3 Way Refrigerator Testing and Performance

grassgd

I have been working with my N180.3 Refrigerator trying to determine the best way to improve the refrigerator performance by improving the air circulation through the side vents on my T@B 320. 

I have been experimenting with improving the natural draft or "chimney effect" by installing temporary a flue vent on the upper vent extending up about 24 inches on the side of the camper and varying the cross-sectional area of the flue. I record the inside refrigerator and outside ambient temperatures to calculate the units achieved differential temp between the refrigerator interior and the ambient air.  This has proved helpful when running on120 volt electricity but for some reason not so good on propane, why is a mystery to me but at any rate since installing a flue or chimney on the side of the camper is at best very limited, this leads to the common solution of adding fans to facilitate better air flow.

I began by blocking off the bottom vent with a 4.5 inch Thermaltake TT-1225 fan in the center of the blocking plate to provide positive air flow up and out the top vent without any air recirculation on the bottom vent. This worked very well on 120 volt power but on propane did not work well, again a mystery to me since I thought it would work nearly as good as on 120 volt electric power - I may elect to re-run this test on propane again to see if the failed performance is repeated.  Actually when running this test on 120 volt electric power, I saw the unit cycle on and off while maintaining internal refrigerator temperatures between  15 and 23 deg F.  This was with ambient temps around 65 deg F.  As ambient temps rose to mid 90's the internal refrigerator temp remained in the low 20's without cycling.

Since I have mixed results that don't make sense to me on propane, I figured I should investigate and better my understanding of how the ammonia refrigeration works.  The best article I found on the internet was found at this location  Ammonia Absorption Refrigerators.pdf (sundancecustomrv.com) by Sundance Custom RV.

As I originally believe and after reading the above referenced article,  I believe  the focus of adding a fan for improved air flow would be best focused on the condenser portion of the refrigerator.  My next attempt will be to devise some sort of baffle to direct a fan located in the bottom vent area to force cool (ambient) air up and across the condenser near the top vent.  If I cannot install such a baffle without removing the unit, I may try making a baffle to pull air up across the condenser and out the upper vent.     

[Deleted User]

I too had considered putting a small fan in the vent compartment. I was thinking of just using a small desk fan I already have. Couldn't you just sit it inside (bolt it down so you can leave it up there) the top compartment where the fins are and plug it in when you get to camp each time? That's what determines the performance isn't it? I mean keeping the fins cooler is what is needed right? There is already a small 12volt fan pointing up at the fins but it didn't seem to cut on until its really hot outside.

I already have two of these little fans I used to use to keep my aquarium lights cool.

Holmes Mini High Velocity Personal Fan, HNF0410A-BM https://a.co/d/iQXtD4z

There is also this little thing you put inside the fridge but it really only helps if the fridge is already cold enough. ( never mind...bad reviews!)

VALTERRA A10-2606 - Valterra Fridge Cool Fan A10-2606 https://a.co/d/66SqtfM

webers3

So the question is; with the mods you made, what is the temp range inside the refrigerator when the outside daytime  temp is 80 plus, which is what you would typically expect in the middle of summer. 

MuttonChops

Interesting.  As @webers3 commented some data on your results (table format?) would be helpful.

After the Fridge was at 55F on three 100F+ days last summer (while on shore power) I added two 4-inch 5Vdc fans.  They are mounted behind the top vent panel and have a USB cable routed to the Kitchen 12V/USB outlet - - - to be plugged in when needed.

My thought/goal was to increase the air flow on those hot still air days.

Since adding the fans I have Zero Data on there effect and so far have only turned them on to confirm they work.

grassgd

TabbyShack said:

I too had considered putting a small fan in the vent compartment. I was thinking of just using a small desk fan I already have. Couldn't you just sit it inside (bolt it down so you can leave it up there) the top compartment where the fins are and plug it in when you get to camp each time? That's what determines the performance isn't it? I mean keeping the fins cooler is what is needed right? There is already a small 12volt fan pointing up at the fins but it didn't seem to cut on until its really hot outside.

