Refigerator ventalation and roof vent fans

[sonic2]

I conducted research; reviewed RV owner web sites where others have installed fans on their RV's. Some RV MFG’s are now installing these as OE. The question is placement; everyone has an opinion, but there is only one right answer. I installed the fan on the roof under my exhaust vent because heat rises; many HVAC and RV web sites recommend this installation; you must REMOVE THE HEAT for the fan to do its job to keep the fridge cool. DO NOT install to blow over or through the coils; this does not remove the heat. Placing a fan inside the RV behind the fridge only creates air turbulence; this does not remove the heat.

VENTING is the most important issue! The below web site explains venting and provides pictures. If your venting is poor, your cooling is poor. http://www.fridge-and-solar.net/fridge_vent.htm

“Theoretically, perfect venting will create a draft that will remove heat from the cooling unit in even the warmest conditions. However, perfect venting isn't always that easy to achieve. The purchase of an add-on fan can solve a lot of problems in border line venting, but is not a cure all for terrible venting. The important thing to remember is that the fan should be installed above the cooling unit, preferably right at the roof vent. The purpose of the fan is to improve the draft, not to blow air onto the cooling unit.”

“The venting of an RV gas/electric refrigerator should be designed to not only provide a place for the warm air from the cooling unit to escape, but designed to actually create a draft that will remove expelled heat as efficiently as possible. Poor venting can cause the cooling unit to overheat and damage the cooling unit. When the cooling unit gives off heat, it causes air around it to warm. Warm air rises causing cooler air from the lower vent to enter the area and to extract more heat from the cooling unit and also rise. The greater the difference in temperature between the warmer air and the cooler air, the faster the air will rise. Narrowing the path of the air flow forces the cooler air through the cooling unit coils as it rises.”

Above my fridge I installed a backing to “prevent dead air space” which is a cause poor ventilation. The RV MFG had a backing in place but it was 5 inches short of coverage (poor workmanship and quality control). I removed the screen from the vent and replaced it with a removable and accessible screen.

I installed two fans for maximum ventilation. Additionally, I placed a fan inside the fridge to circulate the air. Yes! It works! My fridge is much cooler, maintaining 30F to 35F consistent during a camping trip in July 2012 during 100F plus days! I can make ice and maintain cold beer!

Attached is pictures showing before and after. The pictures show no backing above the fridge and the backing I installed; the placement of the two fans; the removable/access screen; fan products, inside fridge fan and roof fan.

1. Remove the top vent cover and cut and remove the screen
2. Correct any ventilation problems
3. Install under the vent cover as instructed, using the tabs on the fan assembly, slide the assembly between the roof and vent cover securely
4. Re-attach a removable/accessible screen
5. Do not use the thermostat (thermo switch) that goes to the heat tube (the fan MFG informed me this thermostat/thermo switch does not always work) install an on/off switch in the line
6. Place battery operated fan inside the fridge
7. Total cost $70

[CincyGus]

When I did the fan mod to my popup frig, it's a little different setup. The fan and frig electronics where in the bottom panel with the coils and air vent above it.

Ideally you DO want to create a wind tunnel effect, pulling (not psuhing) air through the frig coils and out through the top vent. Beside what you have done, the other major thing to look for is to "Duct" the pathway the air travels.

On popups, this was accomplished by taking cardboard and glueing tin foil to it and cutting taping it so that the air entered the bottom vent and was pulled out the top vent by the fan.

On larger RV's such as TT's where air is moving from the side wall vent and is vented through the ceiling, I'm not sure that this is needed. If you can direct the air from the vent towards the coils above, there may be some benefit but I think the way they are vented in non-popup campers, the benefit may be much smaller if any at all.

[RdRmr]

Have used the interior battery powered fan for years. Works well, just don't crowd it to cut air flow around it. I position it on the top full length shelf in the center toward the front and hold it in place with a small bungy.
HAPPY CAMPIN....

