17' Series Installing a circulating fan inside Dometic Fridge

[Boots in Action]

Hi Mike, my own Penguin has a Thetford fridge and only has a drip tray under the evaporator - means I have to empty it manually. My friend's fridge does have a drain pipe (Dometic in an Ecotourer). The drain pipe from the melt tray comes out through a hole in the back of the fridge and into a small tray below to collect water. At the end of the pipe was a bulbous diffuser with small holes in it, I think it was supposed to be immersed in water in the tray. As the tray filled up, no air could get in/out of the fridge through the tube. However, when tray was full, water was directed out of the tray via a small tube to just let water run onto anything below. Shocking system!! As part of his restoration to proper working for his fridge, (the drain tube was broken, more about this shortly), we connected some 10mm plastic tubing over the outlet from the fridge and made a loop IN the collector tray (but below the outlet) and then directed the rest of the tube out through the bottom vent. We made sure that the loop was below the outlet from the fridge so there would not be any flow problems with the water draining.
Sorry I won't be able to give you pics from my Penguin, but will see if I can get some of my Friend's for you. He is just up the road!!
The "S" bend would probably work but I think a complete loop may be better. You just have to make sure that water can drain out and yet there will still be some sort of water lock still remaining to stop air entering the tube and eventually into/out of your fridge. Hope this helps and will send pic as as soon as I can. How did your LED bed lighting go on your last trip??

 

[mikerezny]

How did your LED bed lighting go on your last trip??

Hi @Boots in Action,
great! All finished now.

Here is a post where I discussed this:

http://expandasdownunder.com/thread...n-the-weekend-thread.389/page-111#post-175332

Thanks for all the help.

cheers
Mike

 

[Boots in Action]

Would love a pic or two of these fan placements!

Hi Marv-mart, read your request about positioning of internal fans and should be able to post pictures with a little more explanation by Wednesday. Have to take cover off van and open up to get pictures. My Thetford Fridge worked successfully (on Gas) recently when temperatures at 6.00pm in the evening was still 32 degrees after reaching day time temps of 38 degrees in the shade a couple of months ago. Humidity was very high too around 70% and everything was kept really cold. The installation of fans inside evens out internal temperatures, whilst the external fans remove the hot air around the back of the fridge, even if it is blowing hot air at ambient temp through the back. Only way to go when the going gets tough (hot)!!! Cannot have my drink getting warm.

 

[Boots in Action]

Hi @Boots in Action,
great! All finished now.

Here is a post where I discussed this:

http://expandasdownunder.com/thread...n-the-weekend-thread.389/page-111#post-175332

Thanks for all the help.

cheers
Mike

Glad to hear that you have been successful and done in a professional way. That is what this forum is all about - helping others to enjoy camping. Looks like you had a lot of fun in the wilderness.

 

[Boots in Action]

As I've said before most cooling problems are caused by incorrect fitting of fridge in the first place but drain hose leaking cold is a new one along with letting dust in....lol.

Hi Drover, picked up this info from details on absorption fridges in the US where lots of campers and others have had this problem with their RV's not getting cold enough. After all, you would not put up with a 25mm round hole in the door seal of your fridge, and that is what it actually is, only in back of fridge with all the hot air too. Supposed fridge mechanics claim up to 15% improvement when water outlet is closed to open air by water lock. As you said, there are lots of interesting facts out there and no one is too old to learn something new. Cheers

 

[Boots in Action]

The ice usually forms on the fins after a few days, depends on outside humidity, how often door open, how packed the fridge is but after having one as a food warmer until I fitted it properly, we were happy with ice........................temp depends on loading but too much door opening will keep it warmer.
My fridge has a light in it and looking at things yesterday I think I will fit my fan at back of shelf just below fins to circulate air, but not underneath the fins as I don't want water run off getting into fan plus fitting fan against the fins would only move air around a couple of them.......picking up power from light switch, will see how things go as to whether I will fit a switch set up for it to go off when door opened but will fit a micro switch to shut it down....no light can run power thru the drain.

Hi Drover, try fixing fan on side wall so that at least 50% of air flow will go across evaporator fins. Helps circulate the cold air (as in a frost free fridge at home) and also reduces ice build up on fins. I will post a picture or two of my setup on Wednesday when I can get into my van. Try it out!!

 

[Drover]

Have had a fan set up to fit since this thread started, runs from the light switch just haven't got to fit it yet, my drain hole is only about 10mm if that, so wouldn't think it would matter but 25mm is a tunnel.

 

[Duncanblake36]

I think I'm going to upgrade to 3-4 small CPU fans across the top of the elements. I have the small blue box fan but its not 100%. Hell of a lot better than nothing but I think some fans across the top will be perfect.
The trouble I have with the blue box thing is that it works well if there is not that much in the fridge. If you pack it full then the fan air doesn't hit the elements that well. Last trip away the elements iced a bit but I think that was due to the fridge being full.
Or do I have the fan in the wrong spot? The drip tray is above it so its not really hitting the fins that well....

