Switch above 400 3 way frig (only required to operate frig when on battery as confirmed by nuCamp)

johnfconway

Sharon_is_SAM said:

@TomCanada - that makes more sense, but a nuCamp tech previously identified it’s purpose was to run a fan.  Oh well.  Maybe someone can experiment and get back to us.  Is anyone really running the 400 3 way frig on battery?

The exhaust fan on propane is integrated into fridge. Shops wanting to fix underperforming refrigerators want to "add a fan". Then you can burn propane and battery too! What a deal...

If you're traveling in full sun, the three-way on 12V can hold its own. No net draw.

In less than a week we'll run the expensive experiment with replacement 2-way.

bergger

Ok so I suppose the best way to explain that switch is that it is both a switch for an auxillary fan to help cool the back of the fridge and a switch to allow the fridge compressor to run when you are off grid running it on either 12v or gas.  You still turn the fridge on with it's power button then select either 12v or gas from the control panel.  It will do this without that toggle switch turned on.  However in order to have the fridge  compressor run, either on gas or turn on with 12v that toggle switch needs to be on.  The fridge will not cool if you have in on gas or 12v and the fan toggle is off.  On gas the fridge will not ignite or on 12v the compressor will not run unless the fan toggle switch is turned on.  The fan is then thermostatically controlled and will kick on an off when the temperature behind the fridge hits a certain point.  You do not need to have the toggle switch turned on if you are running the fridge on shore power.  However I just turn it on always even when on shore power as it will still kick on and off to help the fridge run better plus I won't forget to hit the switch if I'm on gas or 12v.  This is how it works on my 2021 400.  Can't say its the same for the other model years.   

Cassie

I can verify that switch is to allow the 3 way fridge to run off the battery. I have a 2021 Tab 400 with 3 way fridge. I was told by the dealer when I got it that was what the switch was for. It will light green when on and only then can the fridge can be set to 12 volt. Without the switch on it will not run off the battery. I use it to cool the fridge while traveling which it does quite well. I never use it in camp where I then use either shore power or propane. I believe the switch was installed to prevent accidentally draining the battery which it would certainly do rapidly if not connected and being charged by the TV. 

Denny16

Since nüCamp tech stated there was no additional fan, and the earlier TaB320s did have an aux fan installed on their 3-way fridges, could this be the confusion issue?
cheers

bergger

 No confusion here with my 2021 400.  As I mentioned before there is a fan in the back compartment of the 3 way fridge.  It is behind the upper vent cover but just down and out of sight.  It is wired into the back of the fridge.   The toggle switch not only operates this fan that cycles on and off based off temperature but it also allows the fridge to cool on 12v and on gas.  The fridge will get power from 12v with the toggle off but will not cool.  The toggle allows it to cool under 12v as well as under gas power.  So the toggle has to be on for the fridge to cool when on 12v or gas.  I assume this is an added safety feature so you do not drain the 12v accidentally. The switch works in my trailer just as mentioned in my previous post.  Here is a picture of the mysterious fan. 

 

Denny16

An, mystery solved, you win.  Thanks @bergger, you put this issue to rest, bergger +10 pts, nüCamp 0 pts.  You win! 
cheers

johnfconway

Absorption cooling was invented by the French scientist Ferdinand Carré in 1858. AB Electrolux established a subsidiary in the United States, named Dometic Sales Corporation. The company marketed refrigerators for recreational vehicles (RVs) under the Dometic brand. In 2001, Electrolux sold most of its leisure products line to the venture-capital company EQT which created Dometic as a stand-alone company. Dometic still sells absorption fridges in 2021.[2]

Kind of makes sense why this technology that has long been eclipsed by highly efficient compressors, continues on. A bit of a cash cow for Dometic. Possibly for Thetford too, in that you run the risk of some quality time on the RV throne from food in a 60 degree refrigerator.

So even NuCamp added a fan in 2021 beyond the small exhaust fan for the propane fumes? Use precious 12V power while boondocking to aid refrigeration technology that can only muster a 35 degree temperature differential in hot weather? I really don't get it...

Denny16

Me either John, I have the 12VDC Compressor fridge in out TaB400, haven’t looked back…. I think nüCamp needs to find a compressor fridge to replace the 3-way fridge, for the larger fridge option in the TaB400.  They have already replaced the propane fridge in the new. 320s with a compressor fridge.
cheers

Sharon_is_SAM

@johnfconway - I think it is just a matter of time before the 3 way frig goes the way of the dodo.  As with so many things, change happens slowly.  Solar and battery progress will eventually win.

ScottG

I'm still confused...

Why would the fan be wired to operate on 12V and propane but not on 120V AC? My understanding of a typical absorption fridge is that the cooling mechanism--and the heat generation--is the same regardless of the heat source. Also, there is no compressor as in a 2-way fridge.

I can understand the switch being a cutoff to prevent fridges with automatic switching (which IIRC is the case in the 400) from automatically switching to 12V at times when the battery may be inadvertently drained.