[diugo]

This may sound counterintuitive, but another thing you want to do is COMPLETELY BLOCK the screening around the fan---preferably fans---so that ALL the hot air is routed through the fan(s). Otherwise you just circulate the air at the top of the vent, rather than pulling out the hot air around the coils. Done right, you should observe a slight suction through the fridge service panel vents.

Note that if you do this---replace passive cooling with active---you really should run the fan(s) all the time.

[rjsurfer]

Originally Posted by diugo

This may sound counterintuitive, but another thing you want to do is COMPLETELY BLOCK the screening around the fan---preferably fans---so that ALL the hot air is routed through the fan(s). Otherwise you just circulate the air at the top of the vent, rather than pulling out the hot air around the coils. Done right, you should observe a slight suction through the fridge service panel vents.

Note that if you do this---replace passive cooling with active---you really should run the fan(s) all the time.

+1

I agree Sonic2 seems to think a fan suspended in the middle of the roof vent will draw only hot air from the coils below but as you said a good portion of the air being moved is just air flowing around the vent. A better solution as you suggested is the need for a complete blocking around the fan to be sure it will only pull hot air from below. You might get away with installing 2 fans side by side without additional fairing.

Personally I think the best mod is to use two fans just below the coils to guarantee that heat will be blown up and away away from the coils and out the vent.

But, no matter what you choose to do, will work, some just not as efficiently.

Ron W.

[AlCorr]

I'm not saying your wrong, but I also think the best mod is to use a fan just below the coils to guarantee that heat will be blown up and away from the coils and out the vent. When the fan is on I can feel the air being draw in and can feel it on top at the roof vent blowing out.

I'd say both way will work. Here is mine.

http://keystonerv.org/forums/showthread.php?t=7814

[SteveC7010]

Originally Posted by RdRmr

Have used the interior battery powered fan for years. Works well, just don't crowd it to cut air flow around it. I position it on the top full length shelf in the center toward the front and hold it in place with a small bungy.
HAPPY CAMPIN....

The interior fans in RV fridges are used for a much different purpose than what the OP and others are discussing here. The interior fans circulate air inside the fridge eliminating warm and cold spots. They will help prevent icing on the cooling fins and will improve cooling in other places.

The fans on the condenser coils on the backside of the fridges or in the roof top vents help to move away the heat generated by the refrigeration process, especially in warmer weather. RV's with roof top vents rely on the "heat rises" principle to move the heat away. This isn't always enough cooling in warmer weather so many folks will add supplemental fans like the OP describes.

RV's with fridges in the slides can not have the roof top vents and MUST have vent fans to move the hot air up and out through the upper side vent. We've discussed the slide mounted fridges and venting in great detail on some previous posts. For those that are interested in those discussions, try a search on slide vent fan and you should quickly locate them.

[bigcitypopo]

I am going to install two of the valterra units this week. Talking to a fridge expert. he told me that installing too much venting retards the heating process which is required to cool. The best place to install the fans is at the top.

my question. Can i wire two of these fans together, and only use one thermo switch?

[sonic2]

YES! But I did not use the thermo switch. I used a on/off switch. The Valterra rep I called even recommended this.

[Beachnut]

For our 230RS Outback, the refer seems to do a fine cooling job, even in hot weather, but the big pantry cupboard right next to the refer, GETS HOT if left closed. You can put your hand inside the pantry cupboard and feel the heat coming through it from the refer compartment as the wood is very warm to the touch. We have to leave the cupboard fully open all day long, or the warmth makes the bread mold, and candy melt, if kept in that cupboard. I am thinking of trying to insulate that wall with something. Maybe a fan in the refer vent would help, too. It seems that the refer vent, is not very well designed for heat dissipation. Even putting a fan under it,, might just cause turbulence as the forced air, simply hits the curved plastic cap and flys back and around the chamber.

Too bad some after market company does not make a retro fit vent cap with a better design, and even fan built in, that would maximize the vent, and not create turbulence.. (Hint, Hint)!