Fixed - Dometic RMD-8551 3 Way Absorption Fridge
Vložit
- čas přidán 11. 09. 2024
- When I purchased a late 2014 Evernew caravan I unfortunately inherited what appears to be one of Dometic's problematic 3 way fridges - the RMD-8551 or RMD-8555 and only rated to Sub Tropical. However the fridge itself is not entirely to blame for the poor performance so I addressed the usual installation issue commonplace in caravans up till recently (hopefully they are better now)
Faced with a hefty price tag to replace it with a newer 3 way fridge or a very expensive transition to a compressor fridge I decided to invest a significant amount of time to getting this thing to work as it should and now it works as good a T rated fridge.
In this video I look at the changes I made based on learning's and experiments from others on Caravaners Forum and understanding the operation of absorption fridges from the web and CZcams tutorials.
Excellent design, workmanship and explanation. Best video I have seen yet on this topic. Cheers from the USA.
Thanks Cary, glad it was of some help. Cheers Tim
Terry my prayers have been answered. I’ve never liked the 8551, but I knew there had to be a solution. Thank you.
It didn't work! Read previous comments.
Thanks for the perfect solution. I replaced the mastic, sealed and insulated the chest/cabinet gaps, and closed of my 150mm rear clearance. Additionally I fitted to 110mm low speed fans in my Roof Mounted top vent comtrolled by a second "button" switch on the hot pipe. The only thing yet to do is upgrade the thermal insulation of the boiler. Still the fridge has gone from a waste of space to now working well. Not difficult to get -15c in the freezer and 3.5c in the fridge on a day of 30+c.
I feel that the masticthermal paste is key. Having a background in Information technology, for me makes this a "no-brainer".
Obviously Dometic were more focused in saving cost rather than delvering a quality product.
Many thanks
Stuart
Great news Stuart. Mine came up great also until I actually drove away on a trip then it was all down hill from that point onwards. Have you been on a trip yet and see if it holds up? - THATS THE ACID TEST! Cheers Tim
Hello from Northern Idaho, USA. Unfortunately the Canadian manufacturer chose the RMD8555 for our 2015 fiberglass trailer. Our door is very narrow and not many choices. They did NOT install the direct vent on the boiler that you have and the lower vent is too small but unless the performance improves, we are not cutting any fiberglass as we will be going to a new refrigerator, possibly a compressor unit. We have already removed our unit and improved the baffles and insulation as much as possible. We are very encouraged to see your video and have ordered the mastic. Ambient temps now are low, around 20 deg C and our refrigerator maintains 3 deg C on a setting of "3" using electric but gas performance is not as good. This is probably due to the venting issues. However even on electric, the freezer is never below -8 deg C. Hoping the mastic will improve this.
We read your latest post of experiences on your trip and hope you find that something unrelated to all your improvements is the cause of the terrible performance and that there is a simple (and inexpensive) solution. Thanks for a lot of helpful information!!
Hi Hikerwood, I dont think you can fix the issues with this fridge beyond getting it somewhat more reliable than ex-factory at ambient temps well below its rated performance. I have achieved better performance than when I bought this van but I definately wont be doing another extended trip with it.
You can pull out the gas burner and clean it to improve the performance. I watched a video on CZcams on how to do this and that certainly improved the flame size and mine works as well on gas AC mains power or gas.
I am currently investigating running a standard household (digital inverter) fridge through an AC inverter which appears to now perform equally as well as dedicated 12V compressor fridges at about 1/3rd the total cost. The DC load on the battery/solar is now pretty much equivalent as compressors have achieved much better efficiency in recent years. The inverter technology means that you can run a small 300 watt inverter to easily run your AC mains powered fridge without adding significant power overhead as was the case in the past due to the high start load on the older compressors.
Anyway all I have read indicates this is a good way to go and a very significant saving over a new 3 way fridge. Cheers Tim
Hi Tim, thanks for the vid. Glad I read all comments to confirm fridge is lemon. Compressor fridge here we come ( or we’re upgrading to a motorhome maybe).
Thank you.
