3 way fridge question - Page 2 - Fiberglass RV


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Old 10-17-2009, 12:10 PM   #15
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[My new text is in green so that I can put stuff in between Robert's quotes, and not have it all confusing.]

Harry,

Yeah, wow! I think you should be crowned



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of Refrigerator Baffling. AND of explaining it.

I love engineers, and they do great things, but one should never underestimate real-world experience. Thank you!

Quick question: Would something like that metallic/air-bubble insulation be an example of a good infrared barrier sheet? If not, then can you name an example?


Quote:
So, what I've gleaned from what you've written, that's directly applicable to my situation (small, under-counter fridge in a 13' Scamp), is this:

1 Properly matched, and appropriately sized, venting, top and bottom is imperative

I have another question now: What are "properly matched and appropriately sized" vents? I have the Dometic vents, and the one at the bottom (large panel that you can remove to access "guts" of fridge) is probably twice the size of the one at the top (horizontal "ribbon" vent). I've seen this arrangement on many Bolers; I believe it is stock. Is this properly matched and sized?

2 Baffles, in theory, are okay--but in my configuration, not necessary, and probably ineffective

3 Using a small fan (or two, in a push-pull arrangement) at the top of the airspace (near fins) is a good thing

I got from Harry's post that both fans should be at the top, and that both should be exhausting (pulling). Harry, can you confirm which one it should be?
This is a great discussion.

Raya

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Old 10-17-2009, 06:29 PM   #16
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If you don't mind, Harry, check out this illustration showing exactly what I've got on my Scamp now. Please send me any advice applicable. Thanks.


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Old 10-17-2009, 07:20 PM   #17
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I'm not Harry (and can't even come close to his advice - by about four orders of magnitude), but I still think you'd want both of those fans exhausting air (vs. the way you have it with one drawing in and one exhausting).

That's because I think you want the fact that the fans are pulling hot air up and out (both of them) to be what makes cold air come in at the bottom.

With them one going each way, and both at the top, I don't see any "reason" that cool air would want to come in at the bottom (not to anthropomorphize cool air...). It seems like your current way would just make for a little enclosed loop at the top, with the bottom all left out and lonely.

Harry?

Raya
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Old 10-17-2009, 08:40 PM   #18
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Robert,

Where is the top of the uppermost fins? In my case it was above the pre-existing vent, that is why I moved the upper vent to above the belly band and the top of the uppermost fins.
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Old 10-17-2009, 11:26 PM   #19
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Harry, that was a wonderfully detailed post. I know how much mental energy and time it takes to put that sort of thing together . . . thanks for taking the time and expending the energy.

--Peter
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Old 10-18-2009, 12:24 AM   #20
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Robert,

I love the drawing!!!

To #1 I agree.
To #2 I agree.

To #3 I would like to say that [b]both fans should exhaust out the top, wire the fans to a single pole double throw switch...the middle position is off, switch up runs one exhaust and switch down runs two...Use computer fans (like C.P.U. fans, .25 to .75 amps) let the fans [b]throw the air out the top vent, mount immediately [b]under the vent blowing out...You will need to use them day time only.

You can buy the little solar fan for daytime use and use the other as a backup for cloudy days or a boost in the god awful heat. See ebay they make a solar refrigerator fan, it comes with the solar panel.

Your on the right track,
You ideas are sound, you need to understand you can [b]PULL more air thru the compartment than you can push with the same size fan fan.

Happy Camping, Safe Trails.

Harry



Quote:
Holy crap, Harry! That was awesome!

So, what I've gleaned from what you've written, that's directly applicable to my situation (small, under-counter fridge in a 13' Scamp), is this:

1 Properly matched, and appropriately sized, venting, top and bottom is imperative

2 Baffles, in theory, are okay--but in my configuration, not necessary, and probably ineffective

3 Using a small fan (or two, in a push-pull arrangement) at the top of the airspace (near fins) is a good thing

Do you concur?

RJ
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Old 10-18-2009, 12:28 AM   #21
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Peter,

I have always enjoyed your posts, and the pics of your work.
A moderator must have cleaned up my different fonts off the two laptops I was using.

(Thanks moderator)

Harry

Quote:
Harry, that was a wonderfully detailed post. I know how much mental energy and time it takes to put that sort of thing together . . . thanks for taking the time and expending the energy.

--Peter
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Old 10-18-2009, 12:32 AM   #22
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Bang on Raya...

