Norcold N7LX.3F can't maintain temperature on 12 or 120 volt

[ArtJoyce]

I think your 12v is working fine. 12v is not designed to maintain the fridge temp. It's ment for traveling. It's watts are lower so if you have a TT the battery Aux wire from the TV might be able to keep up with the camper battery amp discharge and your fridge is not entirely warm when you arrive. So think of the 12v fridge as performing at 75%.

[All_Mountain]

MrMark52 - thanks for your input. I was just curious about when I do get my new cooling unit might I install better R value high temperature insulation that would minimize my propane consumption when I am primative camping and possibly improve the 12v performance. I agee with everything you said about the rabbit hole.

Sorry the pictures are annoying you but I have been including them both for the readers benefit and for mine so I keep track of everything I have tried. There are pictures of my min/max thermometer that I purchased from Amazon. That is how I am getting freezer/refrigerator temperatures. This keeps me from having to open the door get temperatures. Also this unit has the fin temperture in diagnostic window 3. I have been using this method to measure refrigerator temperatures since August of 2016 when my wife and I retired and went full time in a 2005 Dutch Star. The Arctic Fox 990 is my new 6+ month travel solution.

In an approach to make the photos less annoying I have be resizing them so they are not so big as the large size annoys me also.

Thank you for all your input. I will try to minimize my number of photos and resize them smaller.

Respectfully,

Greg

[All_Mountain]

Yesterday I installed 3 LED indicator lights so I can see when the refigerator is actively trying to cool.


- 120v LED connected to the 120v heating element - red in color (top)
- 12v LED connected to the 12v heating element - blue in color (middle)
- 12v LED connected to the propane solenoid - red in color (bottom/illuminated)

I did this on my Dometic refrigerator on my 2005 Dutch Star and liked having the ability to see when the cooling unit was "active".

[Fridge Defend]

Originally Posted by Old-Biscuit

Didn't know about your research but did read my Fridge Manual many years ago

Per Dometic
NOTE: The DC mode is a holding mode not a full cooling
mode. DC should be used once the unit is cooled down on
gas or AC and driving (constant supply of DC) down the
road.

Q1) Could you give us a reference citation for your 'Fridge Manual'?


Dometic document name, such as 'RM2602 Service Manual'.
Often in the footer there is a document ID with date.
And page number.


I have never seen a statement like you quoted above from a Dometic document.



Q2) By the Dometic description, what if the fridge boiler cools off and needs to restart on 12VDC?


Thanks in advance for your response

[Fridge Defend]

Originally Posted by All_Mountain

Yesterday I installed 3 LED indicator lights so I can see when the refigerator is actively trying to cool.


- 120v LED connected to the 120v heating element - red in color (top)
- 12v LED connected to the 12v heating element - blue in color (middle)
- 12v LED connected to the propane solenoid - red in color (bottom/illuminated)

I use LED this on my Dometic refrigerator on my 2005 Dutch Star and liked having the ability to see when the cooling unit was "active".

Nice work, I did the same on my fridge, but have an automatic solar controller for the 120VAC to save propane. Nice to know when the 120VAC is on. I use a Dometic mV meter on the thermal pile to detect LP gas use.



Just us typical household fiberglass to insulate the boiler housing.
Fiberglass melts at 1200 degF.



Paul

[Old-Biscuit]

Originally Posted by Fridge Defend

Q1) Could you give us a reference citation for your 'Fridge Manual'?


Dometic document name, such as 'RM2602 Service Manual'.
Often in the footer there is a document ID with date.
And page number.


I have never seen a statement like you quoted above from a Dometic document.



Q2) By the Dometic description, what if the fridge boiler cools off and needs to restart on 12VDC?