I have an old 3 way. I have been slowly improved its performance and have done all in the video. But for my fridge the biggest improvement was 1/ putting a sliding drawer at the bottom of the fridge ,made from aluminium to act as a cold sink , so now i can open the door without the cold dropping to the floor of the van , There is no drop in temp within 60 second in the fridge section ,2/ putting a gasket around the freezer door, 3/ insulating the freezer door with 1/4 foam and holding it in place with aluminium tape ,4/ Putting the foam and tape under the freezer box .5/ Insulating the rear wall to opposite to the burner. 6/ the door seal is a 100% and critically so along the bottom edge ,using a strong light at night in the fridge to find the gaps . All this has made a big difference. It now freezes water bottles in the fridge ,the fins in the fridge have that much ice on them that you cant see the fins, And the freezer, you cant see the food, All on the lowest setting, I have turned it to full with only a very small increase in performance, 3 weeks on a 9 kgs bottle , if the freezer can made to come down in temp ,the fridge can be made come down as well, do 2/3/4/ first
Hi Chris, good to hear you have had success fixing the issues with your fridge. Not sure what climate your in or if its in a van or motorhome but good to hear its all working well for you. I thought I had mine sorted out till I went on a trip in 35C heat everyday and this thing failed totally. I guess your are referring to the same model fridge because this video is relative to this "lemon" RMD8551 fridge only. I have replaced it with a compressor fridge now. Cheers Tim
@@timterry8714 I am in Newcastle Au . I have a old caravan from 1980 I am in the van now and it's 33.8c inside. In the freezer it's -14 the fridge is - 8.3 The van is in full sun and on concrete Last summer .before the mod. yes just another cool fridge.oops it's down to 8.6 now because I turned the fan on .where are you?
Is it the same model fridge as this. This model was a lemon
hi Thankyou very much . It appears as if thermo mastic dries out and cracks and loses adhesion to cool plate . But not surprising its put on poorly from factory ie not enough .Also there is a PDF showing your tube of mastic in the Dometic Pdf .
Yes along with fans ,ducting ,full service 240/12/gas checks my fridge is starting to work well also .
Hi Paul, glad its working for you it certainly didnt for me and I gave up and bought a compressor fridge - its nice to having to deal with the vagaries of these fridges and their inability to cope with movement. Cheers Tim
Hi Tim.
Understand this was a while ago but I have noticed you moved to the Bushman DC190L. Did this fit in the same cavity as the 8551, and how is it or did it go? How much battery and solar did you go to to run it?
Best move I ever made! No the Bushman is taller and also a bit wider and only just fitted in the space I had between a wall and the back of the dining seat. I had to modify the overhead cupboard to make it shorter and enlarge the opening width. The fridge works brilliantly and hasn't missed a bit. With minimum reliance on electronics and no fan means its absolutely silent and the excellent insulation (which is why its wider and taller) realises power consumption is as low as can be achieved with good performance from the Danfoss BD50 compressor. So many manufacturers are reducing compressor capacity and significantly compromising performance of the latest model fridges. Anyway I thoroughly recommend the Bushman DC190. Cheers Tim
Hi Anthony, Sorry I have been away for a month and still am but with limited network coverage. No idea about the igniter as I haven't investigated or had issues with it on my fridge.
Hi Terry, your video is very helpful, so thank you. Did you consider and then dismiss the significantly cheaper Bostik Heat Transfer Sealer - BOS1128C? I'll need to remove the fridge heat sink to enable removal & hopefully repair of the condensation drip channel below it, so this is a perfect opportunity to reapply the sealant/mastic. Can you believe it's not available from Dometic as a spare part?? Will probably do the same to the freezer as it's performance is abysmal.
No I didn't know about the Bostik product. It was all a waste of time regardless as that fridge is a disaster. It worked really well till the caravan moved! I've changed to a Bushman compressor fridge. Best thing ever.
Fridge newbie here, what speed does the fan run at? keen to put one in, but not one that's too fast.
