Batteries gone ...

[GallenH]

I can't remember the thread but wasn't there a previous discussion of venting? I think in that thread the customary way was to draw air through a vent at the bottom of the fridge inside the RV where it would pass over the compressor and be pushed out the back of the fridge. There was a debate about whether or not you would recirculate that air back into the RV cabin or have it exit to the outside, the former allowing you to not have any exterior penetrations and the latter being a possibility if those penetrations were already there.

[Bud]

Originally Posted by GallenH

I can't remember the thread but wasn't there a previous discussion of venting? I think in that thread the customary way was to draw air through a vent at the bottom of the fridge inside the RV where it would pass over the compressor and be pushed out the back of the fridge. There was a debate about whether or not you would recirculate that air back into the RV cabin or have it exit to the outside, the former allowing you to not have any exterior penetrations and the latter being a possibility if those penetrations were already there.

Yes.

Bud

[themexicandoctor]

I remember that.

At the same time, both the original Fridge Guru who works on high end Marine installations around the World & Novakool stated "my existing cut outs provide the best venting & chimney system..."

Maybe it's the fan placement?

Will know after the other two electrical questions are answered tomorrow I hope.

[themexicandoctor]

Here it is;

https://www.classbforum.com/forums/f...ile-10598.html

[Bud]

"my existing cut outs provide the best venting & chimney system..."

I would not walk off from whomever said that, I would run.

No wait, vs what?

Bud

[mkguitar]

ah, % is degrees...on a mac option and zero = º

[themexicandoctor]

Originally Posted by Bud

"my existing cut outs provide the best venting & chimney system..."

I would not walk off from whomever said that, I would run.

No wait, vs what?

Bud

I am going by what the experts & the manufacturer stated.

Including forum members.

Perhaps once I rule out the other two critical factors & then get to the fan, I can modify my vent system.

[rvsprinterguy]

Re: "A sufficiently agile variable-capacity compressor could address this problem: You would use temperature feedback to continuously modulate an always-running compressor, rather than a Bang-Bang on/off thermostat. Some systems attempt to approximate this. I really don't know how well they do or what the practical difficulties turn out to be."

I believe that's how Danfoss/Secop compressors work; they're variable speed.

[themexicandoctor]

Thank you Gentlemen!

[avanti]

Originally Posted by rvsprinterguy

I believe that's how Danfoss/Secop compressors work; they're variable speed.

Yes, that is true, but the controllers typically used with them are not terribly sophisticated. Many of them still use simple ON/OFF feedback controls. I am uncertain if there exist any really smart ones, but they are certainly not typical.

I know that there is at least one "smart" upgrade available and it is well-reputed. Not sure how far this takes it toward the "always run" ideal.

[rvsprinterguy]

Most fun thing I learned today was how to enter degrees (º) on my Mac keyboard.

Thanks, mkguitar!

[peteco]

I will start by saying I have an absorption fridge; maybe someday a compressor fridge.

It looks like you have the same air venting issue that side vented absorption refrigerators have.

First of all, the orientation of the fan that is in there makes no sense to me. It is not blowing over the condenser or pulling in air and directing up the vent flue efficiently. In fact, it may be making matters worse by recirculating hot air in the cavity.

The attached sketch shows several items to consider. I have installed all of them except the lower vent fan. Each one improved my refrigerator's performance (though I still would like a compressor fridge). I had found that an upper vent fan worked best on my fridge. Others have used lower fans successfully too. The upper turning baffle is just sheet metal or aluminum and should be an easy install for your fridge guy. I would try these first.

I installed a wall baffle per Dometic guidelines. The gap between the fridge and outer wall was much to large according to Dometic specs. Why Roadtrek did not follow Dometic install guidelines I do not know. You should ask Novakool if they have a recommended distance to provide sufficient vent airflow velocity over the condenser.

This site goes into more detail on airflow for absorption refrigerators.

https://www.arprv.com/rv-fridge-fan.php

The other option is to go to an internal venting setup, which is what new install compressor fridge setups use. I have no experience with that; perhaps others can chime in on how they did an internal vent configuration.

[mkguitar]

I have a small fan ( scavenged from a dead vcr or something) internal to my 3way. it is zip tied to the rack near the fins, it is just meant to help circulate the air as my internal thermometer showed at much as 10º diff from top to bottom rack.
(when our GE in the house failed- investigation showed it was a $30 fan internal to the freezer)


I have 3 pusher fans at my top vent ( flow similar to seen in post above)

There is also a fan kit with thermal switch on the bottom side of the fins pushing up ( previous owner) it rarely comes on anymore.
I do have good airflow- the heat coming out the top vent is noticable- makes a huge diff.
Mikeº

[GeorgeRa]

Originally Posted by themexicandoctor

I remember that.

At the same time, both the original Fridge Guru who works on high end Marine installations around the World & Novakool stated "my existing cut outs provide the best venting & chimney system..."

