Re-thinking the RM8551 4.3

[Patandlinda]

Originally Posted by Kountrykamper

I have not found a need to change my sensor. I pulled my sensor out of the mounting bracket to get it away from the coil and out in the air. Before I moved it 3 bars would get me around 42 degrees. With the sensor in this position and not sensing the coil temp but now sensing the air temp instead the fridge runs around 37 on 3 bars. No other changes or mods as this was done long after I had long finished my mods. It's not like moving your thermostat to different walls at your home and still sensing the same air temperature. You sensor is no longer sensing the coil temp but now is measuring the air temp.

Also mine runs runs 31-32 on 4 bars and 28-29 on 5 bars. Yelp I did say 28-29 degrees.

Thanks Alf!

Tom going to move my sensor outside too , out of the holder with my fan blowing up on it . Pat

[Klem]

Originally Posted by Patandlinda

Tom going to move my sensor outside too , out of the holder with my fan blowing up on it . Pat

It will be interesting to see how that works. I've spent too much time on the outside of the box but have some inside fans not in use. The plastic shelves in the RMD look to restrict air flow much more then the steel ones, time for inside fan(s) too.

[cpaharley2008]

I do not believe the sensor is sensing the coil temperature as it is not attached to the coil but sits in a plastic holder, insulated from the coil. I believe it is only sensing the air temperature unless there is conductivity between the coil and the sensor, to which plastic does not. But read my name again.

[Patandlinda]

Originally Posted by Klem

It will be interesting to see how that works. I've spent too much time on the outside of the box but have some inside fans not in use. The plastic shelves in the RMD look to restrict air flow much more then the steel ones, time for inside fan(s) too.

Klem I have same fan as Tom . He helped me to do this before . I am meaning to take sensor out of it's holder . It will still be in frig , with my little fan blowing on it inside frig . I still haven't tested everything else I have done yet , coming soon and will post my results . Pat

[Kountrykamper]

Just sharing my experience after playing with this fridge for 2 years. If the sensor is 1/8in from the coil its affected greatly by the coil temp.

This is the fan and guard I used that I found works best. As you can see it is a very low CFM (13) fan. If you use too high a CFM it can work against you (Been there, done that). I have tried it blowing both directions and find it works best blowing down and not on the sensor.

[Kountrykamper]

This is the fan installed. I have removed our chrisper and have a lower shelf instead I have it mounted to but it could be mounted on the shelf above just do not blow it on the sensor.

[Kountrykamper]

Close up. Just zip tied to the shelf.

[Kountrykamper]

Showing the size

[Patandlinda]

Originally Posted by Kountrykamper

If the sensor is 1/8in from the coil its affected greatly by the coil temp.

This is the fan and guard I used that I found works best. As you can see is a very low CFM (13) fan. If you use too high a CFM it can work against you (Been there, done that). I have tried it blowing both directions and find it works best blowing down and not on the sensor.

Forgot Tom you told me about 3 times now fan blowing down . Sorry Pat

[Kountrykamper]

No problem Pat.

I had to go dig through my box to find this stuff. Guess I was hoping I would never have to deal with it again.

[MyronL]

Some comforting latest statistics, my RM8551:

• Friday, 5:30 PM fridge temp is 49°F trailer temp 97°F (...I had earlier opened the door for several minutes to load stuff).
• Saturday, 7 AM fridge temp is 29°F trailer temp 62°F. (note: fridge has been continuously on 5 dots, shore power since yesterday.)
• Saturday 2:30 PM fridge temp 36°F trailer 94°F
• Saturday 3:40 PM fridge temp 37°F trailer 94°F

Today's a very hot sunny day.

1. All this with original (ETI/Dometic) install of fridge thermistor and two rear fans working (as needed I guess) on automatic.
2. All this with my beefy insulation install and the baffle, and my plastic curtain.
3. I have no fans inside the fridge. Thermistor is taped to left side wall about an inch from the fins.
4. If this kind of performance continues, then my only issue is painful slow recovery of interior temp after opening the fridge door.

