Date: Sun, 22 Aug 2010 11:38:24 -0700
Reply-To: neil n <musomuso@GMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: neil n <musomuso@GMAIL.COM>
Subject: Re: How Hot Behind Dometic Fridge On 100+F Day? (insulation
clearances)
In-Reply-To: <20100822095450.IBVZG.1558673.imail@eastrmwml39>
Content-Type: text/plain; charset=ISO-8859-1
Hi Dave.
I checked my 182 manual, but didn't see clearance measurements. I'll
check it again. Thanks for the offer.
Yes I have to wonder about possible R value gained, and clearance
lost. As it stands, fins at lower 1/3 of fridge protrude furthest (not
by much compared to the other fins), part of which should just touch
the final layer of cement board. But. Part of what I want to
accomplish is a more stream lined air flow behind the fridge. The
insulation should aid in this regard. i.e. instead of hot air
billowing up behind the cabinetry, it is directed more so to the stock
vent behind stove lid. (hopefully most of the hot air will be vented
by the City Water fan) And, the cooling fins are ~ 1.5"- 2" deep
(IIRC) so air flow should be ok. The insulation will be flush, or
close to, the rear of the cabinetry.
I tested yesterday in direct sun. Similar to what I did with bubble
wrap insulation. An IR gun at small spot of bare metal (sun at side),
showed anywhere from 110 -130 F. IR at 2" of blue rigid, 78 - 88 F.
This coincides with tests I did with 3 layers of cheap foil one side
bubble wrap and final layer of cement board. pic:
http://tinyurl.com/28ct5ew But.... my guess is that the bubble wrap
would likely rise in temp over time. The rigid board *might* maintain
a better R value for a longer period. This is what I'd like to believe
(after grunting away cutting my arms stuffing insulation behind
cabinets) :)
I removed the OEM fiberglass material and am hesitant to install
similar (if that's the type you're referring to, if not any links?).
From what I've read, IF water seeps in, the fiberglass matt holds the
water promoting rust. Given the age of the vehicle, and this PNW
clime, that's a concern. :) My city water connection leaked (I
deleted this a while back) and soaked the FG matt. Rust is certainly
present.
Pic looking behind fridge to rear along body:
http://sites.google.com/site/tubaneil2/Rusthold.jpg
Good point on offgassing. Here's some pdf's I found on extruded
polystyrene insulation
OwensCorning pdf: http://tinyurl.com/27rjabq
Dow on blue rigid board http://tinyurl.com/2cos6bj This one makes
mention of proper ventilation IF *large* quantities stored. I don't
know if small quantities would off gas under temps lower than 167F.
In terms of being exposed to sustained temps above 167F, it seems
expansion and melting of material are a concern. As for my main
concern, is this product flammable, Dow claims that: 'there is a
fire retardant to inhibit accidental ignition from a small flame
source. ... but will burn rapidly if exposed to an intense fire.'
I think I'm ok on the combustible side of things.
Neil.
On Sun, Aug 22, 2010 at 6:54 AM, <mcneely4@cox.net> wrote:
> Neil, first a query: Will the reduced clearance offset the advantage of the insulation? I have the Dometic installation manual. I f you don't have it, let me know, and I'll find it and look up required clearances. I suspect the factory installation is close to the specification. Actually, I just remembered that I originally got it from a Google query, so it is available.
>
> I have not measured the temperature in that space. However, when the outside temperature was over 105 F (reached 107 F that day) last week, and my van was in the sun, the refrigerator fan was running. Someone else on here said it kicks on at 145 F. If that is so, it was at least that hot. The driver's side of my van was broadside to the sun.
>
> Why not use fiberglass bat, unfaced or with no vapor barrier anyway? No problem there with either heat damaging the material (or worse, causing toxic outgassing), or with water vapor retention. Dave
>
> ---- neil n <musomuso@GMAIL.COM> wrote:
>> Hi all.
>>
>> Searching but to no avail.
>>
>> If anyone has a quick answer, it would be much appreciated.
>>
>> What's heats have people measured behind the Dometic 182 on a really
>> hot day. Say over 100F.
>>
>> I'm installing 1" rigid board insulation to 2" thick. On average,
>> there's now 1" between fridge cooling fins and the Dow Styrospan. This
>> stuff is rated to 165F. I
--
Neil Nicholson '81 VanaJetta 2.0 "Jaco"
http://tubaneil.googlepages.com/
http://groups.google.com/group/vanagons-with-vw-inline-4-cylinder-gas-engines