 

[Drover]

The idea is to just get the air to move, too much jammed in the fridge restricts air flow and thusly fridge doesn't work properly and you will ice up, as @Boots in Action pointed out fan on the side would be the spot, though blowing directly over the fins probably wouldn't be ideal as you would get variations in the temps and actually could ice up anyway.

 

[Boots in Action]

The idea is to just get the air to move, too much jammed in the fridge restricts air flow and thusly fridge doesn't work properly and you will ice up, as @Boots in Action pointed out fan on the side would be the spot, though blowing directly over the fins probably wouldn't be ideal as you would get variations in the temps and actually could ice up anyway.

I agree with you totally Drover. If you have multiple fans in front of the fins, you will not only have lots of wiring hanging about, but you will be drawing cold air from the evaporator THROUGH the fan blades. The reverse would be no better to blow air back onto the evaporator as there would not be any real air movement. I do not think that is the best way to go in "after fitting". If you have a single 60mm or even a 80mm computer fan on the side wall, it is not only more out of the way but more likely to move more air across the whole face of the evaporator. The little battery fan at the bottom of the picture would be ineffective if anything blocked easy airflow above it. The best place for a fan down there would be on the wall where you have your thermometer? - out of the way and blowing cold air ACROSS the whole bottom of fridge. Incidentally, I have my companion thermometer sensor up higher on the left hand side of the fridge midway from the back to the door where the warmest air is likely to be, but certainly NOT just below the evaporator. Something to think about? I will be posting a couple of pics sometime today for Marv-mart to see where my fans are placed, as soon as it stops raining!!

 

[Drover]

Sunny day up here just did the lawn............

 

[Boots in Action]

Hi @Marv-mart, read your request about positioning of internal fans and should be able to post pictures with a little more explanation by Wednesday. Have to take cover off van and open up to get pictures. My Thetford Fridge worked successfully (on Gas) recently when temperatures at 6.00pm in the evening was still 32 degrees after reaching day time temps of 38 degrees in the shade a couple of months ago. Humidity was very high too around 70% and everything was kept really cold. The installation of fans inside evens out internal temperatures, whilst the external fans remove the hot air around the back of the fridge, even if it is blowing hot air at ambient temp through the back. Only way to go when the going gets tough (hot)!!! Cannot have my drink getting warm.

Hello @Marv-mart, the rain has stopped and here are the pictures you asked for about placement of internal fans. In the pictures, you will see that I have mounted an 80mm fan at the bottom of the fridge as far back as possible. Note that fan is NOT facing towards door opening. Never had any frozen lettuce, cucumber, tomatoes or the like since fitting, which keeps the "boss" very happy. Used white plastic as backing for fixing with velcro (no drilling!) and have 25mm standoffs to allow air to come in from rear.
The top fan is a 60mm one which is placed so that at least 50% of airflow will be swept across whole face of evaporator fins. Cannot go too far back as all air would then be directed at wall of first fin and not too far forward so there is some coverage of fins. Same setup as for lower fan not facing towards door opening. Power was brought in through the rear via grommet for capillary tube. I hate making permanent holes and it is very tricky, especially if still installed. Similarly, the use of velcro means if you don't like the position or it does not work for you, all can be removed without hassle. I have had very little ice buildup on evaporator since top fan was installed. Think it must have something to do with airflow over fins - warmer air from other areas dries off moisture as well as cooling the passing air?? Hope this is helpful to you and other thread followers. Also note position of Companion thermo sensor. All fans are only 10mm or 12mm deep.

 

[mikerezny]

Hi @Boots in Action,

if you preceed a member's name by the '@' symbol, that member will be alerted and possibly emailed to let them know they have been mentioned in a post.

best wishes
Mike

 

[Duncanblake36]

Now that is a much better idea. Good work.
Mmmmm. Is it possible to have a thermo switch that turns on when the fridge is cold so that the fans only run when the fridge is cold. I would also like some lighting so could be a two for one deal or stick with a manual switch. Where do you mount it though?

 

[Boots in Action]

Hi @Boots in Action,

if you preceed a member's name by the '@' symbol, that member will be alerted and possibly emailed to let them know they have been mentioned in a post.

best wishes
Mike

Thanks again for that information. Still learning, but will implement @ before members'names in future. Very grateful as I do not wish to offend any member. Cheers

 

[Boots in Action]

Now that is a much better idea. Good work.
Mmmmm. Is it possible to have a thermo switch that turns on when the fridge is cold so that the fans only run when the fridge is cold. I would also like some lighting so could be a two for one deal or stick with a manual switch. Where do you mount it though?

