General dometic refer temp regulation question

[wacnstac]

When running one of these on propane should the flame size be self regulating, i.e. when the refer gets cold enough it just goes to pilot, or the the flame size regulated entirely by the gas control inside the fridge, ie the higher you have it set the more flame, and then you control the temperature by regulating the knob inside?

[Boondocker]

I'm probally wrong about this but.... I think the flame size differs only between being on and at pilot and what controls the temp is the duration of the burn and the interval between them. Kind of interested in hearing how far off I am....

[Condoluminum]

Wac-

Not sure which model Dometic you have.. Most use electronic sparker to light pilot and then adjust flame (gas flow) to maintain a temperature range in the box, with constant flame heating the ammonia mix. Later models used digital pushbutton controllers (rather than knobs) to define temperature (form 1 to 5), but results shuold be same.

Be advised that many Dometics experience failed "Controller Boards" which cause them to shut down after initial startup and cooling for an hour or two. Many dealers who prefer to sell new Refrigerators will offer you that option first. IF symptom of problem is failure to run on gas only, or failure to continue running after startup, first check burner and flue for obstruction and gas flow, etc. If those OK, and no leaks or yellow powdery mess around back of refirgerator, consider replacing controller with Dinosaur brand P-711 controller (available for ~ $120 and self-installable) to see if that will fix intermittent operation...

John McG

[wacnstac]

My question was meant to be simple. I have the original 1979 Dometic in my airstream. Running on propane it seems to get cold. I wondered if the temperature/flame is self regulating or if it's totally human regulated by adjusting the temperature control on the inside. For example if I set the temp to 4, with the flame constantly stay lit or will it go back down to pilot by itself once the fridge gets cold.

[Condoluminum]

Sorry for too much information...

Burner has to keep putting heat into fluid to enable it to remove heat from insides, and that is ongoing process. Will cycle up and down as thermostat inside refrigerator tells control board that temperature needs to be reduced some more. Never really quits applying heat to coils. Some older ones with rotary know use manual button pushing to light pilot when switching to gas, later pushbutton models use automatic sparker to get fire going...

John McG

[wacnstac]

I'm just not sure if the older ones are self regulating or regulate themselves.

[Condoluminum]

They should all have a thermocouple probe wired inside the refrigerator to signal the controller about inside temps. It is usually along one side or near the fins below the freezer compartment. When temp inside above "set point" (however that is calibrated) unit should expend more heat to lower temp inside...

John

[lewster]

Originally Posted by wacnstac

My question was meant to be simple. I have the original 1979 Dometic in my airstream. Running on propane it seems to get cold. I wondered if the temperature/flame is self regulating or if it's totally human regulated by adjusting the temperature control on the inside. For example if I set the temp to 4, with the flame constantly stay lit or will it go back down to pilot by itself once the fridge gets cold.

Either the LP flame is on at full burn or pilot (or off totalaly on DSI models). There should be only one type of flame. The unit will ignite (open the gas valve) when the thermistor attached to the upper fins of the refrigerator section calls for more cooling and will stay on until satisfied (sort of like a furnace will do).

Condo is correct about the control boards. Dometic used a lot of Fenwall boards that were only soldered on one side...making them prone to broken connections and other problems. The Dinosaur Electronics products are made in the USA, are very high quality with soldered terminals on both sides of the boards AND carry a 3 year warranty!

Can't beat that with a stick .

[Chaplain Kent]

Originally Posted by lewster

Condo is correct about the control boards. Dometic used a lot of Fenwall boards that were only soldered on one side...making them prone to broken connections and other problems. The Dinosaur Electronics products are made in the USA, are very high quality with soldered terminals on both sides of the boards AND carry a 3 year warranty! .

I need to replace either my control board or electronic ignitor. Regardless I need to run a new wire to the ignitor. How do I get at the control board and ignitor. Dometic used to have wonderful diagrams on-line but they have taken them off.

[SafeHarbor]

Hi, wacnstac,

Your Excella should have the RM100. It has three thermostats: one AC-shore power electric, one propane, and one DC 12 V. The gas stays lit all the time while it's running on propane. It goes to pilot when the thermostat lets it, and it runs at a preset level when the thermostat lets it. I think that, and off, are the only modes it has on gas.

It does not have a board in it, and thus no parasitic power draw when running. Come to think of it, you would only use the 12 VDC connection when towing, so that's not much of a factor anyway.

Lamar

[Condoluminum]

Kent-

I really should let Lew answer question about replacing igniter...

As for Control Board, it is mounted on the back of the refrigerator under a plastic cover (about 4" by 7") and is accessed by removing or opening exterior vented door behind refrigerator. If you can't access rear of refrigerator that way, then I'll let Lew deal with that as well...

Replacement pretty easy with instructions from Dinosaur, and connectors are blade type slide-ons. Most important part is studying carefully and making sure no 110V or 12V power coming into unit when you start removing and replacing things...

John McG

[lewster]

Originally Posted by Chaplain Kent

I need to replace either my control board or electronic ignitor. Regardless I need to run a new wire to the ignitor. How do I get at the control board and ignitor. Dometic used to have wonderful diagrams on-line but they have taken them off.

Chappy Kent,

Condo is correct about the control board location. As far as the igniter, you might have to pull the fridge to acess the back and allow you to run the new igniter wire, but if you have a pilot model, then you probably don't have a board. What is the model # of your fridge? I can look it up on the dealer side of the Dometic site for you and probably get the wiring diagrams as well.

[driftwood]

Try this .pdf.