I already have two of these little fans I used to use to keep my aquarium lights cool.

Holmes Mini High Velocity Personal Fan, HNF0410A-BM https://a.co/d/iQXtD4z

There is also this little thing you put inside the fridge but it really only helps if the fridge is already cold enough. ( never mind...bad reviews!)

VALTERRA A10-2606 - Valterra Fridge Cool Fan A10-2606 https://a.co/d/66SqtfM

Small desk fans like you mention are way too big physically and likely overkill on the amount of air needed. 

I would like to add a circulation fan inside the refrigerator, but the N180.3 is really small to begin with and I would not want to take up any space with a fan.

I don't have a small 12 volt fan pointing up at the condenser fins and if your's does that may be all you need to ensure the condenser has enough air flow to condense the ammonia vapor.

Grumpy_G

Adding a fan or two to the exhaust opening is a pretty popular mod on older T@b 320s with the 3163 fridge. The previous owner installed two computer style 12V fans with a manual switch and I do use them when the front of the T@b is baking in direct sunlight. The fridge has an external temperature display added and using the fans brings the temperature down after 15-20 minutes, in my use case anywhere from 5-8F but I've never tried to figure out the maximum. 

grassgd

webers3 said:

So the question is; with the mods you made, what is the temp range inside the refrigerator when the outside daytime  temp is 80 plus, which is what you would typically expect in the middle of summer. 

The best performance was on120 volt power with fan mounted on the lower vent (see attached file).  All test were with refrigerator empty except temperature monitor which is very small.  Lost 120 volt supply at about 20:30 hours until 22:36 hours on 5/21/2022 where temp in refrigerator rises then begins to fall. This is where you can see the refrigerator actually cycle on and off which I had read the unit can do only when on 120 volt power.

grassgd

MuttonChops said:

Interesting.  As @webers3 commented some data on your results (table format?) would be helpful.

After the Fridge was at 55F on three 100F+ days last summer (while on shore power) I added two 4-inch 5Vdc fans.  They are mounted behind the top vent panel and have a USB cable routed to the Kitchen 12V/USB outlet - - - to be plugged in when needed.

My thought/goal was to increase the air flow on those hot still air days.

Since adding the fans I have Zero Data on there effect and so far have only turned them on to confirm they work.

You are correct in using fans to increase the air flow when running on 120 volt power.  I don't think it makes matters much if you have the fans on the upper or lower vent, I like the lower vent where the fan is pushing cooler/denser air than in the hot exhaust air, but not a deal killer. So the fan solution does seem to be the answer when on 120 volt power. It's a shame Narcold did not include a cooling fan and a actual refrigerator internal temperature controller that could be set by the user so you set a temperature and it would cycle on and off at the desired temp.  

My big concern is in improving the performance when on propane and/or towing on 12 volt tow vehicle power.  So far when I added a fan while on propane it got worse.  I saw improvements on propane with the external flue and no fan but as I said in my initial post, that's not very practical to install on a T@B 320. 

[Deleted User]

I recently learned the little thing that is clipped onto the metal fins inside the fridge is a thermostat and you can adjust the temp colder by moving it up like an inch to make fridge colder. I moved mine up barely and inch and it brought temp down in minutes. It only needs slight movement... well I guess depending on outside temp.  It should be on the 5th fin and you adjust up or down on that fin. Down is warmer. Up is colder.

I have a Norcold 3 way model 4104.

bergger

@TabbyShack just to confirm.  You physically move the tstat up or down on the fin to adjust the temp?  or is there a dial or lever on the tstat that is adjusted?

[Deleted User]

You physically unclip whole thing and move it up just a 1/2 inch at most first and check it. It doesn't slide really so removing it and reclipping it is easier. You might want to somehow mark current position for reference.