You don't need a fast fan it's just air movement up through the fins that's important
I think I have the same problem and now a solution. Thank you
Yeah well the update is to get rid of it - waste of time trying to fix this model fridge!
I’ve done similar mods but am looking to go to a compressor fridge. I see you’ve since dumped the RMD8551. Did you go for the Thetford T2175c.
No Steve, I bought a Bushman DC190 after a fair bit of research. Its a great fridge, very efficient and well insulated. I've been very impressed with its performance so far. I wouldn't ever go back to a 3 way. Cheers Tim
What is the insulation product used around the flue? And after this video why did you go to the compressor fridge if the absorption was doing so well?
I dont think I had any new insulation around the flue - only the insulation batts I bought and installed.
Are you familiar with the dometic RM2555 150L 3 way fridge? Just wondering if these are functionally more capable fridge based on design?
No sorry not familiar with that model at all.
Great video thx. I have done some of your mods but my fridge blatently only cools freezer and not fridge! I have removed and tipped upside down like you do with these 3 way fridges but still no joy. Do you know if the fridge is on a seperate control?? It has a sensor near that cooling fins so was wondering if that would control things somehow?? Any help by anyone would be appreciated as this is driving me nuts and I don't want to have to go and buy a new fridge.
Hi, look it worked OK at home but after this I did a long trip and never performed well except from switch on till I drove away - then it just went backwards everyday. I gave up and replaced it with a compressor fridge and haven't looked back. Cheers Tim
So what fridge did you end up replacing it with? I have only found the Dometic RMD 10.5XS and the Thetford T2175C compressor fridge that are the same size to fit in hole without any mods.@@timterry8714
Your presentation is absolutely brilliant, to the point & far more informative than anything I have seen previously, the solutions you suggest are practical & achievable with basic skills.
I have been struggling with a Dometic RMD 8551, in my 2015 Lunar Lexon caravan in the UK. I have installed 4 fans in the outlet vent & improved the air flow path over the condensers to raise performance from terrible to poor. I will definitely be replicating the improved insulation and heat sink mastic mods. Do you have any guidance for clearances for the gas burner / heater stack? I would also like to add the fridge circulation fan mod, can you tell me how you provided the 12 volt feed please (internal light??), I am wary of breaching the fridge casing
BTW the Lunar owners Tech forum is inundated with reports of poor performance so you are addressing a real problem for lots of people, the caravan industry isn't interested in helping, except with extremely expensive fixes. Well done.
Hi Roy, Unfortunately all that work I did to improve the performance of this fridge resulted in a limited improvement in hot weather. I have just returned from 8 weeks away and travelling around northern Australia (Northern Territory and Queensland). We have had an unseasonally hot winter this year which resulted in temps in the mid 30C's everyday for 3 weeks and the fridge was a dismal failure anywhere above about 27C.
Traveling really upset the fridge with internal temps reaching into the mid teens during the day and freezer temps getting down to 0 degrees or even positive. ( we travelled over 11000kms in our trip only stopping 1, 2 or occasionally 3 nites. In some cases the fridge would recover overnite if the temp got down low enough but in many instances it was still at around 10 degrees in the morning. Movement devastates this fridges performance! I could begin my day with the fridge at 1 degree (freezer at -14) and after say 4 hours driving at about 30C degrees ambient I would inevitably finish the day with the fridge at say +10 or usually significantly worse and little chance of it recovering without a quite cool night.
I monitored the fridge and freezer temps while driving via wireless temp sensors to a display in my vehicle.
I tried different fan speeds, etc but nothing helped while ambient temps where anywhere near 30C or above. Too much fan does definately have a negative impact - I found minimal fan speed was all I needed when travelling - you dont want to cool things down to much.
Parked at home in Brisbane the fridge works really well at the moment as temps are below 30 and the movement isnt effecting the refrigerant operation. I spoke to Dometic a couple of days ago and they didnt have any suggestions on what else I can do.
