Date: Fri, 21 May 1999 07:34:28 -8
Reply-To: Wes Neuenschwander <wesn@ESKIMO.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Wes Neuenschwander <wesn@ESKIMO.COM>
Subject: Re: Fridge fan and water behind the fridge
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Sorry, no RPM data on the OEM fan and ditto for the cubic feet/minute
(CFM) data. Personally, I would be skeptical about replacing the motor
without having more OEM performance data available. I suspect that
there's a little more than meets the eye to the OEM motor, it's actually
quite similar, at least in general appearance, to the $30 aftermarket
units available at RV stores.
I've also been considering replacing this fan in my '91 Westy. The
original has gotten progressively more noisy over the years, to the point
now that I expect imminent bearing failure and total lock-up.
I'm also intrigued with the muffin style fans. They're engineering to be
relatively quiet and move a maximum amount of air in a small size package.
The airfoil shaped blades, cowled fan housing and integral fan wheel and
motor, are aspects of this design. They are probably not the most energy
efficient though (since this is not an important consideration in their
design application). Perhaps more important however is the fact that the
muffin style fans are designed for what is essentially a ducted
application: the fan must suck outside air and force it through the
computer case, overcoming the air-flow resistance of the inlet, plenum
(the computer case in this instance) and the discharge grill (and any
filters that may have been included to minimize dust accumulation).
Technically, this air-motive force is called static pressure, usually
expressed in terms of how high a column of water the fan can support (e.g.
"inches of water" or "inches water gauge", "in. w.g.", etc.).
The open blade design fans furnished as OEM or aftermarket equipment on RV
fridges are designed specifically for this application. Low noise levels
and energy efficiency are more important than compactness. Perhaps more
importantly, they are designed to work in an open air, non-ducted
environment where static pressure is less important than air velocity,
since heat transfer at the condensor fins is directly dependant on air
velocity. Also, because of the open blade design, it's likely that air
flow pattern will be broader and more diffuse than with the enclosed
muffin style fan. This is advantageous since the condenser assembly is
pretty wide.
A few weeks ago Bill Davidson posted a message here that had a lot of
excellent information about this issue. Bill looked at several options,
including a Radio Shack muffin style fan, and came to the conclusion that
Fridgemate model A10-2710 Coil Fan (an aftermarket unit, available at RV
stores, designed to be used as an auxilliary fan) delivered the most air
for the power required. And it was the most quiet! I suggest you check
the archives for Bill's article (April 26, 1999) since it has lots of
other useful observations and recommendations for improving fridge
performance (or perhaps Bill would kindly repost his message).
I'm hoping to pull my fridge this weekend (for the semi-annual combustion
chamber cleaning) and will attempt to take some airflow measurements,
using the Fridgemate unit and a small muffin fan, as well as the original
Dometic fan.
Regarding the second issue: I've never (yet) found water behind the
insulation. Also, the fridge itself will NOT cause condensation in this
area - this area is heated by the fridge, not cooled. My guess is that
you've got a water leak, either at the flue vent assembly or from the
window above, or possibly even from some of the plumbing that runs through
that area. It's definitely worth cleaning up the rust (and neutralizing
it with a phosphoric acid based product), but you must find the source of
the leak or the rusting will recur.
-Wes
> Date: Thu, 20 May 1999 19:36:49 EDT
> From: S Sittservl <Ssittservl@AOL.COM>
> Subject: Fridge fan and water behind the fridge
> I've removed my not-terribly-cold fridge from the Westy, and
> (just like everybody else) my fan is broken. I figure I've got
> two choices: replace the motor (which is the broken part), or
> replace the whole fan.
>
> I checked with the local RV place on ordering a new fan motor
> from Dometic. It's $35 - pretty high for a part that's about $2.99
> in an electronics catalog. So, I won't be ordering from Dometic.
> I can get little 12V motors locally or mail order, but I'm not quite sure
> exactly what I need. In particular, does anyone know how many RPM's the
> motor ought to run at? Replacing just the motor has the advatage that I
> don't have to modify the mounting bracket, plus, I assume Dometic's
> original fan was at least adequate, so that gives me some assurance that
> my result would be at least adequate.
>
> The other option is to replace the whole fan. The current option
> is a little 3" muffin fan from Radio Shack, or something similar.
> It blows 27 cubic feet/minute. Does anyone know how that
> compares with the original fan? Also, I of course want the fan
> to be quiet. Does anyone have a sense for how the noise of these
> fans compare with the original Dometic fan, or how noisy
> the Dometic is? I know that's pretty subjective, but is the Dometic
> (when working) more like a whisper, or more like a box of bolts tumbling
> down the stairs?
>
> Second issue: also like everybody else, I found that the insulation
> behind the fridge was wet, and there was water and rust in the
> trough there between the wall and floor. My plan at this point is to
> have Ziebart remove the loose rust, magically turn the rest into metal
> (with rust convertor), and coat the trough with their waxy rust
> preventer. They'll do it for about $30. (I wouldn't generally treat a
> car with Ziebart - I hear it often does as much harm as good - but this
> limited application seemed to make sense.) My question is, does anyone
> have any suggestions for preventing water from collecting there or
> soaking the insulation in the first place? I suspect the water is a
> combination of condensation from the fridge, and water dripped down
> through the vent slots, but I don't know for sure.
>
> Thanks.
>
> -Steven Sittser
>
Wes Neuenschwander
Seattle, WA
wesn@eskimo.com
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