Thanks in advance for your response

Dometic RM2652 Service Manual
Pg 11 Section 5.1 DC Heating Element
https://fourwheelcampers.com/NewDome...atorManual.pdf

[Old-Biscuit]

Originally Posted by Old-Biscuit

Dometic RM2652 Service Manual
Pg 11 Section 5.1 DC Heating Element
https://fourwheelcampers.com/NewDome...atorManual.pdf

Norcold has a similar statement
NOTE: DC electric operation is less efficient than AC electric and propane gas.
Use DC electric operation only to maintain the refrigerator
temperature while in transit and if the other energy sources are not available.
Do not use DC electric to initially decrease the temperature
of the refrigerator

Pg 10 Owners Manual for N6/N8 Series
http://techsupport.pdxrvwholesale.co...anual-N84X.pdf


Dometic and Norcold SHOULD have that statement in any manual for any 3 way model

Norcold N7/N8 Series DC Heater use is lacking clarity ---- ambiguous is an understatement

3 way DC Ops
The DC electric heater will cycle in response to the fin temperature
to maintain the cabinet temperature.

[Fridge Defend]

Originally Posted by Old-Biscuit

Norcold has a similar statement
NOTE: DC electric operation is less efficient than AC electric and propane gas.
Use DC electric operation only to maintain the refrigerator
temperature while in transit and if the other energy sources are not available.
Do not use DC electric to initially decrease the temperature
of the refrigerator

Pg 10 Owners Manual for N6/N8 Series
http://techsupport.pdxrvwholesale.co...anual-N84X.pdf


Dometic and Norcold SHOULD have that statement in any manual for any 3 way model

Norcold N7/N8 Series DC Heater use is lacking clarity ---- ambiguous is an understatement

3 way DC Ops
The DC electric heater will cycle in response to the fin temperature
to maintain the cabinet temperature.

As you said, the statement is ambiguous. And as you said:


"The DC electric heater will cycle in response to the fin temperature
to maintain the cabinet temperature."

Disambiguates:



With just the factory recall, there is noting to prevent the boiler from overheating. Thus, both Dometic and Norcold are stating that damage to the fridge can occur using the 12VDC heaters.


Please reference our post:


Quality of Heat




Thanks for confirming our research, too low of power input results in the boiler overheating. thanks for helping folks with their fridge. Information keeps people safe


Boilers need to be controlled for situations that result in overheating

[Old-Biscuit]

Originally Posted by Fridge Defend

As you said, the statement is ambiguous. And as you said:


"The DC electric heater will cycle in response to the fin temperature
to maintain the cabinet temperature."

Just to be CLEAR........that was NOT my statement

That was the Statement Norcold used in their Service Manual for the N7/N8 Series

Careful with your use of statements.....could leave wrong impression

[MrMark52]

Originally Posted by All_Mountain

MrMark52 - thanks for your input. I was just curious about when I do get my new cooling unit might I install better R value high temperature insulation that would minimize my propane consumption when I am primative camping and possibly improve the 12v performance. I agee with everything you said about the rabbit hole.

Sorry the pictures are annoying you but I have been including them both for the readers benefit and for mine so I keep track of everything I have tried. There are pictures of my min/max thermometer that I purchased from Amazon. That is how I am getting freezer/refrigerator temperatures. This keeps me from having to open the door get temperatures. Also this unit has the fin temperture in diagnostic window 3. I have been using this method to measure refrigerator temperatures since August of 2016 when my wife and I retired and went full time in a 2005 Dutch Star. The Arctic Fox 990 is my new 6+ month travel solution.

In an approach to make the photos less annoying I have be resizing them so they are not so big as the large size annoys me also.

Thank you for all your input. I will try to minimize my number of photos and resize them smaller.

Respectfully,

Greg

Neat instrumentation with the addition of the lights - but not real sure how practical it is when one can open the door of the refrigerator or freezer and see that it’s cold. ESPECIALLY when other issues can occur (boiler failure) that would result in your food being spoiled (but the lights were on or cycling on/off ).
I have found a cheap 12vdc, 2 channel temperature alarm that might be better used for the purposes I think your trying to achieve/understand. (I bought to monitor coolant and transmission fluid temps).
I have a spare one if you want - PM me and we can work something out.

