Understanding Norcold N180.3 Operation and Potential Modifications

grassgd

This refrigerator can be a love hate relationship but part of that maybe due to not fully understanding the details of the operation in 120 ac, 12 vdc and propane modes and their limitations.

Basic operation according to the owners manual wiring diagram as I understand it is as follows:

120 vac Mode:

Looking at the electrical diagram in the owners manual, it appears the refrigerator temperature is sensed with a temperature probe and cycles the 120 vac heating element on and off based on the numerical setting of the refrigerator temperature dial.  I don't know where the temperature probe is actually sensing temperature on the unit though.

12 vdc Mode:

Looking at the electrical diagram in the owners manual seems to confirm in 12 vdc mode, the 12 volt heating element is on all the time and not controlled by any thermostat or temperature probe.


Propane Mode:

Again looking at the electrical diagram in the owners manual the propane gas flow to the burner is only a function of the position of the gas control dial on the front of the unit.  No refrigerator/freezer temperature sensing provided.  The only electrical input controls the on/off gas supply valve controlled by the thermocouple sensing a flame.

I'm always looking how to improve things that could use improvement.  I my opinion, the Narcold 180.3 refrigerator would be better if it has a true temperature controller but can one be added to the unit?  The problem is trial and error getting the temperature setting right to avoid freezing everything or not getting cold enough. The temperature is not by controlled by temperature but buy a number like a lot of residential refrigerator/freezers are. But unlike residential units, the RV unit is in constant varying ambient temperatures that can impact the units performance, so the desired temperature control setting needs to be changed as the ambient environment changes to get the desired temperature maintained. I looked at each Mode's control circuit to see how or if this it could be modified to control the temperature with a temperature controller. 


120 vac Mode:

I always default to 120 vac mode when ever parked where power is available like everyone does.    One could add a simple inexpensive temperature controller in the 120 vac wiring between the front panel temperature control and the 120vac heating element.  This would let you actually set a desired temperature.  This should work if the front temperature control setting is left in the coldest position letting the added temperature controller actually cycle the 120 vac heating element on and off as needed to maintain the desired temperature.   Question as to the mounting of the temperature controller's temperature probe inside the unit or placing it in place of the factory temperature probe location if it is removed and placed outside the unit, where ever it's located.   Pulling the factory probe out would mean it always senses ambient temperature inside the trailer and always trying to cool the unit (ie providing power to the new temperature controller at all times).  If someone knows about the location of the temperature probe of the factory probe I would be glad to know where it is before considering this modification.

12 vdc Mode:

I don't recall ever getting too cold when towing on 12 vdc but a temperature controller could be added to cycle the 12 vdc power to the 12 vdc heating element based on a temperature setting similar to  the 120 vac controller described above.  Problem is this requires 2 separate controllers and temperature probes if you want to control in both electric modes and may not improve the performance if the unit on 12 vdc needs to run all the time to maintain temperature anyway.

Propane Mode:

I have used Propane while towing and remote camping at high altitudes with great success.  Actually when towing, had things get too cold and had to keep tweaking the gas control knob.  Unfortunately there appears to be no simple way to add temperature control to the gas supply since reducing the gas flow to control temperature likely would impact the ability of keeping the flame burning and may cause flame outs resulting in NO cooling until manually re-ignited. A modification to do this would need a gas control valve to throttle the gas supply and a method of keeping the flame going (like a pilot flame or automatic igniter which would be very expensive and add a lot of complexity.

I am not sure if I will attempt either the 120 vac or 12 vdc modifications outlined above. I would like to find out where the 120 vac temperature probe is located first.  In the meantime one modification I found very helpful was to use a pair of Bluetooth temperature monitors (one in the freezer area and one in the refrigerator area)  so I can monitor the temperatures without opening the door and in particular when towing.  This has proven to be very helpful.  Without them, I would always worry about the temps and sometimes find out too late that things were not cold enough.  

webers3

Theory vs practice. Theoretically it should work on all three modes, in practice it does not, it works great as long as the ambient temp is below 80 degrees, and then finding everything frozen in the morning, not good. I spent almost 3 months while work camping in the summer of last year trying to make this fridge work consistently and could not. I tried everything suggested by the folks on this forum; fans inside, fans outside, not packing it tight, etc. When it was 80-90 outside the fridge was between 50-60, in the end I couldn't trust eating any food I had in the fridge and had to buy dorm fridge to get by to the end of my assignment.
You can try different mods to maybe get a few cooler degrees but in the end it's not worth the effort. I am getting rid of mine.

Dutch061

We had a 2017 320-S also, I added fans and a thermal switch to the outside of the refrigerator. This was my 3rd absorption refrigerator in an RV, and my experiences with this type of refrigerator mirrors exactly what @webers3 stated. Frozen or warm, very little time in between. 

Our 2020 400 BDL has the Norcold NR751BB compressor refrigerator in it. Set it and forget it. I would look at Norcold, Isotherm, Truck Fridge, or other compressor style refrigerators to to replace it with and be done with it. 

Brad

MuttonChops

I've been giving serious thought to adding a DC-2-DC Charger and installing a (second) thermostat in the Fridge for 12VDC control.  Goal is less about getting even temperature within the Fridge - - - - more about reducing battery load while on 12VDC.  Assumption is Fridge would cycle on/off providing a lower average Ampere load.

Have ordered a few of the parts.  Have not committed to the project.

webers3

@MuttonChops nice project to keep your mind and hands occupied, but if yours is a 3 way fridge it probably won't help much.