Dorm Size Fridge.

[Kcook]

My Dometic fridge cooling unit failed.
I installed a new dorm size Fridge with an inverter. The inverter is a 2000 with peak at 3000. With two 250ah deep cycle Batts. Voltages are all good.
My problem is while traveling, the inside of fridge warms up to 50*
I have 2.5" of airflow around the fridge for venting.
I'm using a modified inverter, I now know it should be a pure sine one.
But, is my problem because these compressor type fridges shouldn't be going up and down the road or too high of outside temperature (sun)?
Anyone have and solved this type of issue?
Thank you for your help.

 

[autostaretx]

All of the above?
Dorm fridges expect room temperatures (about 70 F)
They're not expecting road vibration, so may have minimal "puddle spots" (reservoirs) for the coolant to accumulate after the compressor.
The only place that needs venting is the exhaust from the compressor area (that's what gets hot).
The evaporator (where it gets cold) only needs enough airflow to satisfy the fan.
As a first attempt, i'd wrap all of the walls (and top) of the fridge in an inch or two of rigid foam, with a layer of Reflectix-like material on the outside (or at least aluminum foil).

How the MSW inverter affects the fridge depends upon its drive motor ... if it's an AC motor, the MSW will merely make it run a bit hotter (some energy loss), but it should still develop full power. If it's a DC motor with its own PWM power supply, then the MSW and PWM can get into hissy-fits. (this is why MSW is not recommended for some power tools' battery rechargers).

And finally... you could have a bad fridge. Does it have a history of working well at home?

--dick

 

[borabora]

My Dometic fridge cooling unit failed.
I installed a new dorm size Fridge with an inverter. The inverter is a 2000 with peak at 3000. With two 250ah deep cycle Batts. Voltages are all good.
My problem is while traveling, the inside of fridge warms up to 50*
I have 2.5" of airflow around the fridge for venting.
I'm using a modified inverter, I now know it should be a pure sine one.
But, is my problem because these compressor type fridges shouldn't be going up and down the road or too high of outside temperature (sun)?
Anyone have and solved this type of issue?
Thank you for your help.

I think you answered your own question. If it works fine when stationary but not so well when moving then the problem is related to the movement and not to the inverter. The inverter should work better when the engine is running (assuming you are charging using engine) because modified sine wave inverters generally do better with higher voltage and become fairly useless with low voltage.
If you unboxed your fridge there probably was a note or something written on the box to leave the fridge on a level surface right-side-up for 24 hours before plugging it in. Home fridges don't like to be tilted. The g-forces of driving as well as the vibrations can make your fridge unhappy.

On the other hand a different design might work better. So, if you can return this fridge and try another model you might just be lucky. Best bet, of course, is a fridge designed for RV/van/boat. My Dometic spec said that it tolerates operation in up to 30 degrees off horizontal.

 

[Kcook]

All of the above?
Dorm fridges expect room temperatures (about 70 F)
They're not expecting road vibration, so may have minimal "puddle spots" (reservoirs) for the coolant to accumulate after the compressor.
The only place that needs venting is the exhaust from the compressor area (that's what gets hot).
The evaporator (where it gets cold) only needs enough airflow to satisfy the fan.
As a first attempt, i'd wrap all of the walls (and top) of the fridge in an inch or two of rigid foam, with a layer of Reflectix-like material on the outside (or at least aluminum foil).

How the MSW inverter affects the fridge depends upon its drive motor ... if it's an AC motor, the MSW will merely make it run a bit hotter (some energy loss), but it should still develop full power. If it's a DC motor with its own PWM power supply, then the MSW and PWM can get into hissy-fits. (this is why MSW is not recommended for some power tools' battery rechargers).

And finally... you could have a bad fridge. Does it have a history of working well at home?

--dick

Thank you.
The instructions say to leave about two inches on sides and top for vented so I guess I shouldn't wrap it.
The compressor is at bottom rear next to RV fridge vent panel.
I do not find nor hear any fan on unit.