I actually bought a wireless outdoor thermometer so I can monitor temp without opening the door. It works great during the testing phase. 

AcuRite 02049 Digital Thermometer with Indoor/Outdoor Temperature,White https://a.co/d/7KQqDMK

webers3

@grassgd Wow! Your results are truly amazing. To achieve 20-30 degrees, basically a freezer temp, with ambient temp between 80-90 is incredible. I camped 3 months in the middle of summer and tried everything to keep the temp in food safe range but nothing worked. Maybe my 3 way was a dud. 

grassgd

webers3 said:

@grassgd Wow! Your results are truly amazing. To achieve 20-30 degrees, basically a freezer temp, with ambient temp between 80-90 is incredible. I camped 3 months in the middle of summer and tried everything to keep the temp in food safe range but nothing worked. Maybe my 3 way was a dud. 

But again that is 120 volt power with a 4.5" 12 volt fan forcing cooling air from the bottom or top vent (almost identical results with either top or bottom fan location).  It was interesting to see the unit actual cycle when outside air temps were lower.   

I can't seem to find and improvement on the performance with propane.  Addin fans always seems to hurt the performance.  I can't figure that out.  I made a simple baffle to pull air up and out the top vent with all the air flowing past the condenser in the top of the unit.  On 120 volt power I saw the same result as with the fan blowing air in the lower vent or pulling air out of the upper vent.  As soon as I switched to propane, the refrigerator temps began rising until about 40 deg F when I pulled the fan off and left the baffle arrangement in place and still on propane and the refrigerator temp began to fall.  Seems any fan used with propane makes things worse!

grassgd

I have a feeling the "tube exhaust extension" which vents the propane hot exhaust when running on propane may be incorrectly installed on my unit.  As can be seen in the picture below, the tube exhaust extension is positioned directly under the forward edge of the condenser:



It doesn't make any sense to route the hot propane exhaust under the condenser.  I thought this did not make any sense.  When running on 12 volt or 120 volt power, there is no hot gases coming out of this tube but on propane there is and it is applying heat to the condenser which is trying to cool the ammonia refrigerant.  

The Norcold parts diagram for the N180 series depicts the tube alongside the condenser exhausting around the top of the condenser.  This may not be accurate but in my mind makes sense.   Has anyone observed the positioning of this exhaust tube near the condenser? 

MuttonChops

grassgd said:
I have a feeling the "tube exhaust extension" which vents the propane hot exhaust when running on propane may be incorrectly installed on my unit. . . . .

Nice observation.  Instead of the Tube Exhaust Extension being installed incorrectly what you are seeing is the result of road travel vibration.  The Tube is rotating in it's single clip/collar/ring mount.

My rig looks just like yours.  Question is how to safely secure the Tube so it stops rotating (without having to remove the Fridge if possible)

Sharon_is_SAM

Nice sleuthing @MuttonChops!  I wonder if this accounts for a lot of the subpar performance of the 3 way frig?

grassgd

MuttonChops said:

grassgd said:
I have a feeling the "tube exhaust extension" which vents the propane hot exhaust when running on propane may be incorrectly installed on my unit. . . . .

Nice observation.  Instead of the Tube Exhaust Extension being installed incorrectly what you are seeing is the result of road travel vibration.  The Tube is rotating in it's single clip/collar/ring mount.

My rig looks just like yours.  Question is how to safely secure the Tube so it stops rotating (without having to remove the Fridge if possible)

I tried to rotate the flue cap heat cap without putting too much force- didn't want to brake anything but it felt pretty secure and did not move.  The tube exhaust extension fells pretty secure like the single mounting point near the fire box end is holding it from rotating.  Do you know how the single mounting point is secured - sheet metal screw?

Do you know how the flue cap heat cap is secured inside the insulating burner assembly,  if that's what is called - will it freely rotate if the single mounting point on the tube extension is loosened? 

