Dump the RM8551 ?

[MyronL]

My fridge is the Dometic RM8551 3-way (installed in 2013) and running it on propane has always been an unhappy thing. But, it runs reliably when on AC or DC. This past week I did some experimenting, running it strictly on DC. Can I ditch using it on propane -- and/or find a fridge I can count on?

EXPERIMENT: Set fridge to battery power, 4 dots. The battery is my 100Watt BattleBorn and my monitor showed 13.21 watts at the start. Trailer also plugged into shore power. Any loss from fridge load should be compensated by the WFCO. The fridge cooled beautifully on 4 dots, battery down to 31°F. and stayed there. After 72 hours the BattleBorn Lithium remained at about 13.17 watts.

Next, I disconnected shore power. At 10 PM dropped fridge to 2 dots on battery. Temp in fridge was 33° F. Temp in trailer 44° and battery 13.01 volts. Then pulled out my portable 100watt solar panel and connected it to the MPPT controller. It was dark all night.

This morning at 8 am we had hazy sun out there when I went out to see if the Battleborn had survived the night alone. BattleBorn was powering the fridge alone for 10 hours - no outside power added. Monitor was showing battery at 13.1 watts. Dometic RM8551 which had been on 2 dots battery all night was, at 8AM, 35° F.

Conclusion: RM8551 works happy on DC with the Battleborn 100 watt battery handling the load. Seems adding a 100watt solar panel will keep it that way. Is this too brief a test? What about in high summer? Seems to me I got here a cost effective solution.

Question is, which flexible 100watt solar panel out there will fit glued down to my trailer roof? Liking that WindyNation 100w at Lowes, $112.44 but it is 42.3 inches and I got 37 inches of flat roof.

[tdf-texas]

Originally Posted by MyronL

My fridge is the Dometic RM8551 3-way (installed in 2013) and running it on propane has always been an unhappy thing. But, it runs reliably when on AC or DC. This past week I did some experimenting, running it strictly on DC. Can I ditch using it on propane -- and/or find a fridge I can count on?

EXPERIMENT: Set fridge to battery power, 4 dots. The battery is my 100Watt BattleBorn and my monitor showed 13.21 watts at the start. Trailer also plugged into shore power. Any loss from fridge load should be compensated by the WFCO. The fridge cooled beautifully on 4 dots, battery down to 31°F. and stayed there. After 72 hours the BattleBorn Lithium remained at about 13.17 watts.

Next, I disconnected shore power. At 10 PM dropped fridge to 2 dots on battery. Temp in fridge was 33° F. Temp in trailer 44° and battery 13.01 volts. Then pulled out my portable 100watt solar panel and connected it to the MPPT controller. It was dark all night.

This morning at 8 am we had hazy sun out there when I went out to see if the Battleborn had survived the night alone. BattleBorn was powering the fridge alone for 10 hours - no outside power added. Monitor was showing battery at 13.1 watts. Dometic RM8551 which had been on 2 dots battery all night was, at 8AM, 35° F.

Conclusion: RM8551 works happy on DC with the Battleborn 100 watt battery handling the load. Seems adding a 100watt solar panel will keep it that way. Is this too brief a test? What about in high summer? Seems to me I got here a cost effective solution.

Question is, which flexible 100watt solar panel out there will fit glued down to my trailer roof? Liking that WindyNation 100w at Lowes, $112.44 but it is 42.3 inches and I got 37 inches of flat roof.

Your test will be irrevelent come summer heat. The RM8551 will run longer and pull more amps during hotter weather - your Battleborn probably will not last the night.

Get rid of the RM8551 and get yourself a reliable fridge. The RM8551 was never intended for the US market and will never be sufficient for the hotter weather we endure.

[Vermilye]

I could be wrong, but I believe the RM8551 on 12V ignores the thermostat setting. According to page 16 of Dometic's Operating Manual "12V: The refrigerator operates without thermo- static control (continuous operation)." If so, where you set the temperature control should not change the current draw - it is continuous at 120 watts. A 100 watt portable panel would not keep up with the draw; the same panel on the roof would likely do worse since the solar angle would probably be further from perpendicular.