[dave1]

I have the 4.3 with one fan on the back. Have the fridge out doing a reinsulate and modifying the escape baffle to 45 degrees. id like to put a fan in the baffle area. Questions are: is it necessary and where how high up would you put it?

Dave

[Ron in BC]

Originally Posted by MyronL

Some comforting latest statistics, my RM8551:

• Friday, 5:30 PM fridge temp is 49°F trailer temp 97°F (...I had earlier opened the door for several minutes to load stuff).
• Saturday, 7 AM fridge temp is 29°F trailer temp 62°F. (note: fridge has been continuously on 5 dots, shore power since yesterday.)
• Saturday 2:30 PM fridge temp 36°F trailer 94°F
• Saturday 3:40 PM fridge temp 37°F trailer 94°F

Today's a very hot sunny day.

1. All this with original (ETI/Dometic) install of fridge thermistor and two rear fans working (as needed I guess) on automatic.
2. All this with my beefy insulation install and the baffle, and my plastic curtain.
3. I have no fans inside the fridge. Thermistor is taped to left side wall about an inch from the fins.
4. If this kind of performance continues, then my only issue is painful slow recovery of interior temp after opening the fridge door.

Those numbers look pretty good. I'm wondering what the result would be if you ran it on propane.

Ron

[MyronL]

That test is yet to come.

Meanwhile.... This week got in mail the correct Snip-the-Tip adjustable thermistor and have installed it. New round of testing began yesterday and is continuing. Will post my fair and balanced results probably tomorrow.

[MyronL]

Dave1 just sent me this picture of the back of his RM8551 4.3. Interesting to note he got it with only one fan, and his motherboard is on the back instead of on top like mine is. Does not leave much space for adding a second fan.

Fan placement could be crucial for best efficient fan cooling. Wondering if all with same as this have made changes and if they are working for you.

[Kountrykamper]

I have not found a second fan is necessary although I have added a second but never use it. I located it about 6" below the roof vent.

I have the same fridge.

[dave1]

Originally Posted by Kountrykamper

I have not found a second fan is necessary although I have added a second but never use it. I located it about 6" below the roof vent.

I have the same fridge.

Thanks for the reply. Good to know you really don't need a second fan. I have a computer fan just begging to be used and am thinking of locating it about a foot above the exhaust stack. My thinking being to pick up the hot exhaust and move it up. What do you think?

Dave

[dave1]

Originally Posted by MyronL

Dave1 just sent me this picture of the back of his RM8551 4.3. Interesting to note he got it with only one fan, and his motherboard is on the back instead of on top like mine is. Does not leave much space for adding a second fan.

Fan placement could be crucial for best efficient fan cooling. Wondering if all with same as this have made changes and if they are working for you.

Myron,

Actually the grey box is low down on your fridge. Your power connections are on top where on the single fan they are low and assessable from the outside.

Dave

[Patandlinda]

Originally Posted by MyronL

Dave1 just sent me this picture of the back of his RM8551 4.3. Interesting to note he got it with only one fan, and his motherboard is on the back instead of on top like mine is. Does not leave much space for adding a second fan.

Fan placement could be crucial for best efficient fan cooling. Wondering if all with same as this have made changes and if they are working for you.

Actually like this the 4.3 we have with 1 fan . Interesting when frig was new with problems , spoke to Dometic and they said there was 2 fans back there ?when I was able to remove there is only 1 fan . Have the snip the tip , did not install it yet . Soon will be testing out everything I did . I put my extra fan above on side , it is larger , a dometic fan just above frig top hopefully if needed to move hot air out to roof. I can't wait to hear your findings with the added snip the tip . Pat

[Kountrykamper]

Originally Posted by dave1

Thanks for the reply. Good to know you really don't need a second fan. I have a computer fan just begging to be used and am thinking of locating it about a foot above the exhaust stack. My thinking being to pick up the hot exhaust and move it up. What do you think?

Dave

From my experience ours seems to cool better just running the lower fan. Pat installed a better quality fan than I did so maybe it will do something mine don't. With just the lower fan running I can feel a draft coming out of the roof vent when standing on a ladder and holding my hand next to it.

It would not hurt to install it while you have the fridge out. May give you more options.