I do believe I have absolutely optimised this fridges performance but it is a subtropical (ST) rated fridge and it shouldn't be - given our warm climate here. Dometic advised that the ceased selling ST rated fridges here in 2013 and my van was built late in 2014 so I assume this was old stock. You cannot upgrade this fridge to T rated fridge as the "plumbing" interface to the heatsinks is greater and heater elements higher wattage as is the gas burner and refrigerant content and mixture (Dometic informed me).
So my change will probably improve the fridge performance in the UK as you probably generally have cooler nites which do significantly assist in the recovery from a hot day.I have not changed anything in relation to spacing of the gas burner and have no suggestions and doubt that anything you do there will help.
My intention was to run over the fridge with a bulldozer when I got back so this could never happen again! I have settled down now and have yet to decide what to do about replacing this fridge before we undertake another long trip (which is probably 2 years away). The logical shift is to a compressor fridge but that means more solar and battery capacity and the new 3 way fridges are significantly more expensive but probably work better.
As to the internal fan i added - I simply ran the very small black/red figure 8 wire in through the back wall grommet with the temperature sensor wiring - there is enough room to do that easily. You need a permanent 12V source so it runs whenever the fridge is on regardless of the energy source and yes the feed to the internal light before the door switch would be the best choice. The little fan works well and that size with the light aluminium frame works really well I found.
Cheers
Tim
@@timterry8714
Hi Tim. Well that’s a real body blow, a lot of effort to little avail.
I wonder whether Dometic really does owe their customers at least a compromise on rectification, were they ever fit for purpose? Not going to happen though is it, despite the many complaints!
I have order the mastic so I’ll at least reseal the fridge heat sink. Since I first wrote to you I’ve noticed that my gas burner vent is different to yours it vents inside the main rear cavity. Apparently I can but the same type of direct vent for combustion gas, and the temp gradient across the main outlet vent is around 6 or 7degc (higher above the burner.) But I’m not sure how much of that is from the fridge boiler, or even whether the burner heat is good or bad for cooling the fridge. I perhaps need to ask a man who really knows the absorption cycle.
I will also improve concentration of cooling air over the condenser cooling pipe fins.
Even in our temps (mid 20’sC) my fridge is getting warm especially in full sun. I have made a cardboard cowl to cover the inlet duct to pull air from ground level and under the van, which seems to help a little. We also freeze a couple of Ice packs at night to augment the fridge during the following day.
I also intend to introduce more control on speed & timing on my 4 cooling fans installed in the top vent by using a thermostat, bringing in middle fans first, then all 4 fans at a slightly higher set point.
BTW . Do you happen to know what temperature the condensers operate at roughly that I can use as a starting point please?
Perhaps for UK use this will be sufficient for acceptable if not good fridge performance for UK use?
Kind regards Roy
Hi Roy, sorry I havent got back to you. Look I have tried everything with the fans and minimal fan is fine. The fan that came with the fridge works well enough I discovered. I experimented with everything imaginable on my recent 2 month trip and nothing worked - that fridge is a dog!
Apparently according to anecdotal evidence from customers, on forums I was reading, this fridge caused so much grief at Jayco (our largest caravan manufacturer in Australia) that they dumped Dometic as a supplier back in about 2013 due to unresolved customer complaints for the RMD8551 and moved to Thretford as there preferred supplier. Even with this Dometic at no point offered to recall any of these fridges. They did fix a couple at Jayco by replacing the refrigeration unit completely I believe.
I have just now tossed this fridge out and moved to a compressor fridge. This is now quite viable as there are a couple of highly efficient 12V fridges now (I bought a Bushman DC190L) and of course Lithium batteries and solar are quite reasonably priced now (on par with lead acid or better and far better usable energy density) and significantly lighter.
Also I can get rid of the 2 larger 8.5Kg LG gas bottles and move to 4.5Kg and save myself a considerable bit of wait. Also our gas consumption will reduce significantly providing a reasonable cost saving over time. Hope you have some success but doubt you will satisfactorily fix the problems. Cheers Tim
hi Bostik 1128 HTS heat transfer sealant around $15 in ozzy Used by refrigeration industry for this application . It is a mastic like thick tooth paste
Thanks, thats good to know there is a local much cheaper equivalent however I dont need it anymore as I got rid of the Dometic lemon RMD8551 fridge. Cheers Tim
(Just a suggestion) I have seen someone pin a comment on their vid comments so it’s always on top, might save someone a lot of grief to let them know RMD 8551 are lemons after all.