I suspect you are going to need at least 300 watts of rooftop, non tilted solar to keep up. There is also the question of whether running the refrigerator on 12V will supply enough cooling for normal operation. Many feel it only provides minimal cooling while traveling, and should be switched to AC or propane when stationary.

[MyronL]

Hate honest suggestions that if acted upon create quarter-ton paperweights and cost money. Norcold, or TruckFridge? Oh de pain., but thanks.

[alanmalk]

My RMD8555 (near cousin to RM8551) couldn't keep up with an Albuquerque summer even with full hookups. Would love a replacement that actually worked, didn't cost a bundle of money, and would run without having to add more solar. Whoops, no such animal...

--Alan

[AllanEdie]

Originally Posted by MyronL

My fridge is the Dometic RM8551 3-way (installed in 2013) and running it on propane has always been an unhappy thing. But, it runs reliably when on AC or DC. This past week I did some experimenting, running it strictly on DC. Can I ditch using it on propane -- and/or find a fridge I can count on?

EXPERIMENT: Set fridge to battery power, 4 dots. The battery is my 100Watt BattleBorn and my monitor showed 13.21 watts at the start. Trailer also plugged into shore power. Any loss from fridge load should be compensated by the WFCO. The fridge cooled beautifully on 4 dots, battery down to 31°F. and stayed there. After 72 hours the BattleBorn Lithium remained at about 13.17 watts.

Next, I disconnected shore power. At 10 PM dropped fridge to 2 dots on battery. Temp in fridge was 33° F. Temp in trailer 44° and battery 13.01 volts. Then pulled out my portable 100watt solar panel and connected it to the MPPT controller. It was dark all night.

This morning at 8 am we had hazy sun out there when I went out to see if the Battleborn had survived the night alone. BattleBorn was powering the fridge alone for 10 hours - no outside power added. Monitor was showing battery at 13.1 watts. Dometic RM8551 which had been on 2 dots battery all night was, at 8AM, 35° F.

Conclusion: RM8551 works happy on DC with the Battleborn 100 watt battery handling the load. Seems adding a 100watt solar panel will keep it that way. Is this too brief a test? What about in high summer? Seems to me I got here a cost effective solution.

Question is, which flexible 100watt solar panel out there will fit glued down to my trailer roof? Liking that WindyNation 100w at Lowes, $112.44 but it is 42.3 inches and I got 37 inches of flat roof.

Have you cleaned the propane orifice? If the fridge works fine on electricity, the failure to do so on propane is likely, in my experience, to be a partially clogged burner orifice. Our old Northern Lights camper required an orifice cleanout every year or two. It was a smaller fridge, and had a smaller orifice, but still...


The other possibility is that your propane regulator is not keeping pressure up.



I would not go to the expense and hassle of replacement until you figure out why it is not performing on propane.



Just my two cents of course.

[MyronL]

As I mentioned in another thread, There is a company in Kentucky that manufactures and sells truck fridges. Truckfridge.com. Their fridges are meant for long haul trucks. Their 4.3 cu. in. AC/DC model is very interesting - will fit in the spot currently occupied by my Dometic 3-way.

Wondering if, when reliance on solar DC is the better option, the Truckfridge 2-way is a practical option that compares favorably to the NovaKool 4500.

[JeffreyG]

In all adsorption fridges, the power supply (12V, 120V, propane) heats an element to drive the cycle. Realistically the propane should be the best and strongest of these three, which is what most people find. If your adsorption fridge does not run well on propane, take a good look at the location and flame pattern from the burner.

[MyronL]

Allan, Jeff -- Been there, done that - many many times.

[JeffreyG]

Originally Posted by MyronL

Allan, Jeff -- Been there, done that - many many times.

Sure, no problem. I don't have any experience with your model. I had a Dometic 6 cu. ft. in the last trailer and it worked great for 11 years, and was best on propane.



Your unit is a conundrum.

[AllanEdie]

Originally Posted by MyronL

As I mentioned in another thread, There is a company in Kentucky that manufactures and sells truck fridges. Truckfridge.com. Their fridges are meant for long haul trucks. Their 4.3 cu. in. AC/DC model is very interesting - will fit in the spot currently occupied by my Dometic 3-way.

