Air circulation fan in fridge

[IdleUp]

Many thanks for all the replies on this interesting topic of gas/electric Refrigerators.

It makes you wonder how over 10 million RV owners camped and used these refrigerators and traveled all over the US for over 50 years with no problems, then all of a sudden, in the past few years when manufactures begin switching out for compressor units to save money, a handful of RV owners are attempting to dis-credit a device that provided use to millions of satisfied owners. While the ultimate choice is only that of the owner, myself, I will continue to only use propane for the advantages listed below:

1) Unlike a compressor and fan equipped units, absorption refrigerators have no moving parts to break or fail when used properly.

2) Propane refrigerators offer the most economical method of fuel.

3) Propane refrigerators reserve valuable battery power for other needed devices.

4) Unlike 120 /12 volt refrigerators, a propane refrigerator is totally silent in operation

5) Most 120 / 12 volt compressor refrigerators vent their heat inside the RV your trying to cool, where a propane refrigerator vents all heat outside.

6) Unlike 12 /120 volt compressor units, absorption refrigerators are specifically built for an RV, where compressor refrigerators are designed for domestic home use.

7) Contrary to what you hear, a propane refrigerator does not require the installation of fans for the evaporator or condenser.

My Midwest Sprinter conversion came with a 12 volt compressor fridge, it worked fine but constantly kept my battery discharged. Making matters worse, the heat from the condenser would heat the coach.

Not to be miss-interpreted, I’m certainly not trying to talk anyone out of owning a 12 /120 volt compressor refrigerator or find fault with them, but only to express the absorption refrigerator has a "Bullet-Proof" documented track record from millions of users for its dependability and advantages for “off the grid” use.

Stay Safe - Mike

[Bud]

"My Midwest Sprinter conversion came with a 12 volt compressor fridge, it worked fine but constantly kept my battery discharged.


Did I mention it? The only reason an absorption refer exists is because there is not enough reliable electrical power, e.g. your b IdleUp.

Bud

[avanti]

Originally Posted by IdleUp

Making matters worse, the heat from the condenser would heat the coach.

The heat from your condenser came from the van, not from the fridge. The fridge just pumps it round and round, Your belief that it is heating your van comes from a basic misunderstanding of thermodynamics,

The only added heat comes from the electricity used to run the fridge which comes from the motor, not the condenser, and at any rate is negligible.

[IdleUp]

Originally Posted by avanti

The heat from your condenser came from the van, not from the fridge. The fridge just pumps it round and round, Your belief that it is heating your van comes from a basic misunderstanding of thermodynamics,

The only added heat comes from the electricity used to run the fridge which comes from the motor, not the condenser, and at any rate is negligible.

Avanti thanks for the reply - however you're incorrect by your saying their is no heat coming from your 12 or 120 volt refrigerator. All refrigeration units work on the same principle of circulating, evaporating, and condensing refrigerant (Freon) to remove heat. The refrigerator is working on the same principles as your roof ac unit where the heat that was once in your RV is carried outside and expelled.

Every single BTU of heat removed by the evaporator coils inside the refrigerator is carried by the "Freon" to the condenser coil located on the exterior of the refrigerator where it is expelled using convection to the surrounding air around the refrigerator and eventually inside coach. You'll find this condenser coil either by the compressor or mounted flush to the rear of the unit.

In addition to this heat, there is also considerable heat generated from the compressor motor itself as the winding create heat which is transferred to the steel enclosure of the hermetically sealed compressor and also vented in the coach.

If you would like to witness an example of this heat transfer process, simply hold your hand over your condenser unit for the AC at your home. You'll feel the heat being removed from your house using the same exact principle as the refrigerator.

Stay Safe - Mike

[avanti]

Originally Posted by IdleUp

Avanti thanks for the reply - however you're incorrect by your saying their is no heat coming from your 12 or 120 volt refrigerator. All refrigeration units work on the same principle of circulating, evaporating, and condensing refrigerant (Freon) to remove heat. The refrigerator is working on the same principles as your roof ac unit where the heat that was once in your RV is carried outside and expelled.

You are deeply confused. Time to "triple-check" your facts.

[IdleUp]

Thanks for the reply Avanti however my last reply is correct. While I'm not a AC sharp-shooter, part of my mechanical training included automotive and marine refrigeration systems. You'll find that most conventional air conditioners and refrigeration systems work on the same principles. I noted a typical AC cycle below to explain how heat is transferred from inside the refrigerator to outside the box.

Starting at the expansion valve, the compressor pressurizes the Freon to roughly 250 lbs which is then forced through either an expansion valve or capillary tube device which restricts the Freon flow, lowering the pressure to around 65 lbs (depending on temperature and Freon type) this drop in pressure turns the liquid into a cold gas.

