Replacing Norcold Fridge: get 2 way or 3 way?

I've never seen the need for 3 way (12v) and have never missed it. We run on propane when on the road. Never a problem.

Get the three way. You only use the 12v when your driving. Switch it over after your parked.
This solves the big controversy about driving with the propane on.

A residential looks to be my choice if I have to replace again. I can buy three larger residentials for the price of a 2 way. I already have a 1500w pure sine wave inverter which was not cheap but a worthwhile purchase.

The big issue is battery bank size & do you have the room to enlarge it. From there you get into the problem of where to put the extra batteries which leads to what type of batteries.

Wet cell batteries need to be in an area that is vented. They are cheap. AGMs can be mounted anywhere. Inside even. They don't vent. They are not cheap but have 2-3 times the service life.

It is number crunch & choice time.

2 way was a good choice1

With my old Dometic 3 way the dc option only works while the engine is running. It does not run off the battery when the engine is off. Then I use propane or electric if I plug into shore power.

I ended up getting the 2 way system. Thanks for everyone's help!

time2roll wrote:
Yes and will then actually keep your food cold ;)
Beef up your 12v system as needed.

Yea just seems like a lot of complaints with 12v fridge running. If yours works for you then you are one of the lucky ones. Like some of these 30' RVs that stay cool with a single air unit in 100+ heat. Just luck of the draw.

That makes sense. Didn't realize that some DC systems don't work. Or maybe I understand that it will kill your batteries and only use it when needed (or by default when the flame blows out halfway across MT!)

Grit dog wrote:
"Otherwise get a 500 watt inverter to run the 120v element on battery power."

But doesn't this suck even more power from the batteries than DC mode alone?
I'm not tracking here.

Yes and will then actually keep your food cold ;)
Beef up your 12v system as needed.

Yea just seems like a lot of complaints with 12v fridge running. If yours works for you then you are one of the lucky ones. Like some of these 30' RVs that stay cool with a single air unit in 100+ heat. Just luck of the draw.

Grit dog wrote:
"Otherwise get a 500 watt inverter to run the 120v element on battery power."

But doesn't this suck even more power from the batteries than DC mode alone?
I'm not tracking here.

Yes, you’re tracking just fine.

The AC element is typically rated at a much higher BTU than the DC element. As an example, on my fridge running in AC mode from the inverter, the Trimetric panel shows about 27 amps coming from the camper battery. Even with my 25 amp DC-DC charger, that leaves me with about a 2 amp deficit. If I set the fridge thermostat at too high a setting so that the cooling unit runs 100% of the time, the camper battery slowly loses ground over the span of a days drive.

If the fridge is running in DC mode, the Trimetric panel shows about 19 amps from the camper battery, and the 25 amp DC-DC charger is more than able to keep up with the load, even if the fridge thermostat is on its coldest setting causing it to run 100%. But, since the DC element is a lower BTU rating, it’s not really able to cool the fridge as much as the AC element anyway. It works well enough to use it in >100* temps though. Since the voltage to the DC element is being maintained at about 14 volts, it performs noticeably better than before.

The voltage used to start out just under 13 volts with a fully charged battery, and get worse as the day wore on, making the DC element put out less and less BTU’s. In really hot weather, the fridge temps would get high enough that I would worry about the safety of some of our food.

:):)

Grit dog wrote:

time2roll wrote:
Fix the flame out issue. I believe there are more restrictive outer covers for some models. Have also read installing a baffle such some furnace filter material to provide a buffer. Otherwise get a 500 watt inverter to run the 120v element on battery power.

I've tried a couple times. Been the same on both (same model) campers.
I've actually installed a bit larger tin shield around it and everything works great, burner's clean, etc....until I hit that 30-40 mph or more head wind or side wind while flying down the highway.
Good call on the furnace filter material. I may try that on the back of the cover.
Honestly if I encountered the issue more than like once or twice a year (about the number of times the camper leaves the shop), Ida been more diligent about fixing it. Can drive all over the mountains, wherever, camper can be parked in dang near a hurricane and the LP stays lit. Once combined ground and wind speed hit triple digits, the batteries end up taking over.
But bottom line, why would one limit their option for a 3 way fridge intentionally if it doesn't cost more? It's like turning down having more horsepower, even if it's for free. What does it hurt? Why the disdain for DC power for the fridge?
I don't believe it decreases the lifespan of the unit. Mine's almost 20 years old and works great still...(knock on wood).

I’ve had the same frustrating experience with my current camper. LOTS of hours and money wasted on trying to fix it, to no avail. I’ve improved the situation, but not fixed it. I eventually gave up and attacked the problem from another direction. First with a small inverter, and now with a DC-DC charger.

:):)