If this fridge is different, or if I'm otherwise missing something, please set me straight. 

bergger

ScottG, the only reason I can think of the toggle switch being tied to the 12v and gas and not 120v is as an added safety measure so you do not accidentally turn it on and burn through your battery or propane.  Just an extra step to make sure you intended to turn it on.  I guess on 120v they figure you won't run out of electricity.  Just my thoughts. Maybe they could not wire it in with the 12v and gas for some reason?  Anyway, like I said, I turn it on even on 120v just for the fan option and it's worked great for us.  I've also got a 12v compressor fridge in my truck and it is awesome.  However running the 3 way on propane for a longer trip is also awesome in that it cools great for us and does not use much battery at all. It's nice having both of them. But I too would not be surprised if they do eventually eliminate the 3 way and go just with a larger 12v compressor fridge.  But with that option solar would need to be standard and I think I would would want a slightly larger panel on the roof.  

ScottG

That's as good an explanation as any, @bergger. I'm still curious as the fan would be included in this circuit, but admittedly I'm curious about a number of the electrical and plumbing decisions I've seen in the T@B (as well as other RVs).  :-/

Am I correct that the 400 3-ways have an auto-switching mode in addition to dedicated AC/DC/propane modes? 

Denny16

Yes, the fridge has an auto switching mode.  Perhaps the fan is not needed on AD, as the heat source is not as hot, or the AC mode has a separate fan, that only works on AC?

cheers

bergger

ScottG, yes as Denny16 says it does have an auto mode.  I actually have not experimented with the fridge on 120v and the fan toggle switch off.  I’ll try to do that tomorrow and see if I can hear another fan activate. But I’ll be surprised if there is another one.

Cassie

Well again I can verify that the switch on the 3 way fridge in my 2021 Tab 400 is ONLY to run off of battery. If I turn on the switch while running on propane it immediately reverts to battery. It will NOT run on propane with that switch on. Therefore I conclude it it not also a fan switch either. Could it be that some Tab 400 3 way fridges are different models and operate differently? Nucamp is constantly making changes. This could be part of the confusion. Again on my fridge the switch is only to use the battery although others may very well be different.

johnfconway

Cassie said:

Well again I can verify that the switch on the 3 way fridge in my 2021 Tab 400 is ONLY to run off of battery. If I turn on the switch while running on propane it immediately reverts to battery. It will NOT run on propane with that switch on. Therefore I conclude it it not also a fan switch either. Could it be that some Tab 400 3 way fridges are different models and operate differently? Nucamp is constantly making changes. This could be part of the confusion. Again on my fridge the switch is only to use the battery although others may very well be different.

@Cassie same is true on our 2020 T@B 400 that was built in January, 2020. I was told by Creed that the fan we hear while on propane is part of the fridge itself and is more for exhausting combustion gases than cooling. Plus cooling doesn't make sense since it's heat that drives absorption cooling.

Sharon_is_SAM

I emailed nuCamp “Help”.  Raphael replied:

“The switch above the fridge in the TAB 400 is to turn on 12 volt battery power to the fridge. It only needs to be turned on when you are running the fridge on the battery alone.  It does not operate a fan. We would not recommend leaving it on all the time as the fridge may try to prioritize the battery as a source of power and it will drain the battery in that situation quite quickly. We recommend only switching it on when you are going to run the fridge on battery power. Most of the time this would be when you are transporting the trailer.”

Here is a nuCamp YouTube video that explains the frig operation.  Notice the switch remains on when he changes to LPG and no error code is thrown.  Hmmm.  https://youtu.be/bP5bBpMJygQ


So, like the Alde, does the 3 way frig require 12V power at all when on LPG?

ScottG

Sharon_is_SAM said:

...

So, like the Alde, does the 3 way frig require 12V power at all when on LPG?

My 3-way certainly does. It will stop running on propane if the battery is disconnected. I'd make a strong guess that all models are the same, as some electric power must be required to operate the unit's circuitry.

That said, on mine the 12V DC circuitry and 12V DC heater are on different legs with different fuses (which are located on the top of the fridge). As such, it would be easy enough to insert a switch that disconnects only the heater circuit. 

ScottG

johnfconway said:
...
Plus cooling doesn't make sense since it's heat that drives absorption cooling.

I think the cooling fans (if that  is what they are) have more to do with removing heat from the heat exchanging fins. At least that is how it works on mine--a thermostatically controlled fan turns on as needed to draw air from below, move it over the fins, and exhaust it out the vent at the top of the unit.

In the earlier 320s, the warm air passed over the top of the fridge on its way out. This had the effect of turning the countertop into a passable radiant heat source and led nuCamp to start installing secondary fans with a manual switch to help exhaust the heat. However, I suspect cabin heat buildup is less of an issue with the 400s given the different placement of the fridge.

Here's a birds-eye-view pic of the old 320 fridge (under the stove) with the top of the fins visible on the left of the unit. 

bergger

So I did some more experimenting today with "the switch."  I have an early production 2021 400 with the N3104 3 way fridge just for clarification.   I can not say if any of the other models operate the same as mine does. 