 

[Midwestdrifter]

You need a fan to blow air over the skin, that will improve cooling.

 

[Kcook]

Will try that.
Thank you

 

[Kajtek1]

Dorm-sized fridges don't have good insulation, so you might try to add something.
Driving pickup, I had just a cooler who would hold frozen bottles for 12 hr, what gives you indication what good insulation can do.
Check where are the fridge heat exchangers. If they are under, or on the back, add good insulation on sides and top, while putting fan on the fins.
Sometimes the heat exchangers are build into fridge skin and that is giving you option of adding insulation only on top.

 

[Kcook]

Thank you.
Heat exchangers are under side skins. Darn.

 

[Midwestdrifter]

Dorm-sized fridges don't have good insulation, so you might try to add something.

It sounds like this fridge has the condenser under the skin. So extra insulation isn't an option.

Well the door might be okay, maybe the bottom.

 

[Kcook]

Thank you.
I recon I bought the wrong fridge.
May try fan to see if it helps.

 

[Kajtek1]

See if you can find that size fridge with outside coils. This way you can put more insulation on the sizes and extra fan at coils.
I do have patio (cheap) fridge who keeps my ice in 119F weather, so it is doable.

 

[Kcook]

That sounds like a good plan.
Do you think there'd be much cooling problem with standard compressor while driving, sometimes we'd drive maybe nine hours in a day but, average 6 hrs per day when traveling.
Thank you

 

[Kajtek1]

My patio fridge in those hot days runs 24/7, so what is your worry about?
I have big absorption fridge, who runs on 120V in my Sprinter. I made relay who will activate it with ignition on, or I can leave it on all the time, for 1-2 hr breaks on the trip.
If you want to run on battery power, you need to do separate evaluation.

 

[Kcook]

I have an inverter for travel.
I read somewhere that these dorm fridges must be level, I was worried about driving up and down hills/ mountains.

 

[Midwestdrifter]

Most are reciprocating compressors, and typically work fine within 15 degrees of level.

 

[Kcook]

Ah. Good to know that. Thank you.
We're going to travel a few days next week and see how it goes. Last time it got 50* inside fridge.
I'm putting insulation on top and a couple little fans for venting.
Thank you. You've been very helpful and I appreciate it.

 

[Kajtek1]

What will also help is freezing couple of water bottles overnight and put them at bottom of the fridge for the day.

 

[Kcook]

Yes, thank you. We are going to try that too

 

[downunder]

I'd get a 12v dc computer type fan (high speed bearing model, quiet and relatively cheap from computer/electronics type retailer) and move air past your compressor continuously. This should be a good help. Wire it in off a switch or even just off your cigarette lighter for a quickie type test.
If that doesn't help enough get another one and move air past your fridge to help lay off the heat from the outer shell.
You'll always be able to use the fan(s) on any other fridge should you change it later as well.
I had success doing this on an Isotherm fridge/freezer that i felt wasn't cutting it.
My experience has also been the the actual door shelf temperature is higher than the internal shelf temperature....
Another 12v fan placed at the internal rear of the fridge helped with that as well.
Remote temperature sensors/readers will give you something to think about as well.
Good luck on it, be interested to see how you end up with it.

 

[autostaretx]

This is one of those things where the "Energy Rating" sticker may help, too.
Obviously if the heat-releasing coils are trapped in the side wall, they've made that side of the fridge's insulating wall (between hot coils and cold food) thinner than the (probaby) symmetric other side walls.
Stylish, but inefficient (power-wise) design.
I would suspect/expect that fridges which use less power (via the "annual cost" chart) would be better over-all performers.

I wonder if cutting slots in the metal side wall (thus helping the hot coils cool) would help the 50 F situation?
Even my $100 Coleman Peltier cooler didn't get *that* warm.
--dick