Dometic 3- Way Fridge

[engnrsrule]

My Dometic 3-way fridge was acting up when on propane on most recent trip. The propane would start and then go blinking mode (not working). I am wondering if this was related to being level. I have gone by the notion that if its level enough to sleep comfortably, the propane mode on the fridge should be OK. But on this trip we parked and slept in sister's house so I did not level it up.

Is out of level tolerance in all axes or is it more sensitive laterally or longitudinally?

Since getting home to my level driveway, propane seems to be working fine. I am cautiously optimistic, as I do not relish the expense or disruption of a fridge changeout. I would also be inclined to stay with a 3-way, since there is no surplus space to expand battery capacity.

 

[ChicagoTom]

Full timer for over a year. Got 2 chargeable fans, one in the fridge and one charging. Changed them out about 2-3 times a day. Fridge ice cold, even in 100 degree weather

 

[engnrsrule]

Permanent inside fridge cooling fan

I found a very compact, quiet set of fin fans that are hardwired into 12v and attach directly to the fins with appropriate space for circulation. Now at $50 this is not much more expensive than some of the battery fans, but they are set and forget. The panel has an off switch.

I mounted it upside down to put the switch at the top- less chance that something bumps into it and turns it off. It is held to the fins by 4 alligator clips.

I took the power from the furnace 12v (same place as I got power for the external fans). The power goes down the condensate drain to the back of the fridge.

https://www.amazon.com/dp/B089BWZ3PX?ref=ppx_pop_mob_ap_share

 

[engnrsrule]

My Dometic continues to behave erratically on propane, sometimes working, sometimes not. I did purchase this really neat 12v inside fridge fan system and it definitely helps, and draws very little current. It attaches to the fins with alligator clips and has an on/off switch. Takes up very little space. I installed it upside down so the switch would be at the top instead of the bottom where it would have a greater chance of being bumped off by shifting food.

https://www.amazon.com/gp/product/B089BWZ3PX/

I finally gave up and ordered a new Dometic 3-way. I appreciate the discussion on low-draw compressor fridges, but I do value the ability to run on propane, and do not have the space to up my battery capacity to support multiple days even on the low draw compressor models. I went with a RM8501 because it is very close to perfect size match. Another feature I like is the freezer compartment on this unit can be removed. We rarely travel with frozen food anyway and even a little more fridge space is a plus. I ran the power from the back up the interior drain line.

I will have the shop add a 12v line to a terminal block to power my interior and exterior aux fans, which I will install on the new fridge. I originally borrowed that power from the furnace power line.

 

[engnrsrule]

New Fridge

I got the RV back and I really like the new Dometic 3 way. I wound up with model RM8505, which unlike the 8501, has the option to automatically flip between 120v, 12v, and propane (120v when available, 12v when engine is running, propane when stationary and no 110). It also locks propane option out for 15 minutes after engine is turned off to avoid flame ignition while refueling.

Other features I like:

1. Exact fit to the space previously occupied by the RM7401, no vehicle mods needed.

2. Equipped with an exterior air circulation fan on back. I am also retaining the forced draft fan arrangement previously described.

3. Freezer compartment snaps out to make the fridge bigger.

4. Much nicer shelving and door compartments.

5. Sturdy locking mechanism that can be disabled if you're going to be stationary for a while, and also has a standoff position that latches the door slightly ajar to prevent mildew when its shut off.

6. Audible alarm if door left open.

Downside, it was expensive, but worth it to have retained the flexibility of having propane. Will update regarding performance after next voyage.

 

[engnrsrule]

Update after several trips...the new fridge works well. I used with freezer compartment a few times but appreciate the larger "fridge only" configuration. The automatic switching is ok but is not to my priorities...I prefer to run on 12v when rolling and its programming calls for propane when available. No bigee, the control panel is easy to use manually on the front. Also there is not separate locking on the door, just a very solid latch that as I said can be switched to a slightly open mode when not in use. Good inside lighting.

The performance of the unit is very consistent across the 3 modes, so less dinkering with the temp setting. So even though I have augmented it with 4 computer fans on the back and 2 inside, their draw is small.

Regarding the aux fans, I had the shop install a 12v hot terminal block behind the fridge from the actual 12v feed to the fridge to power the add-ons off the same circuit.

 

[Davydd]

The downside of 3-way refrigerators is if you run it on 12v while underway and fail to switch on 120v shore power or propane when stopped you can run down an AGM battery of less than 200ah and deplete quickly. I did that a few times just stopping for lunch or mid-way touring in under an hour. You have to be really disciplined to not forget to switch over. One way Compressor refrigerators running on 12v use way less energy and perform better in my experience. However, I have lithium ion batteries with greater amp hour capacity than most Class Bs so I can boondock 3 days off grid without worry.

On my current van I downsized my refrigerator with an Isotherm Freeline 115 liter capacity. I think that is about 4.6 cf vs 6.8 cf I had before. Less beer but still retain a freezer that will hold a half gallon ice cream carton or 4 frozen pizzas. I could have put in a larger refrigerator but valued a 17” high notched space for storage under more.

 

[Hammernine]

Totally agree, we installed GoPower Elite, 360 watts, 2000 watt inverter, 4 AGM batteries. When the dometic died we just put in a standard mini-fridge. The dometic was 3.0 cubic feet, the mini-fridge in same space is 4.6 cubic feet. The solar and battery bank have no problem running the fridge.

