Dometic fridge auto selections

[booster]

There was an interesting discussion on the Yahoo board a few days ago concerning what settings give what results for Dometic 3 way frigs. As it turned out, I think, what we had been told by the dealer, had others tell us, and what made sense to me, all were wrong. The dealer had told us the frig, when on auto, would do AC as first choice, gas as second choice, and DC as third choice, all without any input from the operator. Other folks said the same. We didn't have our 3 way long enough to figure out exactly how it all worked because we quickly decided the off level issue made it desirable to go to the compressor frig.

As it was described on Yahoo, there is an on/off button that turns on the frig, and is on the left. Next is a DC button with indicator light. If it is on when the power switch is on the frig runs on DC, and will NOT switch to AC or gas by itself. If the DC is on, you get DC with no other possibilities. If the power is on, the DC off, then you get to chose auto or gas mode with the third button column. Gas setting you get gas all the time, auto it will use gas unless AC is available.

This all came up in a discussion about things that could try to light a flame while you filling the van with gasoline. One poster said that when you are on DC, as many are while driving, the burner will never try to light, which is correct, and a good thing. Another poster described the operations of the controls, which was spot on. What he said he does is run with the DC on when going down the road, and in auto mode all the time. That way when he stops to camp or in a parking lot for a while, he just turns off the DC, and he automatically goes to gas. Makes sense.

But--what I know some folks do is to ALWAYS shut off the DC on the frig whenever they stop, including for gas. Their goal (maybe misguided) is to save their batteries, as they have heard the horror stories about how quick the frig kills batteries on DC. If they did that, while they had the third button on auto or gas (the only settings, no off), the frig would try to light, right when you don't want it to at the gas station. Maybe I am still misunderstanding, but it sounds like it would be pretty easy to mess up. My thought would be that the DC would disable the auto and gas modes until you reactivated them by pushing the button, not all by itself. You are right there anyway pushing the DC off button, so it would be no big deal and would eliminate the potential problems.

What say you folks that use the 3 way all the time, like we don't!

[markopolo]

Note: this applies to Dometic 3-way fridges with electronic controls. This does not apply to older fridges with manual controls in case anyone is not sure if this applies to their fridge.

This is clearly a potential problem. I read through an owner manual and operation is exactly as you describe.

On or Off is well... on or off
Auto is Electric or Gas with electric having priority
DC overrides all other controls

It would be easy enough to create fire hazard you describe when refueling the van.

Fridge on, auto on, DC on when driving. Turn off DC when you stop to refuel (fridge is still ON and in Auto mode) and the fridge will seek electricity and not finding it the fridge will ignite propane gas............. while you are refueling !

If you have one of these fridges the best habit to get into is to use the on and off button. Only ever have it ON when propane gas ignition is not a potential problem.
If using DC turn the fridge OFF then turn DC ON.

Dometic does advise you to turn off all propane appliances when refueling.

FOR YOUR SAFETY, when refueling, shut off all
LP gas appliances which are vented to the outside.

Thanks for sharing this info booster.

[Rok]

O.K., so we use our 3 way Dometic and we wonder if we are using it correctly. When we turn it on and to auto, it goes to AC first, then to gas, then, if it doesn't find gas, we've been told that it will go to DC. What we get instead is the "Check Refrigerator" light (if we aren't hooked up to shore power and we don't have the propane turned on.

There is also some sort of manual switch that will turn it between the 3 modes. So, when we want DC (12V) we use the manual button and select it.

When we are on Shore power, we set it to auto and it automatically chooses AC. When we are traveling, we have it set on DC at all times, unless we are stopping for more than an hour or so in which case we switch over to LP gas. We turn it off before traveling. We've been told it is a no-no to use propane while driving.

When we are boondocking, we turn on the propane to conserve 12V DC for other stuff.

Not that we have done this a lot. We are still new to all of it.

...........Rocky

[markopolo]

Your description correlates with what I read in a newer Dometic 3-way fridge manual - the fridge will never choose DC - that decision is left up to the RVer. The "Check Refrigerator" light coming on is expected in the circumstance you describe as the fridge can't find AC or Propane so it is alerting you of that problem.

