Fridge score! Wow it’s big.

[Paddy]

SO for my next build I decided to try a propane fridge for the first time. I’d resisted doing propane systems in the past to limit complexity and with the brilliant diesel furnaces it didn’t seem necessary. However, this was flawed thinking for several reasons. One, you always need propane to cook. And additionally I will have many other propane needs that extend beyond the furnace so it shouldn’t ever have been a question based on fuel availability. Secondly the propane fridge is so much more QUIET. You never think about this until you’re camping somewhere very very very quiet and your compressor based fridge sounds like a ww2 emergency generator on steroids. Lastly, compressor based fridges are too damn small. My fancy 12v chest coolers are a pain in the ass to use. A nice big fridge with room to store food with enough room to also SEE what food is there is a necessity, and keeping the beer in there too is only logical. So I said fookit let’s put a big ass fridge in this van build. Keeping it full of seltzer’s and beer will free up storage that was keeping beer warm previously, while increasing the efficiency of the fridge too.
So I got a 6 cu/ft fridge for a great deal. It is a two way, so it has no 12v run option. So what that means I guess is that I need to install it in a way that will allow it to run on propane while underway. So this is where I might need some help. I know that some installations have trouble with that mode while others seem to do fine.
So does anyone have any trick shot or tips to running a fridge like this?

 

[llamalander]

2-way being shore power, yes? Running 120v off of your alternator may be safer and not all that inefficient. A dedicated inverter 120% of the fridge's draw may not tax the electrical system unduly, could be worth a look.

 

[Paddy]

That’s true and any proper mo-ho has an inverter on board anyway, although I don’t really have any need for AC otherwise. I’m not as worried about the fridge section so much if we’d load it with beer and water it will have enough mass to coast for a long drive however I worry about the ice creams and cubes. I was surprised about the lack of 12v backup on these but apparently it is common. Do big RVs run the inverters underway? They must.
What’s the safety considerations running underway?

 

[Mwilliamshs]

Absorption fridges need to be level. They should run, not sit unused, to keep things flowing in the cooling unit. They are very inefficient on electrical power because they replace the heat of a propane flame with a big resistive heater. Dinosaur replacement control boards are the best. THE BEST. A booster fan in the flue makes an appreciable difference. A circulation fan inside does too. A clean flue is a must. Again, they need to be level.

My family are big RVers. My grandparents have had 5th wheels since the 70s and still get a new every couple years. All their kids have RVs too. Everybody runs their fridges on propane while underway. We run ours at deer camp for 3 months a year on propane. Time has taught everybody to plug in the fridge when the camper is parked and fire it up on gas every month or so. They work fine if used constantly. Leave it off for 10 months and even a new one might not circulate. Then you have to take it out, set it upside-down for a day, and try again. If that doesn't work, time for a cooling unit or a new fridge.

 

[Paddy]

Good info thanks. Do you know if they were roof vent or side vent installs?

 

[Mwilliamshs]

Both. The side vent is the intake and the access for maintenace. The roof is the exhaust.

 

[Paddy]

Well it works great on propane! What would a proper expedition be without ICECREAM?!

 

[luthj]

Nice unit. It may not matter for your usage, but the absorption units have a limited temperature differential to ambient. Specifically the air used to cool the condensing coils on the back of the unit. You may find that in 90F+ weather that the freezer becomes marginal. A lot depends on the units design of course. Additionally absorption units can be quite sensitive to being level (older units more than newer ones). Norcold recommends no more than 3 degree left right, and 6 degrees front/back.

There are several MFGs that make DC type stacked units similar to the one pictured. Power consumption is significant, usually around 1kw-hr per day.

 

[Paddy]

Yes I was tempering my excitement about the freezer temps with the knowledge that my shop in February isn’t a worst case scenario by any means, however this model is one of dometics most popular and been around for a long time so I’m confident it should do the job. Not sure what you mean by stacked DC, maybe swing compressor type upright? I have seen those but yes batterie should would be huge to support that. This one seems to draw about .6-.8a.
As far as tilt goes this issue is grossly over stated imo. We traversed Europe last summer and parked on some steep streets for several hours and the fridge never seemed to mind at all. And in the end when it comes to overnight camping, I’m probably more tilt-sensitive than the fridge lol.

 

[86scotty]

I think he meant freezer stacked on top of fridge. I could be wrong.

Looks like a nice score. You wouldn't want a DC (3 way) one for an adventure rig. The DC circuit is incredibly power hungry. They run forever on propane, like a month or so on a tank. Just run it on propane. I've done it too going down the road. Just use common sense and there's a decent chance it will never burn your rig to the ground.

 

[Paddy]

I think the worry about running underway is more from the point of a collision that may rupture a pressure line and spew propane into an accident scene.

 

[Mwilliamshs]

I think the worry about running underway is more from the point of a collision that may rupture a pressure line and spew propane into an accident scene.

Lots of concern by some that the fridge flame could ignite fumes at a gas station.

 

[Mwilliamshs]

...Not sure what you mean by stacked DC, maybe swing compressor type upright? I have seen those but yes batterie should would be huge to support that. This one seems to draw about .6-.8a...

Your fridge is burning propane to cool and ~.7a for controls. The amp draw is higher when the reigniter is firing but that's brief. A DC compressor fridge typically averages about 1.5a/hr. If you had enough solar and battery capacity you could run a DC fridge indefinitely and never need propane. How much is enough? 1.5 x 24 = 36ah. Let's say you need to run 3 days straight without the sun (bad weather, shady parking spot, etc) and want an inexpensive battery, lead-acid (not AGM or Lithium, etc). So 36 x 3 = 108ah and 108ah x 2 = 216ah. That's pretty much 2 basic golf cart batteries (actually 215ah) and about $180 (90 each) at Sam's Club. To recharge them in a single sunny day you would to replace 108ah you'd already used, plus the 36ah you'd need that day, so 144ah in about 6 hours of sun (most places in the USA for most of the year). 144ah/6h= 24a. The Renogy Eclipse 100w panel has been reported to produce 5a by several users. 5 of those panels = 25a per hour x 6 hours = 150ah. That's about $1,500 in solar panels, charge controller, cabling, batteries, etc plus the fridge at $300-1,500. That's a lot of money BUT it'll run forever (barring mechanical breakdowns) without buying any gasoline, propane, or ice. If you connect the batteries to your alternator and drive regularly you can save a lot on solar. Likewise if you didn't go 3 days without charging, you could recharge with less solar.

 

[luthj]

Yeah, i was referring to freezer stacked on fridge. A DC unit with a separate freezer compartment is going to be pretty large, so a 36AH power consumption is probably a bit low unless its cool/cold outside. It all depends on the units insulation though. The bigger units tend to have much better insulation than the smaller ones, especially around the freezer compartment.

Something like this maybe? It likely uses the secop BD-50, (around 3A when running) with that size of fridge 70% duty cycle in warm weather would be possible.
https://www.westmarine.com/buy/norc...Agh016Ltb2quYKeuELavMYVsyPfaBWNxoCNdQQAvD_BwE

The absorption units do have there place. Especially for folks who don't have easy access to sufficient charging sources.

 

[Mwilliamshs]

Yeah, i was referring to freezer stacked on fridge. A DC unit with a separate freezer compartment is going to be pretty large, so a 36AH power consumption is probably a bit low unless its cool/cold outside...Something like this maybe? It likely uses the secop BD-50, (around 3A when running) with that size of fridge 70% duty cycle in warm weather would be possible...

36ah would be ~50% duty cycle in a 24 hour period with 3ah when running. Not outside the realm of possibility but likely optimistic. My figures are for TF130 and the like.