This cold refrigerant is forced through the evaporator inside the refrigerator, where it absorbs heat from the items in the box. As the Freon with heat reaches the compressor, it is compressed again to a liquid, and forced though the condenser coil outside of the refrigerator where it cools the hot liquid Freon which then flows back to the expansion device to start the cycle again.

I included an image below of a typical 120 volt refrigerator similar to the ones installed in some motor homes. The giant black coil on the rear of the refrigerator is actually the condenser coil where the hot liquid refrigerant flows from top to bottom releasing the Freon's heat into the coach.

Stay Safe - Mike

[avanti]

Originally Posted by IdleUp

Thanks for the reply Avanti however my last reply is correct. While I'm not a AC sharp-shooter, part of my mechanical training included automotive and marine refrigeration systems.

I am not sure, but I think you can find a high school physics course at Khan Academy. Start with "Conservation of Energy".

Amazing.

[booster]

I did some quick calcs based on this Danfoss compressor heat extraction and power use.





I assume 4btu per watt hour of extraction and running watts of 30 watts, one watt equals 3.413 btu.


Heat extracted from the frig = 4 X 30 = 120btu/hr for 30whr



Pure heat generated by the power supplied = 30 X 3.413 = 102btu/hr


So when running there is 120 + 102 = 222btu/hr coming off the condenser and compressor.



In watts that would be 222 divided by 3.413 = 65whr


If you assume a typical 30% duty cycle that is 65 X .33 = 21.5whr


So if you take the case of an external vent and assume no leakage of heat from the compressor side into the van, you would be exhausting about the heat from a 20 watt lightbulb 24/7. 54% of it would actually be cooling the inside the van and 46% of it would prevented heat gain the van would have seen.


If you are venting back to the inside the van, the extracted heat would go back into the van, so no heat gain or loss with it. The heat to run it from the power used would heat the van by its actual amount.


So, bottom line,


External vent you would cool the van by the amount of a heat a 12w bulb running 24/7 would generate.


If you vent inside, you would heat the van by the amount of heat a 9.8w bulb would generate.


One would help heating season and one would help cooling season, it appears.


I will leave it to individuals to decide which is better or worse, bu either way they are pretty small amounts of heat.


Calculations are always in need of double (or even triple) checking and welcomed. The calcs are a bit convoluted and assumptions from the chart up for personal choice, I think.

[Bud]

"I will leave it to individuals to decide which is better or worse, but either way they are pretty small amounts of heat."

There could be a poll concerning the 'better or worse'.


"Calculations are always in need of double (or even triple) checking and welcomed. The calcs are a bit convoluted and assumptions from the chart up for personal choice, I think."

Seems like the triple fact checking thing has not worked out well at times, quadruple has been necessary - bforum.

Still, I'm going to open the refer door and see, monitor what happens inside my b with all that heat. Ok, my *&)R*& absorption refer is.......HOT, so I'm going to have to use my kitchen at home.

Ok, I'm back. Wow, opened the freezer for some ice/vodka and one heck of a ....... Well, it was like I had some dry ice here in south Louisiana. Glad I was not barefoot. Quadrupled checked and the vodka is still happy, plenty cold and cool in my kitchen.

Bud

[themexicandoctor]

This might be considered a Rant.

But I earned it.

Just as Doneworking & Chicago earned their successes with the propane technology.

I did all that & more, I must have owned the 3rd lemon in the rig in 15 years. All the same complaints.

I learnt every dark secret of 3 Way ownership & know that my owning & living in an RV Fulltime & seeing patients is not consistent with 3 way technology, no matter what the Salesperson told me.

In fact before I bought the 4th 3 Way Dometic RM2354, I spoke with Dometic for a total of two hours plus that involved several calls only to be told at the end;

"we don't recommend 3 way technology for your needs, the technology has not progressed enough from 2005 until today to compensate for its shortcomings for your particular ownership demands, let us suggest our new Dometic DC Compressor Fridge line otherwise known as CRX ..."

Straight from the Horse's Mouth.

So instead I invested a good 2 weeks back & forth here & on many other forums before I placed an order for Novakool DC R3800 (3.5 cubic feet), to fit the cutout of my Dometic. $1229 including freight.

And I researched the other big names, Engel, National Luna, Vitrifrigo *, TruckFridge*, Isotherm* & others.

*all three are the same company

After I placed my order I got buyers remorse & almost canceled to go with a more efficient Chest type Engel MT45 (only 1.5 cubic feet) Combination Fridge & separate Freezer.

=========

Chest units are far more efficient at keeping the cool than uprights but you must be somewhat more organised & as Msnomer educated me, the use of Tupperware type tubs are essential to that organization.

And while they run using less amps but that is Engel & Engel alone. National Luna are equivalent & even more efficient on the bigger units, they have thier own non-danfoss compressor technology.