 

[engnrsrule]

I think everyone needs to remember that propane is not an all or nothing type of thing. We hear about driving with the propane on, for and against, regularly, but in the real world that is ONLY because of the absorption frig. Nothing else needs to run while you are driving so you just leave the propane off until you need heat, hot water, cooktop, or gas grille. We have camped this way for years, and I would guess our propane gets turned on maybe 2% of the time we are away from home and only when parked. The compressor frig allows that very nice option and safety way of use,

There's the argument for a 3-way...I use 12v going down the road and leave the propane valve on unless I am travelling where it must be closed. I can switch it between modes on the fridge console. I can use automatic switching but need to override the priority to run as I described above. The engine alternator more than handles the 12v load and since getting new fridge the 12v performance is just fine. But it will suck the coach batteries down if I leave it more than a couple of hours. The new fridge has a safety feature - it senses when the engine is turned off and switches to 12v for 15 minutes so that there is no open flame ignition while you are refueling.

 

[booster]

There's the argument for a 3-way...I use 12v going down the road and leave the propane valve on unless I am travelling where it must be closed. I can switch it between modes on the fridge console. I can use automatic switching but need to override the priority to run as I described above. The engine alternator more than handles the 12v load and since getting new fridge the 12v performance is just fine. But it will suck the coach batteries down if I leave it more than a couple of hours. The new fridge has a safety feature - it senses when the engine is turned off and switches to 12v for 15 minutes so that there is no open flame ignition while you are refueling.

Does it go back to propane after 15 minutes?

 

[engnrsrule]

Yes. I think I would've made it 30 minute lockout,to allow for a run to the head first!

 

[engnrsrule]

I replaced my original Dometic an my Roadtrek Adventurous (Sprinter) with a new Dometic 3-way. I appreciate the discussion on low-draw compressor fridges, but I do value the ability to run on propane, and do not have the space to up my battery capacity to support multiple days even on the low draw compressor models. I went with a RM8501 because it is very close to perfect size match. Another feature I like is the freezer compartment on this unit can be removed. We rarely travel with frozen food anyway and even a little more fridge space is a plus. I ran the power from the back up the interior drain line.

I had the shop add a 12v line to a terminal block to power my interior and exterior aux fans, which I will install on the new fridge. I originally borrowed fan power from the furnace power line.

Check out the thread at Dometic-3-way-fridge-10436.html. Lots of good discussion there.

 

[engnrsrule]

Probably a good time for an update. My Domestic RM 8501 replacement 3-way fridge is still performing within its design profile. However I have learned that profile is woefully inadequate as temperatures soar into the 90's/100's. Does not matter whether running on propane, 12v or 110. There are 4 climate classes Subnormal, Normal, Subtropical, and Tropical. These indicate operability up to 90° (SN & N), 100° (ST), and 110° (T). Dometics run in the SN and N climate range.

There are measures one can take to help absorption refrigerators - improve ventilation at the condenser, minimize door opening, overloading. I have pretty much exhausted all these options. So consequently, in that I typically travel in summer, and often south where it's well above 90°, I should consider going to a T rated fridge.

I read that SMAD and Bodega have T rated 3-ways. The only other choices are going to 12v. Recpro compressor fridges supposedly draw 5-6.5 amps. That would theoretically last me 50-60 hours.

Another approach I thought of was to throw a block of dry ice in the fridge on >90° days. Any thoughts on that idea?

 

[booster]

We have used our Isotherm 3.1cf compressor frig up to 103* without hot food and that was with it unshaded and in the sun most of the day in Zion. We normally run it on a very low compressor speed but I moved it up to midrange to be sure it would keep up. It did use more power though, going from our normal 30-45ah per day to more like 80ah per day. At the time we were running on much less battery than now and with 300ah of solar and didn't have any power shortage without moving for over a week.

Lithium batteries are getting smaller, lighter, and cheaper (probably not better along with that however) and a 300ah lithium is barely the size of a gp31 lead acid these days. How long will they last, probably doesn't matter all that much when they are so inexpensive.

 

[GallenH]

Booster: I've often wondered about ability of compressor fridges to cool compared to absorption. I've read that an A-fridge can cool about 40-60max degrees below the ambient outside air. That means you could get a 40º fridge temp at 80º-100º ambient. There must be a range for C-fridges also; a point at which they are running full out but can't keep up a 40º fridge temp. I thought I read somewhere that it was 90º cooler than outside air max. Do you have any more specific info on that? Thx.

 

[booster]

Booster: I've often wondered about ability of compressor fridges to cool compared to absorption. I've read that an A-fridge can cool about 40-60max degrees below the ambient outside air. That means you could get a 40º fridge temp at 80º-100º ambient. There must be a range for C-fridges also; a point at which they are running full out but can't keep up a 40º fridge temp. I thought I read somewhere that it was 90º cooler than outside air max. Do you have any more specific info on that? Thx.

I will have to dig through all my old research on this that I was able to get the tech information about the Danfoss compressor setups online, they hide it all now. The tech sheets said what the power consumption and the temp drop were possible with the various compressor setup and the various compressor speeds.

One of the biggest variables that can influence it all is the condenser (think freezer box) running temps. By changing things a little to raise the condenser temp, efficiency and max temp get very much better. This is why Norcold got great efficiencies but had the reputation for soft ice cream. Their system let freezer run at about 20* instead of zero, which is a big difference. I modified our new Isotherm to more be like the old one that ran the freezer warmer, and the efficiency we got with new one get very much better, equaling the previous one.

 

[GallenH]

As always: thx for the info, booster