If I can rotate mine, I think I will simply try installing a short extension on the top of the tube exhaust extension so it extends to the top of the condenser fins like shown in the parts diagram.  This would not allow it to rotated under the condenser.

VictoriaP

Mine was also rotated. Here’s mine after rotation. Mine doesn’t rotate far, possibly not enough to add an extension that would fully clear the condenser fins.

Three ideas come to mind:
- A block of some sort wedged in behind at this top point to keep it from rotating back. OR
- Some way to strap the upper vertical section to the trailer sidewall 
AND
- A 90° pipe extension or baffle, facing out through the sidewall vent so that exhaust directs where it belongs…outside.

But all our modders are way better at working out the implementation of these things than I am. Will check back in once y’all have a solution. 

MuttonChops

grassgd said:

I tried to rotate the flue cap heat cap without putting too much force- didn't want to brake anything but it felt pretty secure and did not move.  . . .

Do you know how the single mounting point is secured - sheet metal screw?

Do you know how the flue cap heat cap is secured inside the insulating burner assembly,  . . .

On mine I rotated the Tube from the bottom.

To my shock & surprise the Single Mounting Point is a Plastic Tie Wrap.
Mine is very worn.  While I can touch the tie wrap, I don't time I can replace it.  So another securing approach will need thought.

Picture Taken from Fire Box end Looking up the side of the Tube.

I have not looked at the Flue Cap connection in any detail . . . future task.

[Deleted User]

Is this on a 400 or 320? 

MuttonChops

TabbyShack said:
Is this on a 400 or 320? 

320S with N180.3  Norcold 3-way Fridge  (defined in first post)

VictoriaP

TabbyShack said:

Is this on a 400 or 320? 

@TabbyShack The first poster’s signature indicates a 2019 320, as is mine. MuttonChops’ is a 2018 320.

[Deleted User]

When I get a chance I will check my 400 to see if there is a similar issue. 

MuttonChops

Top View of the Super Fancy 'tie-wrap' Tube Mount.
Come on Norcold . . . that's the best you could/would do???

Picture Taken by @VictoriaP

grassgd

I was able to rotate the tube exhaust extension with the flue cap heat cap and the tube exhaust extension is secured down below with a tie wrap which is pulling the assembly under the condenser.

Once pulled over I took some aluminum flashing material and rolled it on a piece of PVC pipe to make it close to the 1 - 1/4 inch diameter required to fit over the tube exhaust extension and used a SS hose clamp to attach it to the top of the tube exhaust extension - see pics below:







This is a quick fix and not too pretty but will allow me to test on propane and see the results now the flue gas from the propane burner will exit above the condenser.  

If I pull the refrigerator in the future I will definitely eliminate the silly tie wrap  and make a proper attachment that holds the tube where it should be and not pull it into the condenser.

VictoriaP

@grassgd Looks like a good start. I’ll be interested to see what changes you find with your next test on propane.

George101

Any update? I’m having cooling issues on propane as well

grassgd

George101 said:

Any update? I’m having cooling issues on propane as well

I will try to post details later today once I can describe in detail the test result and changes but I have good results on propane with the exhaust tube extension plus a simple condenser baffle and 4 1/2 inch 12 volt fan on the upper vent pulling hot air out.  With ambient temps ranging form upper 70's to 98 and 99 degrees I see refrigerator temp (empty with only temp gauge inside) ranging from around 25 to 45 degrees.

grassgd

Here is the data of my Narcold N180.3 running on propane showing the ambient temperature, refrigerator temperature and calculated differential temperature (refrigerator temp – ambient temp) – I will discuss the changes below the graph showing the data:

The first couple days (6/9/22 from 17:42 hours to 6/11/22 at 13:50 hours) with only the extension of the tube exhaust pipe as described on June 8 to have the propane not exhaust under the refrigerator condenser as shown below: 

The refrigerator temperature rose to 58 degrees with 98 degree peak ambient temp– not very good.