NOT the latest craze Dometic, Iceco, Whynter, etc that use 40% more than an Engel minimum when brand new but when you have Dual Zone units, everyone except Engel run another 50% higher amp draw above 75%.

So contrary to all these Millenials who say their non-Engel Fridge & Van Life is fantastic - they are LYING.

Iceco does use the Danfoss Compressor but it still runs 50% higher minimum than what is rated at & higher if you haveva Dual Zone unit.

However the smallest Engel is 26 inches long which meant I would have to install a $380-450 fridge slide into the cutout & then have 8-12 inches of the 20 inch Roadtrek Shower/Aisle floor reduced to 12-16 inches to support the Slide Legs & to have the fridge lid open up for access - too much compromise.

But if I was designing a Class B again, I would design part of the rig around a larger 60-80 quart Dual Zone Engel or National Luna chest type fridge.

No other brand.

Note;

Buyer beware that Engel sell 3 upright style units - over 50% are returned, not the same internals as the Chest Technology.

============

All DC units produce heat but its infinitesimal compared to 3 Way or 2 Way fridges that use Propane.

INFINITESIMAL according to my installer, now semi retired but the leading AC & Refrigerator designer & installer in Mega Yacht Marine Industry - he spent 5 months a year outfitting world class yachts in Spain, Monaco, Italy for many, many years.

And the existing lower & upper cutouts on Class B model vans that had a 2/3 way propane stock, these vents are to a magnitude more than sufficient for the DC Fridges.

Some people like Booster* had to modify the venting for optimal performance which is probably around 2amp hours at most, 12 hours a day.

*Booster would modify the Space Shuttle just because that is his interest.

I already have 250 watts of solar & a 200amp hour battery bank of 2 Lifeline AGM Batteries.

If you have a newer rig or older. adding quality solar & systems should be a fundamental step in being able to boondock longer, practically for Free after the initial investment.

The Solar was to maintain the two new batteries I had just invested in but I think I have enough reserve power in my system to work with the much less sophisticated Novakool R3800 from Canada at 2.2amps, average run time, 12 hours which seems to be the consensus of owners I polled -24-32 amps per day.

Novakools Maintenance wise just keep on working using very simple systems & the Dandfoss compressor.

I chose the R3800 over all the others because the fan & compressor are at the bottom & with the lower & upper vents already carved into the Roadtrek outer body, it creates a perfect chimnet effect.

I agree the Isotherm/Vitrifrigo* family brand have better, more modern technology but all factors pointed to my purchasing the Novakool including an almost seamless retrofit for my model versus size considerations for the others requiring carpentry build out & modifications.

*Ttuckfrudge sell rebranded, small unit, lower quality Isotherms.

Reality will be in two weeks.

==========

Propane fridges are low cost but Life in Los Angeles doesn't always allow one to find parking with the sun off the fridge side.

Sometimes its a choice that is positioning the vehicle for better solar harvest.

And despite the conjecture presented, they need to be parked level if for more than 20 minutes.

A 10-15% degree grade won't stop the operation but the system will work harder, requiring more frequent & expensive gas pressure adjustments & over time, cumulatively they slowly degrade until there is no more regulator adjustment.

And yet, you are increasing the pressure but not releasing the chemicals trapped (moving parts), in suspension because of non level parking & that needs to be addressed by safely disconnecting the gas line/s, disconnecting the 12 volt cables & lugging the dirty, heavy fridge up & out of its cubby, usually out side doors & then burping it for 24 hours on all 4 sides.

Then lugging it back in.

Trust me, your Propane fridge will* have ever decreasing performance over 80%. Even if its been sitting perfectly level unless you are driving & forcing colder air in through the windows or using the ac.

*Gallen is the outlier here but not parked in the hot summer days.

But even more than that, with a battery or dc wired fan inside the fridge keeping the air circulating & a dc fan blowing on the cooling fins of the rear of the fridge & pushing that same hot air up & out the upper vents, you are consuming amp hours even with small fans.

Not mentioning the fact that one of the most frequent insurance claims are for RV Owners whose propane fridges caused major if not total damage.

And then all the safety issues, I love gas for cooking & if I was boondocking for weeks at at time, on a level surface, I still would NOT use a propane fridge because I have Solar instead.

If it was a fixed cabin, no electricity, no solar, I would use Propane.

=========

The switch to DC Fridges is driven by the desire for better, safer, food refrigeration, not Sales Agendas.

Its driven by coming back to a struggling Propane fridge in the summer & having to throw some of the food out if not all or risk food poisoning.

And coincidentally, by the price point availability of reasonable solar sysyems.

Engel & National Luna Chest fridges are the very best in efficiency (plus two other obscure names).

Novakool, Isotherm & Vitrifrigo are the very best in efficiency in Upright technology.

3 Way are Dead & although mine is being repurposed as an off grid unit in a Cabin, I would have taken an axe to it if I hadn't been able to find a home for it.