[booster]

What Rok sees and has been told all looks fine, with the exception of being told the frig will switch to DC when on auto. As was mentioned, you only get DC when you select it manually. Since he only takes it off of DC if they are going to be stopped for an hour+, he is safe in a gas station.

I think the issue really is that Dometic leaves the auto/gas mode active and ready to run as soon as the DC is shut off. It is good from a standpoint of making sure you don't get spoiled food, but could be dangerous if used incorrectly while fueling.

I think it would be good for them to get the word out about how and why it is important to shut the frig to OFF when fueling (as there instructions say), so folks don't do the DC shutoff to save batteries thing.

[Davydd]

I have a manual 3-way Dometic. I run it on propane almost all the time unless plugged in. It's not a big deal to turn it off for a few minutes when fueling diesel. With manual, I don't run DC much unless I know I am not going to stop much. It is too easy to forget to switch over and if we had not done so on a recent 3-1/2 hour stop at House on the Rock we would have certainly drained the battery.

I wonder if Dometic could put in a DC delay to switch over when stopped, of say, 15 minutes or anything you want to program it for to cover those short fueling and bathroom stops. Then you could pretty much run no-brainer.

[mlts22]

What I wouldn't mind having is a "no propane" switch. That way, it can switch from AC to DC at will, without the risk of igniting fumes when filling up. Even better, perhaps a selection mechanism so one can turn off AC, DC, or propane individually.

Of course, the ideal would be having a propane fuel cell that charges a lithium-ion battery bank, then having the fridge be compressor based and completely electric, getting power to charge its batteries from the fuel cell, AC, or DC.

[pattonsr]

I believe Advanced RV has switched from using a propane Dometic to a 6.8 cu ft Nova Kool Danfoss compressor refrigerator/freezer. The Airstream Interstate uses a 3.1 cu ft Nova Kool under the cabinet but the large Nova Kool has the freezer on the bottom and the fridge part on top.

[trekerinsc]

We have the 3 way fridge with the electronic controls in our 2008 C210P Roadtrek. Yes, the controls operate as booster described.

When we are driving, we run the fridge on DC. If we plan on being stopped for longer than an hour or so we will switch it to propane. When we have shore power we run it on AC. When stopping for gasoline, we stop well before we get to the pumps, turn the fridge OFF and then turn the coach battery switch off. That way none of the appliances can try to autostart. After we pull well away from the pumps we will turn the coach battery switch back on and then turn the fridge on and put it on DC.

Robert
Clover, SC2008
C210P Roadtrek

[Mike]

Originally Posted by markopolo

Note: this applies to Dometic 3-way fridges with electronic controls. This does not apply to older fridges with manual controls in case anyone is not sure if this applies to their fridge.

This is clearly a potential problem. I read through an owner manual and operation is exactly as you describe.

On or Off is well... on or off
Auto is Electric or Gas with electric having priority
DC overrides all other controls

It would be easy enough to create fire hazard you describe when refueling the van.

Fridge on, auto on, DC on when driving. Turn off DC when you stop to refuel (fridge is still ON and in Auto mode) and the fridge will seek electricity and not finding it the fridge will ignite propane gas............. while you are refueling !

If you have one of these fridges the best habit to get into is to use the on and off button. Only ever have it ON when propane gas ignition is not a potential problem.
If using DC turn the fridge OFF then turn DC ON.

Dometic does advise you to turn off all propane appliances when refueling.

Thanks for sharing this info booster.

Like trekerinsc, we got into the habit of hitting the "battery disable" switch on the monitor panel when stopping for any kind of refueling to prevent any appliance that requires 12V to fire up a DSI igniter from trying. My old Dometic fridge has a manual push button igniter to fire it up on propane, so it's not a problem(we don't try to run it on propane while driving), but your water heater or furnace could be inadvertently switched on while refueling, causing an unwanted and dangerous propane ignition/flame situation.
Do newer class B vans still come with "battery disable" switches?

[markopolo]

Originally Posted by trekerinsc

.....................When stopping for gasoline, we stop well before we get to the pumps, turn the fridge OFF and then turn the coach battery switch off. That way none of the appliances can try to autostart. After we pull well away from the pumps we will turn the coach battery switch back on and then turn the fridge on and put it on DC..............