I then added a makeshift exhaust flue on the top refrigerator vent to create better natural draft  (6/11/22 from 13:50 hours to 6/12/22 at 19:50 hours).  This dropped max refrigerator temp to 51 and 52 degrees  and min temp at about 32 degrees – better but still not good. I lost the picture of the makeshift flue but it was fitted to the outside width of the upper vent , 12 inches wide and only about 2 inches deep and extended up about 24 inches.  Here is a picture of another makeshift flue I tried earlier which gives an idea I what I was doing:

 

Next I added a small 2 ½ inch 12 volt fan on the outside of the top vent to pull hot air out and installed a baffle on the refrigerator condenser to restrict air bypassing  the condenser fins (6/12/22 from 19:50 hours to 6/13/22 at about 21:00 hours) .  The condenser baffle is only a piece of insulation board that is fitted between the condenser upper fins and the camper side wall.   See below:

The cardboard baffle shown above was attempting to prevent the hot air being blown down to the lower intake vent.

This dropped max refrigerator temp to 49 degrees  and min temp at about 30.6 degrees – not much improvement.

I then replaced the small fan with a 4 ½ inch 12 volt fan to increase the air flow (6/13/22 from 21:00 hours to 6/14/22 at about 19:25 hours)  as shown below:

This dropped max refrigerator temp to 42.6 degrees  and min temp at about 27.7 degrees .  Much better.

I then moved the 4 ½ inch 12 volt fan to inside the upper vent area behind the side vent with the fan tilted with the top leaning against the inside of the side vent and the bottom on top of the condenser baffle, with the assumption it would increase the air flow some more (6/13/22 from 21:00 hours to 6/14/22 at about 19:25 hours)  not really shown but fan is tilted down about 15 degrees to sort of match the down facing vents:

This dropped max refrigerator temp to 43.9 degrees and min temp at about 27.1 degrees. Not much change and ambient temp up about 1 degree from previous day.

Next positioned the 4 ½ inch12 volt fan vertically inside the upper vent against the upper vent (6-14-22 19:30 hours to present time.

This seems to be the best yet with ambient temp ranging from about 76 to 99 degrees and refrigerator temps from about 28 and down to 24 degrees to about 45 degrees during peak ambient temps (one day had a rain shower which reduced ambient temp in afternoon and corresponding refrigerator temp as can be seen on graph above).

I think I will leave the setup as is and switch to 120 volt power for a day or two and will update these results. Other testing with the unit on 120 volt power showed the 12 volt 4 1/5 inch fan on the bottom vent worked fantastic.  I need to see if the fan located in the upper vent provides the same result.

I  hope to fine tune the fan positioning and play with the fan capacity or air flow rate – two fans?  But this appears to be a good solution.  Big question would be in cooler or cold ambient temperature if the fan provides too much cooling to the point where propane cannot provide enough heat to make the process work resulting is high refrigerator temps.  During my testing I have been taking some measurements of the temperatures at the top pipe out of the boiler and pipe out of the condenser.  The final solution for a fan installation may involve a fan controlled by a temperature sensor on the top of the boiler pipe to cut the fan if the temperature falls too low.

webers3

Temp from 25 to 45 is what I had in my 3 way without doing any mods. I either had a frozen food or spoiled food. Your mods and tests are a commendable effort but I am afraid exercise in futility. I finally decided that I  had better things to do when camping than babysit the fridge. 

George101

Very much appreciate the data. I have the 180.3 and I have one 5 inch exhaust fan installed last year.   I’m experiencing worse temperatures with propane while running the fan.

yesterday running the fan my fridge got up to 59, with an outdoor temperature of around 96.  After running the fan all night it was still at 57.

this morning I turned the fan off around 7 and by 830 the fridge was 35.

today without the fan running at all the fridge went up to 49 with an outside temp of around 94.

all of this was with the fridge empty.