The two big 3 way manufacturers, Dometic* & Norcold**, are still producing inferior equipment, on a mass scale - the advertisements are great, the realities of ownership, far less appealing, costly & the last straw for many RV Owners- between myself 9 years & the previous owner 5 years, we replaced the Dometic RM2354 THREE TIMES!

*Dometic have purchased some great brands under thier new roof but calling them for info you get the too big too fail vibe - its the same helpful, courteous but empty answer customer service rep repeating that even a 5% angle leads to immediate reduced performance & its essentially our fault for leaving the flat driveway.

**Norcold NEVER had a reputation for quality rv refrigeration & now they are the joke of the industry & are embroiled in endless litigation.

=========

If my DC Fridge fails to perform, I will be the first to admit it.

[themexicandoctor]

This is Booster's Fridge Poll;

How about a frig poll?
Poll Results: 6 Choices
Only have had absorption and liked it 16 34.04%
Only have had absorption and hated it 4 8.51%
Only have had compressor and liked it 9 19.15%
Only have had compressor and hated it 0 0%
Have had both preferred absorption 1 2.13%
Have had both preferred compressor 17 36.17%
Voters: 47.

I don't know how scientific the collection was but its very clear to me that Propane is becoming a Dinosaur based solely on its inefficiencies, the impossible conditions required for mediocre performance & how food stored poorly poses some immediate food issues.

[themexicandoctor]

10 Million Owners or 50 years didn't have a cost effective way to make the change to DC until the last 5 & they are voting with their hard earned money ...

[Davydd]

300 million have compressor refrigerators. Not necessarily in an RV but generally at home.

With lithium battery technology and gravitation to high amp battery banks a compressor refrigerator is a no brainer for me. We have not had propane for nearly 5 years now and lithium ion batteries paired with a high watt inverter has freed us up to have our van behave electrically boondocking the same as being plugged into shore power. Induction electric cooktops are as controllable as gas, our Keurig and microwave/convection oven and Instant Pot are available 24/7 no matter where we are at a Walmart or a remote wilderness. Heat and nearly instant hot water comes from diesel.

But back to refrigerators. Compressor refrigerators are more energy efficient on DC electric all the time than absorption. You don't have to constantly change sources (or forget to), You don't have to level. You don't have to vent to an outside wall. I think they are more dependable. And, of course, it is one more move to get rid of propane all together as we managed.

[themexicandoctor]

Error;

I correctly stated that the Chest style Engel Combination MT455 Fridge Freezer is 1.5 cubic feet.

I also stated the Novakool R3800 is 1.5 cubic feet.

This is not true, the R3800 has 3.5 cubic feet capacity.

[themexicandoctor]

My rant about my 3 Way experience was justified it seems & I suspect that all owners of Dometic RM2354 units, all suffer from performance problems unless they are driving & driving to & from, perfectly level parking spots, in sub 80% weather.

Because according to my usual Fridge guy, Lodgemobile of Burbank, even if I did the $200 upgrades (pulling the unit out, burping it all ways for 24 hours & then installing fans both in & out of the unit), the RM2354 would still limp along in 80%+ weather which is about 8 months per year here.

Originally Posted by JohnnyFry View Post
The factory spec for leveling (from the Dometic Rep at FMCA rally) is ±3º side to side (of the fridge, in most installations that would be front to back of the vehicle) and ±6º front to back of the fridge.

Screaming hot weather is always problamatic: I have 2 fans in the space behind the fridge switched by the ARP controller and one inside the fridge on the fins running all the time. I also have 1 inch foil backed foam insulation on the inside of the body panel. I always run on gas and I still have trouble keep it inside the food safe range on hot days. It can run up to 48-49º if the side is in the sun. The fridge is a Dometic RM-2354 3 way (Gas, marginal and useless!)

Maybe its just us owners of RM2354's whose units are particularly affected by days hotter than 75% & further compromised by imperfectly level street parking?

[eric1514]

It's been my experience, that the smaller absorption fridges like you'd find in a B are more problematic than larger ones like you find in Class Cs or As. The fridge in my Travato could not maintain 35 degrees during the day often rising into the 40s but at night it would achieve 18 in the refrigerator freezing everything that it shouldn't have. I was constantly chasing it and changing the thermostat setting.

The 8.0 cu ft. fridge in my C will only drop to 34 at night and if I keep the refrigerator side of the coach shaded either by parking or with the awning, it will stay below 40 on the hottest days all without any adjustment. I still will replace it with a compressor one day, but this last week my beer was cold and my lettuce didn't freeze. That's really all I can ask.

[themexicandoctor]

Thank you Eric,

I rarely rant but my ownership experience was crazy making & those stating otherwise have never owned an RM2354, in a Roadtrek, during the summer.

Will share your confirmation with my Psychiatrist ...