that way or cut back after a bit.  Also see if the flame is that way when it is plugged in.   
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« Reply #18 on: December 05, 2007, 06:21:32 PM »

Are you saying that the flame is twice the size of a toothbrush meaning maybe 10 inches long!  If so, that is huge.  It should be a couple of inches at most.  If you mean twice the size of the brush part only, that would be about right.  The question than would be, does the flame stay that way or cut back after a bit.  Also see if the flame is that way when it is plugged in.  
Misspoke when is said toothbrush.... should have said twice the size of my toothbrush bristles... it seems to stay that way when it's on gas.  There is no flame when it is plugged in... there is a resistance heater above the point where the flame would be.
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« Reply #19 on: December 05, 2007, 06:44:04 PM »

Do not blow out the orifice out with an air compressor. The orifice is lined with a plastic sleeve that can be blown out and make a much larger hole. I have seen R-Vs burn because of this.I know you will here people say they do this all the time but beleve me it can happen.
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« Reply #20 on: December 05, 2007, 07:01:25 PM »

Is the flame a nice 'hot' blue flame?  If yellow tips, the draft may not be properly set..or the LP regulator isn't set correctly.  Got a manometer?
The burner could be misaligned and not centered in the heat exchanger. They are a little fragile. 
The burner flame should look like an all blue rosebud....usually between 1/2" and 3/4" high.  No yellow tips. 
My thoughts would be to have someone that can check the regulator and burner for correct adjustment, service the unit.  And hope that you get a bonafide technician.  These days so many 'technicians' don't seem to know Bo! 
My Dometic works far better on LP than on 120Vac.   It pretty much stays on gas whenever we use the coach. 
One good thing, if the fridge cools on 120Vac, don't bother with pulling the unit out and flipping over.  Ammonia "sludge" is not your problem.  The absorption components are working normally.
I would also guess that venting isn't an issue for the same reason...it cools on 120. 
You've probably got a burner or gas problem.   That's my SWAG.  Wink
Another thing...RV fridge burners can start fires.  Be careful working on the burner.
Once repairs are made to the LP components, they should be checked for leaks.
Good luck, JR



 
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« Reply #21 on: December 05, 2007, 07:13:16 PM »

Sorry about my excessive posts, but you say the gas function kicks on only when the 120 is disconnected?  That's usually how the unit functions when the panel controls are set to "Auto".   
You should be able to force "Gas" or "Electric" by selecting the appropriate buttons. 
Do you have the owners manual? 
NO problem.  Looking at the control panel you should see a "gas" button, "Auto" button, and "Elect" button.   Pushing the "Gas" button will switch the unit to gas without unplugging the 120 supply.  And, pushing the "Elect" button will force only AC (or 12Vdc if you have a 3 way).  Most newer units are 2 way.   120 or LP.
Pushing "Auto" button will select 120 as primary, and LP only if the 120 is interrupted.
That's how mine works.  If you don't have these sort of controls....I got no idea.   Huh
JR
BTW, the board likely isn't bad either.  The unit wouldn't light, or cool, if the board was bad.


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JR Lynch , Charlotte, NC
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« Reply #22 on: December 05, 2007, 07:33:17 PM »

Contact Dometic and see if the RM 7030 has had any recalls for the problem you have.
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Jerry Liebler
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« Reply #23 on: December 05, 2007, 07:49:37 PM »

It seems to me you have a 'venting' installation issue.  When it's on gas considerably more heat is generated by the flame compared to either electric heating element.  This heat needs to be 'let out' at the top of the unit, this flow is in addition to the convection induced air flow over the coils.  If your roof vent is not positioned properly to allow both hot air flows you could have the symptoms you describe.  As others have said your situation is very unusual, these refers normally work much better on gas than electric power.
These type of issues is why I have an conventional household electric refrigerator.
Regards
Jerry 4107 1120
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JohnEd
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« Reply #24 on: December 05, 2007, 07:59:19 PM »

DG,

D U D E !!!  You got your nickel's worth on this one, didn't ya?  This place never stops amazing me and I hope you also.  

One bit of confusion is the non-gas power.  There are THREE way units that can go with 12 volts DC OR 120 volts AC OR gas.  The newer ones work on AC or gas and will switch automatically or manually select either. You probably have the two way.