Wondering if, when reliance on solar DC is the better option, the Truckfridge 2-way is a practical option that compares favorably to the NovaKool 4500.

It might be, or not. Long haul truckers don't have to worry about parking for three days and hoping for enough solar. Fridges designed for them do not have to be efficient.

[AllanEdie]

Originally Posted by MyronL

Allan, Jeff -- Been there, done that - many many times.

Damn. The only other thing that comes to mind is some other sort of interference with propane pressure received at the burner. I know that on my old camper setup there were at least two other valves between the main propane line and the fridge burner, the selection switch, and a cutoff valve downstream of it. Either of these could get gummed up by propane impurities. Or perhaps the orifice or something else in there is damaged, or the fridge ventilation stack is plugged up with bug nests or something.


I still think the clue is that the fridge works better on electric. As Jeff points out, the electric option just uses a heating coil to heat exactly the same thing as the propane flame does. Normally, the electric option does not provide as much heat as propane does, so I think something is wrong with the propane flame, which I think is down to propane supply, burner condition, or ventilation of the burner and vent stack.



Did the fridge ever work better on propane? Have any parts been replaced that could have been the wrong ones?


Not at all meaning here to be pedantic - maybe you have been down all these rabbit holes already, I'm just trying to help if I can.

[Mike G]

Originally Posted by AllanEdie

It might be, or not. Long haul truckers don't have to worry about parking for three days and hoping for enough solar. Fridges designed for them do not have to be efficient.

On the contrary, the Truckfridge units contain the Danfoss (now called Secop) compressor, which (as you are probably aware) is known for its relatively power-thrifty nature. The 4.3 cu.ft. TF130 is supposed to use 33 amps in 24 hrs, I believe @ 75 degree ambient to achieve mid-30s interior temp.

A 100W roof panel could do it in NM sun, but for normal travels I'd want to have an additional portable panel in the 70-100W range and some cord, so it could be positioned as/when needed. Power consumption will be higher in hotter weather, of course, and sometimes one can't avoid some shade on the roof.

[Mike G]

BTW, when it comes to rooftop positioning, I've read that any shadow on any part of a panel can halt solar power production. All the cells are usually connected in series. Snugging a panel up close to one side of a roof A/C means that the trailer had better be parked such that the panel is to the south of it. This is another point in favor of unmounted panels.

[Tworainy]

We also had huge problems with our Dometic 8551, so we went with a compressor Nova Kool fridge that fit the 4.3 fridge’s opening, but also was able to get in through the trailer door!
Works off AC or DC only...no more propane. Works on a totally different principal, and uses a fraction of the power, yet cools much faster and efficiently.
We boondock most of the time, and hook up solar to recharge the batteries. Had no issues this summer.
Would do it again.

[John in Santa Cruz]

my RMD8555 has been fine so far, including several times for nearly a week in the open with zero shade and 100F afternoons, running on propane. I never use it on 12VDC, but its plugged in when I have shore power.

if it ever dies, then I'll be looking at compressor fridges, IF I can find one that will fit without major cabinet modifications.... and yeah, I'll probably need to upgrade to dual lithiums instead of my dual golf carts, and getting more solar than the 160W rooftop my trailer came with.

[Greg A]

So far similar experience to John with the rmd8555. If I do start having any issues with it we’re heading to the Amish cooling unit retrofit.
https://jc-refrigeration.com/

[dave1]

Greg it doesn’t appear that the Amish make a replacement for our fridge, that I could find on their site.

Tworainy what novakool unit did you use to replace your 8551? How much solar do you have?

Thanks to both of you for info,

Davel

[MyronL]

Ditto what Dave said, Tworainy. Been waiting to read about some one's real world solutions before I spring with the big bucks.

[alanmalk]

Originally Posted by dave1

Greg it doesn’t appear that the Amish make a replacement for our fridge, that I could find on their site.
...

I'll second that. Should someone discover an Amish replacement (for the RMD8555 innards) kindly let me know.
--
Alan