I misunderstood your purpose for insulation - I thought you were talking about insulating the boiler more, not the whole cabinet or space that the unit is installed.

Free air is the best insulation you can get. That’s not to say that adding insulation isn’t good, but adding insulation properly is most important.

After the info given by Old-Biscuit and FridgeDefend - would you mind restating your objective? Because as I see it from a distance -
1. (I think) your getting a new boiler or refrigerator which would rule out any malfunction of the existing boiler
2. Documentation exists that says use of 12vdc only allows maintaining fridge temps to what could be described as marginal temps for short periods of time
3. My guess is - development of adsorption refrigeration was done long ago when the available use of electricity was pretty much non-existent, but gas was available. The use of a gas fuel pretty much provides the high temperatures needed for proper operation of the boiler.
And adding the 120vac/12vdc cartridge heat was just that, an add-on. The small package size of the heater cartridges, combined with the power requirements needed for proper boiler operation, make the 120v cartridge just adequate, and the 12v cartridge marginal for long term safe boiler operation.

I will say this - our fridge is LP or 120vac only - up until now, we’ve used our fridge as kind of a secondary unit as it sits on a concrete pad at our house - running on 120 volts. I think I’m goi g to change that practices by telling Mama to get everything out and shutting it down. Either that or waste LP thru our Extend-a-Stay (easier to get BBQ bottles refilled than drive the MoHo to the Lp store - although doing so would be good to excercise the coach).

[All_Mountain]

Originally Posted by MrMark52

Neat instrumentation with the addition of the lights - but not real sure how practical it is when one can open the door of the refrigerator or freezer and see that it’s cold. ESPECIALLY when other issues can occur (boiler failure) that would result in your food being spoiled (but the lights were on or cycling on/off ).

In my 2005 Dutch Star that I sold last April after living in it for 5.5 years fulltime I had installed a 120v LED so I could see when the new JC Refrigeration cooling unit was trying to cool. They had installed a defective cooling unit and it took me two years to convince them. Eventually they sent me a replacement and all of my cooling problems went away.
That refrigerator ran on 120v at least 90% of the time as my wife did not like boondocking. Hence the new truck camper. I could have used a Kill-a watt to measure the duty cycle which was very close to 100% This new Norcold unit is doing a poorer job of cooling. I'm convinced it is a defective cooling unit.

I have found a cheap 12vdc, 2 channel temperature alarm that might be better used for the purposes I think your trying to achieve/understand. (I bought to monitor coolant and transmission fluid temps).
I have a spare one if you want - PM me and we can work something out.

Thank you for your offer. The one I have has served me fine for 6 years and I can set an alarm.

I misunderstood your purpose for insulation - I thought you were talking about insulating the boiler more, not the whole cabinet or space that the unit is installed.

I was wondering if there was a higher R value insulaton to use to replace the OEM fiberglass insulation that surronds the boiler. Not to add any more insulation to the cabinet. I was thinking this might possibly reduce the duty cycle on 120 and 12v because it might boil the ammonia more rapidily. I'm assuming that is why the unit cools better on propane because it it boiling the ammonia more rapidly.

Free air is the best insulation you can get. That’s not to say that adding insulation isn’t good, but adding insulation properly is most important.

I understand and agree.

After the info given by Old-Biscuit and FridgeDefend - would you mind restating your objective? Because as I see it from a distance -
1. (I think) your getting a new boiler or refrigerator which would rule out any malfunction of the existing boiler

I have a warranty appointment on March 6th and I am expecting them to replace the entire unit.

2. Documentation exists that says use of 12vdc only allows maintaining fridge temps to what could be described as marginal temps for short periods of time

That's why I'm wondering if you could insulate the boiler better then you would have more watts to boil the ammonia faster like the propane does. My assumption is the manufacturer kept the 12v element at 238 watts to keep the amperage below 20amps. This reduces the wire and relay size for that circuit making both the installation for the RV manufacturer and refrigerator manufacturer less expensive.