Well they have been discontinued a long time now but I guess if you are buying secondhand you have to be careful. I dont think that you would think of checking if a 2 way fridge was OK and the seller would have it going when inspected and probably it would be cold - cause it hasnt moved! You would just expect its OK unless you had researched particular model fridges. Cheers Tim
Thanks mate
It dudnt fix it!
Hi Tim, Great video. I have the same fridge and have been dealing with the same issues for the last 8 years. Can most of what you've done be done without pulling the fridge out ? Cheers John.
I didnt remove the fridge to do any of it. I gave up on this fridge after my last 2 months away - its a disaster. It works great as long as I never drive anywhere!!! I now have a compressor fridge and its brilliant.
@@timterry8714 what compressorfridge did you install?
@RayBan73 I did a bit of research and decided on the Bushman DC190L. It has the best insulation and there is no electronics or fans to minimise power consumption and it works really well. I did a video on it when I got it.
Hey Tim, I also have an RM8551 Dometic fridge and are based in Brisbane and have been told I need a new fridge. The $3k price tag doesn't impress me. Are you up for some contracting work to do the same on my fridge as you did on yours????
No cause its a waste of time. I pulled mine out after a 3 month trip last year and replaced it with a compressor fridge. Upgrade to a compressor fridge you won't look back. That fridge is OK as long as you never move! Its a lemon. I spent hours on that thing and it worked great till we hit the road and didn't recover till we got home and stationary again. I bought a Bushman DC190L fridge freezer. They are very good and power efficient. About $1k less than a 3 way fridge.
@@timterry8714 thanks Tim and I'll definitely look at the Bushman DC190L. Did the Bushman fit into the same space as the Dometic or did it require adjustments? I've always been concerned about the power draw with compressor fridges off-grid but it sounds like the Bushman is very efficient. Thanks for the advice
The replacement does require quite a bit of work as most fridges are taller than the RMD8551 and in this case I think it was about 120mm taller and also the fridge is about 80-100mm wider. After removing the the RMD I had to remove the cupboard above it (deconstruct it) shorten all the panels and the doorto accomdate the additional height. That all worked OK and wasnt too hard. The tricky bit was widening the opening for the fridge as the RMD was what the original space was designed for and probably no thought about replacement down the line. The opening was widened using a reciprocating saw and a steady hand and that was relatatively easy or rather straightforward.
So check your space to make sure the new fridge will fit and that includes space for the door to open fully enough so you can adjust the shelf heights if required. Cheers Tim
Any suggestions on how to remove the cover off the freezer door locking mechanism. Cheers
No sorry.
Hey Tim, where did you get your dual temp gauge from ? Cheers Chris.
Aliexpress:
AU $18.20 | LCD Digital Thermometer Temperature Meter Indoor Outdoor Weather Station+ Wireless Transmitter with C/F Max Min Value Display
a.aliexpress.com/_mOWYIxY
Hi Tim...fantastic video! I have an Rmdx21 with similar issues and keen to try your fix. Totally off topic but I also have an issue with the door requiring heavy pressure to close. No change with the door latch set to lock or not. Because it doesn't close as it should, it is often left slightly open and not noticed until the alarm goes off...further adding to cooling issues. Seal appears fine. Fridge is 4 yrs old and had very little use. Appreciate any help. Thanks. Debbie
Hi Deb, I have seen a couple of issues with the fridge door not closing on the web but don't know what model fridges, so have a search they are there somewhere. I gave up on this fridge, it works brilliantly as long as its not moving. I wasted a lot if time on it and finally moved to a Bushman compressor fridge and very happy with that move.
@@timterry8714 Thanks Tim, I will keep searching. Glad the Bushman worked out for you. Debbie
I had also same problem with the pipe was to far into isolation so heatsink was not reaching. That grey stuff is not leading heat good enough comparing too direct metall connection just a thin layer of it.