It does have an auxiliary fan in the back compartment.  I have confirmed that the fan kicks on and off based on the temperature in the compartment behind the fridge.  It is placed just out of sight and below the heat exchanging fins and blows air up over them and out the upper fridge vent/access cover as mentioned in ScottG previous post.  I assume this helps cool the back of the fridge and help the electrical components run better.  My earlier post shows a photo the fan.  The fan is wired only to the 12v system and kicks on and off when the fridge is on 120v, gas and 12v.  I confirmed this as I found the only way to kill the fan when it was running was to turn the battery kill switch.  Unplugging from shore power did not kill the fan. 

When on 120v and gas the toggle does not need to be on, the fridge operates fine and the fan will also work as described.  So yes the fridge uses some 12v power when on 120v or gas.  For the fridge to operate on 12v, yes the toggle has to be on.  This will allow the 12v mode to cool the fridge and also the fan will still work. 

Now if you have the fridge on 120v or gas and the toggle on it also seems to run just fine.  And this is what I used to always do as I assumed the switch had to be on to enable the aux fan to work.  Now that I know it does not I will not turn the toggle on for 120v or gas.  There is another reason for this as well that I confirmed today and I can't explain why what I am going to describe happens.  

The fridge will run on propane with the toggle switch on.  Whether I first turn the fridge on gas then turn on the toggle switch, or whether I turn on the toggle switch first then turn the fridge on gas it will ignite and run.  However when the toggle is then turned off it kills the gas and turns the fridge off.  It does not indicate that it is running on a different source.  The panel still shows the gas symbol but you can clearly hear the burner and pilot light go out.  It will not reignite unless I cycle back through the panel from 120v to battery then to gas.  So I will no longer touch that switch if I am running on gas as it could inadvertently turn off the fridge if someone messes with that switch.  Another bonus is that I no longer have to cover that bright blue LED light with tape at night!  One less light to dim when sleeping!!

So I will only be using the toggle when running the fridge on 12v when towing, no longer on gas or 120v.  The cooling fan works just fine on 120v and gas with the switch turned off.   I think I have finally got an understanding on how this works on my trailer.  It is nice how discussions like this get you thinking and trying things out to see how they really work.  Even if I don't understand everything behind the scenes.   

Sharon_is_SAM

Great!  So, the fan runs on all 3 power modes and is controlled with a thermostat.
The switch is to be turned on only when using the TaB battery.
Thanks for confirming @bergger!

(I still think it needs a label😁)

bergger

Yes a label and better walk throughs and understanding by the dealers would be nice.  But asking the dealers to actually understand what they are selling may be asking too much! 

ScottG

Wouldn't it be easier to just run the fridge on one of the dedicated settings (AC or propane) if switching automatically to battery is a concern? Is that an option with these fridges?

This seems to me a case where an unnecessary feature (auto switching) creates another problem that requires another feature (DC cutoff switch) which further confounds the confusion!

MuttonChops

I'm trying to understand the T@B 400 Electrical Power Distribution and specific appliance needs/features and came across this interesting year-old thread.

After reading this thread and reviewing NorCold's N4104 {3-way Fridge} installation manual I have some comments/observations to share on the Intended Function of the Not Labeled Switch above the 3-way Fridge.

Disclaimer:  The 400 has changed alot year-to-year as nüCamp adjusts the product features and their production steps. In fact even within a model year there can be changes.  Therefore, my assumptions won't apply to all model 400 trailers 'in-the-field' today.  P.S.  Sure would be nice if folks included the NorCold Model Number in their comments instead of just 3-way or 2-way . . . just too many different models being shipped to provide clear information.

These remarks focus on the NorCold N4104 3-way that replaced the obsolete N3104 that shipped on earlier production 400's.

The N4104 has three 12VDC inputs/circuits:

1 Low Current 12V (Fridge has internal 1.1A fuse) that is used by the Power Control Module,
    Display Module, and Ventilation Fan.

2 High Current 12V (Fridge has internal 20A fuse) that is used only for 12V Cooling
    (Heater elements).

3 Engine Run Control Signal. This signal must be 12VDC for the 12V Cooling to turn-on.

I would assume that nüCamp has one WFCO Power Center DC Panel Fuse for the Fridge
   . . . can anyone verify? . . . at 20 or 25 Amps.

Would also assume nüCamp has shorted the Low Current and High Current input connections at the N4104 Fridge.

So if the above assumptions are correct and since the T@B 400 is a trailer not a motorcoach,
if I was the electrical design person:
-- The Engine Run Control Signal would tap the Fridge main 12VDC input line and include
    a Toggle Switch to simulate an engine is running signal.
- - A switch that would indeed only control the Fridge high current demand heater (cooling) to be
    on when the trailer owner allows.

[Deleted User]

I have that model fridge. It's a 30 amp. Sorry could have done a better job with the pic!