Your Dometic is the only refer that is considered likely to respond to the "remove and invert" fix.  Even at that it isn't usually needed even if it get "clogged up".  The manual I have read says to simply find a rough road to drive on and that will almost always return it to operation.

My guess at this point is that you have a dirty/clogged flu.  At least partially.  The elect element is right above the gas burner so it is a little confusing to me that you have this problem.  At this point a tech might be in order as all the tried and true fixes aren't working.  A one hour labor charge will get you the answer to "whats wrong" and if they won't agree to that go elsewhere.

I only had one Dometic and it has worked since 1990 when I bought the coach and it was 17 years old then.  A Dometic is like luggage in that the only thing that is around longer is Herpies.  That old girl has been off for 3 years at a whack in some cases and it is cold in 5 minutes after lighting the gas.

That gas flame was appropriately described as a "rosebud".  It should also be as big as he said 1/2 to 3/4 inches of light blue flame and no orange.  Still, it does carbon up and needs cleaned about every other month.  I blew mine off with compressed air.  Still, I am not contradicting the Nut that said you could damage a part.  Mine is a model made in 73, remember.

Clean the flu and blow the thing out is my guess.  After you blow it out check the flame to make sure you didn't clog one of the orifices with junk/carbon.  ALL BLUE FLAME!

Good luck and let us know how it worked out.

John
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« Reply #25 on: December 05, 2007, 08:09:36 PM »

Sounds exactly like there is not enough cool air coming in at the bottom and enough exhaust area at the top of the unit.

LP fridges need a vented air inlet at or near the bottom of the cooling unit. They also need a large vertical stack type opening above them to vent heat and fumes.

If you don't have good airflow, It will marginally only work on a.c. because as said previously the electric heater only has to dissipate 250 to 300 watts plus the heat extracted by the ammonia absorbtion cycle. ( On gas ) most burn 1 pound of LP a day.

That's a lot of residual heat to get rid of along with the absorbtion cycle heat.

I would say, Get your vents sorted out and fixed. You may need to close up some of that large open space to let air flow correctly too. ( means taking the unit out. )

And while out you can turn it upside down and lightly bang the boiler section with a rubber hammer to decrystalize the boiler...( Not hard !!! )..

Remember: The unit contains anhydrous ammonia, water and hydrogen. (don't let it out!)

Dave...
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« Reply #26 on: December 05, 2007, 09:35:17 PM »

dg, that 1" minimum is the clearance required to any combustible panel behind the fridge and judging by the stories of RV graveyards with lots of badly-scorched fridge areas, it might be a good idea to line the area with metal sheeting anyway

There is another tech sheet somewhere that describes the problems when there is a deep space -- say 2" or more -- between the cooling fins and the rear wall, or a big empty space above the fridge. Both stop a good strong convective flow up through the cooling fins.  I'll see if I can find it on-line for you. Possibly published for Australian conditions where these standard fridges just won't cope with temperatures over about 30ºC and they now have T(ropical)-rated units.
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« Reply #27 on: December 06, 2007, 06:56:55 AM »

For what it's worth on my S&S when the gas kicks in if I am stading next to it I hear a 'roar'.  I mean I can really tell that the gas is a burning!  If you are not hearing that 'Roaring" noise I would say a simple adjustment at the air intake tube might fix you up!  (Now if you get flames out the top of the bus...you may want to turn it back down a smidgin! Grin)
Jack
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« Reply #28 on: December 06, 2007, 07:14:07 AM »

Yep!  I've gotten my full membership fee's worth outta this one.  Just what you'd expect from the folks that do the bussin' thing.  Gotta good flame going, and so far this morning the frost on the fins inside the fridge hasn't defrosted.  If it's still acting up, I've found a factory authorized repair here in Tampa that's close to the Interstate battery place.  Will get two stones with one bird as I have the batts load tested.  (My $20 HF load tester said they were ok, butt...my 920 amp/hour bank dropped from 13.14v to 12.31v (30% discharged) in just 2 1/2 hours of sat. receiver and tv and a 5 minute load on the microwave.  Didn't mean to hijack my own thread!  Will keep 'ya posted.

dg
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« Reply #29 on: December 06, 2007, 07:18:32 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.

Come back when you have the problem of the refrigerator being too cold on gas. Most dealers don't know the answer for that one!
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