On my unit the 120v element is 300 watts and the propane is 512 watts. Assuming the propane is only 70% efficient that is still 350 watts.


3. My guess is - development of adsorption refrigeration was done long ago when the available use of electricity was pretty much non-existent, but gas was available. The use of a gas fuel pretty much provides the high temperatures needed for proper operation of the boiler. And adding the 120vac/12vdc cartridge heat was just that, an add-on. The small package size of the heater cartridges, combined with the power requirements needed for proper boiler operation, make the 120v cartridge just adequate, and the 12v cartridge marginal for long term safe boiler operation.

I agree.

I will say this - our fridge is LP or 120vac only - up until now, we’ve used our fridge as kind of a secondary unit as it sits on a concrete pad at our house - running on 120 volts. I think I’m going to change that practices by telling Mama to get everything out and shutting it down. Either that or waste LP thru our Extend-a-Stay (easier to get BBQ bottles refilled than drive the MoHo to the Lp store - although doing so would be good to excercise the coach).

Thanks for your input.

I'm on a two month trip and wish I had my Fridge Defend with me so I could install it and get actual boiler temperatures.

Respectfully,

Greg

[Fridge Defend]

Originally Posted by All_Mountain

Thanks for your input.

I'm on a two month trip and wish I had my Fridge Defend with me so I could install it and get actual boiler temperatures.

Respectfully,

Greg

Well we are not much good at selling ourselves. Being engineers that use our logical use of reason. That is, fridge reliability, better performance, troubleshooting data logging, and fire safety should seem like the logical solution.

Based on your comment:

Fridge Defend, do not head out on a trip without it

Remember the 1970s FRAM FILTER ad?

Pay me now or pay me later, just too logical

PS, I am running my Dometic fridge on 120VAC through my PURELINE 700 inverter with 700W (theoretical) of solar mounted flat on the roof.
I am only using LP at night, or when there is rain/clouds and no solar power.
In 2 months I have used about 6 gallons of LP for fridge and cooking.
We use solar for hot water, and do not use the furnace. One 12VDC deep cycle battery for entire RV, if we do not have solar for power, we just use LP.

[powercat_ras]

For those with ample solar systems, one option is to just power the AC heater on the refrigerator from inverter power to use your surplus solar power that otherwise would go to waste, and not mess with using the undersized DC heater fridge mode.

I have a Norcold 8XX series with 300 Watt AC heater - at 50% duty cycle it uses about 2.5 kilowatt hours of electricty per day. I have found 50% is pretty typical for my fridge once it is cooled down given how often I open the door daily.

I have a solar system that can generate 4-8 KWH power per day depending on the season and how I am parked, and 4 KWH of usable LiFe04 battery storage. I'm able to run the fridge off inverter during daytime. I'm being conservative and still switching back to propane evenings and nights when camping without shore power.

I do have the Fridge Defend installed and it has saved my bacon several times and has allowed my 2014 vintage Norcold to continue to perform perfectly even after 8 + years of use.

[ArtJoyce]

Originally Posted by All_Mountain

Yesterday I installed 3 LED indicator lights so I can see when the refigerator is actively trying to cool.


- 120v LED connected to the 120v heating element - red in color (top)
- 12v LED connected to the 12v heating element - blue in color (middle)
- 12v LED connected to the propane solenoid - red in color (bottom/illuminated)

I did this on my Dometic refrigerator on my 2005 Dutch Star and liked having the ability to see when the cooling unit was "active".

Very cool mod. I think you might find the 12v heating element is on all the time when you are running on 12v. At least that is what I found years ago on a three way fridge. I think it was a Dometic fridge. When I called tech support, they told me it ran at a lower cooling rate (watts) and was on all the time when selected with no themostat control to turn it on or off.