Maybe it's the fan placement?

Will know after the other two electrical questions are answered tomorrow I hope.

I am not certain about being “the best”.
There are 2 heat transfer issues which don’t often exist in factory like compressor fridge installations.

1. Your system is using outside air to cool the condenser. No issue if outside temperatures don’t require AC but at over 100oC it could be an issue. Factory installations use inside air which is most often air-conditioned.
2. It looks like your external wall next to condenser is not insulated so it will emit infrared radiation directly on the black condenser. Sun exposure could heat this wall to 130Fo or higher.
This is what I would do:
1. Follow Avanti recommendation to measure condenser space temperatures.
2. Scrap the fridge fan in lieu of one or two pancake fans thermostatically controlled forcing air to the condenser. Snap thermostat disc switches don’t require power.
3. Insulate the wall, for example 1” of Styrofoam. It is possible to use a reflective foil but it would be very difficult, the reflective side would need to face the wall and would need to be mounted ½” away from the wall, styrofoam is easy.
4. As already recommended make a duct to force all cooling air to the condenser.

[rvsprinterguy]

Re: "This is simple. Bring the air in the bottom, don't let it start not leaving the top vent looping around inside the van getting hotter. A one way flow without looping around inside, whatever it takes to do that."

I added some ducting inside the top vent of my absorption refrigerator to make sure it vented out properly. I used Coroplast from Tap Plastics and duct tape to put it together.

My setup is like Peteco's with the baffle at the top. However, I haven't sprung for the fans.

[Bud]

"Your system is using outside air to cool the condenser. No issue if outside temperatures don’t require AC but at over 100oC it could be an issue."

I agree George, it is an additional issue. And with the present venting, it may be The issue vs all the others.

[Bud]

Someone please correct my thinking here:

The fan in picture with the Novacool is Not there for 'venting'. It is there for the compressor, ensuring enough cooling for the compressor. It is not there to specifically enhance 'convention'. Nova folks assumed the installation had appropriate venting.

You don't take a Novacool 3800 and just stick it inside an 05 Roadtrek 190 which is really really lousy to start with concerning convection (as bad as an rv gets?). There is no fan to fix the lousy convention, and as pointed out 100 degrees and looping air in the cabinet getting hotter and hotter.

Bud

[peteco]

Originally Posted by Bud

Someone please correct my thinking here:

The fan in picture with the Novacool is Not there for 'venting'. It is there for the compressor, ensuring enough cooling for the compressor. It is not there to specifically enhance 'convention'. Nova folks assumed the installation had appropriate venting.

You don't take a Novacool 3800 and just stick it inside an 05 Roadtrek 190 which is really really lousy to start with concerning convection (as bad as an rv gets?). There is no fan to fix the lousy convention, and as pointed out 100 degrees and looping air in the cabinet getting hotter and hotter.

Bud

The fan does not look like it would blow much air on the compressor. If the compressor needs cooling then setup fans to blow air over the compressor while also moving air up the flue.

[booster]

Originally Posted by Bud

"Your system is using outside air to cool the condenser. No issue if outside temperatures don’t require AC but at over 100oC it could be an issue."

I agree George, it is an additional issue. And with the present venting, it may be The issue vs all the others.

At least on our Isotherm, if the outside air is delivered cleanly and exhausted cleanly once used, it can handle quite high inlet air temps. We know this because we sat in 100* ambient air in Zion National park a few years ago. Frig side of the van facing south with no shade at all for the entire day. Our Roadtrek is the tan color which gets very hot in the sun. Skin temp as only a few seconds touchable so maybe 120*? Ours is a Chevy 190 like the Dr has the same vents. Our compressor and condenser is the small prebuilt corner style about 9" cube shaped and in the upper r/h rear corner of the frig in a big cutout. We have a sealed and insulated duct to the fan on the condenser assembly that takes air at the lower vent. Exhaust air free flows out the top vent because the fan is pulling more air to push it out. This works only because the area between the skin of the van, duct and frig rear are full of fiberglass insulation to stop all air from going from one vent to the other. The only air moving is going in through the duct and fan to the frig, and then out. The frig held 38* inside on the lowest compressor speed and even cycled regularly. I would guess the inlet air was about 105* or more.


I think this points out that without proper venting and air handling, you can chase yourself forever and not get reliable, efficient, cooling. Peteco's drawing about sealing all the areas between the vents except where the air needs to go is spot on and absolutely required. The two fans locations showed would be in the right places also as long as the air is directed well to the chimney going up so it doesn't go elsewhere.

[Bud]

Originally Posted by peteco

The fan does not look like it would blow much air on the compressor. If the compressor needs cooling then setup fans to blow air over the compressor while also moving air up the flue.

I agree not much air. I may have made a mistake thinking that Nova put it there since in was in the picture George posted. If not, why did Nova put it there? I'm still thinking it is for the compressor, only becuase why else?

I agree with booster's comments about your drawing, very nice.

Bud