Are you talking about the switch or the light inside the fridge?? You have got me thinking now about using some of my excess LED lighting left over from my bed light setup. You usually do not need fans so much when fridge is already cold. They are more used for moving the hot air around to get even and faster cooling. However, I am sure someone knows where a thermostat of that type can be obtained..

 

[Duncanblake36]

We'll I'm thinking a terminal switch that makes a circuit when the temp goes below a threshold (eg 8 degrees). This will activate the fans and a led light that will stay on and light up the fridge while the fridge is in operation.

When we are finished with the fridge we turn it off and leave the doors agar and fans and led lighting will turn off once temp gets above threshold.

I need a light and a better solution for the fans.

I'll have a head scratch this weekend and see what I can come up with.

Thinking about it more. A switch may be full (and fool) proof. Dunno where to install it though. I need a place that is out of the way plus easy to mount.

 

[Boots in Action]

We'll I'm thinking a terminal switch that makes a circuit when the temp goes below a threshold (eg 8 degrees). This will activate the fans and a led light that will stay on and light up the fridge while the fridge is in operation.

When we are finished with the fridge we turn it off and leave the doors agar and fans and led lighting will turn off once temp gets above threshold.

I need a light and a better solution for the fans.

I'll have a head scratch this weekend and see what I can come up with.

Thinking about it more. A switch may be full (and fool) proof. Dunno where to install it though. I need a place that is out of the way plus easy to mount.

Just had a thought about low temp thermostats. When doing some repairs on frost free refrigerators, I quite often had to replace the defrost thermostat. This thermo only operates when fridge is in defrost mode. Normally closed, it opens circuit when temp in freezer goes above 7 or 8 degrees Celsius and closes again at about 3 degrees. This ensures that the freezer temp does not get too high whilst defrost heater is on. When heater goes off and temp in freezer drops down to cut in setting, heater is connected again. Not sure of temp ranges, so may not be suitable for our fridges, but worth a further check. At least switch is positive, but not much use if you do not remember to turn it on/off! Cheers

 

[Boots in Action]

As I've said before most cooling problems are caused by incorrect fitting of fridge in the first place but drain hose leaking cold is a new one along with letting dust in....lol.

Hi @Drover , fitting is always a problem, but far worse is absolute lack of or denial of maintenance! Following is true story.
Good friend tells me his Dometic fridge is not cooling as good as it should. Wife says it's working okay, but later on admits that not cooling things down fast enough and not really cold. Did not want to do anything though. Spoke to friend who admitted that van was over 11 years old and HE HAD NEVER DONE ANY MAINTENANCE AT ALL!! Convinced him to remove fridge and find out what is/not happening at the back. Wife panicking about this work!! Removed fridge without problems to outside. First problem - back of fridge coated in 2mm of fine dust baked on with moisture after 2 round Australia trips. Unable to brush off, so hosed off - can now see clean metal on all pipes. No water used on top area where electrics and controls are, but lots of dust removed. Next noticed that plastic grommet for thermo capillary tube has split with 3 to 4mm gap right through from inside fridge. Resealed with polyurethane sealant. Drain pipe for melt water broken and open to air and no water lock - fixed by fitting new plastic tubing in place and making loop in tube inside water collector. Pipe now extends through bottom vent. Noticed a lot of rust around heating boiler caused by water overflow from melt collector bowl splashing onto housing for electric heaters 12 volt and 240 volt. Removed insulation stack around boiler and found 240 volt heater stuck in badly corroded tubes. Removed (with great difficulty owing rusting) both 12 volt and 240 volt heaters, cleaned all areas of rust and corrosion and re-inserted with much better and cleaner heat transference surface areas. Found nearly burnt out electrical connection on 12 volt heater. Repaired. Cleaned out gas burner and orifice - a lot of soot and dust!! No wonder this fridge was far from operating properly, regardless of what his wife was saying and he was not prepared to admit. Refitted all without problem after adding additional insulation and adding a baffle to direct airflow onto cooling fins. Only had a top baffle above fins!! 2 x 120mm fans installed - one in top vent expelling air and one in bottom vent pushing air in.
Results: On 240 volt operation, pull down time dramatically reduced and fridge temp now able to get down to 0 Degrees when setting on 3. Gas operation very fast and cold temp easily reached. 12 volt now works better - necessary when connected to tug for travel.
A long story of how neglect and denial can prevent a good system from working properly. Just had to tell it!!!

 

[Drover]

I bet a few of them are around as well.......................have seen new from factory back of fridge open to under bench space and opening for cables etc not sealed so fridge hardly worked, cupboards nice and warm, bit of tin, can of foam, tube of silastic and all good, freeze lettuce on 3.