Refrigerator box insulation

[Flyfisher]

I am replacing my 3 way Norcold refrig. with a new one. I am trying to figure out if I can improve refer performance by adding insulation to the wooden box that contains the frig. My question boils down to: What is the purpose of insulating the refer box? I have asked FWC and Norcold as well as others and can't seem to get a clear answer.
Do you add insulation to the outside of the refrig to further insulate the refer? One person said that could cause condensation to occur between the layers.
Do you try to insulate the box from the outside? (still have the air space between the refer insulation and the box insulation).
Or is the purpose of insulating the box, really just to occupy the extra space between the refer insulation and the wall so as to minimize the the amount of hot air from the refer that is allowed to circulate around the refer? This would seem to be the purpose of the fiberglass batting that FWC originally installed. FWC now installs mylared foil bubble wrap in their refer boxes.
Norcold's installation instructions seem to indicate that there should be between 0 and 1/2 inch clearance around the top and sides.
It is rather confusing.

 

[MarkBC]

Sure seems like insulating the fridge walls directly is the way to go -- the only way that makes sense, really (to me, that is ).

A refrigerator consumes propane (or electricity if it's a compressor type) to keep the interior cool because it picks up heat from the environment -- conduction through the walls of the fridge. Better-insulated fridge walls reduce the rate of conduction of heat into the fridge. That's how to make a refrigerator more efficient -- improve the insulation.
There's no point in Insulating the inside or outside of the wooden box -- and leaving a gap around the fridge -- because the back of the box is vented to the outside, exposing it to the warm environment. (at least, that's the way the fridge-box is in my 2005 FWC Hawk)

I wonder why directions say to leave an air-gap around the fridge? To reduce condensation? If there's condensation it's because the outside of the fridge is cool. If it's cool that means it's not as well insulated as it could be. Leaving a gap to eliminate condensation only works because you're warming the outside of the fridge with the warm ambient air -- which means you're increasing heat transfer into the fridge -- which isn't exactly what you want.

 

[PaulT]

Insulation reduces heat transfer from a higher temperature to a lower temperature.

Adding insulation directly to the refrigerator walls should be just as effective as the water heater blankets recommended to reduce heat loss on domestic water heaters, or placing Reflectix or closed cell sleeping pad under your mattress to reduce heat loss through the cabover to reduce condensation in the mattress.

An enclosed air gap is an insulating layer as in double pane windows. If the air gap is open to the environment, the insulation would serve little purpose except that it would insulate between the interior of the camper and the outside air rather than between the outside air and the refrigerator interior.

However, I would certainly pay attention to recommendations of the refrigerator mfg.

Paul

 

[captainphx]

Tired of cold air flowing into the camper from under the frig, when the wind was coming from just the wrong direction, I decided to plug the gap. I placed foam rubber insolation under the bottom, along the left side, and above the top of the frig. to stop the airflow. Bad idea!!! On the first outing, the frig essentially did not work at all. With the gaps plugged, there was no way for the air to circulate efficiently around the frig, to carry the heat away. I have the 110 Dometic two way in a 2012 Raven. I also have the optional frig exhaust fan. I would heed the mfg.'s clearance instructions.

So...I pulled the insulation out and the frig began to work properly again. Now I store the insulation in the camper, for the few occasions when the wind is coming from the wrong direction. I just stuff it back in the gap for awhile if it gets too bad. It only bothers me when I am sitting at the table.

 

[MarkBC]

Seems like it would be enough to just circulate past the heat exchanger, and on a propane-powered fridge (a "Norcold 3-way") the heat exchanger is on the back of the fridge. That's why there's an upper and lower vent on the outer wall of the camper behind the fridge. Air enters the bottom vent, passes up across the heat exchanger and exits the top vent -- that circulation driven by thermal convection.

Doesn't seem like circulation around the sides of that kind of fridge would help, since heat isn't expelled from the sides so isn't part of the thermal convection.

 

[billharr]

I have a Waco 12v compressor fridge. and put insulation on the sides and top. The back where the compressor, fan and coil is not covered in insulation. I also have an extra fan on the vent, only one went top. I have had no problem with the operation of the fridge.

 

[Bwht4x4]

Here's my take on this and what I did on my recent refrig install. I packed insulation tight around the refrig and I do not have an air gap around it, but I made sure the warm air generated by the compressor and fan could get out of the area behind the refrig and to the exterior. I'm betting the air gap requirement is to allow for venting this warm air. I looked at nearly all 2-way refrig when I bought mine and I found out that each one has it's own way of venting the warm air produced by the refrig. As long as you have the venting accounted for I'd think you can pack it tight in insulation.

Mine has been running for a couple months straight on my solar system and have never had a problem due to the insulation I have around the refrig.

 

[Flyfisher]

Thanks to those of you that commented, (especially MarkBC). I finally decided that the goal was to fill the wood box, that houses the refer, with insulation so as to keep as much of the warm air generated by the refer in the back of the box and not around the top or sides. I wanted to put the insulation right onto the outside of the refer but found that cabinetry in the front prevented this. Next best option was to fill the box to create a sung fit around the refer. Lots of options here. Bill's is certainly the easiest. Since my refer has a flame, I opted for solid foam covered with foil and taped the exposed edges with aluminum foil tape. I hope that this helps anyone else with questions about this subject.