Yes its not good design mechanically. Very poor and they should have been recalled.
@@timterry8714 I cant find it now but in Germany there was a group that did a process against Dometic about this refridger, I dont knowe the out come.
This is amazing Tim... I have the same fridge in my British made Bailey caravan and the performance is terrible. It can take up to 24 hours to cool down properly and that’s on a typical UK summer day (20-25 degrees). I have already installed some fans but will definitely look at insulating the boiler + other voids and checking out the thermal compound behind the heat exchange fins. I was about to consider buying a new 10 series but thought I would do some more research and came across this which you posted yesterday! Perfect timing. How many tubes of thermal mastic did you use? Is one enough for the fridge and freezer?
Hi Mark, I used about 75% of 1 tube however I purchased 2 as I didnt know how much I would need. Will sell the other locally I am sure. All these changes make a difference but will be interesting to see if yours is also lacking in Mastic. You should definately not need fans at all in the UK Mark. Please let me know how you go. Cheers Tim
Thanks Tim, I have managed to source 1 x 10.3 fl oz tube of Norcold thermo mastic here in the UK so that should be enough. I have not checked the fridge yet but it’s worth replacing anyway. Will let you know how I get on. Mark.
Sounds good Mark, pretty easy and quick to pull the heatsink fin assembly off and have a look. Yes the Norcold is the same stuff and 10.3 fl oz is the same size tube as I purchased.
Hi Tim, I replaced the thermal mastic on my fridge on Saturday. Here is a photo taken beforehand, just after I removed heatsink fin assembly. I haven’t had chance to test the fridge yet as the caravan is kept in a storage compound but we will be going away at the end of May so will test it out then. www.dropbox.com/s/jvs0uqsw07c1aqp/IMG_2694.JPG?dl=0
Hi Mark, did you think the mastic was applied evenly it looks a bit scketchy but more consistent than mine was. Also was the mastic dried out a bit and like old putty? The thing I noticed immediately was the response time after starting it up improved significantly and the temp in the fridge is much more consistent now. So I think the transfer of cold to the heatsink was much better after doing this. Will be interesting to see how that goes. you should do a before and after test but I guess thats a bit difficult if its in storage. Cheers Tim
hi yes my fridge now gets to temperature BUT. 2 symptoms remain 1/ long initial cooldown 12hrs and
2/ recovery time when in use is that poor u can only open 3x per day . 28deg cel and 60% humid
I suspect not all the thermal paste is doing the job . Van is 15yr old . ThermoMastic is the next job .
Hi Paul, I had no issue with initial cool down after my mods it got to temp within 6 hours on LPG, 240V and indeed 12V. The problem is it just doesnt like movement and fails everytime i drive somewhere. I should just stay home! Recovery is generally poor. I gave up on it and changed to a compressor fridge and it works brilliantly and is surprisingly energy efficient (my greatest concern). No I can holiday without worrying about the bloody fridge anymore.
Tim,
Can you give me a led as to why my RMD 8551 won't ignite on gas?
There is gas flow as I've manually lit it.
Hi Anthony. I have the same fridge and had an issue with it not starting on gas. I took the cover off the housing where the ignitor electrodes are and found that the electrodes had a very wide gap hence there was no spark occuring even though it was trying. I closed the gap to about 40 thou (not sure of what the specs are supposed to be), this has worked well as the gas will now ignite as soon as you select gas on the fridge panel. Hope this works for you if you haven't already sorted your issue. Cheers, Frank
Hi Anthony, Frank's suggestion below is possibly a solution. If you cant hear the Piezo ignition clicking after that it may be a control boarg issue. Check the wire connectors are seated properly to the ignitor. Mine hasn't missed a beat and if it gets blown out by wind gust it reignites instantly. As for the fridge generally its a complete failure from my perspective as all the work I did still resulted in abysimal performance for us on the road for the past 6 weeks. Must do follow up Video when I get home.
We had the same issue - it was our motherboard. Had to be replaced.
to much overkill
What's too much overkill?