Quote:
I'm not Harry (and can't even come close to his advice - by about four orders of magnitude), but I still think you'd want both of those fans exhausting air (vs. the way you have it with one drawing in and one exhausting).

That's because I think you want the fact that the fans are pulling hot air up and out (both of them) to be what makes cold air come in at the bottom.

With them one going each way, and both at the top, I don't see any "reason" that cool air would want to come in at the bottom (not to anthropomorphize cool air...). It seems like your current way would just make for a little enclosed loop at the top, with the bottom all left out and lonely.

Harry?

Raya
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Old 10-18-2009, 12:53 AM   #23
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Raya,

I love the bubble wrap...

I personally use foil backed engine firewall spun fiberglass heat shield, its spun fiberglass tightly compacted that has a foil reflective barrier...This is a personal thing I do, B-Wrap is fine, the reason I use the other is IF I ever had a fire, the spun fiberglass would contain the fire longer and allow me to get a fire extinguisher.

Happy Camping, Safe Trails.

[b]I should not be crowned Raya, I am bored stiff...
I go to surgery Tuesday the 20th and your wonderful question keeps me sane...
I would rather be camping!!!
If not that I will natter.

Harry


Quote:
[My new text is in green so that I can put stuff in between Robert's quotes, and not have it all confusing.]

Harry,

Yeah, wow! I think you should be crowned


Attachment 24342


of Refrigerator Baffling. AND of explaining it.

I love engineers, and they do great things, but one should never underestimate real-world experience. Thank you!

Quick question: Would something like that metallic/air-bubble insulation be an example of a good infrared barrier sheet? If not, then can you name an example?




This is a great discussion.

Raya

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Old 10-18-2009, 01:28 AM   #24
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Harry,

I hope you're up and about and camping ASAP after your surgery Your out-of-the-way-place camping reports are great, too

Until then, if you really are bored, can you explain what you meant by properly sized vents? Real-world, the Bolers are pretty limited (unless one were to put in a chimney/pipe), but I do notice they usually have a larger vent at the bottom (Dometic) and then a smaller one up top (either just below or just above the belly band).

Is the larger/lower smaller/upper the right general idea?

again!
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Old 10-18-2009, 08:10 AM   #25
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Quote:
you need to understand you can [b]PULL more air thru the compartment than you can push with the same size fan fan.

Harry,

Thanks for that comment. You've made up my mind on how to add my fans. My fridge has a small fan built in at the bottom that needs replacing. It is controlled by a thermocouple attached to the fins. You can see it in the picture I posted earlier connected to the blue and yellow wires:
http://www.fiberglassrv.com/board/index.ph...st&id=17779

I'll disconnect the original fan and use that wiring for the computer fans in the upper compartment. I remember reading somewhere that if one connects the fans in series they run slower and draw less power. But that was in reference to the larger 12V computer case cooling fans. Any thoughts on that, with respect to both power and cooling efficiency?

Best wishes for your health.

Roger,
If you look at the picture (link above) you'll see how much room you have for vents above the belly band. You've got about an inch less in height from the rivets for the lower kitchen cabinet.
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Old 10-18-2009, 11:29 AM   #26
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Raya,

As a reference, check out the photo of my vent set-up on my Scamp.

These vents are the ones spec'd by Dometic to fit the small 1.9cuin 2190 model that I have. You can see that the upper vent isn't that much smaller than the lower. I was able to keep the upper vent below my belly band and still keep it positioned slightly above my fridge cooling fins.

Hope this helps...
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Old 10-18-2009, 12:01 PM   #27
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Quote:
Robert,

Where is the top of the uppermost fins? In my case it was above the pre-existing vent, that is why I moved the upper vent to above the belly band and the top of the uppermost fins.


Roy,
Since the fridge install was recent, I was able to put my venting exactly where I felt they should go. My cooling fins are just a couple inches below the top of the fridge (approx. 22" off the floor). They are also centered behind my upper vent. (See bellow.)
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Old 10-18-2009, 12:14 PM   #28
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Quote:
As a reference, check out the photo of my vent set-up on my Scamp.

These vents are the ones spec'd by Dometic to fit the small 1.9cuin 2190 model that I have.
Hi Robert,

Thant looks similar to the vent set-up for my Dometic fridge too, and is what's on my Boler. I was just curious about Harry's take on it, since he's got Real World experience that may or may not agree with what the manufacturer suggested.

Raya
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