Originally Posted by Mike

Like trekerinsc, we got into the habit of hitting the "battery disable" switch on the monitor panel when stopping for any kind of refueling to prevent any appliance that requires 12V to fire up a DSI igniter from trying. My old Dometic fridge has a manual push button igniter to fire it up on propane, so it's not a problem(we don't try to run it on propane while driving), but your water heater or furnace could be inadvertently switched on while refueling, causing an unwanted and dangerous propane ignition/flame situation.
Do newer class B vans still come with "battery disable" switches?

That's great way to handle it. Fridge off and Battery switch off I hadn't thought of using the battery disconnect as an additional safety measure. Makes sense and easy to do.

[booster]

Originally Posted by markopolo

That's great way to handle it. Fridge off and Battery switch off I hadn't thought of using the battery disconnect as an additional safety measure. Makes sense and easy to do.

I totally agree. No power to anything is as safe as you can get.

[Davydd]

Battery disable switches on Bs are not always convenient. On my 2005 Pleasure-way Plateau it was in the back of the B in a cabinet under the ottoman. On my current Great West Van you have to open the sliding door to get to it.

[Mike]

Interesting, that any functional component that might be regularly used, would be located in such a way as to prevent it's ease of use and access. I won't ask where they put the tank hose(s) and drain valves.

[mlts22]

On some Roadtreks, the battery disable is a switch that connects to what essentially is a relay, except that it only takes power to flip the circuit closed or open. Problem is that if one holds the switch on or off for any length of time, the solenoid coils might burn out. I prefer a good old fashioned mechanical switch.

[Davydd]

Originally Posted by Mike

Interesting, that any functional component that might be regularly used, would be located in such a way as to prevent it's ease of use and access. I won't ask where they put the tank hose(s) and drain valves.

I didn't think the purpose of the battery disable switch was for a day to day use and function. I thought the switch was to disconnect the battery for mostly storage when the B was not in use as it shuts off all electrical function include the alarms.

[booster]

Originally Posted by Davydd

I didn't think the purpose of the battery disable switch was for a day to day use and function. I thought the switch was to disconnect the battery for mostly storage when the B was not in use as it shuts off all electrical function include the alarms.

We use our battery disconnect all the time, but not to kill the frig as ours is a compressor model. The frig can be switched to run off of our oversized (115AH) starting battery, so if we are in battery conserving routine, we will turn off the coach batteries when we are not in the van for long periods. The eliminates the drain from the detectors, which can count up over days. The frig takes between 15 and 40AH per day, so we can go 40+ hours off the starting battery without problem. We use about 60AH out of the starting battery capacity.

[Mike]

Originally Posted by Davydd

I didn't think the purpose of the battery disable switch was for a day to day use and function. I thought the switch was to disconnect the battery for mostly storage when the B was not in use as it shuts off all electrical function include the alarms.

I said "might be regularly used". I understand that some might, and some might not use the disable function regularly.
Like booster, we do use ours to limit long and short term coach battery drain, but particularly when we stop to bio-break/refuel. It serves a dual purpose for us by temporarily disabling the common 12V draws including the fridge on DC, and the DSI igniters. We only make short bathroom/fuel stops while travelling with the fridge on DC, so it works for us. And, it's more conveniently located in our older Roadtrek so it's a no brainer for me.

[Davydd]

If you are fuel stops or restroom breaks I don't see much reason to turn the refrigerator off DC. I would venture to bet some day you'll forget to turn it back on. I know I have. Besides, on a manual 3-way refrigerator you can turn the DC off right at the fridge without disabling everything else (which I don't think is a wise practice). But like I originally said, and Booster pretty much repeated, the battery disconnect purpose is for battery conservation when the B is not in use and for taking the battery offline, nor for "might be regularly used" when underway and traveling. Are we over thinking this?

I don't know for a fact and haven't delved into it, but I think as mlts22 mentioned, my two Bs probably had and have a mechanical switch locally and not a relay switch which could explain the inconvenient locations. Well, I am pretty sure they are mechanical as I think about it. They aren't toggles.

[booster]

Our battery disconnect on the monitor panel and very, very accessible. It is a momentary rocker that runs the "no power hold" relay mounted elsewhere. 07 Roadtrek C190P.