Date:         Sun, 19 Aug 2001 14:42:23 -0700
Reply-To:     Coby Smolens <cobys5@HOME.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Coby Smolens <cobys5@HOME.COM>
Subject:      Dometic refrigerator cooling mystery, '89 Westy
Content-Type: text/plain; charset="iso-8859-1"

We're working on Dave Lundgren's '89 Westy refrigerator, and I have to admit
to being stalled for the moment. I'm hoping someone can show me the flaw in
my logic. Here's the scoop:

Dave told us the unit wouldn't cool beyond 10 deg F. below ambient while
operating on propane, but made ice on house current. He cleaned the flue,
checked flame everything seemed normal. Enter Valley Wagonworks. First we
verified his observations - he was right on. Next we removed the unit,
disassembled the burner box, cleaned the orifice and tube, used a boroscope
to check the flue for obstructions, blew everything out with compressed air,
put the orifice and burner back together enough to light and observe the
flame before putting the burner box back together. We set it up to run on
propane outside the van using a barbecue propane tank and new regulator at
measured output (using a Dwyer 18-0-18 slack-tube manometer; Grainger,
$54.00) of 11" WC. The burner always lights, the flame is proper height and
color, never goes out. We reassembled the burner box and verified that
propane flame was lit and heating - we got 386 degrees F. at top of exhaust
stack. We then proceeded to make comparison temperature measurements at
three places (ambient temp around top of fridge, temperature of absorber
inside fridge, top of boiler tube). Measurements were taken over 2 days
after operating unit for 14 hours (overnight) and then in mid-afternoon
first on 110V then on propane. The readings are below.

           AMBIENT   BOILER TUBE   ABSORBER

AC  AM       91          289          29(ICE!)
    PM      112          298          51
DC  AM       86          301          59
    PM      110          295          85


The $64,000 question, of course, is WHY DOESN'T THE THING COOL AT THE SAME
RATE WITH PROPANE WHEN THE AMMONIA-WATER BOILER IS APPARENTLY BEING HEATED
JUST AS WELL OR BETTER WITH PROPANE??? I've thought about the temp control
valve, but if my understanding is correct, that just regulates the propane
flame height to trim it down thereby lowering boiling rate of the
ammonia-water solution in the boiler. Since we have plenty of heat at the
top of the boiler I'm guessing this is not an issue. Other notes: The van
has not sat for long periods of time (correct me Dave, if I'm wrong about
this) with the fridge in disuse, has worked properly (made ice in the desert
using propane) until just recently.

What am I missing?

Coby Smolens
Valley Wagonworks
VW Bus and Vanagon Specialists
"Intimately (but perhaps not intimately enough) acquainted with VW Vans
since 1959"

1535 SF Drake Blvd, San Anselmo, CA 94960
415-457-5628